Ansoft – Antenna/RF Training Guide
Chapter 1 - Introduction
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Introduction Ansoft – Antenna/RF Training Guide Training Manual Ansoft HFSS for Antenna/RF – User Guide
Training Manual
Inventory Number: 002846 4th Edition HFSS Release: 12.1 Designer/Nexxim Release: 5.0.1 Published Date: January 31, 2010 Registered Trademarks: ANSYS® is a registered trademark of SAS IP Inc. All other product names mentioned in this manual are trademarks or registered trademarks of their respective manufacturers.
Disclaimer Notice: This document has been reviewed and approved in accordance with the ANSYS, Inc. Documentation Review and Approval Procedures. “This ANSYS Inc. software product (the Program) and program documentation (Documentation) are furnished by ANSYS, Inc. under an ANSYS Software License Agreement that contains provisions concerning non-disclosure, copying, length and nature of use, warranties, disclaimers and remedies, and other provisions. The Program and Documentation may be used or copied only in accordance with the terms of that License Agreement.”
Copyright © 2008 SAS IP, Inc. Proprietary data. Unauthorized use, distribution, or duplication is prohibited. All Rights Reserved. ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Introduction Ansoft – Antenna/RF Training Guide
Table of Contents
Training Manual
•
Lectures
•
Workshops
1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.
Introduction Simulation Overview Boundary Conditions Mesh Operations/Advanced Solver Settings Phased Array Design Antenna Post Processing Complex Geometry Modeling An Introduction to Optimetrics Field Calculator Radar Cross Section (RCS) An Introduction to HFSS-IE
1.
Examples – Phased Array –
2.
Examples – Push Excitations
HFSS: RCS of a PEC Cube
4-1
Examples – HFSS-IE – –
1-3
3-1
Examples – RCS –
5.
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HFSS: Shorted Patch 2-1 Ansoft Designer: Dual-Band WLAN Antenna 2-2
– Ansoft Designer: Active Antenna Array
4.
1-1
Examples – Optimetrics – –
3.
HFSS: Waveguide Array
HFSS-IE: RCS of a PEC Cube HFSS-IE: Reflector (HFSS DataLink)
5-1 5-2
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Introduction Ansoft – Antenna/RF Training Guide
Welcome to Ansoft HFSS
Training Manual
• What is HFSS? –
HFSS is a high-performance full-wave electromagnetic(EM) field simulator for arbitrary 3D volumetric passive device modeling that takes advantage of the familiar Microsoft Windows graphical user interface. It integrates simulation, visualization, solid modeling, and automation in an easy-to-learn environment where solutions to your 3D EM problems are quickly and accurately obtained. Ansoft HFSS employs the Finite Element Method (FEM), adaptive meshing, and brilliant graphics to give you unparalleled performance and insight to all of your 3D EM problems. Ansoft HFSS can be used to calculate parameters such as S-Parameters, Resonant Frequency, and Fields. Typical uses include: • Antennas/Mobile Communications – Patches, Dipoles, Horns, Conformal Cell Phone Antennas, Quadrafilar Helix, Specific Absorption Rate (SAR), Infinite Arrays, Radar Cross Section (RCS), Frequency Selective Surfaces (FSS) • Waveguide – Filters, Resonators, Transitions, Couplers • Filters – Cavity Filters, Microstrip, Dielectric Package Modeling – BGA, QFP, Flip-Chip • EMC/EMI – Shield Enclosures, Coupling, Near- or Far-Field Radiation • PCB Board Modeling – Power/Ground planes, Mesh Grid Grounds, Backplanes • Silicon/GaAs - Spiral Inductors, Transformers • Connectors – Coax, SFP/XFP, Backplane, Transitions
–
–
–
HFSS is an interactive simulation system whose basic mesh element is a tetrahedron. This allows you to solve any arbitrary 3D geometry, especially those with complex curves and shapes, in a fraction of the time it would take using other techniques. The name HFSS stands for High Frequency Structure Simulator. Ansoft pioneered the use of the Finite Element Method (FEM) for EM simulation by developing/implementing technologies such as tangential vector finite elements, adaptive meshing, and Adaptive Lanczos-Pade Sweep (ALPS). Today, HFSS continues to lead the industry with innovations such as Modes-to-Nodes and Full-Wave Spice™. Ansoft HFSS has evolved over a period of years with input from many users and industries. In industry, Ansoft HFSS is the tool of choice for high-productivity research, development, and virtual prototyping.
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Introduction Ansoft – Antenna/RF Training Guide
Installing the Ansoft HFSS software
Training Manual
• System Requirements –
For up-to-date information, refer to the HFSS Installation Guide
• Installing the Ansoft HFSS Software –
For up-to-date information, refer to the HFSS Installation Guide
• Starting Ansoft HFSS – –
Click the Microsoft Start button, select Programs, and select the Ansoft, HFSS 12 program group. Click HFSS 12. Or Double click on the HFSS 12 icon on the Windows Desktop
NOTE: You should make backup copies of all HFSS projects created with a previous version of the software before opening them in HFSS 12
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Introduction Ansoft – Antenna/RF Training Guide
Web Update
Training Manual
• WebUpdate –
This feature allows you to update any existing Ansoft software from the WebUpdate window. This feature automatically scans your system to find any Ansoft software, and then allows you to download any updates if they are available.
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Introduction Ansoft – Antenna/RF Training Guide
Getting Help
Training Manual
• Getting Help –
If you have any questions while you are using Ansoft HFSS you can find answers in several ways: • Ansoft HFSS Online Help provides assistance while you are working. – To get help about a specific, active dialog box, click the Help button in the dialog box or press the F1 key. – Select the menu item Help > Contents to access the online help system. – Tooltips are available to provide information about tools on the toolbars or dialog boxes. When you hold the pointer over a tool for a brief time, a tooltip appears to display the name of the tool. – As you move the pointer over a tool or click a menu item, the Status Bar at the bottom of the Ansoft HFSS window provides a brief description of the function of the tool or menu item. – The Ansoft HFSS Getting Started guide provides detailed information about using HFSS to create and solve 3D EM projects. • Ansoft Technical Support – To contact Ansoft technical support staff in your geographical area, please log on to the Ansoft corporate website, www.ansoft.com and select Contact. • Your Ansoft sales engineer may also be contacted in order to obtain this information.
• Visiting the Ansoft Web Site – If your computer is connected to the Internet, you can visit the Ansoft Web site to learn more about the Ansoft company and products. • From the Ansoft Desktop – Select the menu item Help > Ansoft Corporate Website to access the Online Technical Support (OTS) system. • From your Internet browser – Visit www.ansoft.com
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Introduction Ansoft – Antenna/RF Training Guide
Technical Support
Training Manual
• For Technical Support –
The following link will direct you to the Ansoft Support Page. The Ansoft Support Pages provide additional documentation, training, and application notes. Web Site: http://www.ansoft.com/support.cfm
• University Support – Email Support:
[email protected]
• North America Commercial Support – –
Email Support: •
[email protected] The names and numbers in this list may change without notice • Technical Support: – 9-4 EST: • Pittsburgh, PA • (412) 261-3200 x199 • Burlington, MA • (781) 229-8900 x199 – 9-4 PST: • San Jose, CA • (408) 261-9095 x199 • Irvine, CA • (714) 417-9311 x199
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Introduction Ansoft – Antenna/RF Training Guide
Ansoft Desktop Terms
Training Manual
• Ansoft Desktop Terms –
The Ansoft HFSS Desktop has several optional panels: • A Project Manager which contains a design tree which lists the structure of the project. • A Message Manager that allows you to view any errors or warnings that occur before you begin a simulation. • A Property Window that displays and allows you to change model parameters or attributes. • A Progress Window that displays solution progress. • A 3D Modeler Window which contains the model and model tree for the active design.
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Introduction Ansoft – Antenna/RF Training Guide
Ansoft HFSS Desktop
Training Manual
Menu bar Toolbars
3D Modeler Window Project Manager with project tree
Progress Window
Message Manager
Status bar
Property Window
Coordinate Entry Fields
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Introduction Ansoft – Antenna/RF Training Guide
Ansoft Desktop Terms
Training Manual
• Project Manager Project Manager Window
Project Design
Design Setup
Design Automation •Parametric •Optimization •Sensitivity •Statistical
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Design Results
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Introduction Ansoft – Antenna/RF Training Guide
Ansoft Desktop Terms
Training Manual
• Property Window
Property Window
Property buttons
Property table
Property tabs
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Introduction Ansoft – Antenna/RF Training Guide
Ansoft Desktop Terms
Training Manual 3D Modeler Window
• Ansoft 3D Modeler Graphics area
3D Modeler design tree
Edge
Vertex
Model
Coordinate System (CS)
Context menu
Plane Origin
Face Model ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Ansoft Desktop Terms
Training Manual
• 3D Modeler Design Tree
Material
Object
Object Command History
Object View Grouped by Material
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Introduction Ansoft – Antenna/RF Training Guide
Design Windows
Training Manual
• Design Windows In the Ansoft HFSS Desktop, each project can have multiple designs and each design is displayed in a separate window. – You can have multiple projects and design windows open at the same time. Also, you can have multiple views of the same design visible at the same time. – To arrange the windows, you can drag them by the title bar, and resize them by dragging a corner or border. Also, you can select one of the following menu options: Window >Cascade, Window >Tile Vertically, or Window > Tile Horizontally. – To organize your Ansoft HFSS window, you can iconize open designs. Click the Iconize ** symbol in the upper right corner of the document border. An icon appears in the lower part of the Ansoft HFSS window. If the icon is not visible, it may be behind another open document. Resize any open documents as necessary. Select the menu item Window > Arrange Icons to arrange them at the bottom of the Ansoft HFSS window. – Select the menu item Window > Close All to close all open design. You are prompted to Save unsaved designs. –
Iconize Symbol
Design icons
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Introduction Ansoft – Antenna/RF Training Guide
Toolbars
Training Manual
• Toolbars –
–
The toolbar buttons are shortcuts for frequently used commands. Most of the available toolbars are displayed in this illustration of the Ansoft HFSS initial screen, but your Ansoft HFSS window probably will not be arranged this way. You can customize your toolbar display in a way that is convenient for you. Some toolbars are always displayed; other toolbars display automatically when you select a document of the related type. For example, when you select a 2D report from the project tree, the 2D report toolbar displays.
• To display or hide individual toolbars: –
–
Right-click the Ansoft HFSS window frame. • A list of all the toolbars is displayed. The toolbars with a check mark beside them are visible; the toolbars without a check mark are hidden. Click the toolbar name to turn its display on or off To make changes to the toolbars, select the menu item Tools > Customize. See Customize and Arrange Toolbars on the next page.
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Introduction Ansoft – Antenna/RF Training Guide
Toolbars
Training Manual
• Customize and Arrange Toolbars – –
Select the menu item Tools > Customize, or right-click the Ansoft HFSS window frame and click Customize at the bottom of the toolbar list. In the Customize dialog, you can do the following: • View a Description of the toolbar commands – Select an item from the Component pull-down list – Select an item from the Category list – Using the mouse click on the Buttons to display the Description – Click the Close button when you are finished • Toggle the visibility of toolbars – From the Toolbar list, toggle the check boxes to control the visibility of the toolbars – Click the Close button when you are finished
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Introduction Ansoft – Antenna/RF Training Guide
Overview
Training Manual
• Ansoft HFSS Desktop –
–
The Ansoft HFSS Desktop provides an intuitive, easy-to-use interface for developing passive RF device models. Creating designs, involves the following: • Parametric Model Generation – creating the geometry, boundaries and excitations • Analysis Setup – defining solution setup and frequency sweeps • Results – creating 2D/3D reports and field plots • Solve Loop - the solution process is fully automated To understand how these processes co-exist, examine the illustration shown on the next page.
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Introduction Ansoft – Antenna/RF Training Guide
Overview
Training Manual
Design
Solution Type Boundaries
Parametric Model Geometry/Materials Excitations Mesh Operations
Analysis Solution Setup Frequency Sweep
Mesh Refinement
Analyze
Solve
Results NO
2D Reports Fields
Converged
Solve Loop YES Update
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Introduction Ansoft – Antenna/RF Training Guide
Opening a Design
Training Manual
• Opening a HFSS project –
Opening a New project • In an Ansoft HFSS window, select the menu item File > New. • Select the menu Project > Insert HFSS Design.
– Opening an Existing HFSS project • In an Ansoft HFSS window, select the menu File > Open. – Use the Open dialog to select the project. – Click Open to open the project –
Opening an Existing Project from Explorer • You can open a project directly from the Microsoft Windows Explorer. • To open a project from Windows Explorer, do one of the following: – Double-click on the name of the project in Windows Explorer. – Right-click the name of the project in Windows Explorer and select Open from the shortcut menu.
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Introduction Ansoft – Antenna/RF Training Guide
Set Solution Type
Training Manual
• Set Solution Type –
This section describes how to set the Solution Type. The Solution Type defines the type of results, how the excitations are defined, and the convergence. The following Solution Types are available: • Driven Modal - calculates the modal-based S-parameters. The S-matrix solutions will be expressed in terms of the incident and reflected powers of waveguide modes. • Driven Terminal - calculates the terminal-based S-parameters of multi-conductor transmission line ports. The Smatrix solutions will be expressed in terms of terminal voltages and currents. • Eignemode – calculate the eigenmodes, or resonances, of a structure. The Eigenmode solver finds the resonant frequencies of the structure and the fields at those resonant frequencies.
–
Convergence • Driven Modal – Delta S for modal S-Parameters. This was the only convergence method available for Driven Solutions in previous versions. • Driven Terminal – Delta S for the single-ended or differential nodal S-Parameters. • Eigenmode - Delta F
–
To set the solution type: • Select the menu item HFSS > Solution Type – Choose one of the following: • Driven Modal • Driven Terminal • Eigenmode – Click the OK button
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Introduction Ansoft – Antenna/RF Training Guide
Converting older files
Training Manual
• Converting Older HFSS file to HFSS 12 –
– –
Because of changes to the HFSS files with the development of HFSS 12, opening a HFSS project from an earlier release may take more time than you are used to experiencing. However, once the file has been opened and saved, subsequent opening time will return to normal Ansoft HFSS 12 provides a way for you to automatically convert your HFSS projects from an earlier version to the HFSS 12 format. To access HFSS projects in an earlier version. • Select the menu item File > Open – Files of Type: Ansoft HFSS Project Files (.hfss) – Browse to the existing project and select the .hfss file – Click the Open button
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Ansoft – Antenna/RF Training Guide
Chapter 2 – Simulation Basics
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Introduction Ansoft – Antenna/RF Training Guide Training Manual
• Core Technology – HFSS – High Frequency Structure Simulator –
Arbitrary 3D Volumetric Full-Wave Field Solver • Ansoft Desktop – Advanced ACIS based Modeling – True Parametric Technology – Dynamic Editing – Powerful Report Generation – Dynamic Field Visualization – Design Flow Automation • Optimetrics/Ansoft Designer/AnsoftLinks • Advanced Material Types – Frequency Dependent Materials – Non-linear Materials – Anisotropic Materials • Advanced Boundary Conditions – Radiation and Perfectly Matched Layers – Symmetry, Finite Conductivity, Infinite Planes, RLC, and Layered Impedance – Master/Slave – Unit Cells • Advanced Solver Technology – Automatic Conformal Mesh Generation – Adaptive Mesh Generation – Internal/External Excitations – Includes Loss – ALPS Fast Frequency Sweep – Eigenmode
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Introduction Ansoft – Antenna/RF Training Guide Training Manual
• Common HFSS Applications – Antenna • • • • •
Planar Antennas - Patches, Dipoles, Horns, Conformal Cell Phone Antennas, Spirals Waveguide – Circular/Square Horns Wire – Dipole, Helix Arrays - Infinite Arrays, Frequency Selective Surfaces (FSS) & Photonic Band Gaps (PBG) Radar Cross Section (RCS)
– Microwave • • • • •
Filters – Cavity Filters, Microstrip, Dielectric EMC/EMI – Shield Enclosures, Coupling, Near- or Far-Field Radiation Connectors – Coax, SFP/XFP, Backplane, Transitions Waveguide – Filters, Resonators, Transitions, Couplers Silicon/GaSa - Spiral Inductors, Transformers
– Signal Integrity/High-Speed Digital • • • •
Package Modeling – BGA, QFP, Flip-Chip PCB Board Modeling – Power/Ground planes, Mesh Grid Grounds, Backplanes Connectors – SFP/XFP, VHDM, GBX, NexLev, Coax Transitions – Differential/Single-ended Vias
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Introduction Ansoft – Antenna/RF Training Guide
HFSS - Results
Training Manual
• Matrix Data –
–
–
–
–
Modal/Terminal/Differential • S-, Y-, and Z-Parameters • VSWR Excitations • Complex Propagation Constant (Gamma) • Zo Full-Wave Spice • Full-Wave Spice – Broadband Model • Lumped RLC – Low Frequency Model • Partial Fraction - Matlab • Export Formats – HSPICE, PSPICE, Cadence Spectre, and Maxwell SPICE Common Display Formats: • Rectangular, Polar • Smith Chart • Data Tables Common Output Formats: • Neutral Models Files (NMF) (Optimetrics only) – Parametric Results • Touchstone, Data Tables, Matlab, Citifile • Graphics – Windows Clipboard
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Introduction Ansoft – Antenna/RF Training Guide
HFSS - Results
Training Manual
• Fields –
–
– –
–
Modal/Terminal/Differential • Electric Field • Magnetic Field • Current (Volume/Surface) • Power • Specific Absorption Rate Radiation • 2D/3D Far-/Near-Fields • Arrays – Regular and Custom Setups • RCS Field Calculator • User Defined Field Calculations Common Display Formats • Volume • Surface • Vector • 2D Reports – Rectangular, Polar, Radiation Patterns Common Output Formats: • Animations – AVI, GIF • Data Tables • Graphics – Windows Clipboard, BMP, GIF, JPG, TIFF, VRML
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Introduction Ansoft – Antenna/RF Training Guide Training Manual
• What is HFSS (High Frequency Structure Simulator)? – “HFSS is the industry-standard software for S-parameter, full-wave SPICE extraction and electromagnetic simulation of high-frequency and high-speed components. HFSS is widely used for the design of on-chip embedded passives, PCB interconnects, antennas, RF/microwave components, and high-frequency IC packages.” – “HFSS improves engineering productivity, reduces development time, and better assures first-pass design success. The latest release of HFSS delivers significant productivity gains to Microwave/RF engineers and expands electromagnetic co-design to a new segment of engineers working in the areas of RF/analog IC and multi-gigabit designs as well as EMI/EMC.”
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Introduction Ansoft – Antenna/RF Training Guide
HFSS – Methodology
Training Manual
• HFSS uses the Finite Element Method (FEM) to solve Maxwell„s equations. – –
The primary advantage of the FEM for solving partial differential equations lies in the ability of the basic building blocks used to discretize the model to confrom to arbitrary geometry. The arbitrary shape of the basic building block (tetrahedron) also allows HFSS to generate a coarse mesh where fewer cells are needed to yield an accuate solution, while creating a finely discretized mesh where the field is rapidly varying or higher accuaracy is needed to obtain an accurate global solution.
• The FEM has been a standard for solving electromagnetic problems since the inception of HFSS in 1990. –
The FEM has been a standard for solving problems in structure mechanics since the mid 1950„s.
Tetrahedron
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Introduction Ansoft – Antenna/RF Training Guide
HFSS - Technology
Training Manual
• Tangential Vector Finite Elements Vertex: Explicitly Solved Edge: Explicitly Solved Face: Interpolated
• Transfinite Element Method
• Adaptive Meshing
Converged
Initial
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Introduction Ansoft – Antenna/RF Training Guide
HFSS – Automated solution process
Training Manual
• The “Solve”
Start
Create Initial Mesh
Solve fields using the Finite Element Method
Max(|DS|)>
1 j
Zs specified as W/sq
2
Layered Impedance 500 in Nickel
Lumped RLC
500 in Gold
Parallel RLC Circuit
0.7mil Copper Zs,Au LAu
Zs,Ni LNi
Zs,Cu LCu
Zs,input ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Introduction Ansoft – Antenna/RF Training Guide
Finite Conductivity Boundary
Training Manual
• Lossy electrical conductor – –
Forces E-field perpendicular to surface Surface impedance includes resistive and reactive surface losses
• Used for non-ideal conductor analysis • Infinite ground plane option simulates effects of infinite ground plane in postprocessing radiated fields • Parameters – –
t >>
Conductivity (S/m) Relative permeability (unitless)
Good conductor in skin depth regime When you define a solid object as a nonideal metal (e.g. copper or aluminum), and it is set to ‘Solve Surface’, a finite conductivity boundary is applied to its exterior faces.
2
Skin Depth
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Zs
1 j
Surface Impedance
1-6 3-6
Field Relationship
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Introduction Ansoft – Antenna/RF Training Guide
Impedance Boundary
Training Manual
• User-defined surface impedance –
Represents thin film resistors or reactive loads
• Infinite ground plane option simulates effects of infinite surface in post-processing radiated fields • Calculate required impedance from desired lumped value, width, and length – –
Length (in direction of current flow) width = number of “squares” Impedance per square = desired lumped impedance number of squares
• Parameters: – –
Resistance (W/square) Reactance (W/square) Example: Resistor in Wilkinson Power Divider Resistor is 3.5 mils long (in direction of flow) and 4 mils wide. Desired lumped value is 35 W.
3.5 0.875 4 R 35 Rsheet lumped 40 W / square N 0.875 N
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Layered Impedance Boundary
Training Manual
• Models multiple thin layers in a structure as single impedance surface – – –
Effect is same as impedance boundary, except that HFSS calculates surface impedance based on data entered for layered structure Surface roughness can be included Plating layers can be modeled by using an equivalent surface impedance
• Not available for fast frequency sweeps • Parameters – – –
Layer thicknesses Material properties Surface roughness (optional)
500 in Nickel
Zs,Au LAu
500 in Gold
Zs,Cu LCu
Zs,input
Impedance of the layered structure is calculated by recursively calling the impedance calculation formulation from transmission line theory
0.7mil Copper
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Zs,Ni LNi
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Lumped RLC Boundary
Training Manual
• Represents any combination of parallel-connected lumped RLC elements on surfaces in terms of circuit definition – –
Supply values for R, L, and C HFSS determines impedance per square of lumped RLC boundary at any frequency
• Fast frequency sweeps are supported • Parameters – – – –
Resistance Inductance Capacitance Line for current flow
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Introduction Ansoft – Antenna/RF Training Guide
Symmetry Plane
Training Manual
• Allows for modeling portion of entire structure • For Driven Modal solutions • Two symmetry options are available – –
Use perfect E when electric field is perpendicular to symmetry plane Use perfect H when electric field is tangential to symmetry plane
• Involve further implications to boundary manager and fields post-processing – –
May need to specify impedance multiplier Existence of symmetry boundary allows for near- and far-field calculation of entire structure
• Parameters – –
Type Impedance multiplier
Conductive edges on all four sides
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Waveguide contains symmetric propagating mode which could be modeled using half the volume vertically or horizontally.
Perfect H Symmetry (left side)
1-10 3-10
Perfect E Symmetry (bottom)
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Introduction Ansoft – Antenna/RF Training Guide
Symmetry Plane Impedance Multiplier
Training Manual
• When symmetry is used, Zpi and impedance line-dependent Zpv and Zvi calculations will be incorrect since entire port aperture is not represented – –
Impedance is halved for model with Perfect E symmetry plane Impedance is doubled for model with Perfect H symmetry plane
• Port impedance multiplier is renormalizing factor used to obtain correct impedance – –
Value applied to all ports Global parameter set during assignment of any port
Rectangular WG (No Symmetry) ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
Half Rectangular WG (Perfect H Symmetry) Impedance Multiplier = 0.5 1-11 3-11
Half Rectangular WG (Perfect E Symmetry) Impedance Multiplier = 2 January 2010 February 23,31, 2009 Inventory #002846 Inventory #002593
Introduction Ansoft – Antenna/RF Training Guide
Symmetry Plane Mode Implications
Training Manual
• Geometric symmetry does not necessarily imply field symmetry for higher-order modes • Symmetry boundaries can act as mode filters – –
Next higher propagating waveguide mode is not symmetric about vertical center plane of waveguide Therefore one symmetry case is valid while the other is not
• Use caution when using symmetry planes to assure that real behavior is not filtered out by boundary conditions
Perfect H Symmetry (right side) Perfect E Symmetry (top)
TE20 mode in full model
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Properly represented with Perfect E symmetry
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Introduction Ansoft – Antenna/RF Training Guide
Radiation Boundary
Training Manual
• Mimics continued propagation beyond boundary plane – – – – –
Absorption achieved via 2nd order radiation boundary Place at least /4 from strongly radiating structure Place at least /10 from weakly radiating structure Absorbs best when incident energy flow is normal to surface Must be concave to all incident fields from within modeled space
• Parameters –
Advanced options used for incident wave and HFSS DataLink problems
Boundary is /4 away from horn aperture in all directions
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Radiation boundary functions well for incident angles less than 25°-30°
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Introduction Ansoft – Antenna/RF Training Guide
Impact of Distance to ABC
Training Manual
• Example probe-fed circular patch • Varied distance between absorbing boundary condition (ABC) and antenna –
λ /20, λ /10, λ /8, λ /4, λ /2, 3 λ /4, λ
• Examined impact on return loss and gain
0.2 dB variation
/4 and cases within 13 MHz of each other (0.1%)
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Introduction Ansoft – Antenna/RF Training Guide
Perfectly Matched Layer (PML)
Training Manual
• Fictitious lossy anisotropic material which fully absorbs electromagnetic fields • Two types of PML applications – –
“PML objects accept free radiation” if PML terminates free space “PML objects continue guided waves” if PML terminates transmission line
• Guidelines for assigning PML boundaries – –
Use PML setup wizard for most cases Manually create a PML when base object is curved or inhomogeneous
• Parameters – – –
Uniform thickness Minimum frequency Minimum radiating distance (between PML and antenna)
PML functions well for incident angles less than 65°-70°
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Introduction Ansoft – Antenna/RF Training Guide
Impact of Distance to PML
Training Manual
• Example probe-fed circular patch • Varied distance between PML and antenna –
λ/20, λ /10, λ /8, λ /4, λ /2, 3λ /4
• Examined impact on return loss and gain
/8 and 3/4 cases within 28 MHz of each other (0.3%)
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Introduction Ansoft – Antenna/RF Training Guide
Radiation Boundary vs PML
Training Manual
Radiation Boundary
PML
Type
2D
3D (occupies volume)
Incident angle from normal
< ~30°
< ~70°
Distance from radiator
> /4
> /10
Setup complexity
Low
Medium
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Introduction Ansoft – Antenna/RF Training Guide
Master/Slave Boundaries
Training Manual
• Used to model unit cell of periodic structure –
Also referred to as linked or periodic boundaries
• Master and slave boundaries are always paired – –
Fields on master surface are mapped to slave surface with a phase shift Phase shift specified either as absolute phase value or using scan angle
• Constraints – –
Master and slave surfaces must be identical in shape and size Coordinate systems must be created to identify point-to-point correspondence
Master Boundary
Slave Boundary
• Parameters
Vaxis
– Master/slave pairing – UV coordinate systems – Phase shift method
Ground Plane
U-axis
WG Port (bottom) Unit Cell Model of Waveguide Array ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Introduction Ansoft – Antenna/RF Training Guide
Screening Impedance Boundary
Training Manual
• Used to efficiently represent periodic screens or grids with impedance boundary condition – –
Can be anisotropic (different values in x and y directions) Can be frequency-dependent
• Periodic grid characterized by unit cell – –
Dynamic link support to import impedance values from unit cell Includes effects of polarization
• Parameters – Resistance and reactance (W/square) – Coordinate system if anisotropic – HFSS design for dynamic link
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Introduction Ansoft – Antenna/RF Training Guide
Default Outer Boundary
Training Manual
• Any exterior face of modeled geometry not given user-defined boundary condition is assumed to be Perfect E boundary –
Default boundary called “outer”
• Imagine entire model buried in solid metal unless HFSS is instructed otherwise • Use HFSS > Boundary Display to view all boundary assignments –
Graphical window shows both user and auto-assigned boundaries
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Introduction Ansoft – Antenna/RF Training Guide
Trace Thickness Effects on Planar Antenna
Training Manual
• Conducting traces often modeled as 2D objects for electromagnetic simulations – –
More computationally efficient since fewer meshing surfaces required Good approximation for many structures operating in skin depth regime
Patch antenna modeled with 2D sheet
Frequency response of both models
Patch antenna modeled with 3D object ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Introduction Ansoft – Antenna/RF Training Guide
Trace Thickness Effects on Planar Filter
Training Manual
• Planar filters which use edge coupling to operate require 3D objects (finite thickness) for modeling conducting traces – –
Applications whose performance depends upon closely-coupled traces End-coupled, parallel-coupled, hairpin filters, etc.
Edge-coupled filter modeled with 2D sheets
Frequency response of both models Edge-coupled filter modeled with 3D objects ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Introduction Ansoft – Antenna/RF Training Guide
Excitations
Training Manual
• Provide means for energy to enter and exit model • Types of excitations –
– – – –
Ports • Wave ports • Lumped ports • Floquet ports Voltage sources Current sources Magnetic biases Incident waves • Plane waves • Hertzian dipole • Cylindrical wave • Gaussian beam • Linear antenna wave • Far-field wave • Near-field wave
• Only ports provide S-parameters –
This presentation will focus on this type of excitation
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Introduction Ansoft – Antenna/RF Training Guide
Driven Modal vs Driven Terminal Solutions
Training Manual
• Driven modal – – – –
S-matrix solution expressed in terms of incident and reflected powers of waveguide modes Always used by wave solver Integration lines set phase between ports and modal voltage integration path (Zpv and Zvi) Use for modal-based S-parameters of passive, high-frequency structures such as microstrips, waveguides, and transmission lines
• Driven terminal – – –
S-matrix solution expressed in terms of linear combination of nodal voltages and currents for wave port Equivalent “modes-to-nodes” transformation performed from modal solution Use for terminal-based S-parameters of multi-conductor transmission line ports (with several quasi-TEM modes, etc.)
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Introduction Ansoft – Antenna/RF Training Guide
Excitations
Training Manual
• Example Solution Types:
Mode 1 (Even Mode)
Integration Line
Mode 2 (Odd Mode)
Integration Line Port1 2 Modes
Modal
Port2 2 Modes
Modes to Nodes Transformation
T1
T2 T1 Port1
SPICE Differential Pairs ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
T1
T2
1-25 3-25
Terminal
Port2 T2 January 2010 February 23,31, 2009 Inventory #002846 Inventory #002593
Introduction Ansoft – Antenna/RF Training Guide
Ports
Training Manual
• Ports are unique type of boundary condition – – –
Allow energy to flow into and out of structure Defined on 2D planar surface 2D field patterns serve as boundary conditions for full 3D problem
• Incorrect port setup will produce incorrect results – If port fields are incorrect, then solution will be incorrect – Assumed boundary condition on port edges should always be considered
Initial Mesh
Seeding and Lambda Refinement (Single Frequency)
Port Solution (Adaptive)
Full Volumetric Solution
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Introduction Ansoft – Antenna/RF Training Guide
Wave Ports
Training Manual
• External port type • Arbitrary port solver calculates natural waveguide field patterns (modes) –
Assumes semi-infinitely long waveguide with same cross-section and material properties as port surface
• Recommended only for surfaces exposed to background object • Supports multiple modes, de-embedding, and re-normalization • Computes generalized S-parameters – –
Frequency-dependent characteristic impedance Perfectly matched at every frequency
Port 1
Port 4
Port 3
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Port 2
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Port Solver
Training Manual
• Wave port solver solves two-dimensional wave equation • Field pattern of traveling wave inside waveguide can be determined by solving Maxwell’s equations • Wave equation is derived directly from Maxwell’s equations 1 E x, y k02 r E ( x, y ) 0 r
• where – – – –
E(x,y) is phasor representing oscillating electric field k0 is free space wave number r is complex relative permeability r is complex relative permittivity
• 2D solver obtains excitation field pattern in form of phasor solution E(x,y) – – –
Phasor solutions are independent of z and time Only after being multiplied by e-z do they become traveling waves Different excitation field pattern is computed for each frequency point of interest
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Introduction Ansoft – Antenna/RF Training Guide
Wave Port Boundary Conditions
Training Manual
• All outer edges are assigned Perfect E boundary by default – – –
Port is defined within waveguide Simple setup for enclosed transmission lines (coax, waveguide, etc.) Challenging setup for unbalanced or non-enclosed lines (microstrip, CPW, slotline, etc.)
• Symmetry or impedance boundaries also recognized at port edges • For port on same surface as radiation boundary, default interface is Perfect E boundary –
Can set option to use radiation boundary on port edges during port solution
• Creating port edges too close to current-carrying lines will allow coupling from trace to port walls –
Causes incorrect modal solution which will suffer immediate discontinuity as energy is injected past port into model
Port too narrow (fields coupled to sidewalls)
Correct port size ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Introduction Ansoft – Antenna/RF Training Guide
Wave Port Sizing Guidelines
Training Manual
• Microstrip port height between 6h and 10h
• Extend stripline port height from upper to lower groundplane (h) • Stripline port width
– Tend towards upper limit as dielectric constant drops and fringing fields increase – Make bottom edge of port co-planar with upper face of ground plane
– 8w for w h – 5w, or on order of 3h to 4h, for w < h
• Can also make side walls of port Perfect H boundaries
• Microstrip port width – 10w for w h – 5w, or on order of 3h to 4h, for w < h
8w, w h or 5w (3h to 4h), w < h
10w, w h or 5w (3h to 4h), w < h
w h 6h to 10h w h
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Port sizing guidelines are not inviolable rules. If meeting height and width requirements result in rectangular aperture larger than /2 in one dimension, the substrate and trace may be ignored in favor of a waveguide mode. When in doubt, run a ports-only solution to determine which modes are propagating. 1-30 3-30
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Introduction Ansoft – Antenna/RF Training Guide
Wave Port Sizing Guidelines
Training Manual
• Slotline port height at least 4h or 4g (whichever is larger)
• Coplanar waveguide port height at least 4h or 4g (whichever is larger)
– Include air above and below substrate – If ground plane is present, port should terminate at ground plane
– Include air above and below substrate – If ground plane is present, port should terminate at ground plane
• Port width should contain at least 3g to either side of slot or 7g total minimum
• Port width should contain 3-5g or 3-5s of side grounds (whichever is larger)
– Port boundary must intersect both side ground planes or they will „float‟ and become signal conductors
– Total width ~10g or ~10s – Port outline must intersect both side grounds or they will „float‟ and become signal conductors
Approx 7g minimum
Larger of approx. 10g or 10s Larger of 4h or 4g Larger of 4h or 4g
g
s h h
g
For Driven Modal solutions, use Zpv for impedance calculation
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Introduction Ansoft – Antenna/RF Training Guide
Wave Port Implications
Training Manual
• Modes, reflections, and propagation – – –
It is possible for 3D field solution generated by excitation signal of one specific mode to contain reflections of higherorder modes which arise due to discontinuities If higher-order mode is reflected back to excitation port or transmitted onto another port, its S-parameters should be calculated If higher-order mode decays before reaching any port (because of attenuation or because it is a non-propagating evanescent mode), there is no need to obtain its S-parameters
• Wave ports require a length of uniform cross-section –
HFSS assumes that each port is connected to semi-infinitely long waveguide with same cross-section as wave port
No uniform cross section at wave ports
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Uniform cross-section added for each wave port
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Introduction Ansoft – Antenna/RF Training Guide
Internal Wave Ports
Training Manual
• Wave ports can be placed internal to model by providing boundary condition normally seen by external wave port –
Create PEC “cap” to back the wave port and enable excitation in proper direction
Example coax feed within solution volume
Coaxial antenna feed with coaxial wave port capped by PEC object
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Introduction Ansoft – Antenna/RF Training Guide
Integration Lines
Training Manual
• Applicable to driven modal solution types • Port vector which can serve several purposes • Calibration line which specifies direction of excitation electric field pattern at port –
Define separate integration line for each mode on multi-mode ports
• Impedance line along which to compute Zpv or Zvi port impedance –
Select two points with maximum voltage differential
Microstrip line
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Slotline Waveguide
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Introduction Ansoft – Antenna/RF Training Guide
Lumped Ports
Training Manual
• Recommended only for surfaces internal to model – – –
Single TEM mode with no de-embedding Uniform electric field on port surface Normalized to constant user-defined Z0
• Lumped port boundary conditions – Perfect E or finite conductivity boundary for port edges which interface with conductor or another port edge – Perfect H for all remaining port edges
Dipole element with lumped port
Zo
Uniform electric field User-defined Zo
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Introduction Ansoft – Antenna/RF Training Guide
Lumped vs Wave Ports for Planar Filters • Lumped ports can be used to feed printed transmission lines
• Wave ports can be used to feed printed transmission lines – S-parameters normalized to computed characteristic impedance – Multiple propagating modes possible – De-embedding available as postprocessing operation – Must touch background object (or be backed by conducting object)
– S-parameters normalized to userspecified characteristic impedance – Single mode propagation – No de-embedding operations available – Must be located inside model
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Training Manual
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Introduction Ansoft – Antenna/RF Training Guide
Lumped vs Wave Ports for Planar Filters
Training Manual
• Same results obtained from both port types
Lumped Ports
Wave Ports
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Introduction Ansoft – Antenna/RF Training Guide
Wave Ports vs Lumped Ports
Training Manual
Wave port
Lumped port
External Faces
Internal to Model
Higher order modes
Yes
No
De-embedding
Yes
No
Re-normalization
Yes
Yes
Setup complexity
Moderate
Low
Accessibility
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Ansoft – Antenna/RF Training Guide
Chapter 4 – Mesh Operations
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Mesh Seeding – Why? and How?
Training Manual
• Mesh seeding is a general term related to the manual manipulation of the tetrahedral mesh. • The Adaptive solution process in HFSS is very robust, and will converge to the correct solution given enough passes and memory. • Mesh seeding uses a priori knowledge of the fields to provide the adaptive solution process a “head-start”. • It can also be used to relax the mesh where the user knows it has little impact on the results. • Mesh operations should be used sparingly as they can are usually un-necessarily
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Introduction Ansoft – Antenna/RF Training Guide
Mesh Seeding - Methods
Training Manual
• Length Based Restriction on Selection –
Restrict maximum length and/or number of tets on surface of objects
• Length Based Restriction in Selection –
Restrict maximum length and/or number of tets in volume of objects
• Model Resolution –
Restrict minimum length of tets on or inside objects
• Max. Surface Deviation / Max. Surface Normal Deviation –
Define facet angle for true surface objects
• Max. Aspect Ratio –
Define tet Aspect Ratio for any objects
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Introduction Ansoft – Antenna/RF Training Guide
Mesh Seeding – Methods 1 & 2
Training Manual
• Restrict maximum length or number of tets on a surface or inside an object’s volume • For areas of known high field gradient, add extra tets to improve convergence – –
HFSS / Mesh Operations / Assign / On Selection / Length Based HFSS / Mesh Operations / Assign / In Selection / Length Based
• Uses: – –
Reduce the number of adaptive passes Help adaptive process find high Q resonances
Fewer passes needed from Seeded Mesh then from Initial Mesh ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Introduction Ansoft – Antenna/RF Training Guide
Mesh Seeding – Method 3
Training Manual
• For imported geometries with electrically insignificant detail • HFSS / Mesh Operations / Assign / Model Resolution
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Introduction Ansoft – Antenna/RF Training Guide
Mesh Seeding – Method 4
Training Manual
• Defines true surface discretization by controlling how tightly the mesh conforms to a curved geometry –
HFSS / Mesh Operations / Assign / Surface Approximation
• Methods: – –
Surface Deviation – specifying maximum distance allowed between curved surface and faceted surface. Normal Deviation – specify the angular separation between facets.
• Uses: – –
Reduce mesh density for low current ground vias. Improve mesh’s conformity to cylindrical or spherical resonant cavities
Initial Mesh (22.5 deg facets)
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Surface Approximation applied (45 deg facets)
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Introduction Ansoft – Antenna/RF Training Guide
Mesh Seeding – Method 5
Training Manual
• Set Aspect Ratio for all tetrahedra within a selected volume –
HFSS / Mesh Operations / Assign / Surface Approximation – Maximum Aspect Ratio
• Mesh quality is directly related to the tetrahedra’s aspect ratio –
E-field calculations in HFSS have reduced accuracy when there are long & skinny tetrahedra (high aspect ratio >10)
• Allows the user to increase the mesh density without determining a specific length • Uses: – – –
Improving mesh quality around dipoles A substitute for length based refinement or virtual objects Not needed as much with improved mesh quality mesh in HFSSv11
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Introduction Ansoft – Antenna/RF Training Guide
Seeding vs. Virtual Objects
Training Manual
• Virtual objects have been used in HFSS to control the aspect ratio of tetrahedra in electrically significant regions. –
The object does not create an electrical boundary condition, but does affect the mesh since the mesh must conform its its faces.
• Uses: –
Dipole
Dipole element
Virtual air object with radius between dipole and radiating boundary box • Now, the Aspect Ratio seed (Method 5) is much easier to use
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Ansoft – Antenna/RF Training Guide
Chapter 4.1 – Solution Process and Advanced Settings
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Introduction Ansoft – Antenna/RF Training Guide
HFSS Solution Process
Training Manual
Setup
Solution
Parametric Model Generation
Design HFSS / HFSS-IE
Solution Type Driven Model Driven Terminal Eigenmode
Mesh Generation
Initial Mesh
Seeding and Lambda Refinement (Single Frequency)
Analysis Mesh Seeding Solution Setup: Frequency Sweep ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
Port Solution (Adaptive)
Full Volumetric Solution (S-Parameters/E-Fields)
Initial Solution
Parametric Model Geometry/Materials Boundaries Excitations
Frequency Sweep
Adaptive Mesh Loop Refine Mesh (Single Frequency)
Full Volumetric Solution (S-Parameters/E-Fields)
4.1-2 1-2
No
Check Convergence (Delta S)
Yes
Frequency Sweep Discrete Interpolating Fast
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Introduction Ansoft – Antenna/RF Training Guide
HFSS Solution Process
Training Manual
Initial Solution Seeding and Lambda Refinement (Single Frequency)
Initial Mesh
Port Solution (Adaptive)
Ports Only & Frequency Sweep
Full Volumetric Solution (S-Parameters/E-Fields)
No Adaptive Meshing
Refine Mesh (Gradient of E-Field at Single Frequency) Adaptive Mesh Loop
No
Check Convergence (Delta S)
YES
Frequency Sweep
Full Volumetric Solution (S-Parameters/E-Fields)
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Introduction Ansoft – Antenna/RF Training Guide
Probe-Fed Patch Antenna Example
Training Manual
Patch Antenna Air
Probe
Substrate Coaxial Wave Port
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Introduction Ansoft – Antenna/RF Training Guide
Initial Mesh
Training Manual
• Initial mesh captures geometrical details of the model • Every vertex in the model is represented in the mesh • The tetrahedral mesh is conformal to complex, non-rectilinear geometries Mesh Plotted on Top Dielectric Surface Only
Initial Mesh
Seeding and Lambda Refinement (Single Frequency)
Port Solution (Adaptive)
Full Volumetric Solution (S-Parameters/E-Fields)
Refine Mesh (Gradient of E-Field at Single Frequency)
No
Check Convergence (Delta S)
Adaptive Mesh Loop
YES
Frequency Sweep
Full Volumetric Solution (S-Parameters/E-Fields)
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Introduction Ansoft – Antenna/RF Training Guide
Seeding and Lambda Refinement
Training Manual
• Seeding is a useful advanced capability inside HFSS which allows the user to influence the mesh • Can be used for several different reasons – – – –
Reducing number of adaptive passes needed to solve project (time savings) Reducing amount of RAM needed to solve project (memory savings) Getting more accurate answers (accuracy/time savings) Addressing meshing issues that arise
• Lambda refinement ensures that first adaptive mesh is no larger than preset value (0.3333*lambda) Initial Mesh
Seeding and Lambda Refinement (Single Frequency)
Port Solution (Adaptive)
Full Volumetric Solution (S-Parameters/E-Fields)
Refine Mesh (Gradient of E-Field at Single Frequency)
No
Check Convergence (Delta S)
Adaptive Mesh Loop
YES
Frequency Sweep
Full Volumetric Solution (S-Parameters/E-Fields)
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Introduction Ansoft – Antenna/RF Training Guide
Port Solution
Training Manual
• Performs 2D FEM Eigenmode solution of port • Adaptive process used to properly determine excitation characteristic impedance and propagation constant • Mesh on the port lines up with the mesh in the 3D volume Initial Mesh on Coax Port
Initial Mesh
Seeding and Lambda Refinement (Single Frequency)
Refined Mesh on Coax Port
Port Solution (Adaptive)
Full Volumetric Solution (S-Parameters/E-Fields)
Refine Mesh (Gradient of E-Field at Single Frequency)
Center Conductor No
Check Convergence (Delta S)
Adaptive Mesh Loop
YES
Frequency Sweep
Full Volumetric Solution (S-Parameters/E-Fields)
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1st Adaptive Pass Initial Mesh
Seeding and Lambda Refinement (Single Frequency)
Training Manual
• The fields throughout the entire 3D volume are solved and the S-parameters are calculated.
Port Solution (Adaptive)
Full Volumetric Solution (S-Parameters/E-Fields)
Refine Mesh (Gradient of E-Field at Single Frequency)
No
Check Convergence (Delta S)
Adaptive Mesh Loop
YES
Frequency Sweep
Full Volumetric Solution (S-Parameters/E-Fields)
Adaptive Frequency
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Introduction Ansoft – Antenna/RF Training Guide
2nd Adaptive Pass Initial Mesh
Seeding and Lambda Refinement (Single Frequency)
Training Manual
Port Solution (Adaptive)
Full Volumetric Solution (S-Parameters/E-Fields)
Refine Mesh (Gradient of E-Field at Single Frequency)
No
Check Convergence (Delta S)
Adaptive Mesh Loop
YES
Frequency Sweep
Full Volumetric Solution (S-Parameters/E-Fields)
Adaptive Frequency
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3rd Adaptive Pass Initial Mesh
Seeding and Lambda Refinement (Single Frequency)
Training Manual
Port Solution (Adaptive)
Full Volumetric Solution (S-Parameters/E-Fields)
Refine Mesh (Gradient of E-Field at Single Frequency)
No
Check Convergence (Delta S)
Adaptive Mesh Loop
YES
Frequency Sweep
Full Volumetric Solution (S-Parameters/E-Fields)
Adaptive Frequency
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Introduction Ansoft – Antenna/RF Training Guide
6th Adaptive Pass Initial Mesh
Seeding and Lambda Refinement (Single Frequency)
Training Manual
Port Solution (Adaptive)
Full Volumetric Solution (S-Parameters/E-Fields)
Refine Mesh (Gradient of E-Field at Single Frequency)
No
Check Convergence (Delta S)
Adaptive Mesh Loop
YES
Frequency Sweep
Full Volumetric Solution (S-Parameters/E-Fields)
Adaptive Frequency
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4.1-11 1-11
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Introduction Ansoft – Antenna/RF Training Guide
8th Adaptive Pass Initial Mesh
Seeding and Lambda Refinement (Single Frequency)
Training Manual
Port Solution (Adaptive)
Full Volumetric Solution (S-Parameters/E-Fields)
Refine Mesh (Gradient of E-Field at Single Frequency)
No
Check Convergence (Delta S)
Adaptive Mesh Loop
YES
Frequency Sweep
Full Volumetric Solution (S-Parameters/E-Fields)
Adaptive Frequency
ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
4.1-12 1-12
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Introduction Ansoft – Antenna/RF Training Guide
9th Adaptive Pass Initial Mesh
Seeding and Lambda Refinement (Single Frequency)
Training Manual
Port Solution (Adaptive)
Full Volumetric Solution (S-Parameters/E-Fields)
Refine Mesh (Gradient of E-Field at Single Frequency)
No
Check Convergence (Delta S)
Adaptive Mesh Loop
YES
Frequency Sweep
Full Volumetric Solution (S-Parameters/E-Fields)
Adaptive Frequency
ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
4.1-13 1-13
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Introduction Ansoft – Antenna/RF Training Guide
10th Adaptive Pass Initial Mesh
Seeding and Lambda Refinement (Single Frequency)
Training Manual
Port Solution (Adaptive)
Full Volumetric Solution (S-Parameters/E-Fields)
Refine Mesh (Gradient of E-Field at Single Frequency)
No
Check Convergence (Delta S)
Adaptive Mesh Loop
YES
Frequency Sweep
Full Volumetric Solution (S-Parameters/E-Fields)
Adaptive Frequency
ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
4.1-14 1-14
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Introduction Ansoft – Antenna/RF Training Guide
10th Adaptive Pass Initial Mesh
Seeding and Lambda Refinement (Single Frequency)
Training Manual
Port Solution (Adaptive)
Full Volumetric Solution (S-Parameters/E-Fields)
Refine Mesh (Gradient of E-Field at Single Frequency)
No
Check Convergence (Delta S)
Adaptive Mesh Loop
YES
Frequency Sweep
Full Volumetric Solution (S-Parameters/E-Fields)
Adaptive Frequency
ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
4.1-15 1-15
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Analysis Setup
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4.1-16 1-16
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Introduction Ansoft – Antenna/RF Training Guide
HFSS Solution Process
Training Manual
Setup
Solution
Parametric Model Generation
Design HFSS / HFSS-IE
Solution Type Driven Model Driven Terminal Eigenmode
Mesh Generation
Initial Mesh
Seeding and Lambda Refinement (Single Frequency)
Analysis Mesh Seeding Solution Setup: Frequency Sweep ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
Port Solution (Adaptive)
Full Volumetric Solution (S-Parameters/E-Fields)
Initial Solution
Parametric Model Geometry/Materials Boundaries Excitations
Frequency Sweep
Adaptive Mesh Loop Refine Mesh (Single Frequency)
Full Volumetric Solution (S-Parameters/E-Fields)
4.1-17 1-17
No
Check Convergence (Delta S)
Yes
Frequency Sweep Discrete Interpolating Fast
January 2010 February 23,31, 2009 Inventory #002846 Inventory #002593
Introduction Ansoft – Antenna/RF Training Guide
Analysis Setup
Training Manual
• The solution setup controls HFSS’s solution process. – – – – – – – –
ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
Set the Solution Frequency Control the initial mesh Set the convergence criteria Control how the mesh is modified between passes Control the port’s solution and convergence criteria Select the basis function used to describe the fields Choose the matrix solver Determine if Adjoint Derivatives will be calculated
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Introduction Ansoft – Antenna/RF Training Guide
Solution Frequency
Training Manual
• The Solution Frequency sets: – The frequency used to create the adaptive mesh. • Defines the spatial resolution of the mesh through the Lambda Refinement step • Lambda Refinement is wavelength dependant.
– Determines the frequency used to evaluate the mesh’s convergence.
• A higher frequency mesh is generally valid at lower frequencies. – A mesh created at a higher frequency will be denser than a mesh at lower a frequency because the wavelength is smaller. – The denser mesh is likely to pickup the field variations associated with lower frequencies behaviors.
• A low frequency mesh is generally NOT valid at higher frequencies. – A mesh created at a lower frequency will be coarser than a mesh created at a higher frequency because the wavelength is longer. – The coarser mesh is less likely to pickup field variations associated with the higher frequencies. ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
4.1-19 1-19
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Introduction Ansoft – Antenna/RF Training Guide
The Starting Mesh
Training Manual
• Lambda Refinement – Controlled at the top of the “Options” Tab – Lambda Refinement controls the minimal mesh density throughout the model. – The default value is established to provide a good starting density for the adaptive process. – Defined in terms of wavelength (at the solution frequency) in the bulk material • Accounts for the material properties
– Its applied before any seeding operations or port solutions.
• Initial Mesh Options – Controlled at the top of the “Advanced” Tab – Allows the use of another simulation’s mesh as an initial mesh for this simulation. – Both Simulations must be geometrically identical – Common Uses include • Changing material properties without re-meshing • Defining multiple solution frequencies for consideration in the Adaptive Meshing Process • Performing Parametric Sweeps on geometrically identical models
– Use the Setup Link to point to the desired mesh ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
4.1-20 1-20
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Introduction Ansoft – Antenna/RF Training Guide Using Dependent Setups: Dual-band Patch Antenna Example
Training Manual
Challenge: Antenna has two resonant frequencies
Solution (Dependent Solve): Create a mesh that is adaptived at both 2.5GHz and 5.0Ghz and add a sweep to capture complete frequency range
Design goal: • Radiate at 2.5 GHz and 5.0 GHz, • return loss of -10dB.
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4.1-21 1-21
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Introduction Ansoft – Antenna/RF Training Guide
Add Dependent Solve
Training Manual
Under analysis right click on Setup1 and select Add Dependent Solve Setup All settings from parent (Setup1) are copied to child (Setup1_1)
The dependent setup uses the mesh from the parent setup ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
4.1-22 1-22
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Introduction Ansoft – Antenna/RF Training Guide
Modify the Dependent Solve Setup
Training Manual
Once Setup1 is complete, Setup1_1 will build off of Setup1’s mesh and create a converged mesh using its own convergence criteria and settings
HFSS will create a converged mesh for Setup1 using its convergence criteria and settings
The result is a single mesh that accurately predicts the antenna’s performance at both frequencies ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
4.1-23 1-23
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Introduction Ansoft – Antenna/RF Training Guide
Adaptive Mesh’s Convergence Results
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4.1-24 1-24
Training Manual
January 2010 February 23,31, 2009 Inventory #002846 Inventory #002593
Introduction Ansoft – Antenna/RF Training Guide
Results
Training Manual
Solutions agree well at the lower frequency where both were adaptively meshed
Slight discrepancy at the higher frequency where only Setup1_1 was adaptively meshed
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4.1-25 1-25
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Introduction Ansoft – Antenna/RF Training Guide
Convergence Criteria
Training Manual
• Adaptive mesh loop has two exit criteria: – Maximum Number of Passes (Time) • Controls how many passes the user is willing to wait • 10 is a reasonable initial value
– Convergence Per Pass (Accuracy) • Indicates the solution’s sensitivity to mesh variations • Relates to the accuracy of the solution
Maximum Solution Variation Per Pass
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4.1-26 1-26
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Introduction Ansoft – Antenna/RF Training Guide
Converging on Maximum Delta S
Training Manual
• Summarizes the S-Parameter’s sensitivity – A single number for the entire S-Matrix – Accounts for magnitude and phase variation for all S-parameters simultaneously. – Reports the worst case violation
Max S Max S N S N 1
– Default value of 0.02 is reasonable for most cases
• DON’T over-specify – Setting the Maximum Delta S too small wastes computer resources and time.
• DON’T under-specify – Setting the Maximum Delta S Too large jeopardizes accuracy. ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
4.1-27 1-27
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Introduction Ansoft – Antenna/RF Training Guide
Setting The Maximum Delta S Criteria
Training Manual
• Always set the deltaS with your error tolerance in mind. • Consider the worst case scenarios when setting the Maximum Delta S – A worst case magnitude error can be determined by assuming the S-parameter magnitude is the only source of error (phase is perfectly accurate) . – Most likely actual solution is much closer since the error will be split between the magnitude & phase
Max S Max S N S N 1
Linear Units
Expected Range for |S| = 0.98 & Max(|S|) = 0.005
dB Units
± 0.005
* plots assume asymptotic convergence ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Introduction Ansoft – Antenna/RF Training Guide
Converging on Matrix Convergence
Training Manual
• Converging on Matrix Convergence –Provides more control over the S-parameter matrix convergence.
• Specify the acceptable magnitude and phase difference between meshes for each individual S-Parameter.
S S S S S S12 S 11 12 11 12 11 S 21 S 22 N S 21 S 22 N 1 S 21 S 22 • 3 Ways To Specify the Convergence: –All – Defines the allowable magnitude and phase difference between meshes. –Diagonal/Off-Diagonal – groups return losses and transmission losses separately –Selected Entries – specifies an individual convergence criteria for each S-parameter.
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4.1-29 1-29
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Introduction Ansoft – Antenna/RF Training Guide
Expression Cache Convergence
Training Manual
• Controlled on the “Expression Cache” Tab • Allows the solution to convergence to a specific quantity – Expressions can be derived from any network parameter or field quantity. – The expressions must be a single, scalar value so HFSS can easily assess it variation as a function of adaptive pass. – Convergence is determined by either a percent change or an absolute change between meshes.
• HFSS continues solving adaptive passes until both: – the S-parameters converge and – the Output Variables converge.
• Variables Defined from Field Quantities must have a context setup • Additional expressions can be defined, but not included in the convergence evaluation. ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
4.1-30 1-30
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Introduction Ansoft – Antenna/RF Training Guide
Other Meshing Options
Training Manual
• Maximum refinement per pass – Controls the maximum number of tetrahedra added between adaptive passes – Higher percentages will allow HFSS to: • Converge in fewer number of passes • Usually with better quality mesh
• Minimum Number of Passes helps avoid premature convergences • Minimum Converged Passes force a couple of consecutive passes be met before declaring a solution converged
ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
4.1-31 1-31
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Introduction Ansoft – Antenna/RF Training Guide
Port Options
Training Manual
• 2D eigenmode solution determines port fields.
• Port’s Adaptive Solution – Ensures accurate model excitation – Port’s convergence is based on Delta Zo – If a more accurate Zo is required reduce the Max Delta Zo percentage
• Use Radiation Boundary on Ports overrides the default Wave Port boundary condition to 377Ohms. • Set Triangles for Wave Port restricts the number of triangles in the port to fall between the Minimum and Maximum values.
ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
4.1-32 1-32
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Introduction Ansoft – Antenna/RF Training Guide
Basis Functions
Training Manual
• HFSS solves the electric field and stores basis functions associated with each tetrahedra. • Basis functions are n-order polynomials that describe how the electric field varies along a tetrahedra’s edge, face or volume. • The higher the basis function order
v0
v1
v3
v2
– the more unknowns HFSS solves for a given tetrahedra. – the more complex field variation a single tetrahedra can describe.
• Higher order basis functions require less tetrahedra to accurately describe the fields. • If the mesh density is reduced enough a problem will require less memory to solve.
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4.1-33 1-33
v0
v3
v1
v2
January 2010 February 23,31, 2009 Inventory #002846 Inventory #002593
Introduction Ansoft – Antenna/RF Training Guide
Solver - Higher Order Basis Mesh
1st Order
Training Manual
2nd Order
Homogenous Materials Require Less Dense Meshes with Higher Order Basis Functions ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
4.1-34 1-34
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Introduction Ansoft – Antenna/RF Training Guide
1D FEM Example
Training Manual
• The finite element method (FEM) can be used to approximate the unknown curve F(x).
• The model is first “discretized” into cells (1, 2, … 5). • Each cell is sampled to create and a polynomial basis function which describes the function along the entire line. ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
4.1-35 1-35
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Introduction Ansoft – Antenna/RF Training Guide
1D FEM Example
Training Manual
• The finite element method (FEM) can be used to approximate the unknown curve F(x).
Error
• The basis functions try to describe the fields in between the sampled points. • A key feature of the FEM, as it is implemented in HFSS, is the ability to locally determine the error. Recall that F(x) is not known, but the ERROR can be determined1 1 D.
K. Sun, Z. Cendes, J.-Fa Lee, „Adaptive Mesh Refinement, h-Version, for Solving Multiport Microwave Devices in Three Dimensions, IEEE Trans Magnetics, pp 1596-1599, Vol. 36, N.4, July 2000 ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
4.1-36 1-36
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Introduction Ansoft – Antenna/RF Training Guide
1D FEM Example
Training Manual
• The finite element method (FEM) can be used to approximate the unknown curve F(x).
Cell 1 Is Divided to Reduce the Error
• One method of decreasing the error is to make the mesh denser in areas of high error. • Note the FEM with tetrahedral elements allows for local control of the mesh density so a uniform mesh is not required. ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
4.1-37 1-37
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Introduction Ansoft – Antenna/RF Training Guide
1D FEM Example
Training Manual
• The finite element method (FEM) can be used to approximate the unknown curve F(x).
Second Order Basis Functions: Requires 4 Solution Points Per Cell
• Another method of decreasing the error is to increase the order of the polynomial basis functions that describe how the fields vary in a tetrahedra • However, the increased order requires more unknowns to solve • Higher order basis functions can reduce RAM requirements if it can sufficiently coarsen the mesh ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
4.1-38 1-38
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Introduction Ansoft – Antenna/RF Training Guide
Solver Technology Overview
Training Manual
• Order of Basis Functions – Hierarchical basis functions • • • •
Introduced in V11 Zero or First or Second order basis functions Higher-order elements have increased accuracy Convergence is a function of basis order
– Mixed Order New • hp-FEM Method – Refines element order(p) and element size(h) • Automatically distributes element order based on element size • Generates optimum combination of hierarchical basis functions (Zero and First and Second) – Efficient use of computing resources
ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
4.1-39 1-39
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Introduction Ansoft – Antenna/RF Training Guide
Log Periodic over EBG Groundplane
Training Manual
• High geometric detail with large homogeneous radiation volume • Compare mixed order vs. 1st order – 28% reduction in solution time – 29% reduction in memory
• Mixed order converges faster – 12 passes vs. 14 passes – Average order = 0.96
• S11 @ 12 GHz – 1st – Mixed
ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
S11 = 0.86584 S11 = 0.86511
4.1-40 1-40
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Introduction Ansoft – Antenna/RF Training Guide
Choosing the Solver
Training Manual
• Each time HFSS solves the Volumetric Field Solution it must solve a matrix of unknowns. – The solution describes the field behavior for that particular mesh – This is done for each adaptive pass and directly solved frequency point.
Ax b • HFSS offers 3 Solvers Options to apply to this matrix equation: 1.
Direct Solver (Default) • • •
2.
Iterative Solver • • •
3.
Traditional solver used in HFSS Very stable Can be memory and time intensive for large matrices Added in HFSSv11 More memory efficient than the Direct Solver Can be more time efficient than the Direct Solver
Domain Decomposition • • •
Added in HFSSv12 Allows the field solution from a single mesh to take advantage of distributed RAM across a network Requires an additional license feature
ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
4.1-41 1-41
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Introduction Ansoft – Antenna/RF Training Guide
Choosing a Solver: Direct Solver
Training Manual
• The Direct Solver obtains an exact solution to the matrix equation
Ax b • Common Direct Matrix Solver Methods: – Gaussian Elimination – LU Decomposition
• Best uses for the Direct Solver – Moderately sized matrices – Large number of excitations
a11 a12 0 a 22 0 0 0 0
a13 a14 x1 b1 a23 a24 x2 b2 a33 a34 x3 b3 0 a44 x4 b4
• Solving for x:
x4
b4 a44
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x3
b3 a34 x4 a33 4.1-42 1-42
x1
b1 a12 x2 a13 x3 a14 x4 a11 January 2010 February 23,31, 2009 Inventory #002846 Inventory #002593
Introduction Ansoft – Antenna/RF Training Guide
Choosing a Solver: Iterative Solver
Training Manual
• How does it work?
Initial guess
– The Iterative Matrix Solver works by “guessing” a solution to the matrix of unknowns, and then recursively updating the “guess” until an error tolerance has been reached
Preconditioner
• What is the advantage? Update solution and search direction
– Reduced RAM and Simulation Time
• Where do you control the Iterative Solver? – Options Tab from Solution Setup dialog
no
• The acceptable relative residual is controlled through text entry field –
Converges ? yes
Reducing the value will reduce the error associated with the Matrix Solution process
MPCG
• Best uses for the Iterative Solver – Large Matrices (>30,000 Tets) – Moderate Port Count (2 Ports Per Processor) – For 1st, 2nd and Mixed Order Basis Functions only
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Introduction Ansoft – Antenna/RF Training Guide
Example: Iterative Solver
Training Manual
How many passes on computer w/8GB RAM? • Direct: 3 Passes • Iterative: 11 Passes
Increased Capacity (4x) Volume: 447cubic wavelengths Copper Wall
4x Capacity on Same Machine
Direct
Iterative
2x Unknowns – 2x Memory
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4.1-44 1-44
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Introduction Ansoft – Antenna/RF Training Guide
Example: Iterative Solver
Iterative
Training Manual
Iterative and Direct Converge in 3 Passes
Direct
3.2x Less RAM
Iterative
Direct
6.4x Faster
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4.1-45 1-45
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Introduction Ansoft – Antenna/RF Training Guide
Choosing a Solver: Domain Decomposition
Training Manual
• Domain Decomposition Method New – Distributed memory parallel technique • Distributes mesh sub-domains to network of processors
– Significantly increases simulation capacity • 64-bit meshing
– Highly scalable to large numbers of processors – Automatic generation of domains by mesh partitioning • User friendly • Load balance
HPC distributes mesh subdomains to networked processors and memory
– Hybrid iterative & direct solver • Multi-frontal direct solver for each sub-domain • Sub-domains exchange information iteratively via Robin’s transmission conditions (RTC)
– Requires an additional license • HFSS_HPC – Provides 8 DDM Nodes or SMP
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4.1-46 1-46
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Introduction Ansoft – Antenna/RF Training Guide
Cellular Base Station Array
Training Manual
• GSM base station tower with radome-enclosed antenna arrays – 950 MHz – Electronic downtilt
• Domain solver used to predict installed antenna patterns – 34 domains – 3.5 GB average RAM per domain – 16M unknowns
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Introduction Ansoft – Antenna/RF Training Guide
Multi-Processing (SMP)
Training Manual
• Multi-Processing – Single workstation solution to increase the speed of the solver – Direct Matrix Solver • Takes advantage of multi-core and/or multi-processor computing resources
– Iterative Solver – Parallelized matrix pre-conditioner – Parallelized excitations
– Requires additional license • HFSS_MP or HFSS_HPC – Provides SMP
Solver - Time Factor 3.5
Factor
3 2.5
v12 - MP1
2
v12 - MP2
1.5
v12 - mp4
1
v12 - mp8 0
10
20
30
RAM [GB] Typical direct solver SMP speed-up for 2, 4, & 8 Processors versus the size of the matrix solve ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Frequency Sweep
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4.1-49 1-49
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Introduction Ansoft – Antenna/RF Training Guide
HFSS Solution Process
Training Manual
Setup
Solution
Parametric Model Generation
Design HFSS / HFSS-IE
Solution Type Driven Model Driven Terminal Eigenmode
Mesh Generation
Initial Mesh
Seeding and Lambda Refinement (Single Frequency)
Analysis Mesh Seeding Solution Setup: Frequency Sweep ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
Port Solution (Adaptive)
Full Volumetric Solution (S-Parameters/E-Fields)
Initial Solution
Parametric Model Geometry/Materials Boundaries Excitations
Frequency Sweep
Adaptive Mesh Loop Refine Mesh (Single Frequency)
Full Volumetric Solution (S-Parameters/E-Fields)
4.1-50 1-50
No
Check Convergence (Delta S)
Yes
Frequency Sweep Discrete Interpolating Fast
January 2010 February 23,31, 2009 Inventory #002846 Inventory #002593
Introduction Ansoft – Antenna/RF Training Guide
Frequency Sweep Options
Training Manual
• Once the adaptive process converges frequency sweep analyses are performed using the “Last Adaptive” mesh. – An adaptive mesh is not created for each frequency point in the sweep.
• HFSS offers 3 Types of frequency sweeps – Discrete • Solves adapted mesh at user specified frequencies. • Can save fields for post-processing if desired • If one solution take N minutes, then M discrete points takes M x N minutes • Set Adaptive Frequency near high end of band
– Fast • Creates a rational polynomial function for Electric field at the adaptive frequency, and then plugs in the frequency range to extrapolate field over specified range • Usually only valid over less than a decade range in frequencies • Don’t use near DC • Set Adaptive Frequency near mid band
– Interpolating • Solves adapted mesh at start, stop and midpoint of frequency range, and then uses this to create a curve-fit for all complex S-parameters. • Then iteratively add solutions to improve curve fit. • Useful for very broadband S-parameters • Only for S-parameters / Fields are NOT saved over frequency range • Can extrapolate S-parameters to DC value • Set Adaptive Frequency near high end of band ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Introduction Ansoft – Antenna/RF Training Guide
Frequency Sweep Guidelines
Sweep Type
Speed
Discrete
Slow for a large number of points
Fast
Fast for a large sweeps Can be slower for small sweeps
Interpolating * †
Fast
Training Manual
# of Freq. Points* 10’s
Bandwidth Limit†
Saved Fields
Memory
All Frequencies
Same as Last Adaptive
Octave
All Frequencies
More than Last Adaptive
None
Only Last Adaptive
Same as Last Adaptive
None
Insert Far Field Setup > Infinite Sphere – Setup is required in order to plot any Far Field quantities – If 2D cutplanes are desired, save post-processing time by only calculating desired points – Relative coordinate systems may be used to modify reference orientation in far-field calculations –
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Introduction Ansoft – Antenna/RF Training Guide
Custom Radiation Surface
Training Manual
• Radiation Surface – –
–
Default integration surfaces for far-field calculations are faces of radiation boundaries • Radiation boundaries automatically defined on base object surfaces of PML objects Consider creating custom radiation surface for better accuracy and reduced simulation time • Place at least /10 from all radiating surfaces • Create using the menu item Modeler > List > Create > Face List Specify custom radiation surface when creating infinite sphere
Default Integration Surface ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
Custom Integration Surface 1-7 6-7
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Introduction Ansoft – Antenna/RF Training Guide
Element 3D Pattern at 10 GHz
Training Manual
• Three-dimensional radiation patterns can be plotted for various far-field quantities – –
Directivity, power gain, and realized gain Total Gain vs. Realized Gain
Total Gain
4 U Accepted Power
Realized Gain
4 U Incident Power
• Polarization components can be examined – – –
Eθ and E components Ludwig3 co-polarized and cross-polarized components Right-hand and left-hand circular polarization (RHCP/LHCP)
Ludwig-3X ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
Ludwig-3Y 1-8 6-8
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Introduction Ansoft – Antenna/RF Training Guide
Antenna Parameters
Training Manual
• Antenna Parameters –
Calculates common antenna parameters for arbitrary frequency and angular region • Note: The values are not expressed in dB
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1-9 6-9
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Introduction Ansoft – Antenna/RF Training Guide
“Edit Sources” Dialogue
Training Manual
• Edit Sources – –
Sets complex power scaling factors for each port • Select the menu item HFSS > Fields > Edit Sources Specifies coefficients used in post-processing • E, H, and J fields on 3D geometry • Far-field plots (patterns) • Active S-parameters
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Introduction Ansoft – Antenna/RF Training Guide
Electromagnetic Field Plots
Training Manual
• Field Plots –
Plot any field quantity by selecting any Object, Face or Plane • Select the menu item HFSS > Fields > Plot Fields > Quantity
MagE Plotted on 2D Antenna Object
Streamline plot of Poynting vector created by selecting originating face
MagE Plotted on XZ Plane of Coordinate System ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Electromagnetic Field Plots and Animations
Training Manual
• Field Plots Plot any field quantity by selecting any Object, Face or Plane • Select the menu item HFSS > Fields > Plot Fields > Quantity – Easily plot fields and export to animated GIF • Select the menu item HFSS > Fields > Animate – Example shown for electric fields in element plane at 10 GHz • Provides insight into balun operation, mutual coupling behavior, etc. –
Elements Phased for Broadside Beam ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
Elements Phased for Scanned Beam 1-12 6-12
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Antenna Trace Characteristics
Training Manual
• Trace Characteristics –
Quickly obtain beamwidth for any dB threshold (3 dB, etc.) and sidelobe levels and locations • Right-click on pattern report to activate menu
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Antenna Trace Characteristics (2)
Training Manual
• Example shown for scanned array beam –
Markers confirm beamwidth and sidelobe information
Co-pol in E-plane (Trace Characteristic)
Ansoft Corporation
array
d(
0 -30 Name Theta Ang Mag m1 -74.00 -74.00 -5.62 m2 14.00 14.00 6.51 m3 50.00 -6050.00 3.57 m4 -10.00 -10.00 3.79
m4
m1
-90
5.00 m2 0.00 -5.00 -10.00 -15.00 -20.00 -25.00
30
m3
60
90
-120 120 Curve Info lSidelobeY lSidelobeX xdb10Beamwidth(3) dB(DirTheta) -5.62 -74.00 61.58 Setup1 : LastAdaptive -150 150 -180 ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
1-14 6-14
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Far-field Pattern Plot Type
Training Manual
• Changing Plot Type –
Easily convert between rectangular and polar format for far-field pattern plots
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Overlay Far Field Plots on Model
Training Manual
• Visualize radiation patterns on model geometry – –
Control transparency and/or size of pattern overlay Uses existing 3D plots generated under Results • Right-Click in 3D modeler window select the context menu Plot Fields > Radiation Fields
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1-16 6-16
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Array Factor Calculator
Training Manual
• Built-in array factor calculator using single element pattern – –
First-order approximation which neglects mutual coupling Uses global coordinate system for array definition
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Array Factor Calculator (2)
Training Manual
• Example shows array factor versus actual two-element array pattern for scanned beam (E-plane cutplane) –
Array factor most applicable when mutual coupling is small
Actual Array Array Factor
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Active S-Parameters
Training Manual
• Includes all mutual coupling from other ports to produce an “active S11” response at a given port – –
Applicable to phased arrays and multi-port antennas Dependent upon excitations at other ports (changes with scan angle, etc.)
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Active S-Parameters (2)
Training Manual
• S-Parameters –
Passive S-parameters assume all other ports are loaded in terminal impedance • No reflections from other terminated ports
Port 2
Port 3
S11 Port 4 –
Active S-parameters represent port response based on coupled signals from other ports • Includes coupling from other ports
Port 2 source1 10o
Port 3
S11
source2 190o source3 1180
o
S11active
10o 190o 1180o 1270o S11 S21 S31 S41 10o 10o 10o 10o
source4 1270o
Port 4 ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Active S-Parameters (3)
Training Manual
• Active S-Parameters – –
Available from modal solution data Dependent upon coefficients entered using Edit Sources
Active Return Loss for Port 1 and Port 2 for 60° Phase Delay Between Ports
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Chapter 7 – Complex Geometry Modeling
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Complex Geometry Topics
Training Manual
• Importing files from other engineering tools – – –
Appropriate format Geometry healing De-featuring
• Creating complex shapes within HFSS – – – – – –
Inherently parametric geometry Boolean operations Equation-based curve and surface Scripting User defined primitive (UDP) Antenna Design Kit
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From Solid Model to Analysis
Training Manual
• Importing Complex Solid Models – – – – –
Each step is important and can impact setup time and simulation time Can use automated or manual healing to analyze and remove problem features De-featuring removes holes, chamfers, and blends Mesh operations (surface approximations) can be used to simplify geometry Model resolution allows mesher to ignore small details in model geometry
Import
Geometry Healing
• HFSS 3D Model Formats –
Select the menu item Modeler > Import • ProE Files (*.prt*,*.asm*) • Unigraphics File (*.prt) • Ansoft 2D Geometry Files (*.sm2) • GDSII files (*.gds) • 3D Modeler File (*.sm3) • SAT File (*.sat) • STEP file (*.step,*.stp) • IGES File (*.iges,*.igs) • AutoCAD Files (*.dxf,*.dwg) • SLD File (*.sld) Formats listed in blue require • GEO File (*.geo) AnsoftLinks MCAD • STL File (*.stl) • NASTRAN File (*.nas) • Catia V4/V5 Files (*.model, *.CATPart,*.CATProduct) • Parasolid Files (*.x_t, *.x_b)
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De-featuring
Meshing
Model Resolution
Analysis
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AnsoftLinks Design Flow
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Training Manual
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Healing Imported Geometries
Training Manual
• Geometry Healing – –
Often necessary due to different model rules and unavoidable geometry database translations • User decides if imported objects should be healed Two healing options provided for imported objects • Automatically analyze imported model and remove problem features • User manually selects criteria for object analysis
Vertices not on a Face
Edges not on a Face ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Manual Healing
Training Manual
• Manual Healing – – –
Manual Healing brings up Healing Options dialog window • User specifies criteria to remove problematic geometry features Remove features such as holes, chamfers, and blends Remove small entities such as edge lengths, faces, and sliver faces
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Healing and Stitching Example
Training Manual
• Healing and Stitching Example – – –
Select menu item Modeler > Model Analysis > Heal If two edges in a part are not touching, healing attempts to extend surface edges to make them touch Some gaps cannot be fixed by healing and stitching is applied to perturb the surface and bring edges together
Model with gap
Healed model
Model with gap Model repaired by stitching
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Simplify Imported Geometries
Training Manual
• De-feature models obtained from mechanical or electrical CAD tools when possible – –
These models typically include geometry details insignificant for electromagnetic analysis Small holes, bends, etc.
• Removing unnecessary model details reduces mesh density and runtime –
Use good engineering judgment to make certain that removed features are electrically insignificant
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Small Feature Removal
Training Manual
• Feature Removal –
User can inspect holes, chamfers, and bends individually or automatically remove features below specified size • Select menu Modeler > Model Analysis > Analyze Object • Automatic defeaturing accessed through Modeler > Model Analysis > Heal (Feature Removal Options)
All Holes Removed
All Holes and Blends Removed
Subset of Blends Removed
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Groundplane Housing Geometry
Training Manual
• Top hat aluminum ground plane structure –
5” diameter ground plane
• Twelve mounting holes on flange –
0.150” diameter
• Blended edge between flange and pedestal –
0.150” radius
Mounting holes
Blended Edge
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De-Featured Groundplane Housing
Training Manual
• Original mesh: 14,520 tetrahedra with 0.353” RMS edge length • Defeatured mesh: 173 tetrahedra with 1.94” RMS edge length • Two orders of magnitude reduction in mesh density
Original Mesh
ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
Defeatured Mesh
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Creating Complex Shapes in HFSS
ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
1-12 7-12
Training Manual
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Parametric Modeling
Training Manual
• HFSS supports inherently parametric geometry creation – –
Variable values can be edited to update model objects Enables efficient modifications to complex models
Parametric geometry created
Variables created
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Geometry Primitives
Training Manual
• HFSS includes primitives for creating simple geometry objects –
ACIS solid modeling engine
• Boolean operations can be applied to multiple primitives to form complex objects
UWB crescent antenna formed by subtracting circle from ellipse
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Equation Based Geometry
Training Manual
• Any line or surface that can be described by an equation in three dimensions can be drawn –
Creates parametric equation or parametric surface
• Accessed through Draw > Equation Based Curve and Draw > Equation Based Surface • Example: Create parametric curve for helix and sweep circular cross-section along helix
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Equation Based Geometry
Training Manual
• Model any parametric surface
Trangluoid trefoil
Mobius strip ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
Conical spiral
Spiral
Conchoid
Conical spiral 1-16 7-16
Toupie January 2010 February 23,31, 2009 Inventory #002846 Inventory #002593
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Geometry Scripting
Training Manual
• VBScript or Javascript can be used to generate complex geometries –
Accessed through Tools > Run Script
• Gather required inputs from user through dialog boxes or hardcode into script • VBScript manual available in HFSS help system
Variable pitch helix element ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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User Defined Primitive (UDP)
Training Manual
• Enables efficient creation and optimization of complex 3D geometric models used by HFSS • Generates objects defined using parametric characteristics –
Parameters can also be accessed for optimization from Optimetrics
• User builds and compiles DLLs –
HFSS includes example C++ source and header files that can be used to generate DLLs
• Accessed through Draw > User Defined Primitive
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UDP Antenna Examples
Training Manual
• Model antennas based on arbitrary mathematical equations –
Exponential, spiral, log-periodic, helix, sinuous, etc.
• Also allows parameterization of number of objects (duplicates) –
Useful for multi-arm elements
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Antenna Design Kit
Training Manual
• GUI-based wizard tool – –
Automates geometry creation, solution setup, and post-processing reports for 26 common antenna elements Assists in learning to use HFSS for antenna design
• Parametric antenna geometry – Easily modify parameters in HFSS after generating initial model – Facilitates parametric sweeps and optimizations
• Synthesis feature for each antenna – –
Automatically generates physical dimensions for desired frequency Provides starting point for new designs
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Antenna Design Kit – Available Antenna Types
Planar Dipole
Pyramidal Horn
Wire Dipole
Rectangular Patch
E-plane Sectoral H-plane Sectoral Horn Horn
Archimedean Spiral ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
Training Manual
Conical Horn
Log-Spiral 1-21 7-21
Elliptical Patch
Circular Waveguide
Rectangular Waveguide
Sinuous Spiral January 2010 February 23,31, 2009 Inventory #002846 Inventory #002593
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Antenna Design Kit – Available Antenna Types
Training Manual
Vivaldi (Tapered Slot) Conical Archimedean Spiral
Conical LogSpiral
Log-Periodic Toothed
ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
Conical Sinuous Spiral
Log-Periodic Toothed Trapezoidal
Bowtie
Stepped Vivaldi
PIFA with Shorting Strip
Bicone 1-22 7-22
PIFA with Shorting Pin
PIFA
Discone January 2010 February 23,31, 2009 Inventory #002846 Inventory #002593
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Antenna Design Kit – Example Project
Training Manual
• Model ready to solve
Ports and Boundary Conditions Solution Setup and Frequency Sweep
Reports for Input Impedance and Radiation Patterns Parameters for Antenna Geometry
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Geometry Wrap
Training Manual
• Geometry Wrap New –
Wrap a 2D sheet on an arbitrary geometry
Slot Coupled Patch Array wrapped on a cylinder ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Imprint/Imprint Projection
Training Manual
• Imprint New –
Projection • Patch Antenna Array Imprinted on a Nosecone – Results in Faces of original object imprinted – Make sure that the distance selected is greater than the distance between the antenna and nosecone
Face created from Imprint projection
Face created from imprint ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Polyline Cross Section
Training Manual
• Polyline Cross Section New –
–
Choose Cross Section Type and Size • Type: Line, Rectangle, Circle • Size can be a variable Section is automatically swept along the polyline
1. Create a Polyline ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
2. Set Cross Section Property
1-26 7-26
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Chapter 8 – Introduction to Optimetrics
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Introduction
Training Manual
• Optimization is “a process of finding a better or more suitable design instance among the possible design variations” • Optimetrics is an add-on module which provides numerous analysis tools – – – – – –
• • • •
Parametric Optimization Sensitivity Statistical Tuning Analytical Derivatives
Allows centralized control of design iterations from one common interface Compatible with all Ansoft 3D products and Ansoft Designer Allows full analysis for multiple variables Optimetrics allows the user to: – – – –
Define model parameters and automate parametric sweeps Perform real time parameter tuning using Analytical Derivatives Identify performance specifications to optimize Perform sensitivity and statistical analysis on optimized model
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Using Optimetrics
Training Manual
• Process 1. Create parameterized model 2. Define design parameters to vary • Model geometry, material properties, etc. 3. Perform analyses • Parametric • Optimization • Sensitivity • Statistical • Tuning
• Where can it be used? –
–
User may apply parameterization at all modeling stages • Geometry (size, shape, orientation, quantity, etc.) • Materials (lossless, complex, anisotropic, etc.) • Boundaries (impedance/conductance boundaries, linked boundary scan angles, symmetry or mode cases, etc.) • Solution setup Once model is parameterized, optimization can be performed toward an extensive array of cost functions • Circuit parameters (S, Z, or Y-parameters) • Antenna patterns (Directivity, gain, axial ratio, etc.) • Emissions • Derived field quantities (radiated power, etc.)
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Parameterizing a Model
Training Manual
• Parameterizing a Model –
Optimetrics relies on using the parametric capability built into Ansoft tools
• Variables can be easily entered – – – –
Project variables (global) Design variables (local) Include units (defaults to meters) Supports mixed units
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Parametric Analysis
Training Manual
• Optimetics Setup: Parametric Analysis – – – – –
Create nominal design with variables assigned to model aspects to change Define one or more variable sweep definitions • Each specifies series of variable values within a range Optimetrics solves the design for each variation • Compare results to determine how each variation affects performance Number of variations limited only by computing resources Parametric analyses often used as precursors to optimization because they help determine reasonable range of variable values
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Optimization Analysis
Training Manual
• Optimetics Setup: Optimization Analysis – – –
Identify cost function and optimization goal Cost function can be based on any solution quantity that HFSS or Designer can calculate • Field values, S-parameters, and Eigenmode data Optimetrics changes design parameter values to meet goal
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Optimization Analysis Parameters
Training Manual
• Several analysis parameters must be specified –
– –
–
–
Cost function • Optimetrics minimizes the cost function. Define this so that minimum location is also optimum location. For example, if you desire to maximize transmission from port 1 to port 2 (S21=>1), define cost function to be mag(S(Port2,Port1)). Acceptable Cost • Value of cost function at which optimization stops (may be negative). Goal Weight • If cost function with multiple goals, you may assign different weight to each goal. The goal with greater weight is given more importance during cost calculation. Step Size • In order to make the search reasonable, the algorithm limits the minimum and maximum step limits for individual optimization variables. Cost Function Noise • Numerical calculation of EM fields introduces various sources of noise to cost function due to changes in finite element mesh. The noise indicates whether change is significant enough to support achievement of cost function.
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Available Optimizers
Training Manual
• Quasi Newton – – – –
Uses gradient approximation of cost function in search for minimum location “Downhill” search iterative method using second order derivatives to accelerate convergence Only accurate enough if there is little noise involved in cost function Use when SNLP optimizer has difficulty and noise is insignificant
• Sequential Non-Linear Programming (SNLP) – – – –
Uses principle similar to Quasi Newton optimizer Assumes that optimization variables are continuous Handles numerical noise slightly better than Quasi Newton optimizer More accurate overall cost approximations and faster convergence
• Sequential Mixed Integer Non-Linear Programming –
Identical to SNLP except that it is able to deal with discrete integer variables as well as continuous variables
• Pattern Search (gradient-free optimizer) – – –
Performs grid-based simplex iterative search using either triangular or tetrahedral simplexes Pattern is defined on grid, and grid is refined according to success rate of search Preferred when numerical noise is significant
• Genetic Algorithm Iterative process which progresses through a number of generations with chromosomes representing combinations of parameter values (possible solutions) – Chromosomes participate in selection, reproduction, and mutation processes to produce best overall result (“survival of the fittest”) – Robust optimization scheme for large solution spaces –
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Sensitivity Analysis
Training Manual
• Sensitivity Analysis – –
–
–
Used to determine design sensitivity to small variations in specific parameters around specific design point Can tolerance a design to ensure design goals are met • For example, determine maximum acceptable deviation for substrate permittivity of microstrip line to ensure impedance is well-matched Preferred over parametric analysis for this purpose • Careful choice of parameter variations required to determine sensitivity and de-embed this from numerical mesh noise and large scale variations in parameter values Optimetrics varies the parameters about design point and automatically fits second order polynomial to requested output
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Statistical Analysis
Training Manual
• Statistical Analysis – –
Used to predict yield of component when subject to random variations in parameter values Optimetrics includes uniform and Gaussian distribution functions • Uniform distribution: User specifies percentage tolerance from variable’s starting value for the analysis. Solves for values within this tolerance range assuming uniform probability • Gaussian distribution: User specifies standard deviation of distribution and upper and lower limits. Solves for values between the upper and lower limits assuming Gaussian probability
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Analytical Derivatives
Training Manual
• Analytical Derivatives Compute the derivatives of SYZ parameters with respect to project and design variables Eliminates need to solve multiple variations with small differences and numerical noise • More efficient and more accurate – Provides real-time tuning of reports to explore effects of small design changes – Improves derivative-based optimization methods – –
2008 IEEE MTT-S Digest, pp. 527-530
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Analytical Derivatives – Example: SMA launch
Training Manual
• Example: Analytical Derivatives – – –
SMA launch is typical multi-variable design problem Design variables: • length, radius of via stub, radius of antipads, radius of signal pads, radius & antipad of ground via Solve for the derivatives of many variables at once
Nominal Values for Design Variables
Specify Desired Derivatives in Solution Setup ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Analytical Derivatives – Example: SMA launch
Training Manual
• Results: Analytical Derivatives –
Real-time tuning shows effects of small changes on S-parameters
S21 S11 S-parameters of Nominal Design
Derivative Context in Report Editor
Quickly Explore Effects of Small Changes on S-parameters ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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ANSYS DesignXplorer and HFSS Integration
Training Manual
• Powerful DOE-based tool suite –
Quantifies influence of uncertainty variables on performance
• Variety of sampling, modeling and optimization routines – Sampling: central composite design and optimal space filling – Modeling: full second-order polynomial, Kriging, non-parametric regression, and neural network – Optimization: screening, multi-objective genetic algorithm, and nonlinear sequential quadratic programming
• Create and execute DOE simulations for HFSS from DesignXplorer –
Entire solution space of HFSS design can be investigated using efficient, accurate DOE algorithms
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Distributed Solve Option
Training Manual
• Distributed Solve Option – – – – –
Distributed analysis used to quickly explore multi-dimensional design space DSO distributes frequency and parametric sweeps to network of processors Approximately linear increase in simulation throughput Highly scalable to large numbers of processors • Up to 10 nodes per Distributed Solve license Multi-processor nodes can be utilized DSO distributes frequency and parametric sweeps to networked processors
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Summary
Training Manual
• Optimetrics – –
–
–
Add-on option integrated into interface of all Ansoft 3D tools and Ansoft Designer Includes variety of powerful analysis capabilities • Parametric sweeps: defined variables automatically changed and corresponding analysis performed • Optimization: properties optimized based on performance goal and defined design variables • Sensitivity analysis: yields design sensitivity for range of values about design point • Statistical analysis: determines effects of statistical variations of design variables on output Integration of Ansoft HFSS and ANSYS DesignXplorer offers new valuable insights into behavior of EM designs • Entire solution space of HFSS design can be investigated using efficient, accurate DOE algorithms • Provides powerful 3D and 2D visualization of solution space to evaluate performance trends • ANSYS R12 supports DSO for efficient characterization of designs Distributed Solve Option can be used to further increase simulation throughput
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Ansoft – Antenna/RF Training Guide
Chapter 9 – Fields Calculator
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January 31, February 23, 2010 2009 Inventory #002846 #002593
Introduction Ansoft – Antenna/RF Training Guide
HFSS Field Calculator
Training Manual
• Tool for performing mathematical operations on all saved field data in modeled geometry – E, H, J, and Poynting data available – Perform operations using model or non-model geometry – Perform operations at single or multiple frequencies – Generate numerical, graphical, geometrical, or exportable data – Macro-enabled
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Introduction Ansoft – Antenna/RF Training Guide
Calculator Layout
Training Manual
Context Selection: Select solution, frequency, and phase
Named Expressions which can be plotted using Report Editor and Field Overlay Data Stack: Contains current and saved entries in scrolling stack similar to RPN scientific calculator.
Stack Operations: Manipulate stack contents
Calculator Functions: Organized groupings of all available calculator functions in button format. Some buttons contain further options as drop-down menus.
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Named Expressions
Training Manual
• Add expressions to Named Expressions to create field overlays and Report Editor plots – Makes these available through standard post-processing capabilities
• Frequently used expressions can be included in user library and loaded into any project – Eliminates need to re-create expressions consistently used across many projects
Lists defined expressions for use in field calculator or postprocessing
Deletes named expression
Includes expression at top of stack to list of named expressions. Named Expressions must be scalar quantities.
Clears all named expressions
Saves added expressions to a user library
Loads named expressions from user library
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Introduction Ansoft – Antenna/RF Training Guide
Usage – Changing Data Types
Training Manual
– As discussed previously, many operations require the correct input data type – Many operations result in a different data type than the inputs • Ex1: The Dot product of two vectors is a scalar. • Ex2: Obtaining the Unit VecNormal to a Surf generates a Vector.
– Some calculator buttons exist primarily to assist in type conversion
Always think of what type of data you are working with and whether or not it is compatible with your desired operation. For example, note the INTEGRAL sign is in the Scalar column, implying that to integrate complex numbers you will have to integrate the real and imaginary components separately, performing an integration by parts.
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• Vec? converts Scl to Vec data • Scal? does the reverse • Cmplx Real or Cmplx Imag takes a Scl component from a CSc or CVc • Cmplx CmplxR or Cmplx CmplxI take a Vec or Scl component and make it the real or imaginary part of a complex value CVc or CSc, respectively
February January 31, 23, 2010 2009 Inventory #002846 #002593
Introduction Ansoft – Antenna/RF Training Guide
Usage – Input Types
Training Manual
Input Quantity
Description
E
The complex vector E field data everywhere in the modeled geometry
H
The complex vector H field data everywhere in the modeled geometry
Jvol
Current density in a volume, computed as ( + jwe'')E which contains both conduction and displacement currents)
Jsurf
Net Surface current computed as n x (H|top tetrahedra – H|bottom tetrahedra) Unlike other quantities, Jsurf can only be output on an object surface geometry
Poynting
The time-average Poynting vector computed from the above as ½ (E x H*)
LocalSAR
Specific Absorption Rate: Measure of the amount of electromagnetic energy absorbed in a lossy dielectric material. Computed from SAR: * E2/(2r).
AverageSAR
SAR averaged over a volume that surrounds that point. The volume is determined by the settings in the Specific Absorption Rate Setting dialog box.
CertificationSAR
IEEE standard procedure for calculating SAR
SurfaceLossDensity
Surface impedance loss computed as (rs = re(S*n)). SurfaceLossDensity can only be output on an objects surface geometry
VolumeLossDensity
The volume loss density computed as rv = 1/2Re(E*J+jwB*H) = 1/2Re(E*J-curl(E)*H)
E and H are Peak Phasor representations of the steady-state fields. Therefore the current representations J derived from n H or E are also Peak Phasor quantities. The Poynting Vector input is a time-averaged quantity. ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Introduction Ansoft – Antenna/RF Training Guide
Data Indicators
Training Manual
• Each stack entry will be preceded by a unique code denoting its data type – Mathematical: • • • •
CVc: Complex Vector Vec: Vector CSc: Complex Scalar Scl: Scalar
– Geometric: • • • •
Pnt: Point Lin: Line Srf: Surface Vol: Volume
– Combinations can also exist • e.g. “SclSrf”: Scalar data distributed on a Surface geometry
• Most data input types are self-explanatory – E and H fields being Phasor quantities will be Complex Vectors (CVc). – An exception to this rule is the Poynting input, which will show up as a “CVc” even though E H should have no imaginary component. The calculator only knows that two complex vectors were crossed, and does not know ahead of time that the imaginary component has been zeroed. ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Introduction Ansoft – Antenna/RF Training Guide
Examples
Training Manual
• Radiated power from pyramidal horn antenna – Horn_wave_impedance.hfss
• Wave impedance along pyramidal horn antenna – Horn_wave_impedance.hfss
• Element port voltage due to mutual coupling between quasi-Yagi array elements – Quasi-Yagi.hfss
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1-8 9-8
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Introduction Ansoft – Antenna/RF Training Guide
Radiated Power from Antenna
Training Manual
• Calculated power flow through radiation boundary by integrating Poynting vector normal to surface – Created face list for radiation boundary surfaces
• 0.25 Watts used as input power for one-quarter model of horn antenna
All radiation boundaries used for integration surface
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Introduction Ansoft – Antenna/RF Training Guide
Calculation of Radiated Power
Training Manual
• Power calculated in Watts (calculator uses MKS units) • Multiply by 4 to obtain total power of full model –
Total power = 0.998 W
Calculator Operation
Stack Display
QuantityPoynting
CVc : Poynting
ComplexReal
Vec : Real(Poynting)
GeometrySurface {radiation_surfaces}
Srf : Surface(radiation_surfaces)
Normal
SclSrf : SurfaceValue(Surface(radiation_surfaces), Dot(Real(Poynting), SurfaceNormal))
Scl : Integrate(Surface(radiation_surfaces), Dot(Real(Poynting), SurfaceNormal))
Eval
Scl : 0.249510973953421
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Introduction Ansoft – Antenna/RF Training Guide
Validation of Radiated Power
Training Manual
• Radiated power also calculated as part of Antenna Parameters – Solver automatically accounts for symmetry planes (uses total Pin = 1W)
• Values also correlate with Prad = Pin(1-S112) since model is lossless
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Introduction Ansoft – Antenna/RF Training Guide
Wave Impedance Along Horn Antenna
Training Manual
• Pyramidal horn antenna fed using WR-90 waveguide – 10 GHz operation
• Two symmetry planes reduce model size to one-quarter of full horn • Impedance line located along antenna centerline
Line for Impedance Calculation
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Calculation of Wave Impedance
Training Manual
• Ratio of transverse component of electric field to transverse component of magnetic field Calculator Operation
Stack Display
QuantityE
CVc :
Smooth
CVc : Smooth()
CmplexCmplxMag
Vec : CmplxMag(Smooth())
GeometryLineimpedance_line
Lin : Line(impedance_line)
Unit Vec Tangent
Vec : LineTangent
Cross
Vec : Cross(CmplxMag(Smooth()), LineTangent)
Mag
Scl : Mag(Cross(CmplxMag(Smooth()), LineTangent))
QuantityH
CVc :
Smooth
CVc : Smooth()
CmplexCmplxMag
Vec : CmplxMag(Smooth())
GeometryLineimpedance_line
Lin : Line(impedance_line)
Unit Vec Tangent
Vec : LineTangent
Cross
Vec : Cross(CmplxMag(Smooth()), LineTangent)
Mag
Scl : Mag(Cross(CmplxMag(Smooth()), LineTangent))
/
Scl : /(Mag(Cross(CmplxMag(Smooth()), LineTangent)), Mag(Cross(CmplxMag(Smooth()), LineTangent)))
Select Add and enter “wave_impedance” ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Creating 2D Report
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Training Manual
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Introduction Ansoft – Antenna/RF Training Guide
Wave Impedance along Horn Antenna
Training Manual
• Flare provides match to free space impedance
Impedance along Horn
Ansoft Corporation
1000 Name m1
X 4.600
WR90_feed_horn
Curve Info wave_impedance Setup1 : LastAdaptive Freq='10GHz' Phase='0deg'
Y 364.762
900 800
wave_impedance
700 600 500 400 m1
300 200 100 0
0.00
0.25
0.50
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0.75
1.00
1.25
1.50
1.75
2.00
2.25 2.50 Distance [in]
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2.75
3.00
3.25
3.50
3.75
4.00
4.25
4.50
February January 31, 23, 2010 2009 Inventory #002846 #002593
Introduction Ansoft – Antenna/RF Training Guide
Wave Impedance Along Open-Ended Waveguide
Training Manual
• Abrupt transition from guided wave to free space Impedance along Waveguide
Ansoft Corporation
1000
WR90_open_ended
Curve Info wave_impedance Setup1 : LastAdaptive Freq='10GHz' Phase='0deg'
900
Name X Y m1 4.60 368.04
800
wave_impedance
700 600 500 400 m1
300 200 100 0
0.00
0.25
0.50
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0.75
1.00
1.25
1.50
1.75
2.00
2.25 2.50 Distance [in]
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2.75
3.00
3.25
3.50
3.75
4.00
4.25
4.50
February January 31, 23, 2010 2009 Inventory #002846 #002593
Introduction Ansoft – Antenna/RF Training Guide
Calculating Port Voltage in Array
Training Manual
• Mutual coupling between array elements changes total voltage at element ports – Sum of incident, reflected, and coupled signals – Vn = 1 + “ActiveS11” for nominal 1V incident voltages1
• Can calculate this voltage using output variable or with field calculator (for modal solutions) – Integration lines placed at each port to calculate total voltage from signal to ground
1Chen,
et al., “Mutual Coupling Effects in Microstrip Patch Phased Array Antennas,” IEEE AP-S Symposium, Vol. 2, June 1998, pp. 10281031. ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Introduction Ansoft – Antenna/RF Training Guide
Calculation of Port Voltage
Training Manual
• Calculated real and imaginary components as intermediate steps • Added result to Named Expressions to plot vs frequency
Calculator Operation
Stack Display
QuantityE
CVc :
ComplexReal
Vec : Real()
GeometryLineport1_integration_line
Lin : Line(port1_integration_line)
Tangent
SclLin : LineValue(Line(port1_integration_line), Dot(Real(), LineTangent))
Scl : Integrate(Line(port1_integration_line), Dot(Real(), LineTangent))
Select Add and enter “V1tot_real” QuanttiyE
CVc :
ComplexImag
Vec : Imag()
GeometryLineport1_integration_line
Lin : Line(port1_integration_line)
Tangent
SclLin : LineValue(Line(port1_integration_line), Dot(Imag(), LineTangent))
Scl : Integrate(Line(port1_integration_line), Dot(Imag(), LineTangent))
Select Add and enter “V1tot_imag”
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Introduction Ansoft – Antenna/RF Training Guide
Calculation of Port Voltage (cont)
Training Manual
• Combines real and imaginary components into final Named Expression for magnitude of total port voltage • Must repeat all steps for each port
Calculator Operation
Stack Display
Select “V1tot_real” in Named Expressions and Copy to Stack
Scl : V1tot_real
ComplexCmplxReal
CSc : CmplxR(V1tot_real)
Select “V1tot_imag” in Named Expressions and Copy to Stack
Scl : V1tot_imag
ComplexCmplxImag
CSc : CmplxI(V1tot_imag)
+
CSc : +(CmplxR(V1tot_real), CmplxI(V1tot_imag))
ComplexCmplxMag
Scl : CmplxMag(+(CmplxR(V1tot_real), CmplxI(V1tot_imag)))
Select “Add” and enter V1tot_mag_from_fieldcalc
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Specify Element Excitations
Training Manual
• “Edit Sources” sets power scaling for modal excitation coefficients – 0.01 Watt input power 1 Vin for 50 port since Pin = |Vin|2/(2*Z0)
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Introduction Ansoft – Antenna/RF Training Guide
2D Report Editor
Training Manual
• Named Expressions available for plotting from report editor
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Introduction Ansoft – Antenna/RF Training Guide
Total Port Voltage
Training Manual
• Port voltages calculated over sweep range
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Ansoft – Antenna/RF Training Guide
Chapter 10 – RCS Analysis
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Introduction Ansoft – Antenna/RF Training Guide
RCS Overview
Training Manual
–
E 2 p 4 r i 2 s = lim r E s2
• RCS Definitions Mathematically RCS is defined by :
Es and Ei are the scattered and incident electric fields respectively
3D
– – – –
Physically, RCS is a measure of a targets effective echoing area and is a measure of the power scattered in a given direction normalized by the incident power RCS is termed Bistatic when scattering is not back towards source of incident radiation RCS is Monostatic when source and receiver are located at same point RCS units are area, but common normalizations are dBsm and dBsl
source location
observation location ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
Monostatic
Bistatic 10-2 1-2
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Introduction Ansoft – Antenna/RF Training Guide
Significance of RCS
Training Manual
• RCS Received Power –
From the radar range equeation one can write the received power as:
Pr =
Pt Gt 4p r 2
s
4p r 2
Ar
Pt is transmitted power, Gt is peak gain of antenna, s is RCS of object illuminated, Ar is the effective aperture of the antenna and given by Ar = Gtl2/4p
• Detection Range –
RCS must be reduced by four orders of magnitude for a reduction in detection range of one order of magnitude • For example, halving the detection range requires a 12dB reduction in the RCS – Detection range reduction assuming s1 detected at r1 and s2 at r2 at noise thresholds
r1 s1 r2 = s2 ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Scattering Regimes for RCS
Training Manual
• Scattering Regimes for RCS Low-Frequency (Raleigh) • Incident wavelength much greater than body size – Resonant • Incident wavelength is on the order of the body size – High-Frequency (Optical) • Incident wavelength is much smaller than the length of the scattering object –
Three regions illustrated for RCS of conducting sphere ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Introduction Ansoft – Antenna/RF Training Guide Training Manual
Boundary Conditions for Radar Cross Section
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Air Region Boundary Type and Size
Training Manual
• Outer Boundary –
–
Air volume should be assigned either radiation boundary or PML • Radiation boundary is simpler to assign • PML is more robust and can be brought closer to strong radiating currents Size airbox appropriately to avoid influencing solution (loading reactive nearfields, etc.) • Place radiation boundary a minimum of l/4 from strong currents • Place PML a minimum of l/8 from strong currents
PML Boundary
Radiation Boundary
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Radiation Boundary
Training Manual
• Radiation Boundary –
–
Mimics continued propagation beyond boundary plane • Absorption achieved via 2nd order radiation boundary • Place at least l/4 from strongly radiating structure – Place at least l/10 from weakly radiating structure • Absorbs best when incident energy flow is normal to surface • Must be concave to all incident fields from within modeled space Parameters • Advanced options used for incident wave and HFSS DataLink problems
Boundary is l/4 away from horn aperture in all directions
Radiation boundary functions well for incident angles less than 25°-30°
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Introduction Ansoft – Antenna/RF Training Guide
Perfectly Matched Layer (PML)
Training Manual
• PML Boundary Fictitious lossy anisotropic material which fully absorbs electromagnetic fields Two types of PML applications • “PML objects accept free radiation” if PML terminates free space • “PML objects continue guided waves” if PML terminates transmission line – Guidelines for assigning PML boundaries • Use PML setup wizard for most cases • Manually create a PML when base object is curved or inhomogeneous – Parameters • Uniform thickness • Minimum frequency • Minimum radiating distance (between PML and antenna) – –
PML functions well for incident angles less than 65°-70°
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Introduction Ansoft – Antenna/RF Training Guide
Radiation Boundary vs PML
Training Manual
• RCS: Radiation Boundary – –
For RCS problems, PMLs are the recommended absorbing boundary condition for the highest accuracy For quicker answers, a Radiation boundary condition can be used • More accurate answers with Radiation BC can be obtained by changing the integration surface
Radiation Boundary
PML
Type
2D
3D (occupies volume)
Incident angle from normal
< ~30°
< ~70°
Distance from radiator
> l/4
> l/10
Setup complexity
Low
Medium
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Introduction Ansoft – Antenna/RF Training Guide
Integration Surface
Training Manual
• Radiation Surface – –
By default, HFSS utilizes the Boundary Radiation Surface for the integration of far fields To change, go into the Far Field Radiation Sphere Setup / Radiation Surface tab, and change surfaces. • The alternate surface must already be defined by selecting the faces, and then 3D Modeler / List / Create / Face List
• Why would you want to change the integration surface? –
–
–
There is no set rule for changing this, however, for some problems, it might be more efficient to use an aperture or other object as the integration surface. The predominant thinking is that the fields are strongest nearest the scattering object, and thus the RCS values will be most accurate near the object. • Contrary to what you might expect, this even works when the object is a PEC In most cases, there will be no difference in final results, but you can use the alternate integration surface method to obtain quicker answers
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Introduction Ansoft – Antenna/RF Training Guide Training Manual
Incident Wave Excitation
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Introduction Ansoft – Antenna/RF Training Guide
Incident Wave Excitation
Training Manual
• Excitations – –
–
RCS models use incident waves to excite the simulation HFSS offers several different incident wave excitations • Plane Wave • Others including: – Evanescent Wave – Hertzian-Dipole Wave – Cylindrical Wave – Gaussian Beam Wave – Linear Wire Antenna Wave – Waves created in other HFSS models Use the menu selection HFSS > Excitations > Assign > Incident Wave > Plane Wave
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Plane Wave Excitation Setup (Cartesian)
Training Manual
• Setup – – –
General Data Window used to specify Vector Input Format and Excitation Location Cartesian Vector Setup Window defines orientation of the E-field (Eo Vector) and direction of propagation (k Vector) in Cartesian Coordinates. Plane Wave Options Window sets up attenuation of evanescent waves and elliptical polarization.
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Plane Wave Excitation Setup (Spherical)
Training Manual
• Setup – –
Choosing Spherical Vector Input Format changes Vector Setup to accept spherical coordinates. Now multiple incident waves can be defined and solved for at the same time • HFSS does NOT need to resolve the entire problem for each incident wave. It simply changes the stimulus and applies it to the already solved matrix. • Mesh is affected by every specified incident wave • Multiple incident waves are solved in a fraction of the time it would take to re-solve the problem for each wave.
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Incidence Angle and Observation Angle
Training Manual
• Distinguishing Between Incidence and Observation Angle – – –
HFSS needs to distinguish between the (q,f) of the incident wave and the (q,f) of the observation point. HFSS does this by specify the wave’s angle of incidence as IWavePhi and IWaveTheta. The observation angles are specified as theta and phi. This is important when setting up RCS plots in the post-processor
IWaveTheta
IWavePhi
q
f
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Introduction Ansoft – Antenna/RF Training Guide
Incident Wave Formulations
Training Manual
Scattered Field Formulation Total Field Formulation
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Introduction Ansoft – Antenna/RF Training Guide
Incident Wave Formulations
Training Manual
• Incident Wave Formulations – – –
The total E-field in a scattering problem is a superposition of the incident and scattered fields Since the incident field is known ,HFSS can solve for either the scattered field or the total field. • The remaining quantity can be derived through superposition HFSS can solve incident waves using either of these formulations
• The Choice of Formulation is Problem Dependent – –
Use the Total Field Solution for models with objects that touch any radiation boundaries or PMLs. Use Scattered Field Solution for scatterers in free space (where the scatterer does not touch the radiation boundary or PML).
E Total = E Incident E Scattered
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Scattered Field Formulation
Training Manual
• Scattered Field Formulation – –
–
HFSS directly solves the scattering field using the scattered field formulation Implementation • HFSS first imposes a plane wave that is present everywhere in the model at all times. • HFSS then creates sources that account for the scattered fields due to material properties and boundary conditions • The scattered fields are calculated using the Finite Element Method • Total Field is derived through superposition As a result of this method, every non-vacuum object is treated as a source for the scattered fields • Can be changed in Boundaries > Edit Global Material Environment
E Total = E Incident E Scattered
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Introduction Ansoft – Antenna/RF Training Guide
Scattered Field Formulation
Training Manual
• The scattered field formulation is invoked – –
by defining a standard radiation boundary or PML. by choosing “Radiating Only” radio button under the advanced options
=
• The scattered field solution is most appropriate for – – – –
Finite Structures Structures do not make contact with Radiation Boundary or PML The scattered field is of interest (RCS) Scattered Field is much weaker than incident and total fields.
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Introduction Ansoft – Antenna/RF Training Guide
Scattered Field Formulation
Training Manual
• Example: Iris in an infinite ground plane (Scattered Field Formulation) –
– –
Non-Vacuum objects become sources in the model. • Radiation Boundaries and PMLs do not behave well when sources are touching the boundary • Scattered Field Formulation should therefore be used with finite scatterers that do not make contact with the absorbing boundaries Incident wave is present throughout the entire volume at all times. • Areas that you do not expect direct contact with the incident wave might indicate erroneous scattering (Iris) Why are we getting non-physical energy using scattered field formulation? • Total field is calculated from scattered field + incident field located everywhere • Scattered field is calculated from artificial sources on every non-vacuum object • Artificial sources are finite in extent and cannot compensate for the incident plane wave fields • Total field magnitude is small and is computed from the subtraction of two relatively large numbers which can result in large relative numerical error
Iris
Scattered Field Formulation: Incident Wave
Infinite Ground Plane
Scattered Field Formulation: Total Field Non-physical Energy
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Total Field Formulation
Training Manual
• Total Field Formulation –
–
Expands the number and type of problems HFSS can solve • Implementation – Incident field originates from Incident Field “Ports” defined on radiation boundary of PML – The total field is then directly solved for throughout the model using FEM • Intuitively similar to typical component modeling with waveports – Scattered Field is derived from the Total Field through superposition Non-vacuum objects do not act as sources
E Scattered = E Total E Incident
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Introduction Ansoft – Antenna/RF Training Guide
Total Field Formulation
Training Manual
• The Total Field Formulation is invoked –
by choosing the Incident Field Option located under the radiation boundary/PML Advanced Options • Determine which faces the wave originates from and set the radiation boundaries associated with those faces to Incident field • All other radiation boundaries should be left in the default or set to Radiating Only
• The Total Field Formulation is most appropriate for – – –
Infinite scatterers Structures that make contact with the radiation or PML boundary Structures with cavities or areas with little field strength.
Wave propagates toward ground plane from above
All 5 faces of upper AirBox are defined as Incident Field radiation boundaries
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Introduction Ansoft – Antenna/RF Training Guide
Solution Setup for RCS
Training Manual
• RCS Setup –
–
–
For wideband RCS simulations, as is the case with most wideband problems, the adaptive Solution Frequency should be chosen to be the maximum desired frequency For Maximum Number of Passes, choose something reasonable based upon the size of the problem, and the resources of the computer • Typically 8-10 passes is sufficient For Maximum Delta Energy, the default value of 0.1 is usually sufficient
• RCS Convergence –
A better approach to the convergence of the adaptive refinement process is to actually use the RCS calculation • We want to stop the adaptive mesh refinement when RCS has settled down to a reasonable tolerance, say 0.2 dB – Create Output Variables – Use Expression Cache
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Introduction Ansoft – Antenna/RF Training Guide
Convergence for RCS
Training Manual
• Output Variables – –
All Far Field calculations require an Infinite Sphere for calculation • Select the menu item HFSS > Radiation > Insert Far Field Setup > Infinite Sphere Create Output Variable • Select the menu item HFSS > Results > Output Variable – Enter name of Output Variable – Report Type: Far Fields – Select Solution – Select RCS Quantity and Function – Click the Add button
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Introduction Ansoft – Antenna/RF Training Guide
Expression Cache for Convergence
Training Manual
• Expression Cache New – Allows the user to get field data vs. adaptive pass. – An expression can be added to the cache and that quantity will be computed and its result stored for each adaptive pass. • Once a quantity has been defined it only takes one button click to add it to the convergence criteria. – Quantities available for the cache include Output Variables, Calculator Expressions and Near or Far Field quantities. – Note: Expression cache quantities are also available to Optimetrics.
Adding Expressions
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Multiple Convergence Criteria
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Training Manual
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Ansoft – Antenna/RF Training Guide
Chapter 11 – HFSS-IE: Overview
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Introduction Ansoft – Antenna/RF Training Guide
HFSS-IE Introduction
Training Manual
• HFSS-IE: Technology – –
A new solver technology in the HFSS desktop A 3D Method of Moments (MoM) Integral Equation technique
• HFSS-IE: Applications –
Efficient solution technique for large, open, radiating or scattering analyses • Antenna placement • Radar cross section (RCS) • S-Parameters
• HFSS-IE: Advantage –
–
Automated results with accuracy • Effective utilization of automated adaptive meshing technique from HFSS – Ensures accuracy • Employs Adaptive Cross Approximation (ACA) technique for larger simulation – Automated matrix based solution for larger problems Utilization of results from HFSS as a linked source • Link can include effects of backwards scattering to the source geometry
• HFSS-IE: User Interface – Implemented as a new design type in the HFSS desktop • Shares same modeler interface and similar analysis setup • Minimal user training required for existing users of HFSS ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Introduction Ansoft – Antenna/RF Training Guide
Examples
Training Manual
VHF 350 MHz
Antenna Placement - UAV drone @ VHF
RCS of Cone-Sphere ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Introduction Ansoft – Antenna/RF Training Guide
Easy to Use
Training Manual
• A new design type in the HFSS desktop – – – – – –
Similar interface as HFSS Same model tree Same project tree Similar solution setup Same reporter Easily share models and materials between types
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Introduction Ansoft – Antenna/RF Training Guide
Automated and Accurate Results
Training Manual
• Adaptive Meshing –
Same adaptive meshing technology as HFSS
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Introduction Ansoft – Antenna/RF Training Guide
Materials, Boundary Conditions
Training Manual
• Material Definitions – – –
Same as HFSS Frequency dependent dielectrics All dielectrics must be isotropic
• Boundary Conditions – – – – –
Finite Conductivity/Perfect Electric Conductors Infinite ground planes Aperture opens up a "hole" in a conducting boundary Impedance Lumped RLC
• HFSS-IE Excitations – –
Terminal Lumped Ports • Rectangular or coaxial Incident Waves • Linked Near/Far-Field sources from HFSS
XY Plot 3
Ansoft LLC -10.00
HFIEDesign_coupled_E Curve Info dB(S(Rectangle1_T1,Rectangle1_1_T1)) Setup1 : LastAdaptive Freq='10GHz'
-11.00
Ref. Data Imported
-12.00
– –
Same as HFSS S-Parameters, Near/Far-Field, RCS
-13.00
Y1
• HFSS-IE Reports
-14.00
-15.00
-16.00
-17.00
-18.00
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0.50
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0.70 Primary Sweep
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Displaying Surface Currents
Training Manual
• Fields/Mesh Display
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Introduction Ansoft – Antenna/RF Training Guide
Additional Features
Training Manual
• HFSS-IE Solver Technology –
Direct and Iterative Solve • For large models uses an adaptive cross approximation (ACA) scheme for matrix compression and fast solutions. – This fast solving technology is automatically implemented • Does not require additional user interaction • Does not require uniform mesh distribution
• Design Flow – –
Dynamic Link to Ansoft Designer Optimetrics Support • Parametric, Sensitivity, and Statistical
• High-Performance Computing – –
Multi-processing enabled by same license as HFSS solver Distributed Solve Option (DSO) support for Frequency Sweeps and Optimertics
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Introduction Ansoft – Antenna/RF Training Guide
Summary
Training Manual
• HFSS-IE – – – – –
New solver technique in the HFSS interface Effective for large open radiating problems Automated and reliable accuracy through adaptive meshing and ACA fast solver technologies Links with HFSS for multi-solver domain studies When combined with HFSS and HPC a comprehensive solution for large radiating and scattering studies
HFSS Horn (Source) Results: Includes Horn Blockage Coupled HFSS-IE/HFSS Reflector
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Ansoft – Antenna/RF Training Guide
Workshop 1.1 – HFSS Example: Waveguide Array
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Introduction Ansoft – Antenna/RF Training Guide
Waveguide Array - Example
Training Manual
• The Waveguide Array – – – –
•
This example is intended to show you how to create, simulate, and analyze a Waveguide array antenna using the Ansoft HFSS Design Environment A WavePort will be used for the waveguide feed excitation A Floquet Port will be used for the phased array’s free space excitation and termination Master/Slave boundary conditions will be used to create the array’s unit cell
Reference: – [1] N. Amitay, V. Galindo and C. Wu, “Theory and Analysis of Phased Array Antennas”, Wiley-Interscience, 1972, ISBN 0-471-02553-4, section5.2.1.
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Overview
Training Manual
• Design Review – –
Instead of modeling the entire array, we will make use of the master/slave boundaries and only model a unit cell. A Floquet Port will be used to excite and terminate the model from free space. This port works in conjunction with the Master/Slave boundaries to enforce the array’s periodicity and allow for a changing scan angle.
• Ansoft HFSS Design Environment –
The following features of the Ansoft HFSS Design Environment are used to create this passive device model • 3D Solid Modeling – Primitives: Box • Boundaries/Excitations – Ports: Wave Ports, Floquet Ports – Boundaries: Master/Slave • Analysis – Sweep: Interpolating • Results – Cartesian plotting • Optimetrics – Parametric sweep
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Introduction Ansoft – Antenna/RF Training Guide
Getting Started
Training Manual
• Launching Ansoft HFSS –
To access Ansoft HFSS, click the Microsoft Start button, select Programs, and select the Ansoft, HFSS 12 program group. Click HFSS 12.
• Setting Tool Options – Note: In order to follow the steps outlined in this example, verify that the following tool options are set : – Select the menu item Tools > Options > HFSS Options • Click the General tab – Use Wizards for data input when creating new boundaries: Checked – Duplicate boundaries with geometry: Checked • Click the OK button – Select the menu item Tools > Options > Modeler Options. • Click the Operation tab – Automatically cover closed polylines: Checked – Select last command on object select: Checked • Click the Drawing tab – Edit property of new primitives: Checked • Click the OK button
• Opening a New Project – –
In HFSS Desktop, click the On the Standard toolbar, or select the menu item File > New. From the Project menu, select Insert HFSS Design.
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Introduction Ansoft – Antenna/RF Training Guide
Creating the Design
Training Manual
• Set Solution Type –
Select the menu item HFSS > Solution Type • Choose Driven Modal • Click the OK button
• Set Model Units –
Select the menu item Modeler > Units • Select Units: in • Click the OK button
• Set Default Material –
Using the 3D Modeler Materials toolbar, make sure that vacuum is the default material
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Introduction Ansoft – Antenna/RF Training Guide
Create Waveguide
Training Manual
• Create Waveguide – – – –
–
Select the menu item Draw > Box Using the coordinate entry fields, enter the box position • X: -12.28, Y: -12.28, Z: -55, Press the Enter key Using the coordinate entry fields, enter the opposite corner of the box • dX: 24.56, dY: 24.56, dZ: 55, Press the Enter key Select the Attribute tab from the Properties window. • For the Value of Name type: waveguide • Click the OK button To fit the view: • Select the menu item View > Fit All > Active View or press the CTRL+D keys
• Create Airbox Select the menu item Draw > Box Using the coordinate entry fields, enter the box position • X: -13.246, Y: -13.246, Z: 0.0, Press the Enter key – Using the coordinate entry fields, enter the opposite corner of the box • dX: 26.492, dY: 26.492, dZ: 55.0, Press the Enter key – Select the Attribute tab from the Properties window. • For the Value of Name type: Airbox • Click the OK button – To fit the view: • Select the menu item View > Fit All > Active View or press the CTRL+D keys – –
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Assign Master/Slave Boundaries
Training Manual
• Create First Master Boundary – –
–
Select the menu item Edit > Select > Faces Select the menu item Edit > Select > By Name • Select Face dialog: Select the object Airbox from the left column – Select different FaceIDs until the side face located on the positive x-axis of the Airbox is highlighted. • Click the OK button Select the menu item HFSS > Boundaries > Assign > Master • Name: Master1 • Coordinate System: U Vector: Click the Undefined pulldown and select New Vector. • Using the coordinate entry fields, enter the start position – X:13.246, Y: -13.246, Z:0.0, Press the Enter key • Using the coordinate entry fields, enter the stop position of the vector – dX: 0, dY: 26.492, dZ: 0, Press the Enter key • For the V vector, check the Reverse Direction: Checked • Click the OK button
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Introduction Ansoft – Antenna/RF Training Guide
Assign Master/Slave Boundaries
Training Manual
• Create Second Master Boundary – –
–
Select the menu item Edit > Select > Faces Select the menu item Edit > Select > By Name • Select Face dialog: Select the object Airbox from the left column – Select different FaceIDs until the side face located on the positive y-axis of the Airbox is highlighted. • Click the OK button Select the menu item HFSS > Boundaries > Assign > Master • Name: Master2 • Coordinate System: U Vector: click the Undefined pulldown and select New Vector. • Using the coordinate entry fields, enter the start position – X:13.246, Y: 13.246, Z:0.0, Press the Enter key • Using the coordinate entry fields, enter the stop position of the vector – dX: -26.492, dY: 0.0, dZ: 0.0, Press the Enter key • For the V vector, check the Reverse Direction: Checked • Click the OK button
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Introduction Ansoft – Antenna/RF Training Guide
Assign Master/Slave Boundaries
Training Manual
• Create First Slave Boundary – –
–
–
Select the menu item Edit > Select > Faces Select the menu item Edit > Select > By Name • Select Face dialog: Select the object Airbox from the left column – Select different FaceIDs until the side face located on the negative x-axis of the Airbox is highlighted. • Click the OK button Select the menu item HFSS > Boundaries > Assign > Slave • Name: Slave1 • Master Boundary: click on Undefined pulldown and select: Master1 • Coordinate System: U Vector: click the Undefined pulldown and select New Vector. • Using the coordinate entry fields, enter the start position – X: -13.246, Y: -13.246, Z:0.0, Press the Enter key • Using the coordinate entry fields, enter the stop position of the vector – dX: 0.0, dY: 26.492, dZ: 0.0, Press the Enter key • Click the Next button Continued on next page
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Assign Master/Slave Boundaries –
Training Manual
To create the Slave Boundary (Continued) • Complete Phase Delay Tab – Make sure that Use Scan Angles To Calculate Phase Delay is checked – For Phi, enter a variable name phi_scan – For Theta, enter a variable name theta_scan • Click the Finish button • For the Add Variable dialog corresponding to phi_scan, – Enter 90deg – Click the OK button • For the Add Variable dialog corresponding to theta_scan, – Enter 0deg – Click the OK button
• Create Second Slave Boundary – –
Select the menu item Edit > Select > Faces Select the menu item Edit > Select > By Name • Select Face dialog: Select the object Airbox from the left column – Select different FaceIDs until the side face located on the negative y-axis of the Airbox is highlighted. • Click the OK button
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Assign Master/Slave Boundaries
Training Manual
• Create Second Slave Boundary (continued) –
–
–
Select the menu item HFSS > Boundaries > Assign > Slave • Name: Slave2 • Master Boundary: click on Undefined pulldown and select: Master2 • Coordinate System: U Vector: click the Undefined pulldown and select New Vector. • Using the coordinate entry fields, enter the start position – X: 13.246, Y: -13.246, Z: 0.0, Press the Enter key • Using the coordinate entry fields, enter the stop position of the vector – dX: -26.492, dY: 0.0, dZ: 0.0, Press the Enter key • Click the Next button Complete Phase Delay Tab • Make sure that Use Scan Angles To Calculate Phase Delay is checked • For Phi, enter a variable name phi_scan • For Theta, enter a variable name theta_scan Click the Finish button
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Create Waveport
Training Manual
• Create WavePort – –
–
Select the menu item Edit > Select > Faces Select the menu item Edit > Select > By Name • Select the object waveguide from the left column – Select different FaceIDs until the bottom face of the waveguide is highlighted. • Click the OK button Select the menu item HFSS > Excitation > Assign > WavePort • Complete the General Tab – Name: p1 – Click Next • Complete the Modes Tab – Number of Modes: 2 – Mode 1: click on the None pulldown located under the Integration Line Column and select New Line – Using the coordinate entry fields, enter the start position • X: -12.28, Y: 0.0, Z: -55.0, Press the Enter key – Using the coordinate entry fields, enter the stop position of the vector • dX: 24.56, dY: 0.0, dZ: 0.0, Press the Enter key
Continued on next page
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Create Waveport –
Training Manual
To create WavePort (continued): • Complete Mode Tab (continued) – Mode 2: click on the None pulldown located under the Integration Line Column and select New Line – Using the coordinate entry fields, enter the start position • X: 0.0, Y: -12.28, Z: -55, Press the Enter key – Using the coordinate entry fields, enter the stop position of the vector • dX:0.0, dY: 24.56, dZ: 0.0, Press the Enter key – Align modes using integration lines: Selected • Selecting align modes using integration lines will cause HFSS to use the analytical waveguide mode solutions to properly polarize the electric field in the port. The analytical solution is only invoked for canonical waveguide structures like rectangular waveguide, circular waveguide and coaxial waveguide. For all other port geometries HFSS will enforce the polarization without the analytical solution. HFSS still performs a numerical solution of the port’s modes, but will orient the field polarizations through its knowledge of the analytical solution. – Click the Next button • Complete the Post Processing Tab • Click Finish
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Introduction Ansoft – Antenna/RF Training Guide
Create Floquet Port
Training Manual
• Create FloquetPort – –
–
Select the menu item Edit > Select > Faces Select the menu item Edit > Select > By Name • Select the object Airbox from the left column – Select different FaceIDs until the top face of the AirBox is highlighted. • Click the OK button Select the menu item HFSS > Excitation > Assign > Floquet Port • Name: FP1 • A Direction Lattice Coordinate: click on the Undefined pulldown located and select New Vector • Using the coordinate entry fields, enter the start position – X: -13.246, Y: -13.246, Z: 55, Press the Enter key • Using the coordinate entry fields, enter the stop position of the vector – dX: 26.492, dY: 0.0, dZ: 0.0, Press the Enter key • B Direction Lattice Coordinate: click on the Undefined pulldown located and select New Vector • Using the coordinate entry fields, enter the start position – X: -13.246, Y: -13.246, Z: 55, Press the Enter key • Using the coordinate entry fields, enter the stop position of the vector – dX:0.0, dY: 26.492, dZ: 0.0, Press the Enter key • Click Next
Continued on next page
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Create Floquet Port –
Training Manual
To create FloquetPort (continued): • Click the Modes Calculator button • Complete the Modes Setup Tab – Number of Modes: 10 – Frequency: 299.79 MHz – Make sure that Use Scan Angles To Calculate Phase Delay is checked • Phi: 90 deg • Theta: 90 deg – Click the OK button •HFSS has a Modes Calculator to help determine the number of modes that should be included in the Floquet Port. Any mode that is not defined in the Modes Setup Tab will be short circuited at the port and reflected back toward the array. For accurate results all modes that have a significant amount of energy at the port must be included in the Modes Setup Tab. • The Floquet Mode calculator is going to request the number of modes that should be evaluated, a frequency and a scan angle to calculate each mode’s attenuation constant. The modes with the least attenuation are going to occur at the highest simulation frequency and at locations in the scan volume that are close to grating lobes. Therefore, we are going to set these conditions in the Modes Calculator to determine the attenuation in dB/length for each mode. We will then restrict the number of modes to only include the modes with a significant contribution to the array’s performance
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Create Floquet Port
Training Manual
•Notice that the first 4 modes have an attenuation of 0.00 dB/length. This indicates that they are propagating modes. The TE00 and TM00 modes correspond to the main beams of the x and y polarized patterns. respectively. The TE0-1 and TM0-1 modes correspond to the grating lobes of x and y polarized patterns. •Modes 5 through 10 have attenuation of 1.67 dB/length or 2.06 dB/length depending the mode. The length portion of this attenuation is calculated in the model’s unit (inches for this example). To calculate a mode’s total attenuation from the array to the Floquet Port, the attenuation value displayed in the Modes Setup Tab needs to be multiplied by the distance between the array face and the Floquet Port. •For this example this distance is 55in. Therefore the TE1-1 mode experiences 1.67*55 = 91.85dB of attenuation as it propagates from the array face to the Floquet Port. •Likewise the TE10 mode experience 2.06*55 = 113.3dB of attenuation across this same distance. •It therefore is safe to only include the first 4 modes in the Floquet Port definition.
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Create Floquet Port –
Training Manual
To create FloquetPort (continued): • Change the Number of Modes: 4 • Click the Next button • Complete the Post Processing Tab – Click the Finish button • Complete the 3D Refinement Tab – Click the Next button
•For this example we only included the modes that propagate at the highest simulated frequency for the largest scan angle in the plane corresponding the closest grating lobe. Although these modes are propagating for this instance, they may not be propagating for other cases where the frequency is lower or the scan angle as extreme. The cases where any of these modes are heavily attenuated can cause an unusually dense mesh concentrated at the port. This will significantly decrease the simulation efficiency and in many phased array cases there is more interest in terminating these modes than exciting them. To improve the simulation’s efficiency HFSS allows you to determine which Floquet Modes are excited for the purposes of refining the mesh during the adaptive meshing process. Which modes affect the adaptive meshing process is controlled by checking the box under the Affects Refinement column on the 3D Refinement Tab. This exercise is only interested in exciting the problem from the waveguide side. Therefore none of the Floquet Modes are going to be excited in the adaptive mesh refinement
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Introduction Ansoft – Antenna/RF Training Guide
Analysis Setup
Training Manual
• Creating an Analysis Setup –
Select the menu item HFSS > Analysis Setup > Add Solution Setup • Click the General tab: – Solution Frequency: 299.79 MHz – Maximum Number of Passes: 6 – Maximum Delta S: 0.02 • Click the Options tab: – Minimum Number of Passes: 5 • Click the OK button
• Creating a Frequency Sweep: –
Select the menu item HFSS> Analysis Setup > Add Frequency Sweep • Choose Setup1 from pop-up window and click the OK button – Sweep Type: Interpolating – Frequency Setup Type: LinearStep – Start: 200MHz – Stop: 300MHz – Step: 0.1MHz – Click the OK button
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Analyze
Training Manual
• Save Project –
Select the menu item File > Save As. • Filename: hfss_array • Click the Save button
• Model Validation – –
Select the menu item HFSS > Validation Check Click the Close button (Note: To view any errors or warning messages, use the Message Manager.)
• Analyze – Select the menu item HFSS > Analyze All
• Solution Data –
Select the menu item HFSS > Results > Solution Data – To view the Profile, Click the Profile Tab. – To view the Convergence, Click the Convergence Tab • Note: The default view is for convergence is Table. Select the Plot radio button to view a graphical representations of the convergence data. – To view the Matrix Data, Click the Matrix Data Tab • Note: To view a real-time update of the Matrix Data, set the Simulation to Setup1, Last Adaptive – To view the Mesh Statistics, Click the Mesh Statistics Tab. • Click the Close button
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Post Processing
Training Manual
• Create Floquet Mode Plot vs Frequency –
–
Select the menu item HFSS > Results > Create Modal Solution Data Report > Rectangular Plot • Solution: Setup1: Sweep1 • Category: S-Parameter • Quantity: S(FP1:3,P1:1), S(FP1:4,P1:1), S(P1:1,P1:1) • Function: dB • Click the New Report button Click the Close button
•This plot shows how the X-Polarized Waveguide mode couples into the TE00 and TM00 modes at boresight as frequency is swept from 200MHz to 300MHz. •Notice that just above 240MHz the return loss spikes to 0dB and the coupling to both the TE00 and TM00 modes show a sharp discontinuity. This is caused by the TE10 waveguide mode transitioning out from being cutoff. ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Optimetrics – Parametric Sweep
Training Manual
• Optimetrics Setup –
For this array design, we want to see the effect of scan angle on the input match of the antenna. To do this, we must sweep the scan angle with a parametric sweep.
• Add a Second Solution Setup – Select the menu item HFSS > Analysis Setup > Add Solution Setup • Click the General tab: – Setup Name: Setup2 – Solution Frequency: 299.79 MHz – Maximum Number of Passes: 6 – Maximum Delta S: 0.02 • Click the Options tab: – Minimum Number of Passes: 2 • Click the OK button
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Parametric Sweep Setup
Training Manual
• Add a Parametric Sweep –
Select the menu item HFSS > Optimetrics Analysis > Add Parametric • Click the Sweep Definitions tab: – Click the Add button Note: The plots shown for the parametric sweep contain an – Add/Edit Sweep Dialog additional sweep for theta_scan to improve the plot resolution: • Select Variable: theta_scan •Type: Linear Step • Select Linear Step •Start: 27.1deg • Start: 0deg •Stop: 27.9deg •Step: 0.1deg • Stop: 90deg • Step: 10deg • Click the Add >> button • Click the OK button • Click the General tab: – Uncheck Setup1 Include • Click the Options tab: – Check Save Fields and Meshes – Check Copy geometrically equivalent meshes • Click OK to accept the Parametric Sweep settings
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• Save Project –
Select the menu item File > Save
• Analyze Parametric Sweep –
Expand the Project Tree to display the items listed under Optimetrics • Right-click the mouse on ParametricSetup1 and choose Analyze
• Optimetrics Results –
Select the menu item HFSS > Optimetrics Analysis > Optimetrics Results • Select the Profile Tab to view the solution progress for each setup. • Click the Close button when you are finished viewing the results
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Parametric Post Processing
Training Manual
• Create Propagation Constant Plot –
–
Select the menu item HFSS > Results > Create Modal Solution Data Report > Rectangular Plot • Solution: Setup2: LastAdaptive • X: theta_scan • Category: Gamma • Quantity: Select All Quantities • Function: Im • Click the New Report button Click the Close button
•Notice that Floquet Modes 1 and 2 do not start propagating until the array is scanned to 29deg. These mode are the TE0-1 and TM0-1 modes respectively and represent the grating lobes associated with the E-phi and E-theta patterns respectively. The main beams (TE00 and TM00) are the 3rd and 4th Floquet Modes. These modes propagate to the edge of real space. ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Parametric Post Processing
Training Manual
• Create S-Parameter Plot –
–
Select the menu item HFSS > Results > Create Modal Solution Data Report > Rectangular Plot • Solution: Setup2: LastAdaptive • X: theta_scan • Category: S Parameter • Quantity: S(FP1:2,p1:2), S(FP1:4,p1:2), S(p1:2,p1:2) • Function: mag • Click the New Report button Click the Close button
•Notice the transmission for the 1st Floquet Mode is not significant until just below 30deg scan. This mode corresponds to the TM0-1 mode which doesn’t propagate until 29deg scan. At this same scan angle a scan blindness is observed in the return loss and the transmission for the 4th Floquet Mode (TM00) drops sharply. ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Parametric Post Processing
Training Manual
• Create Active Element Pattern –
– –
Select the menu item HFSS > Results > Create Modal Solution Data Report > Rectangular Plot • Solution: Setup2: LastAdaptive • X: Switch to theta_scan • Y: 10*log(4*pi*701.8/39.361^2*mag(S(p1:2,FP1:4))^2*cos(theta_scan)) – 701.8 is the unit cell area in square inches – 39.361inches is the wavelength in free space • Click the New Report button Click the Close button Double click on the Y-axis of the plot • Click the Scale tab: – Specify Min: Checked – Min: -60 – Spacing: 10
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Workshop 2.1 – HFSS Optimetrics: Shorted Patch
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Optimetrics: Example
Training Manual
• The Shorted Probe-Fed Patch Antenna with Optimetrics – – – – –
This example is intended to show users how to create a variable, and set up a parametric study of a probe feed patch antenna using the Ansoft HFSS Environment A parametric sweep will be used to determine the effect on the input impedance match as a function of the feed pin position This parametric sweep will be used to seed an optimization analysis that will be used to find the optimal position for the feed pin Analytical derivatives will also be used to perform real time tuning of several dimensions of the patch antenna Only half the model is shown below, and all dimensions are in mm
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Introduction Ansoft – Antenna/RF Training Guide
Getting Started
Training Manual
• Launching Ansoft HFSS –
To access Ansoft HFSS, click the Microsoft Start button, select Programs, and select the Ansoft, HFSS 12 program group. Click HFSS 12.
• Setting Tool Options – Note: In order to follow the steps outlined in this example, verify that the following tool options are set : – Select the menu item Tools > Options > HFSS Options • Click the General tab – Use Wizards for data input when creating new boundaries: Checked – Duplicate boundaries with geometry: Checked • Click the OK button – Select the menu item Tools > Options > Modeler Options. • Click the Operation tab – Automatically cover closed polylines: Checked – Select last command on object select: Checked • Click the Drawing tab – Edit property of new primitives: Checked • Click the OK button
• Opening a Project –
Select the menu item File > Open • Select the project: OptimetricsPatch_training.hfss • Click the Open button
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Design Variables
Training Manual
• Checking Design Variables – –
A design variable has been created that controls the location of the feed of the patch antenna: feed_pos To view a list of any design variables that have been created for this design: • Go to the menu item HFSS > Design Properties – Alternatively, highlight HFSSModel1 in the Project Manger Window, the design variables will be displayed in the Properties Window • Verify that the variable feed_pos is assigned the value 9mm • Press the OK button
Feed_pos
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Parametric Analysis Setup
Training Manual
• Parametric Sweep of Feed Position –
We will now complete the creation of the parametric project using the defined variable to vary the coaxial feed position in order to achieve optimal match between the patch antenna and its coaxial feed line. The ratio of the coaxial feed inner and outer diameters was chosen to achieve a 50 Ohm characteristic impedance. So we will effectively change the value of the feed offset until we find a position which presents a 50 Ohm load impedance on the coaxial feed line. The S11 vs. frequency plot has a dip at the patch resonant frequency, the dip is maximized when the optimal offset is found.
• Create Parametric Sweep –
– –
Select the menu item HFSS > Optimetrics Analysis > Add Parametric... • Under Variable check feed_pos is selected • Select Linear Step – Start: 7mm – Stop: 13mm – Step: 2mm • Click the Add>> button • Click the OK button Click the OK button In the project tree, go to Optimetrics > ParametricSetup1, right click and select Analyze
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Creating a Report
Training Manual
• Create Modal S-Parameter plot – Magnitude –
–
Select the menu item HFSS > Results > Create Modal Solution Data Report > Rectangular Plot • Solution: Setup1:Sweep1 • Domain: Sweep • Trace tab – Category: S Parameter – Quantity: S(P1,P1) – Function: dB • Families tab – Ensure All under Value column for variable feed_pos • Click New Report button Click Close button
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Results
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Training Manual
WS2.1-7 1-7
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Optimization Analysis Setup
Training Manual
• Optimization –
The Parametric Sweep was useful for generating design curves. For this simple design with only a single variable we could use the design curves to make educated guesses at performance targets that are not contained in the Parametric Sweep. Ansoft HFSS and Optimetrics with Optimization takes the guess work out of achieving performance targets. To demonstrate this we will target a minimum of less than -20dB for S11 at 1.8GHz for this shorted patch antenna. From the Parametric Sweep, we can see that the minimum return loss will be achieved when the variable feed_pos is around 11mm.
• Create an Optimization Setup –
Select the menu item HFSS > Design Properties • Click the Optimization radio button: – Name: feed_pos – Include: Checked – Min: 10 mm – Max: 12 mm • Click the OK button
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Optimization Analysis Setup
Training Manual
• Add Optimization Setup –
Select the menu item HFSS > Optimetrics Analysis > Add Optimization
• Setup Optimization Click the Goals tab: • Optimizer: Quasi-Newton • Max. No. of Iterations: 10 • Click the Setup Calculations button • Add/Edit Calculation dialog: – Report Type: Model Solution Data – Solution: Setup1: Sweep1 – Category: S Parameter – Quantity: S(p1,p1) – Function: dB – Click the Add Calculation button – Click the Done button – Calc Range: 1.8GHz – Condition: Optimetrics Analysis > Optimetrics Results • Optimal solution occurs at ~10.50mm • Click the Close button when you are finished viewing the results
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• Create Modal S-Parameter plot – Magnitude –
–
Select the menu item HFSS > Results > Create Modal Solution Data Report > Rectangular Plot • Solution: Setup1:Sweep1 • Domain: Sweep • Trace tab – Category: S Parameter – Quantity: S(P1,P1) – Function: dB • Families tab – Select the value which achieved the desired goal in the optimization solution for variable feed_pos. In this optimization the feed_pos = 10.50mm results in RL < -20dB @ 1.8GHz • Click New Report button Click Close button
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Analytical Derivatives
Training Manual
• Analytical Derivatives –
From the parametric sweep and optimization of the feed position we can see that the optimal position is at about 10.50mm. To further investigate or an alternative to the optimization, we could use analytical derivatives to predict the behavior of our model with respect to small changes in design variables.
• Enable Analytical Derivatives –
Right click on Setup1 in Project Manager Window and choose Properties • Select Derivatives Tab – feed_pos: Use Checked – patch_width: Use Checked • Click the OK button
• Analyze –
Select the menu item HFSS > Analyze All
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Creating a Tuning Plot
Training Manual
• Create Tuning Plot –
–
–
Select the menu item HFSS > Results > Create Modal Solution Data Report> Rectangular Plot • Solution: Setup1: Sweep1 • Domain: Sweep • Click the Trace tab – Category: S Parameter – Quantity: S(p1,p1) – Function: dB • Click the New Report button Create Tuning Trace • Derivatives: All • Click the Trace tab – Category: Tune S Parameter – Quantity: TuneS(p1,p1,All) – Function: dB – Click the Add Trace button Click Close button
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• Tuning Plot – – –
Select the menu item HFSS > Results > Tune Reports … Move the scroll bar on the Tune Report window to get the predicted performance with patch widths and feed positions Click on Close button
Note: The predicted response is based off the nominal solution and partial derivative that was computed during the solution process.
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Workshop 2.2 – HFSS Optimetrics: Dual-band WLAN Antenna
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• WLAN antenna design－ Double L-slits antenna with Optimetrics – – – – –
This example is intended to demonstrate users how to optimize a realistic double L-slits WLAN antenna using the dynamic link concept of Ansoft HFSS and Ansoft Designer/Nexxim Environments First, the W, L1 and W1 are parameterized in HFSS (pre-solved) Then, the solved parameterized HFSS project is linked into Designer/Nexxim, and the antenna is optimized in circuit level Finally, the optimized dimensions are entered in the HFSS model for validation Top View of the model
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Introduction Ansoft – Antenna/RF Training Guide
Getting Started
Training Manual
• Launching Ansoft HFSS –
To access Ansoft HFSS, click the Microsoft Start button, select Programs, and select the Ansoft, HFSS 12 program group. Click HFSS 12.
• Setting Tool Options – Note: In order to follow the steps outlined in this example, verify that the following tool options are set : – Select the menu item Tools > Options > HFSS Options • Click the General tab – Use Wizards for data input when creating new boundaries: Checked – Duplicate boundaries with geometry: Checked • Click the OK button – Select the menu item Tools > Options > Modeler Options. • Click the Operation tab – Automatically cover closed polylines: Checked – Select last command on object select: Checked • Click the Drawing tab – Edit property of new primitives: Checked • Click the OK button
• Opening a Project –
Select the menu item File > Open • Select the project: Ant_WLAN_training.hfss • Click the Open button
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• Check Antenna Model in HFSS –
–
Check antenna variables: • Highlight the design under the project tree, model variables (as W, L1, W1 etc) are shown in the property window Check parametric setup: • Double click the ParametricSetup1 under Optimetrics in project tree
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• Check Pre-solved Parametric Profiles –
Select the menu item HFSS > Results > Solution Data • By default, nominal design solution data is shown • Click „…‟ and Set Design Variation window pops up – Uncheck Use Nominal Design to select parametric combination to see its solution data
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• Plot Pre-solved Parametric Solutions –
–
Select the menu item HFSS > Results > Create Modal Solution Data Report > Rectangular Plot • Solution: Setup1:Sweep1 • Domain: Sweep • Trace tab – Category: S Parameter – Quantity: S(WavePort1, WavePort1) – Function: dB • Families tab – Variables: W1, W and L1 – Values: All • Click New Report button Click Close button
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• Distributed Solve Option —Linear Speed up for parametric study – – – – – –
Allows the user to send multiple instances of an analysis to be solved on different machines simultaneously. The graphical user interface enables users to select computer addresses for analysis distribution. Automated parser management and reassembly of data. Parametric tables and studies. Frequency sweeps for discrete, fast, and interpolating. Per license, distributed analysis allows up to 10 parallel simulations on remote machines, providing near-linear reduction of simulation run times.
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• Ansoft Designer/Nexxim and HFSS Linkage – We will now link the pre-solved double-L slits antenna model from HFSS into Ansoft Designer, and set up optimization and run.
2
• Launch Ansoft Designer/Nexxim
1
– Double click on the Designer 5 icon on the Windows Desktop
• Nexxim-HFSS Datalink Setup – Select the menu item Project > Insert Nexxim Circuit Design • In the Choose Layout Technology dialog box, click None – Select the menu item Project > Add Model > Add HFSS Model... • Name: WLAN_HFSS_Model • File name: \Ant_Wlan_training.hfss • Select Simulation tab – Select Interpolate Options... Button • Check Only use independent variables during interpolation button • Click the OK button • Click the OK button
3
4
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• Components Placement in Designer/Nexxim –
–
–
Placing the pre-solved HFSS project • Highlight Model under Models and drag into schematic window • Choose Implied reference to ground Adding the port • Select the menu item Draw > Interface Port – Left-click to place the ports at input and output as shown. Place the first port (“Port1”) at the input. – Hit the key or space bar to finish placing ports Adding Wiring to connect components • As you place the cursor near a pin of a component, it changes from an arrow to an X. This indicates that the schematic editor is in the wiring mode. In the wiring mode: – Left-click to start drawing a wire. – Left-click again to end the wire.
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• Variables Setup in Designer/Nexxim – –
Right click on the imported HFSS component in the Designer schematic > Properties Input variables LL1, WW1, and WW to the Value column of Name of L1, W1 and W in the Properties window • For example, type WW into the Value column of Name of W, press key, Add Variables windows pops up. Type 3mm in the Value • Click OK button • Same procedures to set LL1 (= 8mm) and WW1 (=0.5mm)
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• Analysis Setup in Designer/Nexxim –
Select the menu item Nexxim Circuit> Add Solution Setup> Linear Network Analysis • Accept the defaults for Analysis Name • Highlight F in the Sweep Variables • Click the Edit button – Click the Add button • Variable type: F • Select Linear Step • Start: 1 GHz • Stop: 6 GHz • Step: 0.01 GHz • Click the Add >> button • Click the OK button – Click OK button.
1
2
3
4 ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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• Save Project –
Select the menu item File > Save As • Filename: optimization_Nexxim_HFSS_training • Click the Save button
• Solve Project – Select the menu item Nexxim Circuit > Analyze
• Optimization Setup in Designer/Nexxim –
–
Select the menu item Nexxim Circuit > Design Properties • In the Properties dialog box, click on Local Variables, and select Optimization • Check Include for WW, WW1, and LL1 • Click the OK button Select the menu item Nexxim Circuit > Optimetrics Analysis > Add Optimization • Click Variables tab • Input Starting Value, Min, Max and Step for each variable – LL1: Starting Value = 8.99mm, Min = 7mm, Max = 9mm, Min Step = 0.01mm – WW: Starting Value = 2.01mm, Min = 2mm, Max = 4mm, Min Step = 0.01mm – WW: Starting Value = 1.49mm, Min = 0.5mm, Max = 1.5mm, Min Step = 0.01mm
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• Optimization Setup in Designer/Nexxim –
1
Select the Goals tab • Optimizer: Quasi Newton • Max. No. of Iterations: 40 • Acceptable Cost: 1 • Click the Setup Calculations button – Category: S Parameter, – Quantity: S(Port1, Port1) – Function: dB • Click Calculation Range tab – Click ... button • Highlight 2.35GHz • Click Add Calculation button – Click Done tab
2
4 3
5 6 7
8
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• Optimization Setup in Designer/Nexxim – – – –
–
Click = under Condition column Select Results> Create Standard Report > Rectangular Plot • Category: S Parameter • Quantity: S(Port1,Port1) • Function: dB • Click New Report button Click Close button Right click mouse on the plot, and click Accumulate… Select the menu item Tools> Options> Report2D Options...> General T • Accumulate Depth: 40 • Click the OK button
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• Run Optimization in Designer/Nexxim – –
Right click OptimetricsSetup1 and click Analyze Right click OptimetricsSetup1 and click View Analysis Result...
Optimized Dimensions ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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• Optimized Solution in Designer/Nexxim –
After optimization analysis, the optimized solution will be auto added to the nominal curve as shown below
XY Plot 2
Ansoft Corporation 0.00
Nexxim2
-5.00
-10.00
dB(S(Port1,Port1))
-15.00
-20.00
Before
-25.00
2.35 GHz: -6.63dB 4.85 GHz: -4.94 dB
After -15.8 dB -14.2 dB
-30.00
Red – Optimized Design Blue – Nominal Design
-35.00
Curve Info
-40.00
-45.00
dB(S(Port1,Port1)) LinearFrequency dB(S(Port1,Port1))
1.00
1.50
2.00
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2.50
3.00
3.50 F [GHz]
4.00
4.50
WS2.2-16 1-16
5.00
5.50
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• Validation with HFSS Right-click on return loss plot and de-select Accumulate Right-click on imported component in schematic window > Edit Model • Click Simulation tab and select Simulate missing solutions • Click the OK button – Right-click on return loss plot and select Accumulate – Right-click LinearFrequency in the Analysis section of the project manager window and select Analyze – –
XY Plot 1
Ansoft Corporation
HFSS_imptPlanarEM
0.00
Curve Info dB(S(Port1,Port1)) Import2 : Optimization_AD_HFSS Circuit dB(S(WavePort1,WavePort1)) Setup_1 : Sweep1 L1='9mm' W='2.743mm'
-5.00
Y1
-10.00
-15.00
Blue—HFSS Final Red—HFSS-AD Optimization
-20.00
-25.00
1.00
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2.00
3.00
Freq [GHz]
4.00
WS2.2-17 1-17
5.00
6.00
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Ansoft – Antenna/RF Training Guide
Workshop 3.1 – Ansoft Designer: Push Excitations
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• Antenna & Subsystem bi-directional co-design－ Push Excitation in Designer/Nexxim –
–
Push Excitation in Designer/Nexxim links the field & S-parameter solutions from an EM simulator, like HFSS or Siwave, and simultaneously allows the circuit excitations to be pushed into the field solvers to see the impact of the total system on the fields – including far-fields. Push Excitations are used by: • Linking the pre-solved HFSS antenna project into Designer/Nexxim • Build a subsystem with the imported antenna model in Designer/Nexxim • Solve the subsystem with antenna model in Designer/Nexxim • Updated excitations (amplitude & phase) are pushed back to HFSS antenna model, and fields, active S parameters etc are automatically updated
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• Quasi-Yagi 2 element array with Subsystem Co-design with Push Excitation in Designer – – – – –
This example is intended to demonstrate the procedures to build the bi-directional co-design with a simple antenna array and feed network First, the Quasi-Yagi antenna array is solved in HFSS Then, the solved array project is linked into Designer/Nexxim as a component, and subsystem components are added Run Linear Network Analysis in Designer/Nexxim Amplifiers’ effect (amplitude and phase) on antenna pattern is demonstrated via push excitation
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Introduction Ansoft – Antenna/RF Training Guide
Getting Started
Training Manual
• Launching Ansoft HFSS –
To access Ansoft HFSS, click the Microsoft Start button, select Programs, and select the Ansoft, HFSS 12 program group. Click HFSS 12.
• Setting Tool Options – Note: In order to follow the steps outlined in this example, verify that the following tool options are set : – Select the menu item Tools > Options > HFSS Options • Click the General tab – Use Wizards for data input when creating new boundaries: Checked – Duplicate boundaries with geometry: Checked • Click the OK button – Select the menu item Tools > Options > Modeler Options. • Click the Operation tab – Automatically cover closed polylines: Checked – Select last command on object select: Checked • Click the Drawing tab – Edit property of new primitives: Checked • Click the OK button
• Opening a Project –
Select the menu item File > Open • Select the project: Quasi-Yagi.hfss • Click the Open button
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Introduction Ansoft – Antenna/RF Training Guide
HFSS Project Setup
Training Manual
• Antenna Setup – – –
The Quasi-Yagi HFSS project consists of 2 antenna elements Each element is driven with a lumped port excitations Check ports setup: • Under project tree, right click P1 under Excitations, and click Zoom to • Under project tree, right click P2 under Excitations, and click Zoom to
• Check pre-solved Antenna Project Solutions –
Double click Principal Cutplanes under Results
Port 2 Port 1
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Introduction Ansoft – Antenna/RF Training Guide
Designer Project setup
Training Manual
• Ansoft Designer/Nexxim and HFSS Linkage – We will now link the Quasi-Yagi antenna elment that has been solved in HFSS with Ansoft Designer using a Dynamic Link
• Launch Ansoft Designer/Nexxim 1
– Double click on the Designer 5 icon on the Windows Desktop
• Create HFSS Dynamic Link Component – To add a Nexxim Circuit design to the project: • Select the menu Project > Insert Nexxim Circuit Design. – In the Choose Layout Technology dialog box, click None – Menu: Project > Add Model > Add HFSS Model... • Name: QuasiYagiArray_HFSS • File name: \Quasi-Yagi.hfss • Select Link Discription tab • Select Design name: array – Click OK tab
3 4
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Introduction Ansoft – Antenna/RF Training Guide Training Manual
• Components Placement in Designer/Nexxim –
–
–
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Placing HFSS Dynamic Link Component • Highlight Model under Models and drag into schematic window • Choose Implied reference to ground Placing Additional Components • Select the Components tab in the Project Manager Window – Place the Component GAIN_NX: Ideal Gain/Loss Model twice as seen in the schematic shown below – Place the Component PWCMB2_NX: Power Combiner/Divider, 02-Way as seen in the schematic shown below Adding the port • Select the menu item Draw > Interface Port • Left-click to place the ports at input and output as shown. Place the first port (“Port1”) at the input. • Hit the key or space bar to finish placing ports Adding Wiring to connect components • As you place the cursor near a pin of a component, it changes from an arrow to an X. Click to begin drawing wire, click again to connect end point.
GAIN_NX PWCMB2_NX HFSS Dynamic Link Component ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Introduction Ansoft – Antenna/RF Training Guide Training Manual
• Analysis Setup in Designer/Nexxim –
To create an analysis setup: • In the menu item, click Nexxim Circuit> Add Solution Setup> Linear Network Analysis • In the Linear Network Analysis, Frequency Domain window – Accept the defaults for Analysis Name – Highlight F in the Sweep Variables – Click Edit – In the Linear Network Analysis, Frequency Domain window • Click Add button • In the Add/Edit Sweep window • Variable type: F • Select Single Value • Value: 8 GHz • Click ADD >> button • Click the OK button – Click OK button.
1
2
3
4 ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Introduction Ansoft – Antenna/RF Training Guide Training Manual
• Edit Port Excitation in Designer –
–
Double Click on Port1 in the Designer schematic to edit the Port Definition • Select Edit Sources – Add new source by selecting Add to selected port – Edit ACMAG equal to 1V – Click OK button • Click OK when prompted to select analysis and OK on Configure ports and sources Click OK to close port definitions window
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• Save Project –
Select the menu item File > Save As • Filename: push_ex_Nexxim_HFSS_training • Click the Save button
• Solve Project – Select the menu item Nexxim Circuit > Analyze
• Push Excitations – Right click the Field Solver component, click Push Excitations... – Click OK button in Push Excitation Information window – Pattern and field plots will automatically be updated in HFSS
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Introduction Ansoft – Antenna/RF Training Guide Training Manual
• Push Excitations – –
To view updated reports after push excitations, switch to view the HFSS Desktop and open any far field report View updated sources in HFSS through the menu HFSS > Fields > Edit Sources • Notice the Scaling Factor and Offset Phase have been updated to reflect the magnitude and phase determined through the circuit simulation in Ansoft Designer • For this first case, the circuit components are providing ideal performance and equal gain between both antenna elements. In the next case we will vary these circuit components and observing the resulting change in field patterns.
Total Gain ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
Edit sources window in HFSS 1-11 3.1-11
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Introduction Ansoft – Antenna/RF Training Guide Training Manual
• Push Excitations – –
– –
Switch the view back to the Designer user interface Modify the gain and phase shift associated with each amplifier by double clicking on the amplifier component • Modify the Gain and Input to Output phase delay of each amplifier – Amplifier 1 • Gain = 2, PG = 180 – Amplifier 2 • Gain 1.8, PG = 0 Solve Project • Select the menu item Nexxim Circuit > Analyze Push Excitations • Right click the Field Solver component, click Push Excitations... • Click OK button in Push Excitation Information window • Pattern and field plots will automatically be updated in HFSS • To view updated reports after push excitations, switch to view the HFSS Desktop and open any far field report
Gain = 2 PG = 180
Gain = 1.8 PG = 0 ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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Introduction Ansoft – Antenna/RF Training Guide Training Manual
• Push Excitations –
View updated sources in HFSS through the menu HFSS > Fields > Edit Sources • Notice the Scaling Factor and Offset Phase have been updated to reflect the magnitude and phase determined through the circuit simulation in Ansoft Designer • Notice the offset phase and magnitudes are no longer equal as we have modified the phase and amplitudes from within the circuit simulation in Ansoft Designer
Total Gain Gain and Phase are equal between antenna elements
•Amplifier 1 •Gain = 0, PG = 0 •Amplifier 2 •Gain 0, PG = 0 ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
Total Gain After push excitations with unequal gain and phase between antenna elements
•Amplifier 1 •Gain = 2, PG = 180 •Amplifier 2 •Gain 1.8, PG = 0
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Ansoft – Antenna/RF Training Guide
Workshop 4.1 – HFSS Example: RCS of a Cube
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Introduction Ansoft – Antenna/RF Training Guide
Example – RCS of a Cube
Training Manual
• Radar Cross Section of a PEC Cube – –
This example is intended to show you how to create, simulate, and analyze the RCS of a PEC Cube, using the Ansoft HFSS Design Environment. This example was taken from the publication, “Electromagnetic Code Consortium Benchmarks,” compiled by Andrew Greenwood and published by the Air Force Research Laboratory.
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Introduction Ansoft – Antenna/RF Training Guide
Example – RCS of a Cube
Training Manual
• Background on RCS and PEC Cube problem – –
–
–
As mentioned previously, this problem was taken from a paper illustrating some simple radar targets that can be used to “calibrate” electromagnetic simulators. The paper used several different university codes for the different targets. In the lecture notes on scattering problems, you were introduced to two different methods of solving for the scattered field off of an object, the Total Field formulation and the Scattered field formulation. • The Total Field formulation is recommended for targets which have an infinite or pseudo-infinite ground plane, where the target would need to touch the PML. • The Scattered field formulation is recommend for targets that do not touch the PMLs, and are thus, finite in size. The PEC Cube will use the scattered field formulation. Also mentioned in the lecture notes are the two measurements of RCS, Monostatic and Bistatic. The measurements from the paper which we will simulate in HFSS are shown below in the graphs, and represents Monostatic RCS.
From this graph, we can obtain some settings for the HFSS simulation: • Adaptive Frequency: 0.43 GHz – Single frequency / no sweep • Azimuth (f) swept with a fixed Elevation – q = 90° – f = 0° to 90° – since the structure is symmetric about the axis, we won’t simulate the remaining quadrants • VV-polarized – Excite the vertical polarization (q) and observe the vertical polarization (q) – Ephi = 0 / Etheta = 1 – Observe MonostaticRCSTheta
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Introduction Ansoft – Antenna/RF Training Guide
Getting Started
Training Manual
• Launching Ansoft HFSS –
To access Ansoft HFSS, click the Microsoft Start button, select Programs, and select the Ansoft, HFSS 12 program group. Click HFSS 12.
• Setting Tool Options – Note: In order to follow the steps outlined in this example, verify that the following tool options are set : – Select the menu item Tools > Options > HFSS Options • Click the General tab – Use Wizards for data input when creating new boundaries: Checked – Duplicate boundaries with geometry: Checked • Click the OK button – Select the menu item Tools > Options > Modeler Options. • Click the Operation tab – Automatically cover closed polylines: Checked – Select last command on object select: Checked • Click the Drawing tab – Edit property of new primitives: Checked • Click the OK button
• Opening a New Project – –
In HFSS Desktop, click the On the Standard toolbar, or select the menu item File > New. From the Project menu, select Insert HFSS Design.
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Introduction Ansoft – Antenna/RF Training Guide
Example – RCS of a Cube
Training Manual
• Set Solution Type –
Select the menu item HFSS > Solution Type • Choose Driven Modal • Click the OK button
• Set Model Units –
Select the menu item Modeler > Units • Select Units: meter • Click the OK button
• Set Default Material –
Using the 3D Modeler Materials toolbar, choose Select • Type pec in the Search by Name field • Click the OK button
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Introduction Ansoft – Antenna/RF Training Guide
Example – RCS of a Cube
Training Manual
• Creating the Cube –
–
–
Select the menu item Draw > Box • Using the coordinate entry fields, enter the box origin – X: -0.5, Y: -0.5, Z: -0.5, Press the Enter key • Using the coordinate entry fields, enter the size of the box: – dX: 1, dY: 1, dZ: 1, Press the Enter key Select the Attribute tab from the Properties window. • For the Value of Name type: cube • Click the OK button To fit the view: • Select the menu item View > Fit All > Active View. Or press CTRL+D
• Creating the base airbox for PMLs – – – – –
–
Using the 3D Modeler Materials toolbar, choose vacuum Select the menu item Draw > Box Using the coordinate entry fields, enter the box origin • X: -0.85, Y: -0.85, Z: -0.85, Press the Enter key Using the coordinate entry fields, enter the size of the box: • dX: 1.7, dY: 1.7, dZ: 1.7, Press the Enter key Select the Attribute tab from the Properties window. • For the Value of Name type: airbox • Click the OK button To fit the view: • Select the menu item View > Fit All > Active View. Or press the CTRL+D key
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Introduction Ansoft – Antenna/RF Training Guide
Example – RCS of a Cube
Training Manual
• Setup the PMLs – –
Switch to Face selection mode by selecting Edit > Select > Faces Select Edit > Select > By Name to bring up a dialog that will enable you to just select faces of an object. • Select airbox from the Object name list, and select all the faces from the Face ID list • Click OK button
• Use the PML setup wizard to define the PML objects –
Select the menu item HFSS > Boundaries > PML Setup Wizard • Enter 0.35 meter for the Uniform Layer Thickness – This corresponds to l/2 at the frequency of operation for this model. This value is just a guideline, but you should always err on the side of thicker PMLs versus thinner ones. • Make sure the Radiating Only option is selected for the Base Face Radiation Properties • Click Next – Enter 0.43 GHz for the Min Frequency field in the specification for PML Objects Accept Free Radiation – Enter 0.35 meter for the Minimum Radiating Distance • Click Next • Click Finished
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Introduction Ansoft – Antenna/RF Training Guide
Example – RCS of a Cube
Training Manual
• Creating the airbox for Far Field integration faces –
– – – –
When simulating radiating problem, we have found it beneficial to use a different set of faces for the far field integration than those defined by default in HFSS. In order to accomplish this, we recommend creating an airbox that is slightly smaller than the one used for the base of the PMLs. A typical size would be to use one that is about 90% of the X, Y, and Z dimensions of the PML airbox. Select the menu item Draw > Box Using the coordinate entry fields, enter the box origin • X: -0.8, Y: -0.8, Z: -0.8, Press the Enter key Using the coordinate entry fields, enter the size of the box: • dX: 1.6, dY: 1.6 dZ: 1.6, Press the Enter key Select the Attribute tab from the Properties window. • For the Value of Name type: integration_box • Click the OK button
• Creating the facelist for Far Field integration –
–
Select the menu item Edit > Select > By Name to bring up a dialog that will enable you to just select faces of an object. • Select integration_box from the Object name list, and select all the faces from the Face ID list • Click the OK button Select the menu item Modeler > List > Create > Facelist • Facelist1 will be defined in the Lists section of the model tree
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Introduction Ansoft – Antenna/RF Training Guide
Example – RCS of a Cube
Training Manual
• Creating the Plane Wave Excitation –
–
Select the menu item HFSS > Excitations >Assign > Incident Wave > Plane Wave • Select Spherical as the Vector Input Format • Click Next – Enter the values for the incident plane wave angles: • IWavePhi – Start: 0 deg, Step: 1 deg, Stop: 90 deg • IWaveTheta – Start: 90 deg, Step: 0 deg, Stop: 90 deg • E0 vector – Phi: 0V/m, Theta: 1 V/m – Click Next • Click Finish The Incident Plane Wave excitation can be viewed by selecting the IncPWave1 in the Excitation section of the Project tree
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Introduction Ansoft – Antenna/RF Training Guide
Example – RCS of a Cube
Training Manual
• Creating an Analysis Setup –
Select the menu item HFSS > Analysis Setup > Add Solution Setup • Click the General tab: – Solution Frequency: 0.43 GHz – Maximum Number of Passes: 8 – Maximum Delta E per Pass: 0.01 • Click the Options tab: – Order of Basis Functions: Second Order – Change the Minimum Number of Passes to 4 • Click the OK button
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Introduction Ansoft – Antenna/RF Training Guide
Example – RCS of a Cube
Training Manual
• Create a Radiation Setup –
–
Select the menu item HFSS > Radiation > Insert Far Field Setup > Infinite Sphere • Infinite Sphere Tab – Name: Infinite Sphere1 – Phi: (Start: 0, Stop: 0, Step Size: 10) – Theta: (Start: 0, Stop: 0, Step Size: 10) • Click the Radiation Surface tab – Select Use Custom Radiation Surface – Verify that Facelist1 is chosen from the list • Click OK NOTE: Since we are going to be creating a plot of Monostatic RCS, HFSS takes the observation angle from the incident angle definition. The far field radiation sphere setup performs little else but to define the integration surface. It is actually easier in the plotting stage to only define one observation angle in the far field sphere setup.
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Introduction Ansoft – Antenna/RF Training Guide
Example – RCS of a Cube
Training Manual
• Save Project –
Select the menu item File > Save As. • Filename: hfss_rcs_cube • Click the Save button
• Model Validation – –
Select the menu item HFSS > Validation Check Click the Close button
• Analyze –
Select the menu item HFSS > Analyze All
• Solution Data –
Select the menu item HFSS > Results > Solution Data – To view the Profile, Click the Profile Tab. – To view the Convergence, Click the Convergence Tab • Note: The default view is for convergence is Table. Select the Plot radio button to view a graphical representations of the convergence data. – To view the Matrix Data, Click the Matrix Data Tab • Note: To view a real-time update of the Matrix Data, set the Simulation to Setup1, Last Adaptive – To view the Mesh Statistics, Click the Mesh Statistics Tab. • Click the Close button
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January 2010 February 23,31, 2009 Inventory #002846 Inventory #002593
Introduction Ansoft – Antenna/RF Training Guide
Example – RCS of a Cube
Training Manual
• Create RCS plot –
–
Select the menu item HFSS > Results > Create Far Fields Report > Rectangular Plot • Solution: Setup1: LastAdaptive • Geometry: Infinite Sphere1 • Category: MonostaticRCS • Quantity: MonostaticRCSTheta • Function: dB • Primary Sweep: IwavePhi • Click the New Report button Click the Close button
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Ansoft – Antenna/RF Training Guide
Workshop 5.1 – HFSS-IE Example: PEC Cubic Monostatic RCS
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February January 31, 23, 2010 2009 Inventory #002846 #002593
Introduction Ansoft – Antenna/RF Training Guide
HFSS-IE Example: PEC Cubic RCS
Training Manual
• Radar Cross Section of a PEC Cube – –
This example is intended to show you how to create, simulate, and analyze the RCS of a PEC Cube, using the Ansoft HFSS-IE Design Environment. This example was taken from the publication, “Electromagnetic Code Consortium Benchmarks,” compiled by Andrew Greenwood and published by the Air Force Research Laboratory.
ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
WS5.1-2 1-2
February January 31, 23, 2010 2009 Inventory #002846 #002593
Introduction Ansoft – Antenna/RF Training Guide Training Manual
• Background on RCS and PEC Cube problem – –
–
As mentioned previously, this problem was taken from a paper illustrating some simple radar targets that can be used to “calibrate” electromagnetic simulators. The paper used several different university codes for the different targets. Also mentioned in the lecture notes are the two measurements of RCS, Monostatic and Bistatic. The measurements from the paper which we will simulate in HFSS-IE are shown below in the graphs, and represents Monostatic RCS.
From this graph, we can obtain some settings for the HFSS-IE simulation: • Adaptive Frequency: 0.43 GHz – Single frequency / no sweep • Azimuth (f) swept with a fixed Elevation – q = 90° – f = 0° to 90° – since the structure is symmetric about the axis, we won’t simulate the remaining quadrants • VV-polarized – Excite the vertical polarization (q) and observe the vertical polarization (q) – Ephi = 0 / Etheta = 1 – Observe MonostaticRCSTheta
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Introduction Ansoft – Antenna/RF Training Guide Training Manual
• Ansoft HFSS-IE Design Environment –
The following features of the Ansoft HFSS-IE Design Environment will be used to create this passive device model • 3D Solid Modeling – Primitives: Boxes • Boundaries/Excitations – Ports: Incident Wave – Boundaries: Default Open Space • Analysis – Adaptive Solution Setup • Results – Far-Field Setup – Cartesian Plotting
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February January 31, 23, 2010 2009 Inventory #002846 #002593
Introduction Ansoft – Antenna/RF Training Guide
Getting Started
Training Manual
• Launching Ansoft HFSS –
To access Ansoft HFSS, click the Microsoft Start button, select Programs, and select the Ansoft, HFSS 12 program group. Click HFSS 12.
• Setting Tool Options – Note: In order to follow the steps outlined in this example, verify that the following tool options are set : • Select the menu item Tools > Options > HFSS-IE Options – Click the General tab • Use Wizards for data input when creating new boundaries: Checked • Duplicate boundaries with geometry: Checked – Click the OK button • Select the menu item Tools > Options > Modeler Options. – Click the Operation tab • Automatically cover closed polylines: Checked – Click the Drawing tab • Edit property of new primitives: Checked – Click the OK button
• Opening a New Project – –
In HFSS Desktop, click the On the Standard toolbar, or select the menu item File > New. From the Project menu, select Insert HFSS-IE Design.
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Introduction Ansoft – Antenna/RF Training Guide
Example – RCS of a Cube
Training Manual
• Set Model Units –
Select the menu item Modeler > Units • Select Units: meter • Click the OK button
• Set Default Material –
Using the 3D Modeler Materials toolbar, choose Select • Type pec in the Search by Name field • Click the OK button
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Introduction Ansoft – Antenna/RF Training Guide
Example – RCS of a Cube
Training Manual
• Creating the Cube –
–
–
Select the menu item Draw > Box • Using the coordinate entry fields, enter the box origin – X: -0.5, Y: -0.5, Z: -0.5, Press the Enter key • Using the coordinate entry fields, enter the size of the box: – dX: 1, dY: 1, dZ: 1, Press the Enter key Select the Attribute tab from the Properties window. • For the Value of Name type: cube • Click the OK button To fit the view: • Select the menu item View > Fit All > Active View. Or press CTRL+D
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Introduction Ansoft – Antenna/RF Training Guide Training Manual
• Creating the Plane Wave Excitation – –
– –
Select the menu item HFSS-IE > Excitations >Assign > Incident Wave > Plane Incident Wave • Vector Input Format: Spherical Click the Next button • IWavePhi – Start: 0 deg, Step: 1 deg, Stop: 90 deg • IWaveTheta – Start: 90 deg, Step: 0 deg, Stop: 90 deg • E0 vector – Phi: 0V/m, Theta: 1 V/m Click the Next button Click the Finish button
• Viewing the Plane Wave Excitation –
The Incident Plane Wave excitation can be viewed by selecting the IncPWave1 in the Excitation section of the Project tree
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Introduction Ansoft – Antenna/RF Training Guide
Analysis Setup
Training Manual
• Analysis Setup –
Select the menu item HFSS-IE > Analysis Setup > Add Solution Setup • Click the General tab: – Solution Frequency: 0.43 GHz – Maximum Number of Passes: 8 – Maximum Delta E per Pass: 0.01 • Click the OK button
• Create a Radiation Setup –
Select the menu item HFSS-IE > Radiation > Insert Far Field Setup > Infinite Sphere • Infinite Sphere Tab – Name: Infinite Sphere1 – Phi: (Start: 0, Stop: 0, Step Size: 10) – Theta: (Start: 0, Stop: 0, Step Size: 10) • Click the OK button • NOTE: Since we are going to be creating a plot of Monostatic RCS, HFSS-IE takes the observation angle from the incident angle definition. It is actually easier in the plotting stage to only define one observation angle in the far field sphere setup.
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Introduction Ansoft – Antenna/RF Training Guide
Example – RCS of a Cube
Training Manual
• Save Project –
Select the menu item File > Save As. • Filename: hfssie_rcs_cube • Click the Save button
• Model Validation –
Select the menu item HFSS-IE > Validation Check • Click the Close button – Note: To view any errors or warning messages, use the Message Manager.
• Analyze –
Select the menu item HFSS-IE > Analyze All
• Solution Data –
Select the menu item HFSS-IE > Results > Solution Data – To view the Profile, Click the Profile Tab. – To view the Convergence, Click the Convergence Tab • Note: The default view is for convergence is Table. Select the Plot radio button to view a graphical representations of the convergence data. – To view the Matrix Data, Click the Matrix Data Tab • Note: To view a real-time update of the Matrix Data, set the Simulation to Setup1, Last Adaptive – To view the Mesh Statistics, Click the Mesh Statistics Tab. • Click the Close button
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Introduction Ansoft – Antenna/RF Training Guide
Results
Training Manual
• Create RCS plot –
–
Select the menu item HFSS-IE > Results > Create Far Fields Report > Rectangular Plot • Solution: Setup1: LastAdaptive • Geometry: Infinite Sphere1 • Primary Sweep: IWavePhi • Category: MonostaticRCS • Quantity: MonostaticRCSTheta • Function: dB • Click the New Report button Click the Close button
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Ansoft – Antenna/RF Training Guide
Workshop 5.2 – HFSS-IE Example: HFSS to HFSS-IE Datalink
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5.2-1 1-1
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Introduction Ansoft – Antenna/RF Training Guide
Example – Horn-Fed Reflector Antenna
Training Manual
• EMI from Slot at Enclosure Cavity –
–
This example is intended to show you efficiently how to create, simulate, and analyze horn-fed reflector antenna system, using the Ansoft HFSS and HFSS-IE Design Environment. • Step I: HFSS Design of horn antenna; • Step2: HFSS-IE design of reflector and horn, with excitation linking to HFSS design in step I. Enhanced datalink from HFSS (Horn) to HFSS-IE (Reflector) takes into account of aperture blockage due to the feed (horn) in the reflector antenna system.
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Introduction Ansoft – Antenna/RF Training Guide
HFSS: Getting Started
Training Manual
• Launching Ansoft HFSS –
To access Ansoft HFSS, click the Microsoft Start button, select Programs, and select the Ansoft, HFSS 12 program group. Click HFSS 12.
• Setting Tool Options – Note: In order to follow the steps outlined in this example, verify that the following tool options are set : – Select the menu item Tools > Options > HFSS Options • Click the General tab – Use Wizards for data input when creating new boundaries: Checked – Duplicate boundaries/mesh operations with geometry: Checked • Click the OK button – Select the menu item Tools > Options > Modeler Options. • Click the Operation tab – Automatically cover closed polylines: Checked – Select last command on object select: Checked • Click the Drawing tab – Edit property of new primitives: Checked • Click the OK button
• Opening a New Project – –
In HFSS Desktop, click the On the Standard toolbar, or select the menu item File > New. From the Project menu, select Insert HFSS Design.
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Introduction Ansoft – Antenna/RF Training Guide
HFSS: Creating the Design
Training Manual
• Set Solution Type –
Select the menu item HFSS > Solution Type • Choose Driven Modal • Click the OK button
• Set Model Units –
Select the menu item Modeler > Units • Select Units: in • Click the OK button
• Set Default Material –
Using the 3D Modeler Materials toolbar, make sure that vacuum is the default material
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Introduction Ansoft – Antenna/RF Training Guide
HFSS: Creating the Design
Training Manual
• Creating the Feed – – – –
–
Select the menu item Draw > Box Using the coordinate entry fields, enter the box origin • X: 5.16, Y: -0.45, Z: -0.2, Press the Enter key Using the coordinate entry fields, enter the size of the box: • dX: 0.315, dY: 0.9, dZ: 0.4, Press the Enter key Select the Attribute tab from the Properties window. • For the Value of Name type: Horn • Click the OK button To fit the view: • Select the menu item View > Fit All > Active View. Or press the CTRL+D key
• Creating the Horn – – – – –
Select the menu item Modeler > Grid Plane > YZ Select the menu item Draw > Rectangle Using the coordinate entry fields, enter the box origin • X: 5.16, Y: -0.45, Z: -0.2, Press the Enter key Using the coordinate entry fields, enter the size of the box: • dX: 0.0, dY: 0.9, dZ: 0.4, Press the Enter key Click the OK button
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February January 31, 23, 2010 2009 Inventory #002846 #002593
Introduction Ansoft – Antenna/RF Training Guide
HFSS:
Training Manual
• Creating the Horn – – – – –
–
Select the menu item Draw > Rectangle Using the coordinate entry fields, enter the box origin • X: 0.0, Y: -1.325, Z: -0.972, Press the Enter key Using the coordinate entry fields, enter the size of the box: • dX: 0.0, dY: 2.65, dZ: 1.944, Press the Enter key Click the OK button Select the menu item Edit > Select > By Name • Select the objects: Rectangle1, Rectangle2 • Click the OK button Select menu item Modeler > Surface > Connect
• Complete the Horn – – –
Select the menu item Edit > Deselect All Select the menu item Edit > Select All Select the menu item Modeler > Boolean > Unite
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Introduction Ansoft – Antenna/RF Training Guide
HFSS:
Training Manual
• Assign a Metal Boundary for the Horn – –
–
Select menu item Edit > Select > Faces Select menu item Edit > Select > By Name • Object name: Horn • Multiple select the faces that make the shell of the horn – Note: Exclude the faces parallel to the YZ plane • Click the OK button Select menu item HFSS >Boundaries >Assign > Perfect E • Click the OK button
• Creating the Airbox Select the menu item Draw > Box Using the coordinate entry fields, enter the box origin • X: 5.475, Y: -2.0, Z: -1.5, Press the Enter key – Using the coordinate entry fields, enter the size of the box: • dX: -6.0, dY: 4.0, dZ: 3.0, Press the Enter key – Select the Attribute tab from the Properties window. • For the Value of Name type: Air_box • Click the OK button – To fit the view: • Select the menu item View > Fit All > Active View. Or press the CTRL+D key – –
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February January 31, 23, 2010 2009 Inventory #002846 #002593
Introduction Ansoft – Antenna/RF Training Guide
HFSS:
Training Manual
• Create Wave Port Excitation – –
–
Select the menu item Edit > Select > Faces Select the menu item Edit > Select > By Name • Object Name: Horn • Select the Face ID that corresponds to the Port – Note: The face is in the +YZ plane – Click the OK button Select the menu item HFSS > Excitations > Assign > Wave Port • Name: 1 • Click the Next button • Click the Next tab • Click the Finish button
• Create Radiation Boundary – –
–
Select the menu item Edit > Select > Objects Select the menu item Edit > Select > By Name • Object Name: Air_box • Click the OK button Select the menu item HFSS > Boundaries > Assign > Radiation… • Click the OK button
ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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February January 31, 23, 2010 2009 Inventory #002846 #002593
Introduction Ansoft – Antenna/RF Training Guide
HFSS: Analysis Setup
Training Manual
• Creating an Analysis Setup –
Select the menu item HFSS> Analysis Setup > Add Solution Setup • Click the General tab: – Solution Frequency: 8 GHz – Maximum Number of Passes: 8 – Maximum Delta S per Pass: 0.02 • Click the Options tab – Order of Basis Functions: Mixed Order • Click the OK button
• Save Project –
Select the menu item File > Save As • Filename: Datalink_example • Click the Save button
• Source Design Analyze –
Select the menu item HFSS > Analyze All
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February January 31, 23, 2010 2009 Inventory #002846 #002593
Introduction Ansoft – Antenna/RF Training Guide
HFSS-IE: Getting Started
Training Manual
• Setting Tool Options –
Note: In order to follow the steps outlined in this example, verify that the following tool options are set : • Select the menu item Tools > Options > HFSS-IE Options – Click the General tab • Use Wizards for data input when creating new boundaries: Checked • Duplicate boundaries/mesh operations with geometry: Checked – Click the OK button • Select the menu item Tools > Options > Modeler Options. – Click the Operation tab • Automatically cover closed polylines: Checked – Click the Drawing tab • Edit property of new primitives: Checked – Click the OK button
• Opening a New Project –
Select the menu item Project > Insert HFSS-IE Design
• Set Model Units –
Select the menu item Modeler > Units • Select Units: in • Click the OK button
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February January 31, 23, 2010 2009 Inventory #002846 #002593
Introduction Ansoft – Antenna/RF Training Guide
HFSS-IE: Creating the 3D Model
Training Manual
• Create Reflector –
– –
Select the menu item Draw > Equation Based Curve • X(_t): (26.625-_t*_t/106.5)*(-1cm) • Y(_t): (_t)*(1cm) • Z(_t): 0 • Start_t: 0 • End_t: 53.25 • Number of Points: 18 • Click the OK button Select the menu item Edit > Select All Select the menu item Draw > Sweep Around Axis • Sweep axis: X • Angle of sweep: 360 deg • Draft angle: 0 • Draft type: Round • Number of segments: 36 • Click the OK button
• Assign PEC – –
Select the menu item Edit > Select All Select the menu item HFSS-IE > Boundaries > Assign > Perfect E • Click the OK button
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Introduction Ansoft – Antenna/RF Training Guide
HFSS-IE: Defining the Linked Excitation
Training Manual
• Create Linked Excitation –
Select the menu item HFSS-IE > Excitations > Assign > Incident Wave > Near Field Wave • Select the Near Field Wave Options tab • Click the Setup Link button – Product: HFSS – Source Project: Use This Project – Source Design: HFSSDesign1 – Source Solution: Setup1: LastAdaptive – Click the OK button • Click the Finish button
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February January 31, 23, 2010 2009 Inventory #002846 #002593
Introduction Ansoft – Antenna/RF Training Guide
HFSS-IE: Analysis Setup
Training Manual
• Creating an Analysis Setup –
Select the menu item HFSS-IE > Analysis Setup > Add Solution Setup • Click the General tab: – Solution Frequency: 8GHz – Maximum Number of Passes: 10 – Maximum Delta E per Pass: 0.01 • Click the OK button
• Create a Radiation Setup –
Select the menu item HFSS-IE > Radiation > Insert Far Field Setup > Infinite Sphere • Infinite Sphere Tab – Name: 3D Pattern – Phi: (Start: 0, Stop: 360, Step Size: 2) – Theta: (Start: 0, Stop: 180, Step Size: 1) • Click the OK button
• Save Project –
Click the menu item File > Save
• Reflector Design Analyze –
Select the menu item HFSS-IE > Analyze All
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HFSS-IE: Results
Training Manual
• Create Current Plot – –
Select the menu item Edit > Select All Select the menu item HFSS-IE > Fields> Fields > J >Mag_J • Solution: Setup1: LastAdaptive • Frequency: 8GHz • Phase: 0deg • Quantity: Mag_J • Click the Done button
• Create 3D Far Field Pattern –
–
Select the menu item HFSS-IE > Results > Create Far Fields Report > 3D Polar Plot • Solution: Setup1: Sweep1 • Geometry: 3D Pattern • Primary Sweep: Phi • Secondary Sweep: Theta • Category: Directivity • Quantity: DirTotal • Function: dB • Click the New Report button Click the Close button
ANSYS, Inc. Proprietary © 2010 2009 ANSYS, Inc. All rights reserved.
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February January 31, 23, 2010 2009 Inventory #002846 #002593
