CST Training Core Module

Welcome to CST !

CST STUDIO SUITE™ Training Class

Core Module

1

About CST  Founded in 1992  170 employees  World-wide distribution network  Focus on 3D EM simulation

3

CST Worldwide

CST West Coast

4

CST of America

CST Europe

CST China

CST of Korea

AET Japan

CST Products

CST MICROWAVE

Common Easy-To-Use Preand Post-processing Engine

STUDIO®

CST CABLE STUDIO™ CST PCB STUDIO™

Our Flagship Product for RF Simulations

CST MICROSTRIPES™

RF Simulations for Special Applications

CST STUDIO SUITE™

CST DESIGN STUDIO™ Circuit Simulator Allows Coupling of 3D Models

CST PARTICLE STUDIO® Interaction of EM Fields with Free Moving Charges 5

CST MPHYSICS STUDIO™ Thermal and Mechanical Effects of EM Fields

CST EM STUDIO® Simulations of Static or Low-Frequency Fields

Built-In Help Mechanisms

6

Documentation \Documentation\

The introductory books are a good starting point to learn the workflow of the CST STUDIO SUITE™ products.

All books are available as pdf documents in the "Documentation" subfolder of your CST installation.

7

Tutorials Step-by-Step tutorials are available for CST MICROWAVE STUDIO® and CST EM STUDIO®.

8

Examples Overview Many pre-calculated examples are available.

Antenna Calculation Examples 9

Online Help (I)

10

Online Help (II) - Links to Online Help -

 In almost all dialogs there is a link to the online help documents which provides you with extensive help for all settings.

Linked page of the online help

Transient solver main dialog 11

CST Webpage

www.cst.com 12

CST Support Site Tutorial Videos

FAQ Section

13

CST User Forum

Ask your questions. Answers are provided by other users or CST engineers. 14

CST Customer Support

CST Malaysia Phone: +60 (3) 7731 5595 Fax: +60 (3) 7722 5595 Email: [email protected] Support available from 9am – 5pm

15

CST Training Courses  The training courses for CST STUDIO SUITE™ provide you with the knowledge needed for an efficient start with the software.  Currently the following trainings are offered on a regular basis. All upcoming courses are announced on the CST webpage. CST STUDIO SUITE™ MW & Antenna Training 2 full days

CST PARTICLE STUDIO® Charged Particle Dynamics Training 1 full day

EMC / SI / PI Training

2 full days Performance Training 1 full day

16

CST EM STUDIO® LF Applications Training 1 full day

CST MICROSTRIPES™ CST MICROSTRIPES™ Training 1-2 full day(s) CST CABLE STUDIO™ CST PCB STUDIO™ Training on Demand

Basic and Advanced Modeling

19

Common User Interface Menu Bar Tool Bars

Primary Window

Navigation Tree

Message Parameter List 20

Window

Customize Your Environment E.g., define a shortcut key to call your favorite macro.

21

View Options  “Rectangle zoom”

allows to zoom in a rectangular domain.

 Change the view by dragging the mouse while pressing the left button and a key.

 ctrl - rotation  shift - in-plane rotation  ctrl+shift - panning

 Some other useful options are:  spacebar - reset view to structure,  ctrl+f - reset view,

 shift+spacebar - zoom into selected shape,  mouse wheel - dynamic zoom to mouse pointer.

22

Primitives Cylinder

Torus

Cone

Sphere

Rotation

Brick

Elliptical

Hints:

Cylinder

 Press the tab-key to enter a point numerically.  Press backspace to delete a previously picked point.

Extrusion 23

Picks Pick a point, an edge, or a face in the structure.

Hints: Picked Edge

Picked Point

Pick circle center (c) Pick corner

 Press "s" to activate all pick tools.

Picked Face

 To pick a point by given coordinates, press “p” and the tab-key.  2nd time picking an element unselects it.

Pick face

Pick face (f)

center (a)

Clear picked elements (d)

point (p) Pick edge center (m) Pick point 24

on circle (r)

Edge from coordinates Pick edge (e)

Working Coordinate System  The working coordinate system (WCS) allows the use of context dependent coordinates.  Use

to switch on/off the WCS.

 Use

to rotate the WCS.

 Use

to move the WCS.

25

Working Coordinate System  The WCS can be aligned, e.g., with a point, an edge, or a face. Align the WCS with a point

Align the WCS with an edge

Align the WCS with a face

Press “w” to align the WCS with the currently selected object. 26

Working Coordinate System  The position of a WCS can be stored for later use.

27

Boolean Operations  Boolean operations can be applied to two or more shapes to create more complex structures. Sphere

Brick

Intersect Brick * Sphere 28

Add

Subtract

Brick + Sphere

Brick - Sphere

Boolean insert Sphere / Brick

Brick / Sphere

Curve Modeling Tools – Overview (I)  Curves can be used for  structure generation,  thin wire generation,  integration path in post-processing,  healing CAD data.

Basic Curves Generation Create new curve 29

Curve Modeling Tools – Overview (II)  Solids can be created from curves. Creation of a Sheet from a Planar Curve

Extrusion of a Planar Curve

Sweep Curve

30

Curve Modeling Tools – Overview (III)  Solids can be created from curves.

Creation of a Trace

Creation of Loft from two Curves

31

Rotation of Profile Rotation Axis

Draw the profile. Press backspace to delete the last selected point.

32

Specify rotation angle, material properties, etc. Double click on any corner point to change its position.

Analytical Modeling (I)  3D curves and faces can be created using analytical expressions.

Enter parameterization 33

Analytical Modeling (II)  3D curves and faces can be created using analytical expressions.

34

Loft Operation  Two picked faces can be used to create a new shape by a loft operation.

Pick two faces.

Choose the properties of the loft operation.

Preview

35

Bending  It is possible to bend a sheet on a solid object. Example: Creation of a Helix Sheet

Solid The solid and the sheet must touch each other.

36

Blend and Chamfer Edges

Specify angle and width.

Select edges.

Specify radius.

37

Shell Operation  A solid object can be shelled. Example: A waveguide bend consisting of three shapes is shelled. solid2

solid3 solid1

Create a single shape by a Boolean add.

Picked faces will be open after the operation. 38

Transform Operation  Existing objects can be translated, rotated, mirrored, and scaled.

Translate

Scale

Rotate

 Use the mouse to translate, rotate, or scale objects interactively.  Perform several transformations to the same shape using the “Apply” button.  Selecting more than one solid will turn the shape center into the common center.

39

Local Modifications – Face Modifications

Offset Face: Interactively move the face of a solid in its normal direction.

Move Face: Interactively move the face of a solid in a coordinate direction.

Local Modifications are especially helpful when you are working with an imported CAD model for which the model history is not available. The "Local Modification" tools help you to modify such geometries. 40

Local Modifications – Remove Feature

Feature to be removed

Remove the feature 41

Pick the feature

View Options  Several options are available to gain better insight into the structure.

Cutting Plane

Wireframe Mode

42

View Options  Several options are available to gain better insight into the structure.

Working Plane

Coordinate Axes

43

Copy / Paste Structure Parts  Ctrl+C stores the selected solids on the active working coordinate system (WCS) to the clipboard. Ctrl+V pastes the clipboard into the active working coordinate system.  Copy and paste of structure parts works even between different CST projects.

Paste the objects in the new WCS.

Press ctrl+c to copy objects to clipboard.

Move the WCS. 44

Align Objects  Copied or imported objects can be aligned with the current model.

Select shape and choose “Align…”

Select faces to align with.

Choose angle.

Final Result

 For copied and imported objects, the alignment is started automatically.  For shapes selected in the “Navigation Tree” start by choosing “Align…” from the “Objects” menu.

45

Interactive CAD Modeling Using the Mouse

1. Adjust the “Snap width” according to the raster of your structure. 2. Use the pick tools, whenever geometrical information is already available. • Pick points to define new shapes / height of extrusion / transform. • Pick edges for rotation axis / to adjust WCS. • Pick face for extrude / rotate / transform / to adjust WCS. 3. Use the local working coordinate system (WCS). 4. Use the keyboard only for new (independent) geometric information (e.g. points which cannot be picked and do not fit into the snapping raster). Relative construction via picks and WCS avoids redundant information. Parameters/Values are entered once and are later referenced via picks. 46

Solver Overview Which solver is best suited to my application?

49

Which Solver is the “Best”?  Unique answer to this question is not easily possible as the performance and accuracy depend on many parameters: • Electrical size and geometry of the problem, • Material models and material parameters used, • Resonant behavior of the model, • Type of the mesh and the boundary conditions, • Architecture of the workstation used for the simulation, • etc. BUT: Some helpful rules of thumb are available. The application engineers of CST are available to discuss the solver choice and the model setup. 50

Transient Simulation - Behind the Scenes Output Time Signal

Excitation Time Signal

Numerical time integration of 3D Maxwell equations

Port 1

Port 2

The simulation duration depends on: 1. Duration of input signal (determined by frequency range selected)

2. Duration of output signal (determined mainly by the size and the resonances of the model under study) 3. Time step width for numerical time integration (determined by the mesh used to discretize your model) 51

Frequency Domain Simulation – Behind the Scenes  The steady state behavior of a model is calculated at different frequency points.

For each frequency point a linear equation system has to be solved.

 The intermediate points in broadband results are calculated by an interpolation. 52

Time Domain + Frequency Domain in out

in out Time Domain

Frequency Domain Calculation

in

in

out

out

TDR 53

Frequency Domain

S-parameter

S-parameter

Solver Choice (I) - Overview General Purpose Solver (3D-Volume) Solver Transient

Frequency Domain

Area of Application (Rule of Thumb)  Electrically medium and large sized problems  Broadband  Arbitrary time signals  Narrow band / Single frequency  Electrically small to medium sized problems  Periodic structures with Floquet port modes

Special Solver (3D-Volume): Closed Resonant Structures Eigenmode FD Resonant

 Strongly resonant structures, narrow band (e.g. cavities)  Strongly resonant, non radiating structures (e.g. filters)

Special Solver (3D-Surface): Large Open Metallic Structures

54

Integral Equation (based on MLFMM)

 Electrically large structures  Dominated by metal

Asymptotic Solver

 RCS calculations for electrically very large objects

Solver Choice (II) - Resonances The following rules of thumb apply: Weak Resonances

Strong Resonances

General Purpose +AR-Filter for S-parameter calculation only

Resonant Fast

F-solver is better suited to strongly resonant applications than T-solver. 55

Solver Choice (III) - Electrical Size The following rules of thumb apply:

Structure under study

Electrically Small

Electrically Large

With MPI also very large problems can be solved.

RCS calculations for electrically very large structures

For electrically very small structures the quasistatic solvers provided in CST EM STUDIO® might be a good choice. 56

Solver Choice (IV) - Bandwidth The following rules of thumb apply: Narrowband

Broadband

F-solver and I-solver are better suited to narrowband applications, while the T-solver is better suited to broadband applications. 57

Specialized Products  In addition to the general purpose solvers of CST MICROWAVE STUDIO® CST offers solvers specialized to certain classes of applications.

CST PCB STUDIO™ Specialized solvers for the simulation of PCB boards. CST CABLE STUDIO™

CST MICROSTRIPES™ Efficient solvers based on the Transmission Line Matrix (TLM) method. Contains special algorithms for EMC analysis. 58

Specialized solvers for the simulation of complete cable harnesses for all kind of EMC investigations.

Optional Workflow Example Patch Antenna Array

Purpose 1: Design a single patch using a parameter sweep & optimization.

Purpose 2: Create a dual patch array using  a farfield array combination  3D array creation

 a beam-forming feeding network 60

Single Patch

61

Single Patch Design  Frequency range: 3 – 8 GHz  Port size:

 ±2*width in y-direction

Copper Substrate (Rogers RT 5880)

 ±5*height in z-direction

40mm

20mm

0.5mm

0.035mm

h = 0.787mm

7.5mm 20mm w = 2.38mm 40mm Copper groundplane, thickness = 0.035 mm 62

Construction (i) Choose template:

63

Load materials:

Construction (ii) Construct the substrate:

Load substrate material

64

Construction (iii) Construct the patch:

65

Construction (iv)

Align WCS with picked point Select edge centre

66

Construction (v) Construct the feed line… Press Shift-Tab

67

Select edge centre

Construction (vi) Pick point

Align WCS with picked point

68

Construction (vii) Construct the feed gaps…

69

Construction (viii) Pick two points to form a translation vector Select solid1 by doubleclicking it

70

Construction (ix) Transform solid1 to make a copy

71

Construction (x) Select component patch

Select component solid1

Hit ENTER to substract solid1 from patch

72

Construction (xi) Pick bottom face of substrate

Extrude face to make ground plane

73

Construct Port Pick face of feed line

74

Construct Port Construct waveguide port

75

Simulation Settings Set freq. range

76

Exploit symmetry plane

Simulation Define monitors (E-, H-, Farfield @ 5.25 GHz) Start transient solver

77

Visualize Results Farfield result

E-field result 78

Parameter Sweep

79

Parameter Sweep Results: S11

80

Optimization of Single Patch Optimizer Parameters

Optimizer Goal

81

Optimizer Results (iii)

83

Farfield Efficiency

Before optimization: 84

Patch Array

85

Combine Farfields (1)

86

Phaseshift = -45° (1R)

87

Phaseshift = 135° (2L)

88

Combine Farfields (2) Transform component1 to make a copy

Combine ground and substrate components

89

Combine Farfields (2) Construct second port and run transient simulation without symmetry.

90

Combine Farfields (2)

1

91

2

Farfield Results (L)

92

Farfield Results (R)

93

Feeding Network Design (DS) lg/4

lg/4 Z0

Z0/sqrt(2)

94

DS – MWS co-simulation

3D MWS model fed with DS circuit network

95

Definition of Ports

98

Available Port Types Ports for S-Parameter Computation

Discrete Ports

Waveguide Ports

(Lumped Element)

(2D Eigenmode Solver)

Input: Knowledge of TEM Mode and line impedance is required. Output: Voltage and current

Input: Area for eigenmode solution Output: Pattern of E- and H-field, line impedance, Propagation constant

Discrete ports can be used for TEM-like modes, not for higher order modes (cutoff frequency > 0). 99

Waveguide ports provide a better match to the mode pattern as well as higher accuracy for the S-parameters.

Discrete Ports S-Parameter Port

Current Port

Voltage Port

Voltage or current source with internal resistance

Coaxial

100

Microstrip

Stripline

Coplanar waveguide

Discrete Edge Port Definition

Pick two points,

or

pick one point and a face,

or enter coordinates directly (not recommended).

Select port type and impedance.

101

Discrete Face Port Definition

Pick two edges

Select port type and impedance.

102

or

one edge and a face.

Available Port Types Ports for S-Parameter Computation

Discrete Ports

Waveguide Ports

(Lumped Element)

(2D Eigenmode Solver)

Input: Knowledge of TEM Mode and line impedance is required. Output: Voltage and current

Input: Area for eigenmode solution Output: Pattern of E- and H-field, line impedance, propagation constant

Discrete ports can be used for TEM-like modes, not for higher order modes (cutoff frequency > 0). 103

Waveguide ports provide a better match to the mode pattern as well as higher accuracy for the S-parameters.

Port Definition (I) – Closed Structures Typically, waveguide ports are defined based on a geometric object. Use the pick tools to select a unique port plane.

The port size is equal to the smallest rectangular area which includes all picked objects.

104

Port Definition (II) – Open Structures

1. Pick three points. 2. Enter port menu 3. Adjust additional port space.

105

.

Port Definition (III) - Backing  For the I-solver and the F-solver waveguide ports must be backed with a PEC solid (or by electric boundaries). Pick port using the pick tools.

Port backed with PEC solid.

106

Extrude the port plane.

Materials & Boundary Conditions

108

Basic Materials Define a new material or load materials from the large material database.

Material Types PEC = Perfect Electrical Conductor (

)

Normal: General material model. This is typically used for dielectric materials.

Anisotropic: Permittivity and permeability depend upon the spatial direction. Lossy Metal: Model for conductors with

Corrugated Wall: Surface impedance model.

Ohmic Sheet: Surface impedance model. 109

.

Material Database

Loaded materials are available for the creation of new shapes.

110

Lossy Metal  Why is it required?

 Sampling of skin depth would require very fine mesh steps at the metal surface when defining conductor as a normal material (skin depth for copper at 1 GHz approx. 2 m).

 This results in a very small time step, which leads to a very long simulation time.  Solution:  1D model which takes skin depth into account without spatial sampling.

111

Boundaries CST MWS uses a rectangular grid system, therefore, also the complete calculation domain is of rectangular shape  6 boundary surfaces have to be defined at the minimum and maximum position in each coordinate direction (xmin, xmax, ymin, ymax, zmin, zmax). Example: T-Splitter ymax

xmin zmin

zmax ymin xmax 112

Boundary Settings (I) Seven different settings are available.

113

Boundary Settings (II) Electric Boundaries (default setting): No tangential electric field at surface.

Magnetic Boundaries: No tangential magnetic field at surface. Default setting for waveguide port boundaries.

Open Boundaries: Operates like free space – Waves can pass this boundary with minimal reflections. Perfectly matched layer (PML) condition. Open (add space) Boundaries: Same as open, but adds some extra space for far field calculation (automatically adapted to center frequency of desired bandwidth). This option is recommended for antenna problems. Conducting Wall: Electric conducting wall with finite conductivity (defined in Siemens/meter).

114

Boundary Settings (III) Periodic Boundaries: Connects two opposite boundaries where the calculation domain is simulated to be periodically expanded in the corresponding direction. Thus, it is necessary that facing boundaries are defined as periodic. The resulting structure represents an infinitely expanded antenna pattern, phased array antennas. F! (hexahedral mesh), T! + 0 phase shift

Unit Cell: Used with F! solver, tetrahedral mesh, similar to F! periodic boundary with hexahedral mesh. A two dimensional periodicity other than in direction of the coordinate axes can be defined. If there are open boundaries perpendicular to the unit cell boundaries, they are realized by Floquet modes, similar to modes of a waveguide port .

115

Boundaries: Symmetry Planes Three different settings are available. Three possible symmetry planes.

116

Meshing Basics

119

How to Get a Proper Mesh? Question: How does a proper mesh look like and what are the best settings to get it? Answer: This depends on your problem under study as well as the type of result you are interested in. However, there are some rules of thumb: • For several classes of application (e.g. antennas, PCB boards etc.) there are some common properties a "good" mesh possesses (project templates make use of this fact). • It is known that the results become more accurate when the mesh is refined (automatic mesh refinement is based on this knowledge). • Geometry and material of the model influences the behavior of the EM fields (fixpoints, material based meshing, and other special techniques are based on this knowledge). 120

Hierarchy of Mesh Settings Global Mesh Properties

General settings usually done by project template. Global settings for mesh controls of automatic meshing algorithms.

Local Mesh Properties

Special settings (fine-tuning) to adjust the global mesh better to the model under study. Defined per shape or per material.

Local mesh properties have precedence over global mesh properties.

121

Mesh Generation - A Typical Workflow Select Project Template

Global Mesh Settings

122

This adjusts the global mesh properties to values which we found to be a good starting point for a certain area of application.

Optimize the global mesh settings for the geometry of your model.

Local Mesh Settings

Fine tune the mesh (if necessary) to meet the really specific requirements of your model.

Perform Simulation

Start the solver and perform a convergence study (e.g. using adaptive mesh refinement).

Results

Simulations and mesh studies provide insight about the dependency of the results on the mesh settings.

Project Templates  A project template makes some basic settings for a new project. A project template can be applied to an already existing project. Information about the settings the template will apply.

Template Title (Area of Application)

123

Initial Mesh Settings

Automatic Mesh Refinement (I)  It is known that the numerical solution calculated by the solvers converges to the analytical solution if the grid is sufficiently refined.  The automatic mesh refinement in CST tries to refine the initial mesh in a clever way such that the results are accurate.

124

Automatic Mesh Refinement (II)

The results for different meshes during an adaptive mesh refinement are shown in the "Navigation Tree". 125

Hexahedral Meshing for Transient Simulations

126

Hexahedral Meshing - Overview 1. Hexahedral Mesh Configuration Options

2. Some Meshing Guidelines 2.1 Some Representative Meshes for Common Structures 2.2 Meshing Pitfalls 3. Influence of the Mesh on Simulation Performance

127

Hexahedral Mesh (I) - Mesh View Mesh lines in one mesh plane are shown in the 3D view. View mesh. Mesh controls are displayed in the mesh view.

Information about mesh plane.

The total number of mesh cells is displayed in status bar. 128

Corner Correction

Fixpoints

Hexahedral Mesh (II) - Global Settings

Absolute and frequency dependent setting to determine the largest mesh step.

Settings to limit the size of the smallest mesh step.

129

Automatically create and use mesh controls. Strongly recommended!

Hexahedral Mesh (III) - Global Settings Largest Mesh Step - "Lines per Wavelength"

"Lines per wavelength" is based on the upper limit of the frequency range. 130

Thus, increasing the upper frequency limit usually leads to a finer mesh.

Hexahedral Mesh (IV) - Global Settings Largest Mesh Step - "Lower Mesh Limit"

"Lower Mesh Limit" is based on the dimensions of the computational domain.

131

The diagonal of the smallest boundary face of the comp. domain is divided by this number. Result is used as the max. mesh step width allowed in the model

Hexahedral Mesh (V) - Global Settings Smallest Mesh Step - "Mesh Line Ratio Limit"  The time needed to complete a time domain simulation heavily depends on the size of the smallest mesh step (see later in section "Performance Aspects of Meshing").  The size of the minimum mesh step can be limited using the "Mesh Line Ratio Limit" or the "Smallest Mesh Step" setting.

Mesh lines are inserted at fixpoints.

Mesh Line Ratio Limit

The "Mesh Line Ratio Limit" specifies the maximum value allowed for the ratio of the maximum mesh step width to the minimum mesh step width. 132

Hexahedral Mesh (V) - Global Settings Smallest Mesh Step - "Smallest Mesh Step"  The time needed to complete a time domain simulation heavily depends on the size of the smallest mesh step (see later in section "Performance Aspects of Meshing").

Smallest Mesh Step

The "Smallest Mesh Step" specifies the minimum value allowed for the minimum mesh step width in terms of the units defined in your project. Note: If the settings for "Steps per Wavelength" or "Lower Mesh Limit" lead to a smaller then the "Smallest Mesh Step" setting is ignored. 133

Hexahedral Meshing - Overview 1. Hexahedral Mesh Configuration Options 2. Some Meshing Guidelines 2.1 Some Representative Meshes for Common Structures 2.2 Meshing Pitfalls 3. Influence of the Mesh on Simulation Performance

134

Representative Meshes (I) - Minimal Requirements The gap between inner and outer conductor should be resolved by at least one mesh cell. Partially filled cells are handled with PBA/FPBA technique.

Coaxial Line 1-2 mesh lines

2-3 mesh lines (depends on thickness)

Microstrip Line 135

Depending on the thickness and the permittivity of the substrate the number of mesh lines should be at least as shown in the picture. It is NOT necessary to resolve the thickness of the microstrip line by the mesh.

Representative Meshes (II) - Minimal Requirements The gap between multiple strip lines should be resolved by at least one or two mesh cells.

Parallel Microstrip Lines A discrete port must be discretized by at least one mesh cell.

Discrete Ports 136

Meshing Pitfalls - Staircase Cells (I) Cells which contain more than two metallic material boundaries are completely filled with PEC (staircase cells).

A warning is shown by the solver to inform you of this modification.

Staircase cells are shown in the mesh view.

137

Meshing Pitfalls - Staircase Cells (II) Staircase cells must be avoided if they influence the electrical behavior of the model, i.e. if they introduce shortcuts. Example: Shortcut between two microstrip lines is introduced by a staircase cell.

Staircase cells which do not change the electrical behavior of a model are usually OK.

138

Example: Staircase cell at a wire in free space.

Online Help - PBA and TST

PBA

139

TST

Whenever a mesh cell cuts more than two metallic material boundaries the cell is filled with PEC material (staircase cell). Quite often such cells do not influence the simulation result much, but if they introduce shortcuts (as shown on the previous slide) this might be critical.

Hexahedral Meshing - Overview 1. Hexahedral Mesh Configuration Options 2. Some Meshing Guidelines 2.1 Some Representative Meshes for Common Structures 2.1 Meshing Pitfalls 3. Influence of the Mesh on Simulation Performance

140

Hexahedral Meshing – Performance (I) For stability, the time step of the numerical quadrature is determined by the smallest mesh step. Increasing the smallest mesh step will increase the time step.

Smallest Mesh Step

tiny t: slow

t

big t: fast

t

The smaller the smallest mesh step width, the smaller the time step for the numerical time integration. 141

Hexahedral Meshing – Performance (II)  The smallest mesh step in a model can be visualized in the mesh view.

142

Hexahedral Meshing Guidelines - Summary  Select a proper project template for your application to get good initial mesh settings.  Perform an adaptive mesh refinement to find a good mesh.  Fine tune the mesh if necessary using the local mesh settings.  Try to avoid critical cells. Quite often they are an indicator that the mesh is too coarse at least in some regions.  Try to avoid to use a mesh with a very high mesh line ratio limit. Consider using subgrids for models which require a very fine mesh at localized positions.

143

Transient Simulation - Memory Consumption - Memory-Consumption versus Mesh Size -

 Some “rules of thumb” are:  A structure with open boundaries and material losses requires about 1 GB RAM to handle 3-4 million mesh cells.  A structure with closed boundaries and without material losses requires about 1 GB RAM to handle 5 million mesh cells.  Subgridding:  The subgridding feature starts to be efficient when the “mesh cell reduction factor” is larger than 3. (“Macros”  “Calculate”  “Subgridding Meshcell Factor”)

144

Tetrahedral and Surface Meshing for Frequency Domain Simulations

145

Global Mesh Properties Steps per wavelength: This value refers to the highest frequency of the simulation. It defines the minimum number of mesh cells that are used for a distance equal to this wavelength. Minimum number of steps: This value controls the global relative mesh size and defines a lower bound for the number of mesh cells independently of the wavelength. It specifies the minimum number of mesh edges to be used for the diagonal of the model bounding box.

Note: A tetrahedral mesh requires a valid ACIS model. (HEX mesh even works with INVALID ACIS model...) 146

Tetrahedral / Surface Mesh (I) -Global Mesh Settings -

"Steps per wavelength" is based on the upper limit of the frequency range. 147

Thus, increasing the upper frequency limit usually leads to a finer mesh.

Tetrahedral / Surface Mesh (II) -Global Mesh Settings -

"Min. number of steps" allows to refine the mesh globally independently of the frequency range settings.

148

It specifies the minimum number of mesh edges to be used for the diagonal of the model bounding box.

Mesh Generation Method The method for surface and volume meshing can be chosen. General purpose: A simple surface mesh generation which is adequate in most cases.

Fast (for complex structures): Especially suited to meshing large or complex structures. If used together with (tetrahedral) volume mesh generation, this method can be combined only with Delaunay volume mesh generation. Delaunay: Fast tetrahedral volume meshing method (recommended).

Geometry accuracy: If the defined or imported geometry is less accurate than the default tolerance 1e-6, it is recommended to select a larger tolerance. Otherwise artificial shapes might arise or the model preparation might fail. 149

Advancing Front: An alternative method to generate a volume mesh. Advantageous in some cases (like thin layers), because the surface mesh can be generated more flexible than with Delaunay, that is, it can be altered during the mesh generation if necessary. This method is available only in combination with the general purpose surface mesh generation.

Curvature Refinement (I)

30

100

default = 100 If cylinders are still not well discretized, increase it to, e.g., 200-300.

150

Curvature Refinement (II)

The “Curvature refinement ratio” specifies the ratio of the maximum deviation (d) of the surface mesh from the actual shape of the structure divided by the edge length (h) of the surface triangle (as shown in the picture above). Smaller values lead to better approximation of curved objects.

Volume optimization: If this field is checked (recommended), the mesh connectivity of the preliminary volume mesh is changed to improve the mesh quality.

Volume smoothing: If this field is checked (recommended), the position of mesh vertices will be changed in order to enhance the mesh quality. 151

Adaptive Mesh Refinement  Multi-frequency adaptive mesh refinement  The adaptation frequency samples are sequentially processed before the broadband sweep.  Example: Diplexer

Mesh adaptation at 75.1 GHz and 77 GHz.

Initial mesh 152

Optimized mesh

Open Discussion

153