Dipole Simulation Using ANSYS EDT (1)

 EEL 4461 / 5462  –  Antenna  Antenna Theory

Tutorial for Modeling Printed Antennas in ANSYS EDT (ver18.2): Wire and Strip Dipole Antenna Examples 

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This tutorial demonstrates how to model a printed antenna in ANSYS Electronics Desktop (EDT) version 18.2 by going through examples of a wire dipole and a strip dipole antenna example. The HFSS Design solver from ANSYS EDT will be used to generate a full-wave electromagnetic model of the antenna. The EDT software is based on the highly highl y accurate finite element method (FEM), the large scale method of moments (MoM) technique, the ultra-large scale asymptotic methods of physical optics (PO), and shooting and bouncing rays (SBR). This course will be focused on using the HFSS Design option of ANSYS EDT, employing  primarily the FEM solver. The antenna structure (conductor and dielectric components) is modeled by discretizing its complete 3D geometry in much smaller elements, defined as a mesh. In such a mesh, the elements have a range of sizes and orientations such that, rather than forming a regular grid, they conform to the geometry of the model, mod el, respecting all its details. The geometry of the antenna, number of materials, type of layer metallization, and material  properties (permittivity and permeability) permeability) can be defined by the users. With the FEM solver of EDT, an almost realistic 3D geometry of a given antenna can be designed, making it is possible to model finite size substrate and ground plane effects. In contrast to other solvers based on the Method of Moments (MoM), such as Keysight’s ADS Momentum, where it is only possible to model 2D -layered structures.

The following presents the design steps of modeling a wire and strip dipole antenna in ANSYS EDT using the HFSS Design solver. From this point on, it is assumed that: (i) you have access to ANSYS EDT software, (ii) you have knowledge of b oundary conditions for electromagnetic fields, and (iii) you are familiar with some basics of Computer-Aided Design (CAD) (such as geometry creation and Boolean operations).

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 EEL 4461 / 5462  –  Antenna  Antenna Theory

Contents Basics of ANSYS EDT and HFSS Design: ............................................................................ ............................................................................ 3 Wire Conductor Half-Wavelength Dipole Antenna Example: ............................................. 5 Planar Conductor Half-Wavelength Dipole Antenna (Printed Dipole) Exa mple: .............. 26

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 EEL 4461 / 5462  –  Antenna  Antenna Theory

Basics of ANSYS EDT and HFSS Design: 

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ANSYS EDT is powerful suite for simulating electromagnetic phenomena and components at high frequencies. During the course, we will focus on using the HFSS Design component of EDT. The software categorizes your main files into Projects, that is where your main geometry is going to be solved, simulation parameters are defined and the output data is plotted in different formats. The main software window and its controls might look like this (on ANSYS EDT ver. 18.1):

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The Project Manager (1): It allows you to browse quickly through the simulations settings (Excitation, Boundary Conditions, Analysis Setup and Results), defined variables and components included in your current Project(s) (Note that you can have multiple projects open at the same time). The Properties box (2): It displays the current properties of the item you have selected. The Modeler window (3)  It allows you to browse the different 3D component and elements included in your model. It also shows the materials that you are using, coordinate systems and work-planes. The Toolbars (4): It contains all necessary tools for using the software. 3

 EEL 4461 / 5462  –  Antenna Theory

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The Message Manager (5):  It shows an output of any warnings ( ), errors ( ) or notifications ( ) that are relevant to the user. The interface usually changes depending on what you are selecting or doing. See the picture  below as an example of the interface when you select the Results menu in the Project Manager and select or specify a specific king of Plot (in this case is a 3D Radiation Pattern Plot in spherical coordinates).

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 EEL 4461 / 5462  –  Antenna Theory

Wire Conductor Half-Wavelength Dipole Antenna Example: 1)

Start the ANSYS EDT software.

2)

Create a new file by going to File  New, or click the New File icon:

Or:

3)

In the Project Manager box, you will see that a new Project has been created. Assign the name that you desire to identify your new project with. In this tutorial, we will call it WireDipole:

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 EEL 4461 / 5462  –  Antenna Theory

4)

Insert a new HFSS Design by going to the menu Pro ject  Insert HFSS Design, or by clicking on the Insert HFSS Design button:

Or:

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After inserting the HFSS Design, you should see a rectangular (Cartesian) coordinate system along with a grid-plane for 3D modeling at your right:

Cone

Box

Cylinder  Rectangle

Sphere Ellipse

Circle

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If you are not already familiar with 3D modeling this would be a good time to get some  practice on creating three dimensional models. The main tools you will be using are the ones that allow you to create basic polygons and geometric forms, as shown in the figure above. 6

 EEL 4461 / 5462  –  Antenna Theory

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If you focus your attention on the Project Manager box, you can see that now you have an HFSS Design in your Project. We will rename the HFSSDesign1 to FreeSpaceDipole and if you expand the Design you will be able to see the different options for Modeling, Boundary Conditions, Excitations, Analysis Setup and Results processing:

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For now, we will focus on generating the dipole 3D mode. To create the Wire Dipole model we will add two cylinders and assign variables that will control the geometry dimensions. When done creating the mode, it should look like this: Wire Diameter (_)

   h    )    t        ℎ   g          n         e    L               e        _    l   o         p           i            D   (

Feed Gap ( _ )

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 EEL 4461 / 5462  –  Antenna Theory

9)

Add a cylinder to the 3D model, centered at the origin with any radius and length:

10) On the 3D Model Navigation Panel search for the CreateCylinder object that was generated and double-click on it to change its properties:

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 EEL 4461 / 5462  –  Antenna Theory

11) Assign the Center Position to 0,0, _/2. Change the Radius value to be _/2 and the Height as _ℎ/2 – _/2. You will notice that when you assign a variable that is not already defined, the software will automatically prompt you a window for you to  provide a definition. We will model a 3 GHz half-wavelength dipole antenna in free space. Assign the variables as _ℎ = 50 mm, _ = 1  mm and _ = 1 mm: Units are important. If you forget to enter/specify u nits, HFSS will likely take it as meters and geometry can grow/disappear from the modeler window. If this happens, check your units again.

12) After clicking the OK button, the cylinder dimensions should update automatically.

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 EEL 4461 / 5462  –  Antenna Theory

13) Create another cylinder for the second dipole arm. Repeat the same steps as above but this time we will make the Center Position of the cylinder to be 0,0, −_/2, and the Height assign it to −(_ℎ/2 − _/2). This will place the second dipole arm in oppo site directon along the z-axis aligned with our previous cylinder and separate the by  _ :

14)  Now let’s assign a material and color to the cylinders to identify them as conductors. Select one of the cylinders on the model window and change its name and color in the Properties window:

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 EEL 4461 / 5462  –  Antenna Theory

1 - Select Object

2 - Change Properties

15) Assign a “Perfect Conductor” material to the dipole arms (in realistic simulations, you will select copper to model conductor loss as well –   we are selecting the pec option just for this tutorial). Select “Edit…” option first then search for “pec” material in the next widow:

Change Material and choose “Edit…” on drop-down menu

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 EEL 4461 / 5462  –  Antenna Theory

16) Repeat the previous two steps for the other arm of the dipole. You will notice that the “pec” material is defined and will appear on the drop-down menu from now on:

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 EEL 4461 / 5462  –  Antenna Theory

17) When done, your dipole should look like this:

18) Define the solution and boundary conditions. Go to menu HFSS  Solution Type. Make sure that “Modal” is selected in Solution Types, and mark the checkbox for Auto-Open Region. This will ensure that radiation boundary conditions are created automatically for the model:

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 EEL 4461 / 5462  –  Antenna Theory

19) One useful tool to verify if you are missing any important definition on the model is the Validate button. It will verify that your model has the main things needed in order for the software to run a simulation. In the Message Manager you will see which are the problems with your model. In this case, we are still missing the excitation definition:

20) To define the excitation for the dipole, we will create a Sheet. This is a rectangular patch that will correspond to a Port source that is driving our dipole element. When you create Sheets, these are created as 2D geometries in a specific plane in space, which makes it necessary to select an adequate working plane. In our case, since the dipole is oriented along the z-axis, we want to work in any plane that contains the z-axis. For this example, we will select the ZX  plane:

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 EEL 4461 / 5462  –  Antenna Theory

21)  Now that you are have the ZX plane selected, change the view of the dipole from isometric to Left view and Zoom-in to the dipole gap with the mouse wheel or trackpad. This will simplify the following operations:

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 EEL 4461 / 5462  –  Antenna Theory

22) Select the Draw Rectangle icon from the toolbar, or go to the menu Draw  Rectangle. Draw a rectangle that covers the dipole gap and touches both of the arms:

Or:

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 EEL 4461 / 5462  –  Antenna Theory

23) To assign the excitation, select the rectangle object. Right-click on it, and in the pop-up menu select Assign Excitation  Lumped Port:

24) On the Lumped Port window click Next and in the Integration Line item select Ne w Line…:

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 EEL 4461 / 5462  –  Antenna Theory

25) This will prompt you to define an integration line for the Lumped Port surface. We will define it from the bottom arm to the top arm of the dipole. The process should be like the one below and at the end the red arrow of the integration line should be visible:

26) After finishing just click Next and Finished. If you Validate your model again you should see that all checks are passed:

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 EEL 4461 / 5462  –  Antenna Theory

27) The only thing left before running the simulation is to define your Solution F requency for the radiated fields and a frequency sweep. Define the simulation frequency by going to Analysis in the Project tree and double-click on the automatically generated Solution Setup, Auto1. If there is no Solution Setup, right-click on Analysis and on the pop-up menu select Add “Solution Setup…”. In the Solution Setup Window, in the General tab make sure to select 3 GHz as solution frequency, Maximum Number of passes as 15. Then, select the Options tab and set Minimum Number of Passes to 6 and Minimum Converged Passes to 3:

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 EEL 4461 / 5462  –  Antenna Theory

28) Add a frequency sweep by right-clicking on your Analysis Setup (Auto1) and select “Add Frequency Sweep…”, then set a sweep for 1GHz to 7 GHz with 301 points and click OK. You can run the simulation after that by going to the menu HFSS alternatively by clicking on the Analyze All icon:

  Analyze All, or

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Or:

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 EEL 4461 / 5462  –  Antenna Theory

29) After a few minutes (or seconds  –   depending on your computer) the model will be solved. You can observe the progress in the Progress box and when the software is done calculating the Message Manager should notify you:

30) To plot the , 3D Radiation Pattern and Azimuth and Elevation cuts of the Directivity of the antenna, go to the Project navigation tree and right-click on Results.

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 EEL 4461 / 5462  –  Antenna Theory

31) For the  frequency response, select Create Modal Solution Data Report  Rectangular Plot and then select S(1,1) in dB in the next window. Click on New Report button to create the plot:

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 EEL 4461 / 5462  –  Antenna Theory

32) For the 2D Radiation Patterns in the Elevation Plane, select Create Far Fields Report  Radiation Pattern and then select Realized Gain in Category and RealizedGainTotal as your variable in dB in the next window. Select Elevation plane in the Geometry option, and in the Families tab select the 0deg option for Phi. Click on New Report button to create the plot.  Notice that the simulated dipole gain is 1.88 dB (compare to expected values!):

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 EEL 4461 / 5462  –  Antenna Theory

33) For the Azimuth cut, change the Geometry to Azimuth, and then Primary Sweep to Phi and select the Add Trace button to view both traces in one plot:

34) For the 3D Radiation Pattern select Create Far Fields Report  Radiation Pattern and then select 3D Polar Plot. In the next window select Realized Gain as before and in dB. Click on  New Report to create the plot:

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 EEL 4461 / 5462  –  Antenna Theory

35) Optimization: If you notice the antenna gain, it is 1.88 dB. Furthermore, the  response clearly shows that the antenna appears to be resonating below 3 GHz. We can change the _ℎ variable to try and bring the resonance frequency to 3 GHz (this is the advantage of creating parameterized geometries!). To do this, select the HFSS Design (FreeSpaceDipole) in the Project Navigation Tree, and in the Properties box you should see the variables you have defined. After changing the variable and analyzing again we have:

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 EEL 4461 / 5462  –  Antenna Theory

Planar Conductor Half-Wavelength Dipole Antenna (Printed Dipole) Example: For this part of the tutorial we will use a feature of the ANSYS EDT suite called the HFSS Antenna Toolkit. With it, we can create quickl y most common antenna geometries in an automated fashion. Note: For the first CAD assignment you will not be allowed to use the toolkit. You will need to create the antenna geometry and assign the materials following the procedures explained in the previous example. 1)

Open ANSYS EDT.

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Go to the menu View  ACT Extensions. A panel called ACT Extensions should appear on your software User Interface (UI). Click on Wizards:

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In the Wizards window, select HFSS Antenna To olkit:

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 EEL 4461 / 5462  –  Antenna Theory

4)

Select Dipole  Planar Dipole antenna:

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In the Planar Dipole Settings, change the Center Frequency to 3 GHz, Material to Vacuum, Substrate Height to 0.1524 cm (1.524 mm or 60 mils) and click on Synthesis button (you might have to click twice). The values should update similar as the ones shown below:

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 EEL 4461 / 5462  –  Antenna Theory

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Click Finish and wait for the Toolkit to generate your new Planar Dipole Project:

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The Antenna Toolkit will create boundary conditions, excitations and analysis setup for you. Go ahead and review the setup created by the Toolkit and run the simulation. You might notice that the Toolkit creates a model with a Driven Terminal solution type while the  previous example was with a Driven Modal solution type (you should learn to differentiate  between these two and why use one or the other).

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 EEL 4461 / 5462  –  Antenna Theory

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After running the simulation, you can review the Results section of the Project navigation tree and see that plots for 3D and 2D radiation patterns, return loss and input impedance of the antenna have been created automatically as well by the Toolkit:

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 EEL 4461 / 5462  –  Antenna Theory

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The sweeps that are created by default can be modified by selecting the Solution Setup in Analysis from the Project navigation tree and change the frequency range. The FF_Sweep corresponds to a Discrete Sweep Type that is performed at specific frequencies. To investigate this antenna in a wider frequency range we will change the range to be 1.5GHz to 9.5GHz and assign 17 points. It is also necessary to mak e sure that Save Fields for All Frequencies is selected:

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 EEL 4461 / 5462  –  Antenna Theory

10) The S_Param sweep is an Interpolating sweep that covers the desired frequency range with an interpolating algorithm. Change this to be 1.5GHz to 12.5GHz with 301 points:

11) If we observe the results we can see that there is a second resonance at 9.42GHz, that is now visible due to the frequency range increase:

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 EEL 4461 / 5462  –  Antenna Theory

12) However, this frequency point is not included in the Discrete Sweep (FF_Sweep) and therefore we have no information of the radiating fields at that specific frequency. We can include the resonance frequency and try to plot the 3D radiation pattern by editing the FF_Sweep and adding a Single Point to the sweep:

13) We can plot the 3D Radiation Plot now by selecting the FF_Sweep and 9.42GHz at the ff_3D_GainTotal plot in Results. Change the Solution to FF_Sweep and look for 9.42GHz and click Apply Trace to update the plot:

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 EEL 4461 / 5462  –  Antenna Theory

14) However, when we see the 3D pattern from the Discrete Sweep, it does not quite match what it should really look like in theory. We are expecting a smooth rippled-donut shape. We get this instead:

15) The reason we see this is because our solution frequency in the Analysis Setup is 3GHz, which is considerably smaller than 9.42GHz. The software needs the solution frequency in order to generate and adequate size mesh that can provide an accurate solution. Therefore, we need to change the Solution Setup as well to include the resonance frequency that we want to investigate.

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 EEL 4461 / 5462  –  Antenna Theory

16) Change the Solution setup to Multi-Frequencies and include 9.42GHz:

17) Solve the model again. This time it might take a few minutes, the time will increase considerably because of the increased frequency and relatively larger electrical structure that needs to be meshed at 9.42GHz 18) Go back to the ff_3D_GainTotal plot in Results and change the following to observe the correct radiation pattern, Solution to LastAdaptive, in Families tab select Freq to be 9.42GHz :

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 EEL 4461 / 5462  –  Antenna Theory

19) The radiation pattern at 9.42GHz (second resonance) should now look like this (which is what is expected):

20) The current distribution can also be plotted by going back to the 3D Model, selecting the conductor surfaces and right-clicking and selecting in the pop-up menu Plot Fields  J Mag_JSurf:

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 EEL 4461 / 5462  –  Antenna Theory

21) A window will appear, here you can select at which frequency you want to plot the current. Select 3GHz, and click Done:

22) You should see now the current distribution on the dipole arms for 3GHz:

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