HFSS电磁仿真最简单教程

Ansoft HFSS Tutorial:StriplineDr.Ryan S.AdamsMarch12,2008

This tutorial introduces the interface of Ansoft’s HFSS,and walks the student through an example problem ofcreating,simulating and evaluating the response of a standard stripline structure.1Starting HFSS

At UNCC,the HFSS application resides on a Linux based server by the name of“hertz”which is part of the Recon?gurableComputing System(rcs).The best way to access this server is through the Mosaic system.1.1Logging Into Mosiac Linux Server

When you are logged in to one of the Mosaic windows computers,you?rst need to log in to Exceed Linux.This is done byselecting the start menu=>All Programs=>MOSAIC XP =>Unix Connectivity=>Exceed Linux,as shown in Figure1.1.This

should bring you to a screen that looks something like Figure1.1.In the box,lxs-sm1and lxs-sm2are identical linux servers thatare maintained by Mosaic.Highlight whichever one you prefer and click OK.You should then be presented with a loginscreen for Red Hat Enterprise Linux5;use your normal Mosaic login ID and password to login to the linux server.

1.2Logging into the Recon?gurable Computing System Network At this stage,you should be looking at a linux

desktop(probably with a red background).To log in to the RCS network,start from a command prompt.To do this,right clickanywhere on the desktop and click“Open Terminal”in the pop–down menu that appears.In the terminal that appears performthe following commands:

1.type ssh-C-Y rcs you should now be prompted to log into the rcs system–do not use your mosaic password,use your rcs password instead.

2.type ssh-C-Y hertz you should now be prompted to log into hertz–use thesame password that you used to log into the rcs network.3.type hfss and wait a few moments for the gui to appear.1

Figure1:Path in Windows Mosaic to access Exceed Linux servers.

Figure2:Selecting a Linux server.

Note:The?rst time you log into hfss,it will prompt you for certain?le

http://www.doczj.com/doc/457015781ed9ad51f01df261.html e the defaults and follow the prompts until the gui appears.Youmay?nd yourself back at a command prompt.If this happens,just retype hfss and the gui should come up.2The HFSS Interface

The main HFSS interface is shown in Figure2,which illustrates the main components of the gui.They are summarized asfollows:

3D Modeler Window This is the area where you create the model geometry.This window consists of the model view area(orgrid)and the history tree as shown in Figure2.The history tree documents the actions that have been taken in the model viewarea,and provides an alternative way to select objects in the model view area.

Project Manager with Project Tree The project manager window displays details about all open HFSS projects.Each projectultimately includes a geometric model,its boundary conditions and material assignments,and?eld solution and postprocessing information.An expanded view of the project manager is shown in Figure2

Properties Window The properties window consists of two tabs.The command tab displays information about an actionselected in the history tree that was performed to either create an object or modify an object.The attribute tab displaysinformation about the material and display properties of a selected object.

Progress Window This window is used when a simulation is running to monitor the solution’s progress.

Message Manager This window displays messages associated with a project’s devel-opment(such as error messagesabout the design’s setup)3Setting up HFSS

Before you can use HFSS for the?rst time,there are a couple of items that need to be con?gured for e?cient and accurateoperation.

1.On the Tools menu,select Options=>General Options...,click the Default Units taband ensure that Length is set to mm.Click OK.

2.On the Tools menu,select Options=>HFSS Options...,ensure the Include ferrite

materials check box is checked.Click the Solver tab,set the number of Processors to 4,Desired RAM Limit(MB)to6000and theMaximum RAM Limit(MB)to8000.Click OK.

You should now be ready to use HFSS.

WindowProjectManagerwith

ProjectTree MessageManager

WindowPropertyWindow

Figure 3:Main screen of HFSS.4An Example:A Simple Stripline Circuit

To begin to appreciate the functionality of this simulation tool,we will create and simulate a simple stripline transmissionline.Before we can begin to work through the simulation,we need to design the circuit on paper.We wish to design a 50?stripline transmission line that is 10cm long using te?on ( r =2.08,tan δ=0.0004).The overall material thickness we’ll chooseto be 1cm.Therefore,√eprZ ?=72.11<120and the following equation should be used to compute the trace width of thistransmission line:W b =30π√ r Z ??0.441.(1)

With our choice of material thickness,W =0.866cm.

Now that we have the geometry completely de?ned,we are ready to open HFSS and build the model.We’ll do this in the 3Dmodeler window.4.1Creating the Dielectric

The ?rst component of the geometry that we’ll draw is the dielectric.This is a solid rectangle of te?on,which can be drawn byselecting Draw =>box in the ?le menu.To make the box the correct size,you can either1.input the x ,y ,z coordinates of each component of the box into the appropriate ?elds

at the bottom of the 3D model window,or

Tree Model View

Area

Figure4:3D Modeler Window,which consists of the model view area and the history tree.2.click randomly in the3D model window three times to create a box and edit the size

in the properties box.To do this,click the command tab in the properties box and input the correct start position,andxsize,ysize and zsize for our box.

For our stripline circuit,we want to box to be200mm in the x-direction,40mm in the y-direction and10mm in the z-direction.Thebox should start at the location(-100mm, -20mm,-5mm)with XSize=200mm,YSize=40mm and ZSize=10mm.The materialparameters are set by clicking on the attribute tab in the properties window.Click on the block that says Vacuum and a

window should open titled“Select De?nition.”Highlight Te?on in the materials list and click OK.If you wish to change the coloror transparency of the box you may also do so in the attribute tab.

At this point,the box should cover the entire screen.To view the entire box,click the button with a picture of a magnifying glasswith a white square in the middle.This button “?ts all the contents in the view.”All that remains is to create the center trace ofthe stripline.

4.2Creating the Center Trace

We will create the center trace as an in?nitesimally thin strip.To do this,we select Draw =>rectangle in the?le menu.We cande?ne the size and location of the rectangle in the same manner as for the dielectric above.Our strip width

is8.66mm,and1000mm long,so the position is(-100,-8.66/2,0)and XSize=200mm,YSize=8.66mm.Since the trace has nothickness,we do not apply any material attributes to it.We will make it into a conductor using the boundary conditions.

Figure5:Project Manager window illustrating the boundery conditions,excitation,etc.of the current model.4.3Boundary Conditions

The following boundary conditions must be applied to this device:Perfect E boundary on the top of the dielectric(simulates a metal layer)Perfect E boundary on the bottom of the dielectric(simulates a metal layer)Perfect E boundary on the trace(simulates a metal layer)

Radiation boundary on the long sides of the dielectric(simulates the material extending to innity in that direction)

To apply these boundary conditions,right click in the3D modeler window and click“Select Faces”.Now,select the top

face,bottom face and the strip using the control key.Note:to select faces beneath what you can see,click the face you wantand press the“b”key until the desired face is selected.With these three items selected,right click in the“white–space”of the3Dmodeler window and highlight“Assign Boundary,”and click“Perfect E...”.Click OK. Next,select the long sides of the dielectricusing the control key.Right click in the white–space of the3D modeler window and highlight“Assign Boundary,”andclick“Radiation...”Click OK.

To check that the boundaries are created correctly,expand the“Boundaries”item in the Project Tree,and you should

see“PerfE1”and“Rad1”or similar.Highlight PerfE1,and you should see hash marks indicating which regions of the modelapply to this boundary. Highlight Rad1to see the same information for the radiation boundary.4.4Excitations

We will create a“Waveport”excitation at each end of the circuit.To do so,we perform the following steps:1.Select the face of the nearest end of the circuit

2.right click in the3D modeler window and select Assign Excitation=>Wave Port.3.Click Next

4.Under“Integration Line,”click the word None,and select New Line...

5.In the3D modeler window,click the center of the bottom of the selected face(a trianglewill appear)

6.Click the center of the trace7.Clck Next8.Click Finish

The same steps should be performed to create a wave port at the other end of the circuit.

4.5Analysis

Perform the following steps to set up the analysis options:

1.Right click on Analysis in the Project Tree,and select“Add Solution Setup”2.Under the General tab:

(a)Set the solution frequency to20GHz(b)Set the maximum number of passes to30(c)Set maximum Delta S to0.013.Under the Options tab:

(a)Set the Maximum Re?nement per pass to20%(b)Set the Order of Basis Functions to Second OrderPerform the following steps to set up the frequency sweep:1.Under the Analysis item in the Project Tree,right-click on Setup12.Select Add Frequency Sweep...3.Set start frequency to1GHz4.Set stop frequency to20GHz5.Set step size to0.25GHz6.Click OK

4.6Final Checks and Running the Simulation

Select HFSS=>Validation Check...to ensure the project is prepared for simulation(click close).Save the project by clicking on the save icon at the top of the screen.

Right-click setup1under Analysis in the project tree,select Analyze to begin the sim-ulation.At this point the progress windowshould show the progress of the simulation, beginning with the mesh generation.4.7Simulation Results

To view the results of the simulation,perform the following steps:1.Right click on the results item in the Project Tree

2.Click Create Modal Solution Data Report=>Rectangular Plot

3.Under the trace tab,select the?rst S-Parameter that you wish to view and click NewReport

4.Add additional S-Parameters by highlighting them and clicking Add Trace5.Click Close