Getting Started with HFSS: 3D Layout Microstrip Filter

Getting Started with HFSS 3D Layout:Microstrip Filter

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Getting Started with HFSS 3D Layout: Microstrip Filter

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Conventions Used in this Guide

Please take amoment to review how instructions and other useful information are presented in thisguide.

l Procedures are presented as numbered lists. A single bullet indicates that the procedurehas only one step.

l Bold type is used for the following:o Keyboard entries that should be typed in their entirety exactly as shown. For example,“copy file1” means the word copymust be typed, then a spacemust be typed, andthen file1must be typed.

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l Another alternative is to use the short-cut menu that appears when you click the right-mousebutton. An example of a typical user interaction is as follows:

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“Right-click and selectAssign Excitation> Wave Port” meanswhen you click the right-mouse button with an object face selected, you can execute the excitation commands fromthe short-cut menu (and the corresponding sub-menus).

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Table of ContentsTable of Contents Contents-1

1 - Introduction 1-1

Sample Project –Microstrip Bandstop Filter 1-1

2 - Set Up the Project 2-1

Launch ANSYS Electronics Desktop (EDT) 2-1

Set Options 2-2

Insert HFSS 3D Layout Design 2-4

3 - Create the Layout 3-1

Create Stackup 3-1

Draw Ground Plane 3-4

Create L1 3-6

Parameterize L1 3-7

Create S for Stub1 3-8

Parameterize S for Stub1 3-9

Create L2 for Stub1 3-10

Parameterize L2 for Stub1 3-11

Create S for Stub2 3-12

Parameterize S for Stub2 3-13

Create L2 for Stub2 3-13

Parameterize L2 for Stub2 3-14

Create Input 1 3-15

Parameterize Input 1 3-15

Create Input 2 3-16

Parameterize Input2 3-17

Create Edge Port 1 3-17

Create Edge Port 2 3-18

DoNot Unite TraceObjects 3-19

Set Port Excitations 3-20


Contents-1




4 - Analysis and Post-Processing 4-1

Create HFSS Analysis Setup 4-1

HFSS Bounding Box 4-4

Create Planar EMAnalysis Setup 4-6

Validate and Analyze 4-8

Convergence 4-9

Plotting the HFSSMesh 4-9

Create S-Parameter Plot - Magnitude 4-10

Add and Analyze a Discrete Sweep 4-13

Create and Animate a Current Overlay 4-14

Create and Animate an E-Field Overlay 4-19

Optional Challenge Exercise 4-21

Contents-2



1 - IntroductionThis document is intended as supplementarymaterial to HFSS 3D Layout for beginners andadvanced users. It includes instructions to create, solve, and analyze amicrostrip bandstop filterusing the HFSS 3D Layout design type in the ANSYS Electronics Desktop software.

This chapter contains the following topic:

l Sample Project - Microstrip Bandstop Filter

Sample Project – Microstrip Bandstop FilterThis example is intended to demonstrate how to create, simulate, and analyze a planar microstripbandstop filter using HFSS 3D Layout. A bandstop filter (also known as a band-rejection filter) is adevice that attenuates signals within a target frequency band while passing higher and lower fre-quencies unaltered. It is the opposite of a bandpass filter.


Introduction 1-1




Figure 1-1: Microstrip Bandstop Filter

Note:

This figure was captured with theHFSS 3D Layout> HFSS Extents option enabled. Theouter envelope represents the boundary of the default air box surrounding themodel,which is the extent of the solution regionmeshed and solved when you perform anHFSSanalysis.

In the precedingGetting Started with HFSS 3D Layout guides (Slot Fed Patch Antenna and LowPass Filter) the ground plane layer of the stackup was defined asNegative, and any objects drawnon that layer represented areas of removed conductor. In this exercise, the ground layer is notNeg-ative, and you will draw the ground plane conductor object.

You will draw themodel using parametric design variables for the signal layer. You will also eval-uate and compare the filter response using both HFSS and Planar EM analyses.

Model Diagram:The following figure is a diagram of the Trace (signal) layer of themicrostrip bandstop filter model:

Figure 1-2: HFSS 3D Layout – Trace Layer with Dimensions and Variable Names

In addition, there is a 150 x 50mil rectangular ground plane conductor that you will draw on a sep-arate layer.

Introduction 1-2



2 - Set Up the ProjectThis chapter contains the following topics:

l Launch ANSYS Electronics Desktopl Set General Optionsl Insert HFSS 3D Layout Design

Launch ANSYS Electronics Desktop (EDT)For convenience, a shortcut to the EDT application is placed on your desktop during program install-ation. Optionally, youmaywant to pin the shortcut to your WindowsStart Menu too.

1. Double-click ANSYS Electronics Desktop (or click the same shortcut on your StartMenu) to launch the application.

ANSYS Electronics Desktop opens


Set Up the Project 2-1




Figure 2-1: ANSYS Electronics Desktop

2. If a project is not listed at the top of the Project Manager, click New on theDesktop rib-bon tab to include one. If the Project Manager window does not appear after launching theapplication, go to theViewmenu and select theProject Manager option.

Set OptionsIn this procedure, you will define the default length unit and choose themethod of defining rect-angles, as follows:

1. On theDesktop ribbon tab, click General Options.

TheOptions dialog box appears.





2. In the options tree on the left side of the dialog box, expand theGeneral settings group andselect theDefault Units subgroup.

3. From the Length drop-downmenu, selectmil.

Figure 2-2: Setting the Default Length Unit

4. ClickOK to close theOptions dialog box.5. Expand the Layout Editor group and select theObject subgroup.6. UnderRectangle Description Style selectCenter/width/height:

Figure 2-3: Setting the Rectangle Description Style





Note:

For the settings in the Layout Editor group of theOptions dialog box to take effect amodel, youmust define them before adding theHFSS 3D Layout Design to yourproject. The general options control the default settingswhen the design type isadded.

To change the Layout Editor options after a design has already been added to your project,

click Layout Settings on the Layout ribbon tab.

7. ClickOK to accept the options and close the dialog box.

Insert HFSS 3D Layout Design

1. From theDesktop ribbon tab, choose HFSS 3D Layout from the HFSS drop-downmenu.

Note:

Alternatively, you can use themenu bar and clickProject> Insert HFSS 3D Lay-out Design:





Figure 2-4: Design Types in the Project menu

The Project Manager window is populated withEMDesignx and, if configured to appear,theChoose Technology dialog box appears.

Figure 2-5: Choose Technology Dialog Box

2. Since you are going to create your own stackup, clickNone.

3. On theDesktop ribbon tab, click Save As.4. In theSave As dialog box, navigate to the folder where you want to store thismodel, enter

MicrostripFilter in the File name text box, and clickSave.




PDF layout 2-6




3 - Create the LayoutThis chapter contains the following topics:

l Create Stackupl Draw Ground Planel Create L1l Parameterize L1l Create S for Stub1l Parameterize S for Stub1l Create L2 for Stub1l Parameterize L2 for Stub1l Create S for Stub2l Parameterize S for Stub2l Create L2 for Stub2l Parameterize L2 for Stub2l Create Input 1l Parameterize Input 1l Create Edge Port 1l Create Input 2l Parameterize Input 2l Create Edge Port 2l DoNot Unite TraceObjectsl Set Port Excitations

Create Stackup1. On the Layout ribbon tab, click Layout dialog.

TheEdit Layers dialog box appears.

2. Under Stackup, deselect the Laminate mode option.3. Click Insert above and set the options for the ground plane in theAdd Stackup Layer dialog

box, as follows:a. EnterGND in theName text box.b. Choose signal from the Type drop-downmenu and clickOK.


Create the Layout 3-1




Figure 3-1: Adding the Ground Layer

4. Click Insert above and set the options for the substrate layer as follows:a. Enter Sub1 in theName text box.b. Select dielectric from the Type drop-downmenu and clickOK.

5. In theSub1 (dielectric) layer row, change the Thickness to 5mil.6. In theSub1 (dielectric) layer row, selectEdit from theMaterial drop-downmenu.

Figure 3-2: Select Edit in the Sub1 Material Column.

7. On theSelect Definition dialog box, clickAdd Material. Then:a. On theView / Edit Material dialog box, enterMy_Alumina in theMaterial Name text

box.b. Set theRelative Permittivity value to 9.9.c. ClickOK to close theView / Edit Material dialog box.

8. ClickOK to close theSelect Definition dialog box.9. With theSub1 layer still selected, click Insert above and set the options for the trace layer

as follows:





a. Enter Trace in theName text box.b. Select signal from the Type drop-downmenu and clickOK.

10. With the Trace layer selected, hold downCtrl and click the first column of theGND layer toselect it too. Both layers should be highlighted in the layers table.

11. In theEdit selected section, chooseEdit from theMaterial drop-downmenu:

Figure 3-3: Edit GND and Trace Material

12. In theSelect Definition dialog box, choose pec (perfect electrical conductor) from the list oflibrarymaterials and clickOK.

13. Ensure that the second checkbox in theAttributes section is selected for all three layers. Thisoption shades in objects drawn on the layers, as opposed to displaying a wireframe view (out-line only).

Figure 3-4: Shaded View Option

The final stackup is shown in the following figure:





Figure 3-5: Final Layers Stackup

14. ClickApply and close.

Draw Ground Plane1. Set the working layer by selectingGND in the Layerswindow or use theActive Layer drop-

downmenu in the Layout ribbon tab.

or

Figure 3-6: Selecting GND as the Active Layer

Note:

Tomake the Layerswindow visible, from theViewmenu, select the Layers option.

2. On the Layout ribbon tab, click Draw rectangle.3. Enter the starting corner location, using the coordinate text boxes in the status bar at the bot-

tom of the programwindow:l X = 50l Y = 0l PressEnter to accept this point.

4. Enter the size of the rectangle, using the coordinate text boxes:l Delta X = 150l Delta Y = 50l PressEnter to accept the specified width and height of the rectangle.





Note:

Regardless of the rectangle definitionmethod specified in the Layout Editor set-tings, the points you click or enter via the coordinate text boxes specify two oppositecorners of the rectangle. The difference is that, for theCenter/width/height defin-itionmethod, the location displayed within the docked Properties window is adjus-ted to reflect the coordinates of the rectangle's centroid.

5. With the rectangle still selected, ensure that the 2 pt Description option in the dockedProp-ertieswindow isnot selected.

6. Type 50, 0 for theCenter value and pressTab to accept the change.

The rectangle relocates to be centered at (50mil, 0 mil), and the width and height remain150mil and 50mil, respectively. The dockedPropertieswindow should look like the fol-lowing figure:

Figure 3-7: Ground Plane Rectangle Properties

7. Click in the Layout window's background area to clear the selection and pressCtrl+D to fitthe view:





Figure 3-8: Ground Plane Rectangle Drawn

Create L11. Set the working layer to Trace using either the Layerswindow or theActive Layer drop-

downmenu on the Layout ribbon tab.2. On the Layout ribbon tab, click Draw rectangle.3. Using the coordinate text boxes, enter the starting corner location:

l X = 0l Y = 0l PressEnter to accept this point.

4. Using the coordinate text boxes, enter the rectangle size:l Delta X = 96l Delta Y = 4.8l PressEnter to accept this point.l For now, leave the rectangle selected. You will parameterize its properties in the nextprocedure.





Figure 3-9: L1 Drawn

Parameterize L1When you parameterize an object, you define variables for the coordinates and dimensions ratherthan absolute numeric values. In this way, you can define additional objects based on parametersof previously defined ones, and you can quickly alter the geometry of themodel by editing thedesign parameters. All geometry directly or indirectly based on an altered parameter is auto-matically updated.

To parameterize the object:

1. With the L1 rectangle still selected, in the dockedPropertieswindow, ensure that 2 ptDescription isnot selected.

2. For theWidth value, type L1 and pressTab.

TheAdd Variable dialog box appears.

3. Ensure that theValue is specified as 91.2 mil and clickOK.4. For theHeight value, type:W and pressTab.5. In theValue text box of theAdd Variable dialog box, type: 4.8 mil and clickOK.6. For theCenter value, type: L1/2, W/2 and pressTab or Enter to accept the coordinates.

The resulting rectangle properties are shown below:





Figure 3-10: L1 Properties – Parametrized

Create S for Stub11. On the Layout ribbon tab, click Draw rectangle.2. Click the lower-left corner of the first rectangle to snap to that point. This point (0, 0) is the

starting corner of the new rectangle.

The cursor changes from a rectangle to a square when the snapping point is detected.

3. Using the coordinate entry fields, specify the rectangle size:l Delta X = 4.8l Delta Y = -4.8l PressEnter to accept this point.

Keep the new rectangle selected. You will parameterize it in the next procedure.





Figure 3-11: S for Stub 1 Added

Parameterize S for Stub11. Ensure that the second rectangle just drawn is still selected.

The rectangle's properties should be displayed in the dockedPropertieswindow.

2. In the dockedPropertieswindow, enter the following settings:a. Ensure that 2 pt Description isnot selected.b. ForWidth, type:W and pressEnter.c. ForHeight, type:S and pressEnter.d. In theAdd Variable dialog box for S, specifyValue = 4.8 mil and clickOK.e. ForCenter, type:W/2 , -S/2and pressTab or Enter to accept the coordinates.






Figure 3-12: S for Stub 1 Parameterized Properties

Create L2 for Stub11. On the Layout ribbon tab, click Draw rectangle.2. Click the lower-left corner of the first rectangle to snap to that point. This point (0, -4.8) is the

starting corner of the new rectangle.

The cursor changes from a rectangle to a square when the snapping point is detected.

3. Using the coordinate text boxes, enter the size of the new rectangle:l Delta X = 86.4l Delta Y = -4.8l PressEnter to accept this point.

Leave the new rectangle selected. You will parameterize it in the next procedure.





Figure 3-13: L2 for Stub1 Drawn

Parameterize L2 for Stub11. Ensure that the rectangle you just added is still selected. It's properties will be displayed in

the dockedPropertieswindow.2. In the dockedPropertieswindow, enter the following settings:

l Ensure that the 2 pt Description option isnot selected.l ForWidth, type: L2 and pressEnter.l In theAdd Variable dialog box for L2, set Value = 86.4 mil and clickOK.l ForHeight, type:W and pressEnter.l ForCenter, type: L2/2, -S-W/2 and pressTab or Enter to accept the coordinates.






Figure 3-14: L2 for Stub1 Parameterized Properties

Create S for Stub21. On the Layout ribbon tab, click Draw rectangle.2. Click the upper-right corner of the first rectangle drawn to snap to that point. This point (96,

4.8) is the starting corner of the new rectangle.3. Using the coordinate text boxes, enter the size of the new rectangle, as follows:

l Delta X = -4.8l Delta Y = 4.8l PressEnter to accept this point.

Figure 3-15: S for Stub2 Drawn





Parameterize S for Stub21. Ensure that the fourth rectangle just drawn is still selected.

The rectangle's properties should be displayed in the dockedPropertieswindow.

2. In the dockedPropertieswindow, enter the following settings:a. Ensure that 2 pt Description isnot selected.b. ForWidth, type:W and pressEnter.c. ForHeight, type:S and pressEnter.d. ForCenter, type: L1-W/2 , W+S/2 and pressTab or Enter to accept the coordinates.


Figure 3-16: S for Stub 2 Parameterized Properties

Create L2 for Stub21. On the Layout ribbon tab, click Draw rectangle.2. Click the upper-right corner of the last rectangle drawn to snap to that point. This point (96,

9.6) is the starting corner of the new rectangle.3. Using the coordinate text boxes, enter the size of the new rectangle:


Leave the new rectangle selected. You will parameterize it in the next procedure.





Figure 3-17: L2 for Stub2 Drawn

Parameterize L2 for Stub21. Ensure that the rectangle you just added is still selected. It's properties will be displayed in


l Ensure that the 2 pt Description option isnot selected.l ForWidth, type: L2 and pressEnter.l ForHeight, type:W and pressEnter.l ForCenter, type: L1-L2/2, W+S+W/2 and pressTab or Enter to accept the coordin-ates.






Figure 3-18: L2 for Stub2 Parameterized Properties

Create Input 11. On the Layout ribbon tab, click Draw rectangle.2. Click the lower-left corner of the first rectangle drawn (the longest one) to snap to that point.

This point (0, 0) is the starting corner of the new rectangle.3. Using the coordinate text boxes, enter the size of the new rectangle, as follows:


Leave the rectangle selected. You will parameterize it in the next procedure.

Figure 3-19: Input 1 Drawn

Parameterize Input 11. Ensure that the rectangle you just added is still selected. It's properties will be displayed in


l Ensure that the 2 pt Description option isnot selected.l ForWidth, type: Li and pressEnter.l In theAdd Property dialog box for Li, specify:Value = 14.4 mil and pressEnter.l ForHeight, type:W and pressEnter.l ForCenter, type: -Li/2, W/2 and pressTab or Enter to accept the coordinates.






Figure 3-20: Input 1 Parameterized Properties

Create Input 21. On the Layout ribbon tab, click Draw rectangle.2. Click the lower-right corner of the first rectangle drawn (the longest one) to snap to that

point. This point (96, 0) is the starting corner of the new rectangle.3. Using the coordinate text boxes, enter the size of the new rectangle, as follows:

l Delta X = 14.4l Delta Y = 4.8l PressEnter to accept this point.

Leave the rectangle selected. You will parameterize it in the next procedure.





Figure 3-21: Input 2 Drawn

Parameterize Input21. Click on the object in the layout window.2. In the dockedPropertieswindow enter these settings:

a. Ensure that the 2 pt Description option isnot selected.b. ForWidth, type: Li and pressEnter.c. ForHeight, type:W and pressEnter.d. ForCenter, type: L1+Li/2, W/2 and pressTab or Enter to accept the coordinates.

Figure 3-22: Input 2 Parameterized Properties

Create Edge Port 1To select the edge that represents the first port:

1. Click in the Layout window's background area to clear the current selection and to ensurethat this is the active window.

2. PressE to begin theSelect Edgesmode.3. Click the far-left edge of themodel to graphically select it.





4. On the Layout ribbon tab, click Create edge port.

Figure 3-23: Port 1 Applied

Create Edge Port 2To select the edge that represents the second port:

1. Click in the Layout window's background area to clear the current selection and to ensurethat this is the active window.

2. PressE to begin theSelect Edgesmode.3. Using themouse, graphically select the far-right edge of themodel.4. On the Layout ribbon tab, click Create edge port.

Figure 3-24: Port 2 Applied

5. Click in the Layout window's background area and pressO to restore the defaultObjectselectionmode.





Note:

In an earlier Getting Started Guide, the individual objects comprising the trace layer wereunited into a single object. However, because thismodel is parametric, you do notwantto unite the objects. Unlike the 3D Modeler used for conventional HFSS designs, the Lay-out Editor does not maintain the full parametric history of themodel construction. If youunite the trace objects, the parameters defined for the individual rectangleswill no longerhave any effect on the geometry. Once the individual rectangles aremerged into a com-plex polygon, the vertices of that polygon are defined using their absolute numericalcoordinates. Therefore, altering the design variables would no longer have an effect onthemodel because the variables are no longer used to define the united object.

Do Not Unite Trace ObjectsIn an earlier Getting Started Guide, the individual objects comprising the trace layer were unitedinto a single object. However, because thismodel is parametric, you do notwant to unite theobjects.

Unlike the 3D Modeler, which is used for conventional HFSS designs, the Layout Editor does notmaintain the full parametric history of themodel's construction. If you unite the trace objects, thevariable design parameters you defined for the individual rectangleswill no longer have any effecton themodel geometry. When the individual rectangles aremerged into a single complex polygon,the vertices of that polygon become defined based on their absolute numerical coordinates at thetime. Therefore, altering the variables (that is, design parameters) afterward would no longer haveany effect on themodel, because the united object is no longer based on those variables.

In any case, it is not necessary to unite objects drawn on amodel layer if the edge of one objectexactlymatches the edge location of an adjacent object. The solver will treat the objects as a con-tiguous conducting part. All edges of the conducting objects in this exercise are coincident with theiradjacent objects' edges.Whether united or not, the trace objects will behave like a single con-ducting part.

Note:

There is an advance analysis setup option that forms polygon unions beforemeshing.This option allows elements to span across the border between adjacent objects. Theconductor ismeshed as if the objects were united, without actuallymodifying themodelgeometry. In later steps, you will verify that this option is enabled for your HFSS andPlanarEM analysis setups.





Set Port ExcitationsBy default, a 1 volt excitation at 0 degrees phase is applied to both ports that you assigned (Port1andPort2). In a later procedure, you will create and animate a current overlay. In order for the cur-rent results to bemeaningful, one port should be the input to themicrostrip filter, and one the out-put. To achieve this result, you will modify the port excitations to specify zero volts at Port2, makingit the output of the filter, as follows:

1. Using themenu bar, clickHFSS 3D Layout> Port Excitations.2. In thePort Excitations dialog box that appears, change theMagnitude for Port2 to 0V:

Figure 3-25: Port Excitations

3. ClickOK.

4. Save your project. (This command is available from all ribbon tabs.)




4 - Analysis and Post-ProcessingThis chapter contains the following topics:

l Create HFSS Analysis Setupl HFSS Bounding Boxl Create Planar EMAnalysis Setupl Validate and Analyzel Review HFSS Convergence Datal Plotting the HFSSMeshl Create Comparative S-Parameter Plotl Add and Analyze a Discrete Sweepl Create and Animate a Current Overlayl Create an E-Field Overlay

Create HFSS Analysis Setup

1. On theSimulation toolbar, click HFSS (AddHFSS Solution Setup).

TheHFSS Setup 1 dialog box appears.

2. Under theGeneral tab:a. Specify 20 GHz in the Frequency text box.b. Select theSave Fields option.


Analysis and Post-Processing 4-1




Figure 4-1: HFSS Setup 1 – General Tab

3. Under theSolver tab, selectMixed Order from theOrder of Basis Functions drop-downmenu.ClickOK.





Figure 4-2: HFSS Setup 1 – Solver Tab

4. ClickOK.

TheEdit Frequency Sweep dialog box appears.

5. Edit the sweep as follows:l Select Interpolating from theSweep Type drop-downmenu.l Distribution = Linear Stepl Start = 4.0 GHzl Stop = 20.0 GHzl Step = 0.02 GHz





Figure 4-3: Edit Frequency Sweep – HFSS Sweep 1

6. ClickOK.

7. Save the project.

HFSS Bounding Box1. From themenu bar, clickHFSS 3D Layout> HFSS Extents, set the values as shown for

Dielectric Horizontal Padding andAirbox Horizontal Padding.

TheSet HFSSModel Extents dialog box appears.

2. Ensure that theOpen Region andRadiation options are selected and set the remainingproperties as shown in the following figure:





Figure 4-4: Set HFSS Model Extents

3. On theView ribbon tab, clickHFSS Extents to display the bounding box and rotate themodel for a good view:





Figure 4-5: HFSS Bounding Box Visualization

4. Repeat the last step to once again hide the bounding box.

Create Planar EM Analysis Setup

1. On theSimulation toolbar, click PlanarEM (Add Planar EMSolution Setup).

ThePlanarEMSetup 1 dialog box appears.

2. Under theGeneral tab, specify the following settings:l Select the Fixed Mesh option.l Enter 20 GHz in theSolution Frequency text box.l Select theUse Edge Mesh check box.l Set anAbsolute edge length of 1 mil.





Figure 4-6: PlanarEM Setup 1 – General Tab

3. Under theAdvanced tab, ensure that the Form polygon unions before meshing option isselected.

4. ClickOK.

TheEdit Frequency Sweep dialog box appears.

5. Edit the sweep as shown in the following figure:

Figure 4-7: Edit Frequency Sweep – PlanarEM Setup 1, Sweep 1





6. ClickOK.

Validate and Analyze

1. On theSimulation ribbon tab, click Validate.

If the design passes, theValidation Check dialog box appears as follows:

Figure 4-8: Validation Check

2. ClickClose.

Note:

To view any errors or warningmessages, use theMessageManagerwindow.

3. In theProject Manager, selectAnalysis.

Note:

When you use a ribbon or menu bar command to start an analysis, the currentlyselected item in the Project Manager determineswhich setup to run. You can firstselectHFSS Setup 1 or PlanarEMSetup 1 to run either setup individually.However, it's more convenient to select themainAnalysis branch heading, in whichcase every setup beneath it is analyzed via a single command execution.

4. In theSimulation ribbon tab, clickAnalyze to begin solving both analysis setups (HFSSand PlanarEM) and their associated sweeps.





Convergence1. Under Analysis in the Project Manager, right-clickHFSS Setup 1 and chooseCon-

vergence from the shortcut menu.

TheSolutionswindow appears with theConvergence tab displayed.

2. For theView options, selectPlot for a graphical view of the convergence history:

Figure 4-9: HFSS Convergence Plot

3. ClickClose.

Plotting the HFSS Mesh1. In the Project Manager, right-clickField Overlays and choosePlot Mesh.2. Accept the default settings and clickDone to display themesh for theHFSS Setup1 : Last

Adaptive solution.3. In theSelect Geometrywindow that appears, select theSub1 and Trace check boxes to

only plot themesh on these two layers. Then, clickOK.





Note:

If you wish to change the selected layers after generating themesh plot, right-clickMesh 1 under Field Overlays> MeshPlots in the Project Manager and chooseReassign.

4. Under Field Overlays in the Project Manager, right-clickMeshPlots and chooseModifyAttributes.

5. Set the Transparency to 60 % to improve the visibility of themesh lines (element edges)and clickClose.

6. Zoom, pan, or rotate themodel as needed for a good view of themesh:

Figure 4-10: HFSS Mesh plot

7. Under Field Overlays> MeshPlots in the Project Manager, right-clickMesh 1 and deselectPlot Visibility to hide themesh.

Create S-Parameter Plot - MagnitudeIn this procedure, you will create an S-Parameter plot with four traces, two from the HFSS analysisand the same two from the Planar EM analysis. In this way, you can directly compare the results ofthe two different solution types.





1. On theResults ribbon tab, click 2D from the Standard Report drop-downmenu.

TheReport dialog box appears.

2. Under the Traces tab, specify the following settings for the first two traces:l Solution = HFSS Setup 1 : Sweep 1l Domain = Sweepl Category = S Parameterl Quantity = S(Port1,Port1) andS(Port1,Port2)l Function: = dB

Figure 4-11: Report Settings – HFSS Sweep 1 Results

3. ClickNew Report and the following plot appears:

Do not close the Report dialog box yet. You will be adding twomore traces to the plot.





Figure 4-12: S-Parameter Plot – HFSS Results

4. From theSolution drop-downmenu in theReport dialog box, choosePlanarEM Setup 1 :Sweep 1. Leave all other settings as they are.

5. ClickAdd Trace and then clickClose.6. Click in the plot background to deselect the just added traces.7. Right-click in the plot background and chooseAdd Note.8. In theNote text box of the dialog box that appears, add a two-line note, as follows:

a. TypeHFSS and Planar EM and pressEnter.b. TypeResults Comparison.c. ClickOK.d. Drag the note and legend to a suitable location.





Figure 4-13: S-Parameter Plot – HFSS and Planar EM Results Comparison

Observation:Notice the close correlation between the two solutions. Both clearly demon-strate the bandstop behavior over the range of about 10 to 17GHz. The only somewhat sig-nificant difference is in themagnitude of the threeminimal points along the traces (at about8.75, 12.5, and 15.2 GHz).

Add and Analyze a Discrete SweepBefore viewing surface current results on the conducting layers, define a discrete sweep under thePlanar EM analysis setup. In HFSS 3D Layout designs, surface current results are only availablefor the last pass of an adaptivemesh or for discrete sweeps. Define a discrete sweep with results attwo frequencies (one at a low pass-through frequency and one in themiddle of the bandstoprange), as follows:





1. In the Project Manager, under Analysis, right-click PlanarEM Setup1 and selectAdd Fre-quency Sweep.

2. In theEdit Frequency Sweep dialog box:1. From theSweep Type drop-downmenu, chooseDiscrete.2. In the first row of the table, chooseSingle Point from theDistribution drop-down

menu.3. In the first row of theStart column, type 4GHz.4. ClickAdd Below.5. In the second row of theStart column, type 14GHz.6. Select theGenerate surface current option.

Figure 4-14: Edit Frequency Sweep – PlanarEM Setup 1, Sweep 2 (Discrete)

3. ClickOK to add the sweep.4. In the Project Manager, under Analysis> PlanarEMSetup 1, right-clickSweep 2 and select

Analyze from the short-cut menu.

Create and Animate a Current Overlay1. Using theWindowmenu, return to the Layoutwindow, which is likely covered or partially

covered by the S-Parameter plot.





2. In the Project Manager window, right-clickField Overlays and selectPlot PEM Fields>Mag_SurfaceJ.

TheCreate Field Plot dialog box appears.

3. Specify the following field plot settings:a. In theSolution drop-downmenu, ensure that PlanarEM Setup 1 : Sweep2 is selec-

ted.b. In the Intrinsic Variables section, select 4GHz from the F (frequency) drop-down

menu.c. SelectMag_SurfaceJ andSub1 from theQuantity and In Volume lists, respect-

ively.4. ClickDone.

TheSelect Geometry dialog box appears.

5. Select the Trace andGND layers and then clickOK.6. Double-click the J Surf plot legend to access the plot settings.7. Click theScale tab and specify the following settings:

a. In theNum. Divisions text box, type 10.b. Select the Log option for a logarithmic scale.c. In theNumber Format section, chooseDecimal from the Type drop-downmenu.d. In thePrecision text box, type 2.





Figure 4-15: Current Overlay Plot Settings

8. ClickClose.





9. Rotate, pan, and/or zoom themodel for a suitable viewpoint:

Figure 4-16: Surface Current Overlay – 4 GHz

Observation:Notice that the current at Port 2 (at the right end of themodel) is relativelyhigh, indicating that current is passing through the device fromPort 1 to Port 2. This result isto be expected at 4 GHz, since this frequency is significantly lower than the bandstop fre-quency range.

10. Under Field Overlays> JSurf in the Project Manager, right-clickMag_SurfaceJ1 and selectModify Plot.

11. In theModify Field Plot dialog box, choose 14GHz from the F drop-downmenu and clickDone.

The current overlay plot now shows the results at 14 GHz:





Figure 4-17: Surface Current Overlay – 14 GHz

Observation:Notice that at this frequency, the current fromPort 1 is flowing into one of thefilter stubs, and the current at Port 2 is significantly attenuated. This behavior is consistentwith the expected bandstop filtering effect.

12. To animate the plot: under Field Overlays> JSurf in the Project Manager, right-clickMag_SurfaceJ1 and selectAnimate.

13. In theCreate Animation Setup dialog box, specify the following settings:a. SelectSingle variable andPhase, respectively, from the two drop-downmenus.b. Accept the default phase angle settings (Start = 0deg,Stop = 170deg, andSteps =

17) and clickOK to start the animation.

You can see that the current at Port 2 remains relatively low throughout the animation, asexpected:





Figure 4-18: Surface Current Overlay, Phase Animation – 14 GHz

14. Use the animation controls to stop, restart, reverse, or change the speed of the animation.15. ClickClose in theAnimation dialog boxwhen you're done reviewing the animated surface

current results.16. Under Field Overlays> JSurf in the Project Manager, right-clickMag_SurfaceJ1 and

deselect thePlot Visibility option.

Note:

In the final procedure, you will create an E-Field overlay on the samemodel geo-metry. This is the reason for hiding the current overlay before proceeding.

Create and Animate an E-Field Overlay1. In the Project Manager window, right-clickField Overlays and selectPlot Fields > E >

Mag_E.





2. In theCreate Field Plotdialog box, verify the following settings:l Solution = HFSS Setup 1 : Last Adaptive.l Phase = 0deg.l Quantity =Mag_E.

3. ClickDone.4. In theSelect Geometry dialog box, select the Trace andGND layers for the field plot. Then,

clickOK to generate the overlay.5. Double-click the E Field plot legend to access the plot settings.6. Select theScale tab and specify the following settings:

a. In theNum. Divisions text box, type 10.b. Select the Log option for a logarithmic scale.c. In theNumber Format section, chooseDecimal from the Type drop-downmenu.d. In thePrecision text box, type 2.

7. ClickClose.

The E Field overlay should resemble the following figure:

Figure 4-19: E Field Overlay – HFSS Last Adaptive Pass (20 Ghz)





8. To animate the E Field overlay, right-clickMag_E1 (under Field Overlays> E Field in the Pro-ject Manager) and selectAnimate.

9. In theSelect Animation dialog box that appears, clickOK to accept the previously definedphase animation options and start the animation:

Figure 4-20: E Field Animation – HFSS Last Adaptive Pass (20 Ghz)

Observation: You can see the highest magnitudes of the E-field propagate the whole wayfromPort 1 to Port 2. The solution frequency for the Last Adaptive pass is 20GHz, which isabove the bandstop range of the filter. Therefore, this is the expected behavior.

10. Close theAnimation dialog boxwhen finished.11. Right-clickMag_E1 in the Project Manager and deselect thePlot Visibility option to hide

the E-field overlay.

12. Save your model.

Optional Challenge ExerciseSince you parameterized the geometry of thismodel, youmaywant to experiment with how easy itis to alter the geometry and reanalyze the results. Parameterization is a convenient way to perform"what if" analyses, to see the effects of different design variations.





To edit the design variables, follow the steps below:

1. From themenu bar, clickHFSS 3D Layout> Design Properties.2. In theProperties dialog box, select the Local Variables tab.

The variables you defined while parameterizing the various rectangles are listed in the dialogbox:

Figure 4-21: Design Properties – Local Variables

The variables are listed in the order in which theywere defined.

3. Adjust any of the five variables to alter the length or width of the rectangles comprising themodel. PressEnter to accept each revised value and clickApply to see the geometry imme-diately updated. Then, clickOK to close theProperties dialog box.

Warning:

Be careful not to make excessive adjustments to these variables. The ground planewas drawn at a fixed size, and you need to ensure that the trace objects remainwithin the perimeter of the ground plane.

4. Right-clickAnalysis in the Project Manager and selectAnalyze to rerun all analysis setups.5. Observe any changes in the S-parameter plot once the solution is finished.





Note:

You can also automate the selection of design property values to achieve targeted res-ults. For more information, search for "optimization" or "design of experiments" in theHFSS help.

You have completed theMicrostrip Filter getting started guide.




Documents

Getting Started with HFSS: 3D Layout Microstrip Filter