Processing Section 8: Fields Post- Training · Field Post-Processing Exercise 1: Plot Field on Existing Geometry 1. Since we have not changed the default excitation, only Port 1,

smart software for high-frequency design8-1

Ansoft HFSS Version 7Training

Section 8: Fields Post-Processing

shared by:www.cnantennas.com

www.cnantennas.com


SynopsisGeneral Functions

� 3D Post-Processor Interface� Mesh Plotting� Excitations

� Driven Solutions� Eigenmode Solutions

� Field Plotting� Quantities, Geometry, Settings, Animation� Plot Management

Field Processing Exercise 1: Local FieldsNear/Far Field Processing

� Computing and Displaying Antenna and EMIpatterns

The Field Calculator� Calculator Layout

Field Processing Exercise 2: Antenna Processing


www.cnantennas.com


HFSS 3D Post-Processor Interface

Graphical Display Window (E-Field Magnitude Display shown)All rotate, pan, and zoom view manipulations are available!

Side Window Similar to other modules.Contains coordinate fields,snap options, and drawingcommand prompts duringgeometry creation.

Field Calculator Icon Direct access to Field Calculator

Plot Menu (shown open) Most commonly used menu inFields Processor; plot fields, mesh,and pattern data, control animations,manage plots, etc.

Radiation Menu Compute far field or field ata specific distance (“near” or“EMI” fields), display antennaparameters

Geometry Menu Define additional geometryfor post-processing (lines,cutplanes, face and objectlists, etc.)

Data Menu Controls Source Excitations


www.cnantennas.com


Plotting the Mesh� The mesh used in the solution can be

viewed by picking Mesh from the Plotmenu

� At least one object must first beSelected to plot the mesh upon

� Mesh plot options include:� Scale Factor: Individual tets can be

displayed scaled down slightly toenhance visibility by spacing themapart

� Transparency: Mesh display can bemade transparent to allow geometryto show through from behind

� Wire Frame, Hidden Line, or Shadedoptions control the rendering of themesh display itself

� The Surface Only checkbox limitsmesh plotting to the exterior ofselected objects


www.cnantennas.com


3D Post-Processor Excitations� Excitations are controlled via the

Data menu, Edit Sources pick� All ports or other sources (incident

waves, voltage gaps, currentsources) can be variedindependent of one another

� Arbitrary magnitude andphase combinations

� Excitation takes into accountsymmetry planes used in modelconstruction

� Excitation defaults to 1 watt at{Source1}, assuming a “full” modelgeometry

� Wattage is reduced byappropriate factor forsymmetry

� {Source1} could be Port1,Mode1; Gap Source 1, etc....

NOTE: If the Solution run is a FAST Sweep, the fieldexcitation can also be tuned to different frequencieswithin the sweep range. Adaptive and Discrete Sweepsolutions contain single-frequency field data only.


www.cnantennas.com


3D Post-Processor Eigenmode Excitation� For an Eigenmode solution,

individual mode excitations can beviewed

� Eigenmode excitations can not beviewed in combination

� Field Values are Normalized to thepeak data value

� Since there is no actual ‘input’into the model (voltage source,port, etc.) exciting the resonantfield behavior, the fieldmagnitudes are all scaledrelative to a peak value of 1.0

� Symmetry is again taken intoconsideration in excitation scaling

Mag E, First Eigenmode in Cylindrical Dielectric Resonator


www.cnantennas.com


3D Post-Processor Field Quantities� The 3D Post Processor can directly

display the listed quantities� All units in MKS system, regardless of

units used in geometry construction� e.g. E-field is in V/m, H-field in A/m, etc.

� Non-complex Magnitude quantities and allVector quantities can be Animated vs.Phase

� Shows changing field on the displaygeometry as excitation phase is rotated

� Most Quantities can be displayed onsurfaces, along lines, and within 3Dvolumes

� Other quantities not listed can be derivedusing the Field Calculator and displayed inthe graphical window following calculation


www.cnantennas.com


3D Post-Processor Plot Geometry� All field plots are generated on Geometry� The available geometry list will automatically include all

objects built in the 3D modeler and used in the problemsetup

� Surfaces of all 3D solids and 2D sheets� Volumes of all 3D solids

� Other default geometry identities for plotting are alsoincluded

� Principle Plane cutplanes (XY, XZ, YZ)*� Volume -all- (entire modeled volume)� Animation Surfaces for multi-surface frame lists

� The user can create additional geometry for plottingusing the Geometry menu

� Cutplanes and face lists create additional surfaces� Line command creates lines for integration, plotting

*NOTE: The principle plotting planes (XY, XZ, and YZ) will recognizechanges to the local coordinate system while in the post-processor.


www.cnantennas.com


Plotting FieldsFields are plotted by selecting Field...From the Plot menu

� Select a Quantity to plot in theleft column

� Select a Geometry on which toplot in the center column

� (Optional) Select a Volume(domain) limit for plotting in theright column

� For a single phase snapshot,enter desired phase and pressOK (n/a for Cmplx quantities)

� For Phase Animation, check thebox and press OK

� A plot settings dialog will launchwith different entries dependingupon the Quantity and Geometryselected (see next slide)

NOTE that the above Plot Quantities can all be classified ascontaining either scalar or vector data


www.cnantennas.com


Plot Settings Dialogs: Stills

Scalar Surface andVolume plots differ onlyin ability to fill in colormaps

Requesting a plot of a scalarvalue along a line results in a2D graph, rather than acolormap plot in the graphcialdisplay window


www.cnantennas.com


Plot Settings Dialogs: Animation� Selecting any AnimSurf entry in the On Geometry

column results in a series of snapshots at differentplanar or object surface faces in the model

� The appropriate variable will be given in the topfield; user sets start, stop and step limits

� Selecting the Phase Animation button results indisplay of multiple field plots (each at a differentexcitation phase) on the same geometry.

� The variable is Phase; user sets limits� For either animation, checking the Store Frames

button saves the individual snapshots as a separatelyviewable plot

� Stored Frame Lists contain full plots that can beviewed from alternate angles, zooms, etc, andare maintained in memory until manually deleted(see Plot Management, next slide).

� Leaving Store Frames unchecked creates ascreen animation, which cannot be viewed fromdifferent orientations after creation, and is auto-matically deleted after the display is dismissed.

Dialog for “AnimSurf XY” selection(Variable is Z position of XY planes)

Dialog for Phase Animation


www.cnantennas.com


Plot Management� All 3D Field Plots are maintained in local memory, and can

be managed during your post-processing session� Plots can be Saved and Opened in later sessions

� Field views (scalar colormaps or vector plots) are savedas 3D Plots, while Graphs (plots of scalar quantitiesalong lines) are saved as 2D Plots

� Modify allows you to re-select the settings for any currentlyopen plot

� Visibility allows you to show or hide any currently open plot.� Plots which are hidden are still in memory

� Delete allows you to remove any currently open (visible orhidden) plot from memory.

� To see the same plot again, you will have to re-createthe plot using the Field pick in the Plot menu

� The Animation menu pick allows management of variousframe lists created using Store Frames

� It can also be used to assemble user animations fromany available individual plots!


www.cnantennas.com


Field Post-Processing Exercise 1: Plot aMesh

1. Find and open the project named “orth_slv”, anorthomode coupler. Proceed directly to PostProcess...Fields.

2. Using either the select tool icon or the Edit...Selectmenu pick, select the object “wavegda”.

3. From the Plot menu, pick Mesh.

4. In the mesh display dialog, leave the Scale Factorat 80, and leave all radio button options where theyare. Press OK to create the mesh plot.

5. From the Plot menu, pick Visibility. In the resultinglist box, click on the entry for Plot1 (our mesh plot) totoggle visibility to “No”. The mesh plot disappearsfrom the screen, but is still maintained in memory.

1. (Not shown)

2.

3.

5. (result not shown)

4.


www.cnantennas.com


Field Post-Processing Exercise 1: Plot Fieldon Existing Geometry

1. Since we have not changed the default excitation,only Port 1, Mode 1 is currently being driven. In thismodel, Port 1 is the rectangular port entering alongthe Y axis of the coordinate system.

2. From the Plot menu, pick Field...

3. In the resulting dialog, select Mag E as thequantity, Surface XY as the geometry, and leave thethird column unaffected (defaults to Volume -all-domain if nothing is selected). Press the OK button atthe bottom of the dialog to confirm selections.

4. A scalar plot settings dialog will now open. Leaveall settings at their default values, except for Divisions.Increase from the default of 11 to 21. Press the OKbutton to create the scalar colormap.

5. If you wish, manipulate the view by zooming,panning, or rotating it to a different orientation. Thecolormap plot may take a moment to refresh, but willbe displayed regardless of the model’s size andorientation.

Note that the color scale shows little detail of fieldbehavior, because we accepted the Autoscalesettings in the dialog and high field values near theinput arm are weighing the results. We can modifythis plot to show more detail by altering the scale.

1.

2.

3.

4.

5. (shown zoomed)


www.cnantennas.com


Field Post-Processing Exercise 1: Modify Plot

1. From the Plot menu, select Modify.

2. A list of plots available for modification appears.Select Plot2 (our Mag E field plot) and press OK.

3. The scalar surface plot dialog appears. Notice thatin the Plot Scale area, the Maximum field value of theplot is identified as about 28,000 V/m. Select theradio button for Use Limits to enable entry in this field,and change the maximum to 10,000. Increase thenumber of Divisions to 31. Press OK.

4. The plot will be modified to the new scale settings,showing more detail in the circular waveguide section.

SHORTCUT: You can also modify any plot withoutusing the menu and selecting its name from a list bydouble-clicking directly on the plot color ‘legend’.

5. In the Plot menu, pick Visibility, and toggle Plot2 to“No”.

1.

2.

5. (not shown)

4.

3.


www.cnantennas.com


Field Post-Processing Exercise 1: CreateNew Geometry

1. From the Geometry menu, pick Create...Cutplane.

2. The dialog shown opens in the side window, and atransparent plane and normal indicator show in thegraphical display window. We are now ready tocreate a cut plane (or slice through the model) onwhich to display field quantities.

3. Snap the cursor to one of the two points at the endof the 2D sheet trace threading the horizontalwaveguide arm.

4. Press the Set button beneath the Origin header inthe side window. This sets the present cursor positionas the origin of our new cutplane.

5. To change the orientation of the cutplane about theaxis, we could pick a second point and click the Setbutton beneath the Normal header, or we can use the“” buttons to rotate the plane about theappropriate axis manually. Each click of thesebuttons is a 10 degree rotation increment. Click the “>” button next to the Y indicator ninetimes, to rotate the notional plane 90 degrees aboutthe Y axis.

6. Change the name of the plane to port_cut and clickthe OK button at the bottom of the side windowdialog.

1.

2. 3.

4.

5.

6.

Desired Plane


www.cnantennas.com


Field Post-Processing Exercise 1: Plot VectorAnimation

1. In the Plot menu, pick Fields.

2. Select Vector E as the field quantity andSurface port_cut as the geometry on which to plot.Check the Phase Animation button, then pressOK.

3. In the animation dialog, leave the startingphase at zero, and change the Stop phase to 360and the Delta to 10. Check the Store Framesbutton and press OK.

4. In the Vector surface plot dialog, notice that ourlimits from the prior plot are remembered. Leavethem be, but change the vector Size to 0.05, theSpacing to 0.05, and uncheck the Map Sizebutton. Press OK to create the animation.

5. After a few seconds for calculation of all theframes, an Animation Plots control dialog willappear. You can play the frames in sequence bypressing the play [�] button, or show them one ata time by highlighting them in the list and pressingShow.

This completes the first post-processor exercise.You may press Done on the Animation controldialog and Exit the 3D post-processor via the Filemenu.

1.

2.

4.

5.

3.


www.cnantennas.com


Antenna and EMI Processing: ComputingFields

� Projects with some form of open exteriorboundary condition (either radiation or PML)can have fields calculated external to themodeled space.

� Fields are computed using the Radiationmenu, selecting Compute...Far Field or NearField

� Far Field is the field at a radius of infinityfrom the coordinate system origin

� Near Field permits a user-enteredradius

� Fields are computed over user-specifiedangular ranges in phi and theta

� Once computed, the fields are savedand may be plotted

� If a plot of a near/far field cut outside ofthe computed range is desired, thefields will need to be re-computed first


www.cnantennas.com


Antenna and EMI Processing: DisplayingComputed Fields

� Computed fields are plotted using thePlot menu, Far Field or Near Field

� Plot dialog permits plotting of antennagain, directivity, axial ratio,polarization ratio, rE component fields,and rE total fields

� Plots may be polar 2D, Cartesian 2Dor polar 3D.

� Displayed patterns can be saved as2D Plots under the Plot...Save menuselection

� The field computation and plottingdoes take symmetry planes intoaccount


www.cnantennas.com


Antenna and EMI Processing: DisplayingComputed Field Parameters

� Computed Near and Far Fieldresults can also be displayed intabular format, showing the peakE-field magnitudes and locations

� Far Field parameters includeAntenna Parameters such as

� Beam Area� Directivity� Radiated Power� Accepted Power� Efficiency� Maximum U (radiation power

density)


www.cnantennas.com


The HFSS Field Calculator

� Allows manipulation of modeled fields in the entire problem region� Permits direct access to , , and Poynting Vector with all real,

imaginary, and vector components� Includes Scalar, Vector, Complex, Integration, and Differentiation

functions� Results can be Output to Post-Processor Graphical Display window

for color maps, vector plots, or 2D Graphs� Results can also be exported to external data files

� Contains a large registry stack with standard RPN-type stackmanipulation features

� Push, Pop, Exchange, Rotate...� Is Unique to Ansoft HFSS!!

E H k


www.cnantennas.com


Accessing the Field Calculator

� The Field Calculator isaccessed using either thetool icon or theData...Calculator menupick

� Once open, the calculatoris a separate window fromthe 3D Post-Processor,and can be moved off ofthe Post-Processorbackground, minimized,etc.


www.cnantennas.com


Field Calculator Stack� The calculator stack builds from

the top down� The top entry is the most

recently added, withsubsequently older entriesflowing downward

� Stack manipulation buttons arelocated immediately beneath thestack display

� Push duplicates the top entry� Pop deletes the top entry� RlDn and Rlup ‘rolls’ the

stack contents upward ordownward

� Exch swaps the two topentries

� Clear empties the stack� Undo reverses the last

operation

NOTE: Most calculators using RPN and stack operation rollsubsequent entries so that the bottom of the display is thelatest value entered. The Ansoft Field Calculator uses theopposite convention. Therefore, to subtract 3 from 5, the stackmight resemble:

Scl: 3Scl: 5

before the subtraction is performed, NOT the reverse as onemight initially expect.


www.cnantennas.com


Field Calculator Data Types� Field Calculator stack entries are all classified

by data type� Available data types are:

� Complex Vector� Complex Scalar� Complex� Vector� Scalar� Volume� Surface� Line

� The type of each stack entry is indicated withan abbreviation to the left of the stack entry

� In some cases, certain mathematicaloperations require specific data types inspecific positions in the stack


www.cnantennas.com


Field Calculator Layout� Field Calculator Functions are organized in

columns, by classification� Input column functions create inputs

[E-field, H-field, Poynting data,Geometry, Numerical values (scalar,complex, and vector), etc.]

� General column functions work on moststack contents

� Scalar column functions operate only onscalar quantities

� Vector column functions operate only onvector quantities

� Output column functions produce outputfrom the calculator[graphs, color or vector displays, outputfiles, integral evaluations, etc.]


www.cnantennas.com


Post-Processor Exercise 2: AntennaPost-Processing

The following exercise will walkthrough antenna patterngeneration for a CPW-fedpatch antennaThis exercise may be omitted ifthe class as a whole has nointerest in far-field computationand post-processing


www.cnantennas.com


Post-Processor Exercise 2: SelectFrequency for Antenna Pattern Analysis

1. Open the Project titled “ptch_slv”, andproceed directly to Matrix Plot from the PostProcess dropdown in the Executive Window.

2. In the Plot menu, pick New Plot. Generate aplot of S11 Magnitude vs. frequency, with thevertical axis scaled in dB.

3. Use the Show Coordinates tool button toselect the trace, and move to the frequency oflowest return loss (minimum S11). This is theantenna’s best match frequency, and thefrequency at which we are most likely to beinterested in antenna performance.

4. Make a note of the frequency at theminimum point (37.4324 GHz) and Exit theMatrix Plot interface.

5. Proceed to Fields... from the Post Processdropdown in the Executive Window. Wait forthe field solution to load.

NOTE: As this is a large project (over 24,000tetrahedra) it may take several seconds for thefield solution to load into the Fields Post-Processor.

2.

3.

1, 4, 5 (not shown)


www.cnantennas.com


Post-Processor Exercise 2: Set Excitations

1. From the Data menu, pick Edit Sources...

2. A dialog window will open showing availablesources and their settings. Since this is a one-port problem, changing the phase is irrelevant.Changing the magnitude is relevant only if weare concerned with absolute field values in themodel, rather than dB-relative antenna patterns.However, we do need to specify the frequencyto match that at which we desire antennapattern data. Check the box for SpecifyFrequency to activate the entry field, and enterthe value found in the prior operation, 37.4324GHz.

NOTE: The specify frequency box is onlyavailable with a fast sweep solution. Note alsothat it is not necessary to pick an exactfrequency point obtained in the fast sweep,merely that the value entered be within thefrequency sweep range that was solved.

3. Click the OK button to complete theoperation. There may be a delay and a warningnotice as the post-processor resets the fielddata to the desired excitation frequency.

1.

2.

3.


www.cnantennas.com


Post-Processor Exercise 2: Compute Fields

1. From the Radiation menu, pickCompute...Far Field.

2. A dialog box requesting Far Fieldcomputation parameters will open. Set theangular limits as shown to obtain two principle-plane antenna pattern cuts with fixed azimuthangles of 0 and 90, spanning 0 to 360 inelevation.

3. Click the OK button. A progress bar willappear as the E and B fields are computed onthe radiation boundary, and the resulting farfields are computed from them. When thecomputation is complete, a dialog requestingplot information will automatically launch.(Proceed to next page)

NOTE: Had we desired to specify a surfaceother than that assigned as the “radiation”boundary for our far field computation, we wouldhave done that using the Custom Surfacecheckbox and resulting selection options.

1.

2. Phi: Start: 0 Stop: 90 Steps: 1 Theta: Start: 0 Stop: 360 Steps: 360

3.


www.cnantennas.com


Post-Processor Exercise 2: Plot AntennaPattern

4. In the Plot Far Field dialog which wasautomatically launched following computation,select Antenna Gain Pattern as the plotquantity, check the dB box to scale in dB.

Leave Polarization set to Total, the plot Type setto 2D Polar, the Fixed Variable set to Phi andclick the Select All button beside the listed fixedphi angles of 0 and 90 to highlight them both.

Click the OK button to close the dialog andgenerate the antenna pattern.

If you wish, you may generate additionalantenna plots by selecting Far Field from thePlot menu of the post-processor to re-open thePlot Far Field dialog box shown here.Quantities which may be plotted include gain,directivity, axial ratio, and polarization ratios.

You may also display summary antennastatistics (valid over the computed angularvalues only!!) by selecting Display Data...FarField from the Radiation menu.

4.


www.cnantennas.com

Documents

Processing Section 8: Fields Post- Training · Field Post-Processing Exercise 1: Plot Field on Existing Geometry 1. Since we have not changed the default excitation, only Port 1,