WIXLIB

Ansys High Frequency StructureSimulator (HFSS) TutorialMARK JONESPACIFIC NORTHWEST NATIONAL LABORATORY8/21/18August 16, 20181

AgendaOverview of HFSSCapabilities and key featuresExample measurement comparisonsCylindrical cavity tutorialEigenmode solverParametric geometryCurvilinear elementsModal frequenciesQ-factorsField plotsField calculatorAugust 16, 20182

Overview of HFSSFull-wave frequency-domain 3-D field solverbased upon finite element methodIndustry-standard accuracyAdaptive meshing of arbitrary geometryFully parametric modelingOptimization and HPCMulti-physics via Ansys WorkbenchWidely used for RF/microwave designAntenna design and platform integrationFilters and waveguide structuresElectronic packages and PCBsConnectors and transitionsEMC/EMIRadar cross-sectionIntegrated into Ansys Electronics DesktopPart of Ansys Electromagnetics SuiteAugust 16, 20183

Recent Capability Additions to HFSSBase license includes multiple solversFrequency-domain 3D finite element solverFrequency-domain 3D finite element eigenmode solverTransient finite 3D element solverFrequency-domain 3D integral equation solverFrequency-domain FEBI hybrid solverFrequency-domain 2.5D planar integral equation solverLinear circuit solverBase license enables use of 4 processor coresHPC, Optimetrics, and Distributed Solver licenses increase computingcapabilitiesHFSS offers two different interfaces to same solver to accommodatedifferent workflows3D view (for CAD)3D Layout view (for ECAD such as Cadence, Mentor Graphics)August 16, 20184

HFSS R19 User Interface within AnsysElectronics DesktopRibbon /ToolbarsProjectManager3DModelEditorTree3D sWindowAugust 16, 20185

Frequency-domain FEM Solution TypesEigenmode solutionSolves for natural resonances of structurebased on geometry, materials, and boundariesProvides modal frequencies, unloaded Qfactors, and fieldsCan solve for up to 20 modes at onceDriven solutionPort or incident field used to excite thestructureDriven modal method commonly used forRF/microwave designsDriven terminal method commonly used formulti-conductor transmission lines (nowaveguides, symmetry boundaries, or Floquetports)Provides S-parameters and fieldsAugust 16, 20186

Adaptive Mesh AlgorithmTetrahedral mesh automatically generatedand refined below user-defined electricallengthTetrahedral element shape conforms toarbitrary geometriesIterative algorithm solves fields and refinesmesh until user-defined convergencethreshold value is reachedCan be performed for set of user-specifiedfrequencies (broadband adaptive meshing)Driven modal: S-parameter convergenceEigenmode: Frequency convergenceProduces graded mesh with finediscretization only where needed toaccurately represent field behaviorEfficient use of computational resourcesTunes mesh to capture EM performanceAugust 16, 20187

Mesh ControlsMesh seeding allows user to directlyinfluence initial meshReduce number of adaptive passesFocus mesh elements in critical areasNot required for accurate resultsCan improve field plotsSeeding radiation boundary canimprove far-field dataLambda refinementEnsures that initial mesh is refined tofraction of electrical wavelengthElectrical size depends on solver basisorderZero: /10, First: /3, Second: 2 /3,Mixed: 2 /3Initial geometric meshElectrical mesh afterlambda refinementAugust 16, 20188

Curvilinear Mesh ElementsGlobal mesh approximation settingfor all true surfaces in modelHigher order (curvilinear) elementsused to represent the geometryPulls midpoints of tetrahedrasurfaces to true surfacePillbox resonator with analytical fR 22.950 GHz for TM010 modeDefault setting: 23.269 GHzFiner segmentation: 23.012 GHzCurvilinear elements: 22.950 GHz6024 DOF1.38% error6140 DOF0.03% error4966 DOF0.00% errorAugust 16, 20189

Port Excitations for Driven SolutionsWave ports2D FEM solver calculates requested numberof modes (treated as t-line cross-section)Solves for impedances and propagationconstantsSupports multiple modes and de-embeddingSimple for closed t-linesMust allow room for fields of open t-linesMust touch external boundary or backed byconducting objectLumped portsUser-assigned constant impedanceUniform electric field on surfaceSingle TEM mode with no de-embeddingCan be internal to modelAugust 16, 201810

Frequency Sweeps for Driven SolutionsDiscrete sweepSolves adapted mesh at every frequencyMatrix data and fields at every frequencyFast sweepAdaptive Lanczos-Padé Sweep (ALPS) solverextrapolates rational polynomial function forelectric field over specified range from centerfrequency field solutionUsually valid over less than 10:1 BWMatrix data and fields at every frequencyInterpolating sweepSolves minimum number of frequencies tocreate rational polynomial fit for S-parametersUseful for very broadband S-parametersMatrix data at every frequencyAugust 16, 201811

FEM Solvers for Driven SolutionsDirect matrix solver is default techniqueExactly solves matrix equation Ax bMulti-frontal sparse matrix solver to findinverse of A (LU decomposition)Solves for all excitations b simultaneouslyIterative matrix solver is optional techniquefor driven solutions B t D H J t D B 0 E Reduces RAM usage and often runtimeSolves matrix equation Max Mb where Mis preconditionerBegins with initial solution and recursivelyupdates solution until tolerance is reachedIterates for each excitation bMore sensitive to mesh quality, reverts todirect solver if it fails to convergeAugust 16, 201812

Boundary ConditionsCan be used to simplify geometry ormake meshing more efficientMaterial properties for surfacesFinite conductivity (imperfect conductor)Perfect electric or magnetic conductorSurface approximations for componentsLumped RLCLayered impedanceRadiationAbsorbing boundary conditionPerfectly matched layers (PML)FE-BI boundaryAny object surface that touches thebackground is automatically defined asPerfect E (perfect conductor) boundaryAugust 16, 201813

FEM Basis FunctionsBasis functions are n-order polynomials thatdescribe how E-field varies along mesh elementsedge, face, or volumeHierarchical basis functionsZero or first or second order basis functionsHigher-order elements have increased accuracy butmore unknowns (6, 20, 45)Mixed order basis functionsZero and first and second order basis functionshp-FEM method refines element order p and elementsize hAutomatically distributes element order based onelement size to optimize use of resourcesChoice of ideal basis function is problem dependentMixed order efficiency is comparable to or better thanbest of single order basis functionsAugust 16, 201814

Fields CalculatorTool for performing math operationson saved field dataE, H, J, and Poynting dataGeometric, complex, vector, andscalar dataUses peak phasor representationsof steady-state fieldsPerform operations using model ornon-model geometryGenerate numerical, graphical,geometrical, or exportable dataNamedexpressionsData stackReverse Polish notationFrequently used expressions canbe included in user library andloaded into any projectEliminates need to re-createexpressions used across unctions1Re{E H *} ds2 s1 E 2 dv2 vAugust 16, 201815

Quality Factor of Eigenmode SolutionsProvided with solution data for eachrequested modeObtained from complex frequency𝑄𝑢 𝑓𝑟𝑒𝑞2 𝑖𝑚𝑎𝑔(𝑓𝑟𝑒𝑞)Can also be calculated using fieldscalculator H d 2Qu s22n Hd tg H d 2 August 16, 201816

Example Comparison with MeasurementExcellent agreement for ADMX cylindrical cavityHFSS solution includes 12 modes in vicinity of TM010 modeBlue markers indicate mode with largest form factor at each rod locationMeasured and COMSOL results(Lyapustin 2015)August 16, 201817

Example Comparison with COMSOLModel presented by SungWoo Youn at January 2017 Workshop onMicrowave Cavities and Detectors for Axion ResearchDielectric rod moved from center to wall in 1.5 mm incrementsYoun 2017HFSS ResultsAugust 16, 201818

Other Comparisons with MeasurementsAugust 16, 201819

Cylindrical Cavity ExampleAugust 16, 201820

Cylindrical Cavity ExampleEmpty copper cavityRadius 21 cmHeight 100 cmExpected results for TM010 modefR 546.42 MHzQ-factor 61,391 (Li and Jiang, 2006)Form factor C 0.69 (Peng et al., 2000)Form factor C 0.692 (Stern et al., 2015) H R Qu R H August 16, 201821

1: Create HFSS ProjectInsert into Electronics Desktop using NewAugust 16, 201822

2: Set Eigenmode Solution TypeSelect HFSS Solution Type EigenmodeAugust 16, 201823

3: Set Model UnitsSelect Modeler Units cmAugust 16, 201824

4: Set Dialog Data Entry ModeSelect Tools Options General Options 3D Modeler Drawing DialogAugust 16, 201825

5: Set Default Transparency of 0.7Select Tools Options General Options Display RenderingAugust 16, 201826

6: Create Parameterized CavitySelect Draw CylinderAugust 16, 201827

6: Create Parameterized CavityCavity rad 21 cmCavity height 100 cmAugust 16, 201828

6: Create Parameterized CavityFit cavity to view using View Fit All All ViewsAugust 16, 201829

7: Assign Cavity Wall ConductivitySelect cavity in 3D modeler tree and Edit Extend Selection AllObject FacesAugust 16, 201830

7: Assign Cavity Wall ConductivitySelect HFSS Boundaries Assign Finite ConductivityAugust 16, 201831

7: Assign Cavity Wall ConductivityEnter name “cavity walls” and use default 5.8E7 S/mAugust 16, 201832

7: Assign Cavity Wall ConductivityShould have boundary condition as shown hereAugust 16, 201833

8: Apply Curvilinear Mesh ElementsSelect cavity in 3D modeler tree and apply curvilinear elementsSelect HFSS Mesh Operations Assign Apply Curvilinear MeshingAugust 16, 201834

8: Apply Curvilinear Mesh ElementsCan also apply curvilinear elements as global settingRight-click Mesh Operations Initial Mesh SettingsAugust 16, 201835

9: Add Solution SetupSelect HFSS Analysis Setup Add Solution SetupAugust 16, 201836

9: Add Solution SetupEnter Minimum frequency 540 MHz, Number of Modes 3, Maximum Numberof Passes 12, Max Delta Frequency / Pass 2%, Minimum Passes 4August 16, 201837

10: Save ProjectSelect File Save and save project as “cavity tutorial.aedt”August 16, 201838

11: Perform Validation CheckSelect HFSS Validation CheckConfirms that required steps to solve model have been performedAugust 16, 201839

12: Solve ModelSelect HFSS Analyze AllAugust 16, 201840

13: View Solution DataSelect HFSS Results Solution DataAugust 16, 201841

13: View Solution DataSelect Eigenmode Data tab to view modal frequencies and Q-factorsTM010TM011TE113August 16, 201842

13: View Solution DataSelect Convergence tab to view adaptive pass informationAugust 16, 201843

13: View Solution DataSelect Profile tab to view run log file (20 sec runtime)August 16, 201844

14: View E-Field Phase AnimationSelect XZ and YZ planes in 3D modeler tree and select HFSS Fields PlotFields E Mag EAugust 16, 201845

14: View E-Field Phase AnimationSelect Done to create plot of electric field magnitudeAugust 16, 201846

14: View E-Field Phase AnimationRight-click on Mag E1 plot to animate phasor fieldAugust 16, 201847

15: View E-Field Vector AnimationSelect XZ and YZ planes in 3D modeler tree and select HFSS Fields PlotFields E Vector EAugust 16, 201848

How to Activate Mode of Interest for FieldPlots and CalculationsSelect HFSS Fields Edit SourcesAugust 16, 201849

16: Calculate Form FactorOpen field calculator using HFSS Fields CalculatorAugust 16, 201850

16: Calculate Form Factor AssumingUniform Z-directed Magnetic FieldMust use integration by partsStep 1: Calculate integral of real(Ez)Quantity EScal? ScalarZComplex RealGeometry Volume cavityIntegrate, EvalStep 4: Calculate cavity volumeNumber - 1Geometry Volume cavityIntegrate, EvalForm factor (1471252 1.82512) /(0.13854*225763387957) 0.692Step 2: Calculate integral of imag(Ez)Quantity EScal? ScalarZComplex ImagGeometry Volume cavityIntegrate, EvalStep 3: Calculate integral of E 2Copy ComplexMag E to stackPushMultiply (*)Geometry Volume cavityIntegrate, EvalCan save operations as Named Expressionwhich can be evaluated in single stepAugust 16, 201851