Getting-Started-Ansoft-HFSS-8.0

1-1GettingStarted:AnsoftHFSS8.0BaofuJiaPhysicalElectronicsInstituteUniversityofElectronicScienceandTechnologyofChina1-2Section1:IntroductiontoHFSSandtheFiniteElementMethodGettingStarted:AnsoftHFSS8.01-3SynopsisofIntroductionGeneralFEMIntroduction,Usage,andDefinitionsFEMinElectromagneticsPositioningvs.OtherSolutionTechniquesPossibleApplicationsHighFrequencyStructureSimulatorIntroductionTheHFSSFieldEquationandMatrixSolutionHFSS“Adaptive”Convergence1-4WhatisFiniteElementMethod(FEM)Software?FEMsoftwareisadesigntoolforengineersandphysicists,utilizingrapidcomputationstosolvelargeproblemsinsolublebyanalytical,closed-formexpressionsThe“FiniteElementMethod”involvessubdividingalargeproblemintoindividuallysimpleconstituentunitswhichareeachsolubleviadirectanalyticalmethods,thenreassemblingthesolutionfortheentireproblemspaceasamatrixofsimultaneousequationsFEMsoftwarecansolvemechanical(stress,strain,vibration),aerodynamicorfluidflow,thermal,orelectromagneticproblems1-5FEMProblemConstraintsGeometrycanbearbitrary,3-dimensionalModel‘subdivision’isgenerallyaccomplishedbyuseoftetrahedralorhexahedral(brick)elementswhicharedefinedtofillanyarbitrary3DvolumeBoundaryConditionswithinandwithoutproblemcanbevariedtoaccountfordifferentcharacteristics,symmetryplanes,etc.SizeconstraintsarepredominantlysetbyavailablememoryanddiskspaceforstorageandsolutionoftheproblemmatrixSolutioncreatedisinthefrequencydomain,assumingsteady-statebehavior1-6MajorIndustriesusingFEMSoftwareCommunications/TelecomAerospace/AviationAutomotivePowerConsumerElectronics(Audio/Visual,Computer)Medical(Imaging,ElectricalEquipment)Universities(ResearchandInstructional)1-7CommonlyUsedTermsinFEMAnFEM“Element”isasinglesubdivided‘unit’oftheoverallproblemtobesolved.HFSSusestetrahedralelements,withtriangularfaces.The“Mesh”isthemappingoftetrahedralelementstothe3Dgeometryforwhichasolutionisdesired.Meshingistheprocessofdefiningthepositionofverticeswhichcompriseallthetetrahedrallocationsinaproblemspace.The“Matrix”istheassemblyofsimultaneousequationsrelatedtothemeshwhichpermitsolutionofbehaviorinadefinedsolutionspaceHFSS’smatrixequationsareformulatedtosolveforelectromagneticfieldbehavior1-8DifferentMethodsofElectromagneticAnalysisMOM1-9WhenisanFEMsolverappropriateforElectromagneticProblems(LowerBound)?/1000UseaQuasi-StaticSolverWhentheElectricalLength(inwavelengths)requiresphaseconsideration/10isaguideline;thereareexceptionsWhenradiationfromthedevicemustbeconsideredWhenS-ParametersarethedesiredoutputWhenlossydielectricmaterialshavesignificanteffectsUseaFEMFull-WaveSolverProblemScaleExample:FindingSignalIntegrityimpactsofaViainthesignalpath/10(OVERLAP)Example:CoaxtoWGTransformer1-10WhenisaFEMsolverappropriateforElectromagneticProblems(UpperBound)?WhenthestructureunderevaluationisnottoolargetobereasonablysolvedwithavailableresourcesThislimitisVERYproblemandhardwaredependentROUGHrule-of-thumb:Projectsshouldbewithin5x5x5wavelengthsinvolumeWhenthestructure’saspectratiodoesnotexceedmany-thousandstooneExample:extremelylong,thinwireantennasmightbemoreefficientlysolvedusingaWire-MoM(e.g.NEC)Entirely‘planar’structureswithstratifieddielectricsmightbemoreefficientlysolvedusinga2.5DMoM(e.g.Ensemble)Whenthestructure’sbehaviorisnotmoreeasilyapproximatedusingOptical(GTDorRay-Tracing)TechniquesExample:ParabolicDishantenna,generallymany10’sofwavelengthsindiameterExample:RadarCrossSectionofalargevehiclebody,suchasanaircraftorhelicopter1-11SomeTypicalHigh-FrequencyElectromagneticApplicationsWaveguideComponentsAntennaRFIntegratedCircuitsEMC1-12HighFrequencyStructureSimulator(HFSS)FlowchartofGeneralDesignProcessInputModelParametersGeometryMaterialPropertiesBoundaryConditionsDefineSolutionCriteriaFrequencyAdaptive?ConvergenceParameters?Sweep?SweepParameters?ReviewResultsS-Parameters(TabularandPlotted)FieldVisualizationDataOutput/ExportationPerformSweepSolutionDefineExcitationacrossbandSolve3DFieldsacrossbandAdaptive?Sweep?IterateonSolutionEvaluatevs.ConvergenceParametersRefineMeshandResolveExitonlywhenConv.ParametersMetYESNOYESNOPerformInitialSolutionGenerateMeshSolveExcitationsSolve3DFieldsSOLUTION1-13HFSSSolutionProcessSubdividemodelintoElements(tetrahedra)DefinebasisfunctionspertetrahedraBasisfunctions,Wndefineconditionsbetweennodallocationsintheoverallmeshoftetrahedra,basedonprobleminputsFunctionsaresimpleandnonzeroonlywithinthetetrahedraMultiplyBasisFunctionsbyFieldEquationHFSSSolvesFieldEquationDerivedfromMaxwell’sEquations:IntegrateresultoverVolumeIntegrationreplicatedinthousandsofequationsforn=1,2,...NIntentistoobtainNequationswithNunknownsforsolution012EkErorVnrorndVEWkEW0121-14HFSSSolutionProcess,cont.RewriteEquations,UsingGreen’sandDivergenceTheorems:SetEqualtoExcitation/BoundaryTermsWriteEfieldassummationofunknowns,xm,timessamebasisfunctionsusedingeneratingtheinitialseriesofequations:ResultingEquationsallowsolutionofunknowns,xm,tofindENote:EquationhasthebasicformAx=B,whereAisthebasisfunctions