ie3d教程CHAP12Word格式文档下载.docx

ie3d教程CHAP12Word格式文档下载.docx

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TheIE3Demploysanintegralequation,methodofmomentformulation.Integralequationformulationitselfisnotanapproximatemethod.However,theGalerkin’sprocedureandthefinitetruncationofthebasisfunctionsintroduceapproximation.Basically,weusefinitedimensionalfunctionstoapproximatetheinfinitedimensionalcurrentdistributiononacircuit.Becauseitisanumericalprocedure,manyfactorsinvolvedinthenumericalcalculationareaffectingtheaccuracyofasimulation.FollowingaresomeofthemajorfactorsmayaffectanIE3Dsimulation.

（1）.MeshingFrequency（orFmax）;

（2）.MeshingCellSize（CellsperWaveguideWavelength,Ncell）;

（3）.De-embeddingSchemes;

（4）.TheNumberofCellsinDe-embeddingRegion（De-embeddingCells）;

（5）.TheMeshingSchemes（WithorWithoutEdgeCells）.

（6）.ThenumberofimagesusedintheenclosedorperiodicGreen’sfunctions,whichwewilldiscussinthenextchapters.

Usually,morecellsinasimulationyieldhigheraccuracy.LargerMeshingFrequency（Fmax）orCellsperWavelength（Ncells）meansmorecellsandmeansmoreaccurateresult.However,wecannotjusttrytoincreasetheFmaxorNcellsindefinitelybecausewewillrunoutofmemoryverysoon.Ifweusethecellssmartenough,wecanachievehighaccuracywithsmallnumberofcells.

Inthischapter,wewillconcentrateonhowwecanimprovethesimulationaccuracybysmartlyconstructingastructure.

Section1.AddingEdgeVerticestoControlMeshing

WhenwediscussourfirstexampleinChapter3,wehavedemonstratedhowwecanuseAutomaticEdgeCells（AEC）toimprovesimulationaccuracy.Edgecellsarecertainlyverycriticalincapturingtheedgeeffectsofmicrostripstructures,anduseofedgecellscanimprovethesimulationaccuracysignificantlyespeciallyforstronglycoupledstructures.WecanclaimthatAECguaranteeshighaccuracyfornoviceusers.IntheIE3D11,wedefineAECbaseduponAECRatioortheratiobetweentheedgecellsizeandtheregularcellsize.Inthisway,itsignificantlyreducesthechanceforausertousetoosmallortoolargecellsaccidentallybecausetheedgecellwidthisautomaticallyscaledwiththemeshingfrequency.

IntheIE3D11,wealsoimplementedthemulti-layerAECandAECforthicknesstraces.Multi-layerAECallowsausertodefinemultipleedgecellsalongtheedgestofurtherimprovetheaccuracy.Itcanyieldextrememodelingaccuracyforhighaccuracyrequirementssuchasdesigning40-dBdirectionalcouplers.AECforthicknesstracesfurtherimprovetheaccuracyformodelingtraceswithtruethickness,whichnormallydonotneedAECunlessextremehighaccuracyisrequired.

AECiscertainlyverygoodforaccuracy.Forsmallandmediumsizeproblems,wenormallyshouldenableAEC.Itwillyieldhighaccuracywithoutextrageometrymodelingeffort.However,AECnormallyincreasestheproblemsize（numberofunknowns）significantly.Foralargestructure,enablingAECandwithoutenablingAECmaymakeabigdifferenceinthesimulationtime.Itwouldbeniceifwecangethighaccuracyresultswhilewemaynotneedtouseedgecellseverywhere.Forsomepartsofastructure,wemaygethighaccuracyresultswithoutedgecells.Normally,iftwoedgesarenotveryclose,edgecellsmaynotbeveryimportant.IfatraceisnotacriticalpathforatransmissionandtherelatedS（i,i）,asasmallquantity,isnotaverycriticalparameter,wecanalsoomittheedgecellsonit.

ForexperienceduserswhoknowaboutwhereedgecellsmightormightnotbecriticalcandisableAECwhiletheycancreatetheedgecellsbyinsertingverticestocontrolthemeshing.Wewilldemonstratesomeexamplesonmanuallyinsertingverticestocontrolthemeshing.

Ourfirstexampleisthesuspendedstriplinestructurein.\ie3d\samples\one_cell.geo.Itisthesameoneasthe.\ie3d\samples\connect.geo.Wehaveusedthisexampletodemonstratetheimportanceofpolygonconnection.Wewillusethisexampletodemonstratehowwecaninsertverticestocontrolthemeshingprogramtocreateedgecells.

Step1RunMGRID.Openfile.\ie3d\samples\one_cell.geo.Saveitinto.\ie3d\practice\one_cell.geo.

Step2SelectProcess->

DisplayMeshingcommand.TrytodoitwithAECdisabledandAECenabledwithAECRatio=0.05.ThemeshingresultsareshowninFigure12.1.

（a）AECdisabled（b）AECenabledwithAECRatio=0.05

Figure12.1Themeshedstructureofone_cell.geo.

（a）BeforeRectanglization（b）AfterRectanglization

Figure12.2ThestructurebeforeandafterRectanglization.

Step3Wearegoingtomodifythegeometrytoforceittobemeshedinto3-cellsinthetransversedirection.ThecommandweareusingistheEdit->

AddEdgeVerticescommand.However,beforeweapplythiscommand,wewouldliketorectanglizethestructurefirstbecausetheEdit->

AddEdgeVertice