ie3d教程CHAP13.docx
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ie3d教程CHAP13.docx
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ie3d教程CHAP13
Chapter13.SimulationofAntennaArrays
WehavedemonstratedhowtouseIE3Dtosimulateantennaelements.Certainly,wecanusetheIE3Dtosimulateantennaarray.WehavetouchedthistopicinChapter12onmatrixsolvers.Inthischapter,wewillconcentrateonantennaarraysimulationanddesign.IE3Dcanacceptarbitrarilyshapedstructureswithanynumberofports.Thereisnodifficultyforausertoenteranantennaarraylayoutandsimulateit.However,therearesomepointswemayneedtotakeintoconsideration.Dependinguponthenatureofanarrayorhowaccuratewewanttomodelanarray,wecanusedifferentapproaches.Table13.1liststhe4mostcommonlyusedapproaches.IntheIE3D8.0,wehavesuccessfullyimplementedtheperiodicGreen’sfunctionformulationforprecisemodelingofplanarphasearray.Wewillalsouseittosimulatethefollowinglinearphasearray.
Table13.1Thecommon4approachesinarraysimulationanddesigninIE3D.
Approach
Features
ArrayFactor
(orNoCoupling)
Anarrayissimplifiedasanelementplusanarrayfactor.Noelementcouplingandfeednetworkradiationisincluded.Thisisthefastestscheme.Thereisnolimitationonthesizeofthestructure.However,itistheleastaccuratemodel.Theradiationfromthefeednetworkisnormallynotincluded.Itissuitableforlooselycoupledandequallyspacedarrayelementswithwell-shieldedfeednetwork.
PeriodicWall
Anarrayisconsideredasanelementwithduplicationsfromtheperiodicwalls.Themajorcouplingsbetweenelementsareincludedfromtheperiodicwallcondition.Theradiationfromthefeednetworkisnormallynotincluded.Thisisalsoafastscheme.Itissuitableforlargephasedarrayswithidenticalandequallyspacedelements.Theexcitationphasecanbetempered.One-dimensionalperiodicarrayisanapproximationusingfinitenumberofimages.MorediscussioncanbefoundfromAppendixH.StartingfromtheIE3D8.0,weareabletomodelthe2Dperiodicarrayprecisely.Wecanalsouseittomodel1Dperiodicarrayaccuratelybecausewecanalwaysdefinemuchlargerelement-to-elementdistanceintheotherdirection.Itseemsthatthe2dperiodicarraymodelingisabetterapproachthanthefiniteimagesone.
Separation
Thewholestructureisdividedinto2portions:
alltheantennaelementsandthefeednetwork.Alltheantennaelementsaremodeledin1simulation.Thefeednetworkissimulatedinanothersimulation.Theradiationfromtheelementsandthefeednetworkwillbemerged(youcanoptionallyneglecttheradiationfromthefeednetwork).Thisapproachincludesthecouplingamongelements,andthecouplingwithinfeednetwork.Thesimulationtimeandresourcerequirementsaremoderate.Oneadvantageusingthisschemeisthatyoucanaccessthepower,voltageandcurrentdistributioninthewholearray.Suchafeaturemayprovideveryimportantinformationinarraydesign.Thisnewfeatureisalsoavailabletotheprevious2schemes.ThenewfeatureinIE3D7.0allowsyoutochecktheradiationfromdifferentpart.
CompleteArray
Thecompletearrayincludingelementsandfeednetworkismodeledinonesinglesimulation.Thecouplingandradiationfromallcomponentsareincluded.Thiscertainlyisthemostaccuratescheme.However,itrequiresthemostcomputationalresources.Thepower,voltageandcurrentinformationatportsisnotavailableforthisscheme.Forrelativelargearrays,theiterativematrixsolver(IMS)orthepartialmatrixsolver(PMS)isrequiredtoreducethesimulationtimeandRAMrequirement.
Inthischapter,wewillconcentrateona16-elementlineararraydesign.Thesameprocedurescanbeappliedtoplanararraydesign.Thelayoutofthe16-elementlineararrayisshowninFigure13.1.Wewouldliketooptimizeitfortheresonantfrequencyat1.88GHz.Wealsowouldlikethearraytobeuniformlydistributed.
Figure13.1The16-elementlineararraytobemodeled.
Section1.ElementAnalysisandOptimization.
Anarraydesignstartsfromelementanalysis.Theinitialarrayelementissavedin.\ie3d\samples\ar_elem.geo.Theinitialarrayelementcanbefromsomesimplertoolorformula.
Step1RunMGRIDandopengeometryfile.\ie3d\samples\ar_elem.geo.TheelementlayoutisshowninFigure13.2.Thefeedlineoftheelementwasoptimizedfor50-ohms.Pleasesaveitinto.\ie3d\practice\ar_elem.geo.Simulatethestructurefrom1.85to1.9GHzwithoutedgecells.Theresonantfrequencymaynotbepredictedverypreciselywithouttheedgecells.WedisableAECforsimplicityhere.Inpracticaldesign,youmayconsiderusingitforhigheraccuracy.ThesimulationresultisdisplayedinFigure13.3.
(a)(b)
Figure13.2Theinitialarrayelement.
Asyoucansee,theresonanceisslightlyoff.Wewouldliketooptimizetheresonantfrequencyat1.88GHzwithperfectmatch.
Step2SelectEdit->SelectVerticescommand.SelecttheverticesusingWindows1inFigure13.2b.
Wewouldliketocontrolthelengthofthepatchbymovingitsverticesattheleftendinthe=0angle.
Step3SelectOptim->VariableforSelectedObjectscommand.MGRIDpromptsyoutodefinetheoptimizationvariable.
Step4SelectVerticesMappedto:
NewVariable.EntertheTuningAngle=0degreeandselectOK.Wewouldliketochangethex-coordinatesoftheselectedvertices.
Step5Movethemousetosomewhereonthelefthandsideoftheselectedvertices.Clicktheleftbutton.Enter“-200”milsfortheLowBoundofthevariable.
Figure13.3TheSmith-Chartdisplayoftheinitialdesign.
Step6Movethemousetosomewhereontherighthandsideoftheselectedvertices.Clicktheleftbutton.Enter“200”milsfortheHighBoundofthevariable.
Theoptimizationvariableforthelengthisdefined.Wecanuseittotunethepatch’sresonantfrequency.However,wecannotguaranteethematch.Wewouldliketochangethelengthoftheinsetssimultaneouslyfortheperfectmatch.
Step7SelectEdit->SelectVerticescommandagain.SelecttheverticesusingtheWindow2inFigure13.2b.Wewouldliketocontrolthelengthoftheinsetsbymovingtheverticesatthemiddle.
Step8SelectOptim->VariableforSelectedObjectscommand.MGIRDwillpromptyoutherearetotal22verticesand8distinctiveverticesselected.
Step9SelectVerticesMappedto:
NewVariable.EntertheTuningAngle=0andselectOK.Wewouldliketochangethex-coordinatesoftheselectedvertices.
Step10Movethemousetosomewhereonthelefthandsideoftheselectedvertices.Clicktheleftbutton.Enter“-200”milsfortheLowBoundofthevariable.
Step11Movethemousetosomewhereontherighthandsideoftheselectedvertices.Clicktheleftbutton.Enter“200”milsfortheHighBoundofthevariable.Theoptimizationvariableforthelengthoftheinsetsisalsodefined.Wecanuseittotunethepatch’smatching.
Step12Savethegeometryas.\ie3d\practice\ar_ele1.geo.WewilloptimizeRe[S(1,1)]=Im[S(1,1)]=0at1.88GHz.SelectSetOptimizationinProcessmenu.Enter1frequencyat1.88.SelectAddbutton.DefinetheParameterTypeasRe(S),1stParameteras(1,1).ObjectiveTypeasOptimizationQuantity=Objective1,Objective1=0.SelectOKtoaddthe1stoptimizationgoal.SelectAddbuttonagain.DefinetheParameterTypeasIm(S),1stParameteras(1,1).ObjectiveTypeasOptimizationQuantity=Objective1,Objective1=0.SelectOKtoaddthe2ndoptimizationgoal.SelectPowellfortheoptimizationscheme.SelectOKtostarttheoptimization.
Thedefaultgenerationnumberis565times.Interestingly,theoptimizerachievesthegoalsinonlytensofsimulations(Youcancheckthe.\ie3d\practice\output\ar_ele1.logfilefortheoptimizationinformation).Thebestresultissavedin.\ie3d\practice\ar_ele1m.geo.
Figure13.4Thecomparisonbetweenresultsbeforeandafteroptimization.
Step13Opentheoptimizedgeometry.\ie3d\practice\ar_ele1m.geo.Simulateitfrom1.85to1.9GHz.Wewilluseitlater.DisplaytheresultbeforeandaftertheoptimizationusingMODUA.Youwillseetheoptimizerreallydidthejob(seeFigure13.4).
Section2.The“CompleteArray”Approach
Forconveniencereason,wewilldiscussthe“CompleteArray”approachinthearrayanalysis.Wewouldliketheelement-to-elementdistancefromcentertocentertobe3,500mils.Thisdistanceisalittlebitmorethanhalfofawavelengthinfreespace(about3,140mils).Nogratinglobeiscreatedbecausetheelementpatternwillsuppressit.Theinputimpedanceforeachelementis50-ohms.Wewillcombineeachpairoftheelements.Beforewecombinethem,weneedtotransformthe50-ohmsto100-ohms.Therefore,weneedatransformerfrom50-ohmsto100-ohmsandweneedapowercombinerfromtwo100-ohmlinesbackto50-ohmline.Thegeometryfileforthetransformerissavedin.\ie3d\samples\ar_trans.geo(seeFigure13.5a).Thepowercombinerissavedin.\ie3d\samples\ar_comb.geo(seeFigure13.5b).Thear_trans.geoisaquarterwavelengthpowertransformerwiththemiddlesectionofZc=70-ohmsandquarterofawavelength.Thetotallengthforar_trans.geois1,200mils.Thetotallengthforthear_comb.geois300mils.WecanusetheSymmetricalT-JunctionandSymmetricalStepinEntityofMGRID4.16tobuildthe2structureseasily.Anothersmallgeometrywewanttobehandyisa50-ohmbend.Thegeometryissavedin.\ie3d\samples\ar_bend.geo.Thehorizontallengthofthebendis400milsandtheverticallengthofthebendis600mils.The2dimensions,especiallythehorizontallength,areplannedfortheelement-to-elementseparation.
(a)Transformer(b)PowerCombiner(c)Bend
Figure13.5The3smallstructuresneedtobehandy.
Step1Open.\ie3d\practice\ar_ele1m.geo.Droptheoptimizationvariablesinthegeometryf
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