具有高隔离度和任意功分比的平行带状功分器中英文对照翻译.docx

具有高隔离度和任意功分比的平行带状功分器中英文对照翻译.docx

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具有高隔离度和任意功分比的平行带状功分器中英文对照翻译

AParallel-StripRingPowerDividerWithHighIsolationandArbitraryPower-DividingRatio

Abstract—Inthispaper,anewpowerdividerconcept,whichprovideshighflexibilityoftransmissionlinecharacteristicimpedanceandportimpedance,isproposed.Thispowerdividerisimplementedonaparallel-stripline,whichisabalancedtransmissionline.Byimplementingtheadvantagesanduniquenessof

theparallel-stripline,thedivideroutperformstheconventionaldividerintermsofisolationbandwidths.Aswapstructureofthetwolinesoftheparallel-striplineisemployedinthisdesign,whichiscriticalfortheisolationenhancements.Alumped-circuitmodeloftheparallel-stripswapincludingallparasiticeffectshasbeenanalyzed.Anequalpowerdividerwithcenterfrequencyof2GHzwasdesignedtodemonstratetheidea.Theexperimentalresultsshowthattheequalpowerdividerhas96.5%—10-dBimpedancebandwidthwithmorethan25-dBisolationandlessthan0.7-dBinsertionloss.Inordertogeneralizetheconceptwithanarbitrarypowerratio,wealsorealizeunequalpowerdividerswiththesameisolationcharacteristics.Theimpedancebandwidthoftheproposedpowerdividerwillincreasewiththedividingratio,whichisoppositetotheconventionalWilkinsonpowerdivider.Unequaldividerswithdividingratiosof1:

2and1:

12aredesignedandmeasured.Additionally,afrequencyindependent1800powerdividerhasbeenrealizedwithlessthan20phaseerrors.

IndexTerms—Arbitrarypower-dividingratio,parallel-stripline,ringstructure,unequalpowerdivider.

I.INTRODUCTION

THEWIKINSONpowerdividerisoneoftheconventionalandfundamentalcomponentsinmicrowaveengineeringandexistsinmanymicrowavecircuits.BothdistributedandlumpedWilkinsonpowerdividershavebeenappliedinmicrowaveintegratedcircuitsandmonolithicmicrowaveintegratedcircuits[1].Recently,extensivestudieshavebeenmadetoenhancetheperformancesoftheWilkinsonpowerdivider,includingsizereductionsbycapacitiveloading[2],foldedcircuitry[3]andresonatingstructure[4],[5],multibandoperation[6],[7],unequalpowerdividing/combining[8],andactivedevice[9]andwaveguideimplementations[10].Thepowerdividersdiscussedinthispaperarefocusedontheisolationenhancement.Theproposeddividerisrealizedintheparallel-striptransmissionline.Someparallel-stripcircuitswerereportedwithperformanceenhancement[11],[12].Theparallel-striplineprovidesmoredesignflexibilitythanamicro-stripline,especiallyinrealizationofahigh-impedancelineandtransitions.

Manybalancedcircuitssuchaspush–pullamplifiers,balancedmixers,frequencymultipliers,andantennaarraysemploytheWilkinsonpowerdividerbecauseofitssimpledesignwithhighport-to-portisolation.Isolationisoneoftheimportantissues

inthedesignofthepowerdivideranddirectionalcoupler.Highisolationimpliestheminimizationofunwantedcouplingbetweenactivedevices,aswellastheeliminationofunexpecteddistortionsandoscillations.Itisbecauseitmayprovideapositive

feedbackpathforotherfrequencies,e.g.,inFig.1,asunwantedoscillationatf1maybesetupoutsideoftheoperationfrequencyf0.Therefore,awidebandisolationoperationisalwayspreferredtosuppressthecouplinginotherfrequencybands.

Fig.1.Balancedcircuitatfrequencyf0andunwantedfeedbackatf1.

Theparallel-striplinebelongstoafamilyofbalancedtransmissionline.Theconventionalprintedcircuitboard（PCB）fabricationtechniqueisabletoeasilyrealizeparallel-striplines.Itisasimplestructureofadielectricsubstratesandwichedbetweentwostripconductors.Thesignalsflowingontheupperandlowerstripconductorsarealwaysequalinmagnitudeand1800out-of-phase.Thequasi-TEMmodeelectricandmagneticfieldsdistributionsareclosedtothemicro-stripline.Inthispaper,aparallel-stripswapisemployedtoenhanceisolationperformanceofthepowerdivider.Theswapisapassivemicrowavecomponent.Itformsacompactrealizationof1800phaseshiftbyinterchangingtheconnectionoftwoconductorsinthebalancedtransmissionline.Variousswapswereproposedforperformance

enhancementina1800hybridcoupler[13]–[15].

Anewequalpowerdivider,whichisrealizedonaparallel-striplinewitharing-likestructure,wasfirstdemonstratedin[16].Thefourarmsandtwoshuntresistorsinthedividerprovideahighdegreeoffreedomforchoosingthecircuitparameters.Inthispaper,theproposedconceptisgeneralizedtobearbitrarypowerdividingwithoutanincreaseindesigncomplexity.Itshowsafrequency-independentisolationcharacteristic,arbitrarypower-dividingratiowithoutanexternalmatchingnetwork,avoidanceofaverythinstriplineforachievinghighcharacteristicimpedance,andeaseofrealizingwideband1800dividing.WhiletheconventionalWilkinsonpowerdividerexhibitslimitedisolationbandwidth,unequalWilkinsonpowerdividingreliesonanexternalquarter-wavetransformerforrealizingunequalpowerdividingforthesameportimpedances.Highcharacteristicsimpedancetransmissionlinesarerequiredfortheunequalpowerdivider.Theunequaldividerhasbeenusedwithstrictrestrictionsindesignandfabricationbecauseitrequiresatransmissionlinewithveryhighimpedance[8].Ontheotherhand,theverythintransmissionlinelimitsthepowerhandlingofthedevices.Toovercomethislimitationinrealizingcharacteristicimpedance,theupperandlowerstriplinesoftheparallel-striplineareoffsetsothatitwillbeeasiertohighlyincreasethecharacteristicimpedance.Threepowerdividerswithpower-dividingratiosof1:

1,1:

2,and1:

12weredesigned,fabricated,andtested.

Fig.2.Schematicdiagramofproposedpowerdividerwithfourarms,aswap,andtwoshuntresistors.

II.THEORETICALANALYSIS

ThestructureoftheproposeddividerisillustratedinFig.2.In[13],theequalpowerdividerhasbeenanalyzedusingevenandodd-modeanalysisbecauseofsymmetryofthedivider.Forthesamereason,thecircuitparameters,suchasportimpedanceandlineimpedances,shouldbethesameastheircorrespondingparametersZA=ZC,ZB=ZD,andZ2=Z3.Inthispaper,wetrytogeneralizetheanalysistoanunequalpowerdividerwithanarbitrarydividingratio.

Itconsistsofan1800swap,fourquarter-wave-longarms（withcharacteristicimpedancesZA,ZB,ZC,andZD）andtwoshuntresistorswithresistance.Thesefiveparametersdeterminetheinputimpedances,isolation,anddividingratioofthedivider.Inordertodeterminethearmcharacteristicimpedancesandresistorvalues,severalparametersshouldbeknown,includingportimpedancesZ1,Z2,andZ3andpowerratioK.

Firstly,theimpedancematchingisconsidered.Toachievemaximumpowertransfer,alltheportsshouldbematched.Theinputimpedanceatport1isdeterminedbyZAandZCandportimpedancesZ2andZ3.AsillustratedinFig.3,itisassumedthatasignalisinjectedtoport1andwillonlypassthroughports2and3.Thereisnonetcurrentflowingfromports2to3duetoportisolationbetweenportsintheshadedregion.ArmsBandDwithcharacteristicimpedancesZBandZD,respectively,thetwoshuntresistors,andtheswapcanthusbereplacedbyanopencircuitinanalysis.Thetwoarmsareconnectedinshunt;theinputimpedanceatport1canbeexpressedas

（1）

Thesignalinjectedtoport2canbedividedintotwoparts,oneflowingtoport1andtheotherbeingabsorbedbyshuntresistorsasshowninFig.4.Obviously,thereisnonetcurrentflowingfromarmtoarmandport3intheshadedregion,whichcanbereplacedbyanopencircuitinanalysis.Theinputimpedanceatport2canbegivenas

（2）

Similarly,theinputimpedanceatport3canbeexpressedas

（3）

Fortheunequalpowerdividingandassumingthepowerratioofports2and3tobeK,thepowerratiocanbedeterminedbytheratioofinputimpedanceofthearmsAandC,asshowninFig.3,asfollows:

（4）

Bysolving

（1）,

（2）,and（4）,ZAandZCaredeterminedandareexpressedin（5）and（6）,respectively.

Solving（4）and

（1）,

（5）

Solving（4）and

（2）,

（6）

Hence,theratioofthesquareofZBandZDandshuntresistorcanbedeterminedbysolving

（2）,（3）,（5）,and（6）.

Solving（5）and

（2）,

（7）

Solving（6）and（3）,

（8）

Therearefourconditions,butfiveunknownparametersZA,ZB,ZC,ZD,andR.Therefore,thesolutionsaresingular,whichimpliesthereisnouniquesolution.Theinfinitenumberofsolutionsprovideahighdegreeoffreedomwhenthedividerisdesigned.Forexample,thedividercannotonlybedesignedforanyportimpedancewithoutexternalmatchingcircuits,butalsoprovidesunequalpowerdividingwithequalportimpedance.

Isolationisaveryimportantdesignissue.Thesymmetricalstructureandtheswapprovidethepossibilityoffrequency-independentisolationcharacteristics.SignalsflowingthroughpathsA–CandB–Dshouldbeequalinmagnitude,but1800out-of-phase.Inordertoprovidefrequency-independentisolation,thephasedifferencebetweenpathsA–CandB–Dshouldbefrequencyindependentat1800out-of-phaseandwithequalamplitude,whichisprovidedbytheswap,andthecharacteristicimpedanceshouldbethesame

ZA=ZDandZB=ZC（9）

Equation（9）representsthefifthconditionfordesigningadividerwithfrequency-independentisolationandarbitrarypowerratio.Aftercombiningthepreviousconditions,theparametersZA,ZB,ZC,ZD,andRbecomeunique.Thedesignformulascanbesummarizedas

R=2Z1（10a）

（10b）

（10c）

Fig.5.Geometriesofparallel-stripswapandparallel-striplinewithequalphysicallength.

II