A Dual-Frequency Wilkinson Power Divider

ADual-FrequencyWilkinsonPowerDivider:ForaFrequencyandItsFirstHarmonic

L.Wu,H.Yilmaz,T.Bitzer,andA.Pascht.M.Berroth,SeniorMember,IEEE

Abstract—AWilkinsonpowerdivideroperatingnotonlyatonefrequency0,butalsoatitsfirstharmonic20ispresented.Thispowerdividerconsistsoftwobranchesofimpedancetransformer,eachofwhichconsistsoftwosectionsof1/6-wavetransmission-linewithdifferentcharacteristicimpedance.Thetwooutputsarecon-nectedthrougharesistor,aninductor,andacapacitor.Allthefea-turesofaconventionalWilkinsonpowerdivider,suchasanequalpowersplit,impedancematchingatallports,andagoodisolationbetweenthetwooutputports,canbefulfilledat0and20,simul-taneously.

IndexTerms—Dual-frequency,powercombiner,powerdivider,Wilkinsonpowerdivider.

Fig.1.

Dual-frequencyWilkinsonpowerdivider.

I.INTRODUCTION

T

HEWilkinsonpowerdividerandcombinerareveryim-portantcomponentsformicrowavepoweramplifiers.TheconventionalWilkinsonpowerdividerandcombineroperateatadesignfrequencyandallofitsoddharmonics[1].However,theycannotperformthepowerdivisionandcombiningatandallevenharmonics.Thedual-bandoperation,suchastheglobalsystemformobilecommunications(GSM)andpersonalcommunicationssystems(PCS)bandsformobilecommunica-tionrequiresapowerdividerandcombineroperatingatafre-andatthedoubledfrequency.Thislettershowsquency

adual-frequencyWilkinsonpowerdividerwhichcanfulfilla

.powerdivisionatbothfrequenciesand

II.THEORYANDDESIGNEQUATIONS

AschematicdiagramoftheproposedWilkinsonpowerdi-vider,whichrealizesthepowerdivisionatthefundamentalfre-anditsfirstharmonic,isshowninFig.1.Eachquency

1/4-wavebranchofaconventionalWilkinsondividerissub-stitutedbytwosectionsof1/6-wavetransmission-line,which

and,respectively.havethecharacteristicimpedanceof

Theoutputportsareshuntedwithaparallelconnectionofare-sistor,aninductor,andacapacitor.Thepowerdividerissymmetricandwecanusetheeven-andodd-modeanalysistodeterminethecircuitparametersforthedual-frequencypowerdivision.

Fig.2.Circuitofthepowerdividerfortheeven-modeanalysis.

A.Even-ModeAnalysis

Inthecasewheretwosignalsofthesamemagnitudeandphase(even-modesignals)areappliedtoports2and3ofthecircuitshowninFig.1,nocurrentflowsthroughtheplaneofsymmetry.ThecircuitisbisectedattheplaneofsymmetryasshowninFig.2.Becausenocurrentflowsthroughtheplaneofsymmetry,thecircuitelements,,and,whichshuntthe

atport1isports2and3,canbeomitted.Theimpedance

doubledonthebisectedcircuit.Foranimpedancematchingat

atport1mustbetransformedtoport2theimpedance

throughthetwosectionsof1/6-wavetransmission-line.Toful-,thechar-fillthistransformationatbothfrequenciesand

acteristicimpedanceofthesetwotransmission-linesmustbe

(1)

accordingtothetheoryofdual-frequencytransformer[2].Withthesetwocharacteristicimpedancestheimpedance

atport2toatport1isnaturallytransformationfromandfortheevenmode,whichgivesthealsofulfilledat

atthesetwofrequenciesforthepowerinputimpedanceof

dividershowninFig.1.

ManuscriptreceivedApril21,2004;revisedAugust11,2004.ThereviewofthisletterwasarrangedbyAssociateEditorA.Weisshaar.

L.Wu,H.Yilmaz,andM.BerrotharewiththeUniversityofStuttgart,Stuttgart70049,Germany(e-mail:wu@int.uni-stuttgart.de).

T.BitzerandA.PaschtarewithAlcatelSELAG,Stuttgart70435,Germany.DigitalObjectIdentifier10.1109/LMWC.2004.842848

1531-1309/$20.00©2005IEEE

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108IEEEMICROWAVEANDWIRELESSCOMPONENTSLETTERS,VOL.15,NO.2,FEBRUARY2005

Fig.3.Circuitofthepowerdividerfortheodd-modeanalysis.

B.Odd-ModeAnalysis

Inthecaseofodd-mode,thetwosignalsappliedtoport2and3havethesamemagnitudebutare180outofphase,thereisavoltagenullalongthemiddleofthecircuitshowninFig.1.Thus,wecanbisectthiscircuitbygroundingthemidplanetogivethenetworkofFig.3.

atthefundamentalfrequencyTheimpedanceand

are

(2)(3)

respectively.Becausetheport2isshuntedwithaparallelcon-,and2C,theoutputimpedanceatportnectionof

2becomes

(4)

whereobtain

.Forimpedancematchingto

atport2,we

(5)

and

(6)

At

theimpedance

,and

are

(7)(8)

Fig.4.SimulationandmeasurementresultsoftheS-parameters.(a)MagnitudeofS.(b)MagnitudeofS.(c)MagnitudeofS.(d)MagnitudeofS.

(9)

respectively.Forthesameimpedancematchingatlowingequationmustbesatisfiedbesides(5):

,thefol-

Equations(6)and(10)arethereforetwoequationsfortwoun-knownsofLandC,fromwhichweobtain

(11)

(10)

(12)

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WUetal.:DUAL-FREQUENCYWILKINSONPOWERDIVIDER109

III.SIMULATIONANDEXPERIMENT

Andual-frequencyWilkinsonpowerdividerisdesignedfor1GHzand2GHz.Letbe50,thedesignpa-rametersofthedual-frequencyWilkinsonpowerdividershouldbe

Thereisagoodagreementbetweenthesimulationandmeasurementresults.Fig.4(a)indicatesthattheinputsignalisalmostequallydividedandtransmittedtotheoutputports2and3,bothat1and2GHz.Agoodisolationbetweentheports2and3isalsofulfilledatthesetwofrequenciesasshowninFig.4(b).Fig.4(c)showsthatthepowerdividerpassesthe1-GHzfundamentalsignalanditsfirstharmonicverywell,whereasaimpedancematchingattheoutputportsisalsorealizedasshowninFig.4(d).

IV.CONCLUSION

nHpF

accordingtothedesignequationsof(1),(5),(11),and(12).Thispowerdividerwasfabricatedona0.81-mm-thickRO4003sub-strate,whichhasarelativepermittivityof3.38andaconductorthicknessof35m.Thetwooutputsareconnectedwithapar-allelcircuitconsistingoftheresistor,theinductor,andtheca-pacitor.SimulationwithmodelsoftheselumpedcomponentsandthepropertiesoftherealsubstratehasbeenimplementedapplyingthesoftwareADS2003[3].Themeasurementandsim-ulationresultsarepresentedinFig.4.

Anovelandelementarydual-frequencyWilkinsonpowerdi-viderhasbeenpresented,whichfulfilsallthefeaturesofacon-ventionalWilkinsonpowerdividernotonlyatadesignfre-.Theanalyticso-quency,butalsoatitsfirstharmonic

lutionfordeterminationofitscomponentshasbeenderivedandbeenprovenbythesimulationandthemeasurement.

REFERENCES

[1]D.M.Pozar,MicrowaveEngineering,2nded.NewYork:Wiley,1998,

pp.363–368.

[2]C.Monzon,“Asmalldual-frequencytransformerintwosection,”IEEE

Trans.Microw.TheoryTech.,vol.51,no.4,pp.1157–1161,Apr.2003.[3]ADS,AgilentTechnologies,2003.

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