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1、1094IEEETRANSACTIONSONCOMMUNICATIONS,VOL.COM-33,NO.10,OCTOBER1985EfficiencyofOutphasingRFPower-AmplifierSystemsAbstract-Theoutphasingtechnique(LINC)combinestwononlinear11.PRINCIPLESOFOPERATIONRFpoweramplifiersintoalinearRFpower-amplifier(PA)system.TheAsimpleoutphasingPAsystemisshowninFig.1.Fortw
2、oPA’saredrivenwithsignalsofdifferentphases,andthephasesaresimplicity,theinputsignalisanamplitude-modulatedcosinecontrolledsothattheadditionofthePAoutputsproducesasystemcarrier.Thecontrol/&-ivecircuitsgeneratetwosinewaveoutputofthedesiredamplitude.However,theresultanttime-varyingsignalswithphases
3、of++,and-+,,asshowninFig.2.impedancespresentedtothePA’saltertheirdcpowerconsumptionandThesetwosignalsarethenamplifiedandaddedtoproduceefficiency.Powerandefficiencycharacteristicsarederivedforboththesystem-outputsignal.Thepeakoutputisobtainedwith+,simple(transformer-coupler)andChireix(transmissio
4、n-line-couplerwith=?r/2=90”,whichcausesthetwoPAoutputstoaddinshuntreactance)outphasingsystemsusingsaturatedclass-BPA’s.Simplephase.Zerooutputisobtainedwith+,=0,whichcausestheoutphasingsystemshavetheefficiencycharacteristicofalinearclass-BtwoPAoutputstocanceleachother.IntermediatevaluesofPA.Throu
5、ghproperselectionoftheshuntreactance,theefficiencyofa+,produceintermediatevaluesoftheamplitude(envelope)Chireixoutphasingsystemcanbemaximizedataspecificoutputoftheoutputsignal.amplitude.Theaverageefficiencywithvariousamplitude-modulatedByinspectionofFig.2,theoutputsofthetwopowersignalsisdetermin
6、edasafunctionofshuntreactance.Selectingtheshuntamplifierscanbewritteninphasorformasreactancetofitthesignalcanimproveefficiencybyasmuchasafactorof2.VI=(VornpEP/2)(Sin9m-jCOS9m)(1)andI.INTRODUCTIONUTPHASINGpower-amplifier(PA)systemswerefirstVZ=(Vomp,~/2)(-sin9rn-jcos(2)0developedduringthe1930’s[l]
7、,[2]toimproveboththewhereVomPEPrepresentstheamplitudeoftheoutputcosine-efficiencyandlinearityofAM-broadcasttransmitters.Theywaveatpeakenvelopepower.ThetransformercouplerwereusedcommerciallyintheRCA“ampliphase”transmit-differ
