应用于TD-SCDMA系统的高线性10W功率放大器设计-豆柴文库

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应用于TD-SCDMA系统的高线性10W功率放大器设计
Introduction
Apoweramplifierisavitalcomponentinwirelesscommunicationsystemsasitisresponsibleforamplifyingthesignalstotherequiredlevelfortransmission.InTD-SCDMA(TimeDivision-SynchronousCodeDivisionMultipleAccess)systems,whichisa3Gmobilecommunicationstandard,thepoweramplifiermustmeetarangeofrequirementsincludinghighefficiency,highoutputpower,linearoutput,andlowdistortion.Inthispaper,wewilldiscussthedesignofahighlinear10WpoweramplifierforTD-SCDMAsystems.
TD-SCDMAPowerAmplifierSpecifications
TherequirementsfortheTD-SCDMApoweramplifierincludeoutputpower,linearoutput,efficiency,andbandwidth.Theamplifiermustbeabletodeliverupto10Wofoutputpower,whichispossiblebyoperatingtheamplifierinaclassABconfiguration.TheamplifiermustalsohavealinearoutputasTD-SCDMAisacomplexmodulationschemeandrequireshighlinearitytoavoidintermodulationdistortion.Theamplifiermusthaveanefficiencyofatleast40%toreducethepowerconsumptionandtheamplifiermusthaveabandwidthfrom1910MHzto2170MHztocovertheTD-SCDMAfrequencyband.
PowerAmplifierDesign
TheTD-SCDMApoweramplifiercanbedesignedwithavarietyofamplifiertopologies.However,forthisdesign,aClassABamplifiertopologywaschosen.Thistopologyiswell-suitedforTD-SCDMAsystemsasitcombinestheadvantagesofClassAandClassBamplifiertopologies.
ThekeycomponentsoftheClassABamplifiertopologyincludethepowersupply,theinputmatchingnetwork,theoutputmatchingnetwork,thepowertransistor/s,andthebiasnetwork.Thepowersupplymustprovideastablevoltagetotheamplifiercircuit,whichinthisdesignis28V.TheinputmatchingnetworkhelpstomatchtheRFinputsignaltotheinputimpedanceoftheamplifier,whichis50ohmsinthisdesign.Theoutputmatchingnetworkhelpstomatchtheoutputimpedanceoftheamplifiertotheloadimpedance,whichisalso50ohms.
Thepowertransistor/sarethemostsignificantcomponentsintheamplifierdesign.Forthisdesign,apairofbipolarjunctiontransistor(BJT)MRF911waschosen.MRF911isahighlinearitytransistorthatisidealforTD-SCDMAapplications.Ithasamaximumpoweroutputof2Wandamaximumgainof18dB,makingitper