低输出功率应用的E类CMOS功率放大器设计

182YuanCheng,LiZhiqun,LiuJihua.andWangZhigongpactthecircuitperformance,especiallythemaximumPAoperatingfrequency.Accordingtotheruleofthumb,thewidthmakingroeonetenthoftheloadresistorRLisarec—ommendedinitialvalue,whichmakesE髓about88%fromEq.(5.2.2Implementationofcuotalpower-controlOneimportantissueinthedesignistoimplementtheOHtptitpowercontrolwhichisoftenrequiredinpracticalap-plications.Sincetheinputsignalprovidesonlytiminginfor-marioninaclass-Eamplifier。theoutputpowercannotbecontrolledbychangingthewidthoftheinputtransistorasisnormallydoneinalingaramplifier.Instead.theoutputpow.ercontrolcanberealizedthroughavariablesupplyimple-mentedbyaDC.DCconverter.Butinpracticalapplica.tions.itisnoteasytoapplysuchanadditionalvariablesup-plyandtIleDC—DCconvertercircuitwillconsumeextrapowerwhichreducestheoveralle1啊ciency.Inthispaper,athree-bitcontrolpad(Bit2-BitO,asshowninFig.2,isdesignedtochangetheoutputpowerdigitally.Withacontrolword“11r’.themaximumpowerisavailable.whiletheminimumisat“000”.Thecontrolofontputpowerisachievedbychangingthedutycycleandtheamplitudeofthesignal(‰whichistheinputtothegateofswitchtransistorSW.Sincetheturn.onresistancer^.ofswitchtransistorSWisafactorwhichdegradestlleoutputPOwerandefficiency.changingtheamplitudeofK.willaccordinglychangetheoutputpower.TlleamplitudeofVi。iscontrolledbythegainofthefirststage.whichcanbealteredbythewidtllofthecascadetransistor.Bit2controlsthestateofM[22inFig.2.ⅥmenBi匕ishigh.M22isparalleledintothecircuitandthegainofthefirststageincreases.SoistheamplitudeofVi。.Anotllermethodtocontrolt11epowerisbyalteringthedutycycleof山eK.,becausealltllevaluesoftlleloadnet-workcomponentsdependontIIesignal’sdutycycle¨J.ThismethodisimplementedbycontrollingthebiasvoltageofswitchtransistorK加inthispaper.When%dulyincreases,thedutycycleofK。increases,soahigheroutputpowerisobtained.111ewaytocontrolK蛳isverysimple.AresistorvoltagedividercanbeutilizedasshownatthebottomofFig.2.BitlandBitOaleusedheretocontrolthetwoswit-chestochangethebiasvoltageK撕.CombiningthechangeofamplitudeandthedutvcycleoftheinputsignalVi。willgiveawideradjustableoutputpow-el"range,andnomorecomponentsareneededwhencom-paredwi山thetraditionalmethod.3ExperimentalResultsandAnalysis11圮circuitisdesignedinastandard6.metallayer.0.18lanRFCMOStechnology.Fig.3showsthelayoutofthePAincludingpadsthatoccupiesanalgaof0.95nlm2.仙majorinterconnectionsandinductorsarelaidOUtusingthetopmetallayertominimizetheparasiticeffects.Fig.4shows只。andPAEoftheclass.EPAvs.inputpowerwitha1.2Vsupplyvoltageat2.45GHz.APAEof44%isachievedwitlla10-dBminputpowerwhiledeliveringanoutputpowerof8.8dBm,asshowninFig.4.Fig.3LayoutoftheproposedClass・EPAAsthesupplyvoltage‰increases,theoutic}utpoweraswellasthee衔ciencybecomesgreaterasshowninFig.5.田肥minimumoutputpowercanbeaslow3s0.3dBmata0.4VsupplywithaP觚of21%.whichcanbeusedinaWSNsystemwherea0一dBmoutputPOweristypicallynee—ded.menusingthedigitalcontrollingmethod.aDC.DCconverterwhichdissipatesextrapowerisnotneeded.Withthecontr01word“lll”。themaximumpowerisavailable。whiletheminimumiSat“000”.Apowerfrom一3.0t08.8dBmisobtainedinmiscasewiththePAEfrom9%to44%.asshowninFig.6.Fig.