Oscillator Phase Noise Reduction Using Nonlinear D

OscillatorPhaseNoiseReductionUsingNonlinearDesignTechniquesbyDavidS.M.SteinbachThesissubmittedtotheFacultyoftheVirginiaPolytechnicInstituteandStateUniversityinpartialfulfillmentoftherequirementsforthedegreeofMASTEROFSCIENCEinElectricalEngineeringDr.W.A.Davis,ChairmanDr.C.W.BostianDr.D.G.Sweeney8May2001Blacksburg,VirginiaKeyWords:Design,Nonlinear,Oscillator,Phasenoise,Copyright2001,DavidS.M.SteinbachOscillatorPhaseNoiseReductionUsingNonlinearDesignTechniquesDavidS.M.Steinbach(ABSTRACT)Phasenoisefromradiofrequency(RF)oscillatorsisoneofthemajorlimitingfactorsaffectingcommunicationsystemperformance.Phasenoisedirectlyeffectsshort-termfrequencystability,Bit-Error-Rate(BER),andphase-lockedloopadjacent-channelinterference.RFoscillatorcircuitscontainatleastoneactivedevice,usuallyatransistor.Theactivedevicehasnoisepropertieswhichgenerallydominatethenoisecharacteristiclimitsofanoscillator.Sinceallnoisesources,exceptthermalnoise,aregenerallyproportionaltoaveragecurrentflowthroughtheactivedevice,itislogicalthatreducingthecurrentflowthroughthedevicewillleadtolowernoiselevels.Atheorybasedonthetime-varyingpropertiesofoscillatorsproposesthatnarrowingthecurrentpulsewidthintheactivedevicewilldecreasethetimethatnoiseispresentinthecircuitandtherefore,decreasephasenoiseevenfurther.Thetime-domainwaveformsandphasenoiseofanactive-biased700MHzoscillatorareanalyzed,showingheavysaturationandhigh-harmoniccontent.Redesignsoftheexampleoscillatorinactive-biasandfour-resistor-biasconfigurationsshowimprovedphasenoiseandlowerharmoniclevelsattheoutput.Fiveoscillatordesignsofeachbiasconfiguration,eachhavingadifferentpulsewidth,aresimulated.Aspredictedbythetheory,thenarrowestcurrentpulsecorrespondstothelowestphasenoiseofthesimulatedoscillators.iiiAcknowledgmentsIwishtothankmyadvisor,Dr.WilliamA.Davis,forofferingmemuchneededdirectionandagreatdealofknowledgeandexperiencefromwhichtodraw.Mycommitteemembers,Dr.CharlesW.BostianandDr.DennisG.Sweeney,alsodeservethanksfortheirmuchappreciatedencouragementandinsightintoproblemsencounteredoverthispastyear.IamverygratefulforencouragementprovidedbymyfamilyandfriendSharonSmith.HadIbeenwithoutsuchsupport,mygraduatestudiescouldnothavebeenpossible.ThisworkwasfundedbyBAEthroughtheVirginiaTechCenterforWirelessTelecommunication(CWT)affiliateprogram.BAEisaleadingmanufacturerofcustomanaloganddigitalradiocommunicationshardware.ivTableofContentsChapter1.Introduction..........................................................................................11.1LiteratureReview..........................................................................................2Chapter2.Background...........................................................................................42.1OscillatorFundamentals.................................................................................42.2Design...........................................................................................................52.2.1NonlinearSources...........................................................................52.2.2ThreeTerminalModel....................................................................72.2.3OscillatorDesign............................................................................92.3Noise...........................................................................................................15...........................................................................162.3.1SourcesofNoise................................................................182.3.2OscillatorNoiseModelsChapter3.Verification.........................................................................................233.1HowADSSimulatesNoise..........................................................................243.2BasicOscillatorSimulations.........................................................................253.2.1700MHzExample..........................................................................253.2.2RedesignwithActiveBias.............................................................273.2.3RedesignwithFour-ResistorBias.................................................30..........................................................323.2.4RedesignNoiseComparison3.3PhaseNoise-PulseWidthComparison........................................................32Chapter4.ConclusionsandRecommendationsforFutureWork......................38References...............................................................................................................40Vita.........................................................................................................................41vListofFiguresFigure2.1.Feedbackoscillatormodel.........................................................................4Figure2.2.ExponentialcharacteristicofBJT..............................................................6Figure2.3.FouriercoefficientsforBJTcharacteristic.................................................8Figure2.4.Common-base,common-collector,andcommon-emitterColpitts