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MeasuringtheLoopBandwidthAppliedRadioLabswww.radiolab.com.auMeasuringtheLoopBandwidthofaPLLDesignFile:DN00315October1999IntroductionManymoderncommunicationsystemsutilisePLLfrequencysynthesizers.ThePLLisafeedbackloop,andthefrequencydomaincharacteristicsofthelooptransferfunction(gainandphaseresponse)havesignificanteffectonthePLLoperation,forexample:§§§Lockingtimes(e.g.overshootandringingforpoorphasemargin)Phasenoise‘ears’ifphasemarginispoorFrequencyresponseofmodulation/demodulationLink1VCOFoutMainDivider1/NKv/sF(s)PhaseDetectorKd1/MReferenceDividerFrefLoopFilterFigure1-PLLSynthesizerMeasuringtheLoopBandwidthForthePLLinFigure1,weinsertalow-passfilterinplaceofLink1.Asuitablefilterist……