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UHF频段锁相环型频率综合器设计与实现的中期报告.docx

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UHF频段锁相环型频率综合器设计与实现的中期报告 Abstract Thisreportdescribesthedesignandimplementationofaphase-lockedloop(PLL)frequencysynthesizerforUHFfrequencyband.Thesynthesizerincludesavoltage-controlledoscillator(VCO),aphasedetector,aloopfilter,andafrequencydivider.Detailedtheoreticalanalysisandsimulationresultsarepresented.Thereportalsoincludesanoverviewofthehardwareimplementationandpreliminarytesting. Introduction PLLfrequencysynthesizersarewidelyusedinradiofrequency(RF)applicationsforgeneratingstableandaccuratesignalsatvariousfrequencies.ThebasicprincipleofaPLListocomparethephaseandfrequencyofareferencesignalwiththatofavoltage-controlledoscillator(VCO)andadjusttheVCOfrequencytolockontothereferencesignal.ThefrequencyoftheVCOisthenscaleddownbyafrequencydividertoobtainthedesiredoutputfrequency. Inthisreport,aPLLfrequencysynthesizerisdesignedandimplementedfortheUHFfrequencyband.Thegoalistodesignasynthesizerthatcangeneratestableandaccuratesignalsinthefrequencyrangeof400-500MHz.ThemaincomponentsofthesynthesizerincludeaVCO,aphasedetector,aloopfilter,andafrequencydivider.Thedesignandimplementationofeachcomponentarediscussedindetailbelow. VCODesign TheVCOisthemostcriticalcomponentofthePLLfrequencysynthesizerasitdeterminesthefrequencyrangeandstabilityofthesynthesizer.TheVCOusedinthisdesignisbasedontheColpittsoscillatortopology.ThecircuitschematicisshowninFigure1. TheVCOincludesaninductorL,twocapacitorsC1andC2,andanactivedeviceQ1.ThevalueofLischosentobe22nHtoresonatewithC1andC2atthedesiredfrequencyrange.TheactivedeviceQ1isaNPNbipolarjunctiontransistor(BJT)withahigh-frequencycutofffrequencyof8GHz. TheVCOisdesignedtohaveatunablefrequencyrangeof400-500MHz.ThetuningisachievedbyvaryingthebiasvoltageofthebaseofQ1usingavaractordiodeD1.Thevaractordiodehasacapacitancethatchangeswiththeappliedvoltage,whichresultsinachangeintheresonantfrequencyofthetankcircuit.Thetuningrangeofthevaractordiodeisfrom0to20V,whichcorrespondstoafrequencychangeofapproximately100MHz. PhaseDetectorDesign Thephasedetectorisresp