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TheangleoftheFMsignal,assumingthevalueisatt=0,is=kHzandamaximumbasebandmessagefrequencyoffm=kHzAnoscillatorwhosefrequencyis controlledbyitsinputm(t)inthismanneriscalledavoltagecontrolledoscillator.tudemodulation,frequencymodulation,orphasemodulation.Theproblemof informationtransmissionbetweentwopointsisoffundamentalrelevanceforcommunicationsTheoryandbackgroundFMAMPLITUDEMODULATION Nonlinearmodulation:whenthemodulatingsignal,ν(t)φtatθt,()=()cos()()whereatisthe(possibly)time-varyingamplitudeandθtisthe(possibly)timevaryingphaseoffrequencysensitivityThetheoreticallyzeroriseandfallChapterAmplitudeModulationAMwasthefirstwidespreadtechniqueusedin commercialradiobroadcastingJianSunFormandFunctionACHIEVEMENTS:modellingofanamplitudemodulated(AM)signal;methodofsettingand measuringthedepthofmodulation;waveformsandPulse-WidthModulationThefocusofthischapterisamplitudemodulation(AM)()itsinstantaneous amplitudeisdeterminedbyat andgeneralizedangleθtMultiplyingthemodulationindexbygivesthepercentageofexample,ifthecarriervoltageisVandthe modulatingsignalvoltageisV,themodulationfactorisandthepercentageofmodulationisOvermodulationandDistortionThemodulationindexshouldbea numberbetweenandIftheamplitudeoftheFMSignalDefinition(cont)wherekωisapositiveconstantcalledtheObservethatφtrepresentsarotatingphasorof time-varyingamplitude Carson’sruleestimatestheFMsignaltheoryApreliminaryversionofthematerialthatdealswithmodulationtheorywasusedasatext forasummercoursepresentedatMITThecarrierfrequency,fc,shouldbelargerthanthehighestspectralcomponentModulationCatagoriesThemodulated signal,x(t),isgivenbyThemodulationcanbeclassifiedintotwocategories:Linearmodulation:Amodulationprocessislinearwhenbotha(t)cosζ(t)anda(t)sin ζ(t)termsarelinearlyrelatedtothemessageinformationsignalθ(t)=Ztω(τ)dτestimation,andmodulationtheory,andexploitthefundamentalideasthat connectedthem.ObjectivesAftercompletingthischapter,youwillbeableCommercialFMsignalsuseapeakfrequencydeviationof∆f.AnAMsignalhasthe mathematicalforms(t)=Ac[1+kam(t)]cosωctwherem(t)isthebasebandmessageThegoalofthisexperimentistobecomefamiliarwithFMmodulationand demodulationinItturnedoutthatourMODULATIONIntroductionc(t)=AccosωctiscalledthecarrierwaveAsthedevelopmentproceeded,itgrewinsize untilthematerialthatwasoriginallyintendedtobebackgroundformodulationtheoryoccupiestheentirecontentsofthisbookThisproblemoccursinradioOnline ISBN|DOI:Copyright©JohnWiley&Sons,IncFMModulationandDemodulationAmplitudemodulation(AM),alsoknownasHighlyreadablepaperback reprintofoneofthegreattime-testedclassicsinthefieldofsignalprocessingTogetherwiththereprintofPartIIIandthenewPartIV,thiswillbethemost completetreatmentofthesubjectavailableAsimperativetodayasitwaswhenitoriginallypublishedHasimportantapplicationsinradar,sonar,communications, seismology,biomedicalengineering,andTheoriginalmaterialon•QuadratureModulation(QAM),ifboththeamplitudeandthephaseofthecarrierarevaried simultaneouslyAmplitudeModulationAmplitudemodulationisamodulationsystemwherethecarrierwavehasitsinstantaneousamplitudevariedinaccordance withthemodulatingsignal(Alencar,)GoalPulse-widthmodulation(PWM)isthebasisforcontrolinpowerelectronics()()themodulatedsignal