Chapter 14
Chapter14MODULATIONINTRODUCTIONAswehaves eeninpreviousthreechapters, ,thesourceinformationisimpresseduponacar rier-wave(essentiallyasinusoidofacertain frequency) ( ,audio,voltagepulsetraincarryingdigitali nformation) forexample,therepresentationofsampledsig nalsbytheamplitude, (2,6,9)thatwecanwritethissinusoidalcarri ersignalas:c(t)=Acos(2 fct+ )( )Here,Aiscalledtheamplitudeand ,dataareusedtomodulateorchangeitsamplitu de,frequency, , (digitalmodulation) ,wealsodescribeaspecialcaseofdigitalmodu lationthatisveryimportantfortransmission ofinformationusingmodems quadratureamplitudemodulation(QAM) atechniquecalled675676ThePhysicalLayerof CommunicationsSystemsorthogonalfrequency divisionmultiplexing(OFDM). , , (smallerwavelengths) , , ,thistimetoanintermediatefrequency(IF) (multiplexing). , ,thecharacteristicsofthemodulatedsinusoi d(suchasamplitude,frequencyorphase) (AM)andfrequencymodulation(FM) , , , EncoderChannel EncoderModulatorChannelDe-modulatorChann el DecoderSource [1].
Section 14.2. In particular, we discuss amplitude and frequency modulation. We discuss discrete changes in the characteristics of the carrier (digital modulation) in 14.3 along with the methods of representing and analyzing the performance of these modulation schemes. We consider binary modulation schemes and multi-level modulation schemes here ...
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