[工学]通信原理5章复习

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1、signalprocessingcarriercircuitsTransmissionMedium(channel)carriercircuitssignalprocessingoutputinputModulatingsignalModulatedsignalBasebandsignalBandpasssignalBasebandsignalBandpasssignalChapter5AM,FM,andDigitalModulationSystem10/6/20211modulatedbandpasssignal:Thespectru

2、mof:andthePSDis:10/6/20212要求：关于模拟调制1.掌握AM、DSB-SC、SSB调制原理和解调方法，会计算各种已调信号的调制效率、AM信号的调制百分比、平均功率、峰值包络功率、功率谱、带宽。了解AM、DSB-SC信号的波形特点；2.了解FM、PM的各种基本概念，了解FM、PM两种调制之间的关系，会估算FM、PM信号的带宽（掌握卡森公式）。3.了解频分复用的基本概念。10/6/20213关于数字调制1.掌握2ASK、2PSK、2FSK的调制原理和解调方法，会计算各种已调信号的功率谱、带宽（包括无ISI系统）。会画2

3、ASK、2PSK、2FSK信号波形；2.了解MQAM、QPSK、MPSK的调制原理和解调方法，了解OQPSK、π/4QPSK、MSK的调制原理，会计算各种已调信号(MQAM、QPSK、MPSK、OQPSK、π/4QPSK)的功率谱、带宽（包括无ISI系统）。了解各种调制的星座图。会画TypeIMSK、TypeⅡMSK同相路和正交路基带波形x(t)、y(t)。10/6/20214§5.1AmplitudeModulationUppersidebandLowersideband10/6/20215一般：Completeamplitudemo

4、dulationanenvelopedetectorcanbeusedtodemodulatingthemodulatedsignal10/6/20216ThepercentageofmodulationonanAM*thepercentageofpositivemodulation*theoverallmodulationpercentage*thepercentageofnegativemodulation调制百分比影响功率分配10/6/20217ThepowerallocationofAMsignalandmodulationef

5、ficiencyThepowerallocationofAMsignalThenormalizedaveragepoweroftheAMsignal:Often:10/6/20218ModulationefficiencyThenormalizedPEPoftheAMsignal:10/6/20219CharacteristicofAMsignal:EnvelopedetectorisusedtodetectingtheAMsignal.ThepowerefficiencyoftheAMsignalislower.Thebandwidt

6、hoftheAMsignalistwotimesthatofm(t).10/6/202110§5.3Double-SidebandSuppressedCarrier(DSB-SC)Thepercentageofmodulation:Itisinfinitebecauseofnocarrier.ThemodulationefficiencyofDSB-SCis10/6/202111spctrum10/6/202112载波反相点waveform:10/6/202113ModulationDemodulationThetransmittera

7、ndreceiverLPF10/6/202114Thepercentageofmodulation:Itisinfinitebecauseofnocarrier.CharacteristicofDSBsignal:10/6/202115§5.5AsymmetricSidebandSignals1.Singlesidebandsignal(SSB)(1)RepresentationThecomplexenvelopeofaSSBis:Thesinglesidebandsignal:10/6/20211610/6/202117Thenorm

8、alizedPEP(2)ThepowerThenormalizedaveragepower10/6/202118(3)Thereceiveraproductdetector:LPF10/6/20211910