通信原理第5章模拟调制系统课件

1、本章研究各种模拟调制、解调方式、系统的可靠性本章研究各种模拟调制、解调方式、系统的可靠性和有效性。和有效性。基带信号m(t)调制器Sm(t)C(t)载波0( )coscc tAt( )( )cosmcstAm tt( )()2mccASMM00( )( )coscos( )cosAMcccstAm ttAtm tt01( ) ()()()()2AMccccSAMM 载频分量载频分量载频分量载频分量上边带上边带上边带上边带下边带下边带下边带下边带HAMfB222202222200( )( ) coscos( )cos2( )cosAMAMccccPstAm ttAtm ttA m tt0)(tm

2、ScAMPPtmAP2)(22202/ )(2tmPs 2220SAMAMmtPPAmt22( )/2mmtA 222222002mAMmmtAAAAmtttmtscDSBcos)()()()(21)(ccDSBMMS1,( )( )0,cUSBcHH1,( )( )0,cLSBcHH ( )( )SSBDSBSSHtAtmmmcos)(ttcccos)(tAtAttAtsmcmmcmcmmDSB)cos(21)cos(21coscos)(1( )cos()2USBmCmstAt11coscossinsin22mmcmmcAtAt1( )cos()2LSBmCmstAt11coscossins

3、in22mmcmmcAttAtt两式仅正负号不同ttAttAtscmmcmmSSBsinsin21coscos21)(tAtAmmmmsinso c11( )coscoscossin22SSBmmcmmcstAttAtt11( )coscoscossin22SSBmmcmmcstAttAttttmttmtsccSSBsin)(21cos)(21)(的希尔伯特变换是)()(tmtm ( )VSBDSBSSH1()( )2ccMMH VSB2( )cospcststt ( )VSBVSBstScccosct ()()pVSBcVSBcSSS ()()pVSBcVSBcSSS ( )VSBDSBSS

4、H1()( )2ccMMH 1(2)()2pccSMMH1( )(2)()2ccMMH1( )( )()()2dccSMHH1( )( )()()2dccSMHH()()ccHHH 常数，)(cos)()(thttmtscm)()(21)(HMMSccm)()(thH)(cos)()(thttmtscm( )( )cos( ) inmIcQcsts ttst st( )( )( )IIs th tm t( )( )cosIch th tt( )( )( )QQsthtm t( )( )sinQchth tt( )( )cos( ) inmIcQcsts ttst stttmAtscAMcos)

5、()(0cHfRCf /1 0( )dstAm tisciNtntntn)()()(222BnNi0( )( )cos( )siniicscn tn ttn tt2oo2oo( )( )SmtNn t解调器输出有用信号的平均功率解调器输出噪声的平均功率iiNSNSG/00)()(22tntsNSimii功率解调器输入噪声的平均平均功率解调器输入已调信号的OONSm0ifnS31H0ifnSH0ifnS 性能比较性能比较: 可靠性可靠性 优优劣劣:SSB（DSB），），AM 有效性有效性 优优劣劣:SSB，VSB，AM（DSB） VSB的可靠性，无分析结论。的可靠性，无分析结论。 ( )mst

6、BPF )(tn ( )mst )(tni )(tno o( )m t 包络检波 ttmAtscmcos)()(0ttnttntncsccisin)(cos)()(2)(2)(2202tmAtsSmiBntnNii02)(BntmANSii02202)(0( )( )( )( )cos( )sin( )cos( )miccsccstn tAm tn ttn ttE ttt220( )( )( )( )csE tAm tn tn t)()()()(0tntmAtnarctgtcs)()()(220tntntmAsc220( )( )( )( )csE tAm tn tn t)()()()( 2)

7、()(22020tntntntmAtmAtEscc200120000( )2( )( )2( )( ) 1( )( )( ) 1( )cccAm tAm t n tn tAm tAm tn tAm tAm t0( )( )cAm tn t12(1)1,12xxx 当时2o( )Sm t22o0( )( )ciNn tn tn B2oo0( )Sm tNn B2oo220/2( )/( )AMiiSNm tGSNAm t2oo220/2( )/( )AMiiSNm tGSNAm t32AMG220( )( )( )csAm tn tn t220( )( )( )( )csE tAm tn tn

8、t)()(2)()()()(02220tmAtntntntmAtEcsc)()(2)()(022tmAtntntncsc)()()()(21)()(22022tntntmAtntntnsccsc)(cos)()( 21)(0ttRtmAtR)()()(22tntntRsc)()()(tntnarctgtcs)()(0tmAtR)(cos)()(1)(ttRtmAtR)(cos)()( 21)()(0ttRtmAtRtE）时1(21)1 (21xxx)(cos)()(ttmAtR)(cos)(ttAtscm)()(tmKtp)(cos)(tmKtAtspcPM)(cos)(ttAtscm)()(

9、tmKdttdf( )( )ftKmd( )cos( )FMcfstAtKmd)(cos)(ttAtscm)(cos)(tmKtAtspcPM( )cos( )FMcfstAtKmd( )coscos2mmmmm tAtAf t)(cos)(tmKtAtspcPMPM( )coscoscpmmstAtK AtcosscpmAtm cot( )coscos2mmmmm tAtAf tFM( )coscoscfmmstAtK Ad ( )cos( )FMcfstAtKmdcosncfmAtm sitfmfmmmK AfmffmK Afmfmf )(cos)(tmKtAtspcPM( )cos( )

10、FMcfstAtKmd （a a）直接调频）直接调频 （b b）间接调频）间接调频(c) (c) 直接调相直接调相 (d) (d) 间接调相间接调相）（或 5 . 06)(tfdmK( )cos( )tFMcfstAtKmdcoscos( )sinsin( )ttcfcfAtKmdAtKmd1( )tfKmdcos( )1sin( )( )tfttffKmdKmdKmd( )os( )sintNBFMcfcstActAKmdt)()(sin)()(cos)()(ccccccjttMtmjMdttm)()(（设（设m(t)的均值为的均值为0） ()()1( )sin2cccccMMm t dtt

11、NBFM( ) ()()ccsA ()()2fccccAKMM1( ) ()()()()2AMccccSAMM NBFM( ) ()()ccsA ()()2fccccAKMMtAtmmmcos)( )cos( )sintNBFMcfcstAtAKmdt1cossinsincmfmcmAtAA Kttcoscos()cos()2mFccmcmmAA KAttt(cos)cosAMmmcsAAttscoscoscmmcAcotAtcoscos()cos()2mccmcmAAttttfAtAtmmmmm2coscos)(sincos)(tmtAtsmfcFM( )coscos(sin)sinsin(

12、sin)FMcfmcfmstAtmtAtmttnmJmJtmmfnnfmf2cos)(2)()sincos(120tnmJtmmfnnmf) 12sin()(2)sinsin(112tnmJmJtmmfnnfmf2cos)(2)()sincos(120tnmJtmmfnnmf) 12sin()(2)sinsin(112( )coscos(sin)sinsin(sin)FMcfmcfmstAtmtAtmt)cos(21)cos(21sinsin)cos(21)cos(21coscosBABABABABABA为奇数时当nmJmJfnfn)()(为偶数时当nmJmJfnfn)()( )()()()F

13、MnfcmcmSAJ mnn )(2) 1(2mmfFMfffmBmFMfB2)( 2) 1( 2mmfFMfffmBfBFM2 2FMFMPst22FMcAPP0( )( )iftK m t NBFM( )st LPF BPF )(tSi o( )m t ( )c t 微分 )(tSp ( )dst ( )cos( ) sintNBFMcfcstAtA Kmdtttccsin)( )sin2( ) (1 cos2)22tpcfcAAsttKmdt tFddmKAts)(2)()(2)(0tmAKtmF NBFM( )st LPF BPF )(tSi o( )m t ( )c t 微分 )(t

14、Sp ( )dst ( )cos( )tFMcfstAtKmdo( )( )fm tK m to( )( )dfm tK K m tFMAMdt) t (mKtsin) t (mKAdt) t (dSdt) t (mKtcosA) t (SFcFcFMFcFM FM( )st BPF )(tn )(tSi )(tni LPF )(tno o( )m t 限幅 鉴频 FM( )cos( )tcFstAtKmd2/2ASiFMiBnN0FMiiBnANS022o( )( )dfmtK K m t222oo( )( )dfSmtK Kmt 2220o222302483mmmmffddffdmK nNPf dff dfAK n fA222o23o03( )8fmA K m tSNn fttmmcos)(sincos)(tmtAtsmfcFMffmmmKfmf22oo03/22fmSAmNn f2ooFMFM/3/2fiimSNBGmSNf)(2) 1(2mmfFMfffmB23(1)FMffGmm33FMfGm2oo0( )Sm tNn B22( )2Am t 2oo0/2SANn B2oo0/2()2AMmSANn foo2FMooAM/3/fSNmSN22