●●● The demodulator LO is identical in frequency and phase ●●●● ●●●● ●●0 with the modulator--synchronous or coherent demodulator) ●●●●0 ●●●0 解调器的本振与调制器同频同相，或者说相干。 ●●●色 ● v (1)=Acos(@+@)t+n(t) n(t)=x(t)cos@urt-y(t)sin@irt cosacosB=cos(a+B)+cos(a-B)/2 v (t)=v,(t)cos@t cos2a=(1+cos2a)/2 sin2a =2sinacosa A A ccos() +x(I+cos2@rt)-y(I)sin2@rl Out oftheLBF:()cos+x() 14The demodulator LO is identical in frequency and phase with the modulator -- synchronous or coherent demodulator) 解调器的本振与调制器同频同相，或者说相干。 14 ( ) cos( ) ( ) ( ) ( )cos ( )sin i IF m IF IF v t A t nt nt xt t yt t                2 cos cos cos cos / 2 cos 1 cos2 / 2 sin 2 2sin cos                  1( ) ( )cos cos cos(2 ) 2 2 1 1 (1 cos2 ) ( )sin 2 2 2 i IF m IF m IF IF vt vt t A A t t x t yt t           0   1 ( ) cos 2 2 m A Out of the LBF: v t t xt   