5.3.2 Passband Passband signals are cos-like,and are generally in the form of, s(t)=r()cos[2πft+0t)】] =r(t)cos0(t)cos(27ft)-r(t)sin0(t)sin(2zft) =a.)cos(2πft)+a,()sin(2πft) With y4,0=kocos(2πf) y,)=k,oSin(2πfI】They are2 signals. Note that w1Ψ2=k,okcog7(t)sin(2πft)cos(2πft)dh=0 UESTC-Digital transmission through the AWGN channel Prof李晓峰 7
5.3.2 Passband Carrier-phase modulated signals M.0=8z0c0s2rf1+ 2πm m=0,1,.,M-1 M It is often called PSK(Phase shift keying) Take M=4,QPSK.There are 4 possible phases:0 2πm=0,元/2，元，3元/2 UESTC-Digital transmission through the AWGN channel Prof李晓峰 8