sh2_b_jt.rar

%以上边带解调为例 clear; t0=0.15; ts=0.001; Fc=250; snr=20; Fs=1/ts; df=0.3; t=[0:ts:t0]; snr_lin=10^(snr/10); m=[ones(1,t0/(3*ts)),-2*ones(1,t0/(3*ts)),zeros(1,t0/(3*ts)+1)]; c=cos(2*pi*Fc.*t); b=sin(2*pi*Fc.*t); u=m.*c-imag(hilbert(m)).*b; y=u.*c; [M,m,df1]=fft_seq(m,ts,df); M=M/Fs; [U,u,df1]=fft_seq(u,ts,df); U=U/Fs; [Y,y,df1]=fft_seq(y,ts,df); Y=Y/Fs; [C,c,df1]=fft_seq(c,ts,df); f=[0:df1:df1*(length(m)-1)]-Fs/2; %////////////////////////////////////////////////////////// %SSB已调信号解调 f_cutoff=150; n_cutoff=floor(150/df1); f=[0:df1:df1*(length(y)-1)]-Fs/2; H=zeros(size(f)); H(1:n_cutoff)=2*ones(1,n_cutoff); H(length(f)-n_cutoff+1:length(f))=2*ones(1,n_cutoff); DEM=H.*Y; dem=real(ifft(DEM))*Fs; %调制信号的功率. W=1*t0/3+4*t0/3; P=W/(2*t0/3) %//////////////////////////////////////////////////////// clf subplot(2,2,1);plot(t,m(1:length(t))); title('未调制信号'); subplot(2,2,2);plot(t,u(1:length(t))); title('已调制信号'); subplot(2,2,3);plot(t,dem(1:length(t))); title('解调波形'); subplot(2,2,4);plot(f,abs(fftshift(U))); title('已调制信号频谱');