通信原理实验波形图.doc

AM相关解调AM包络检波AM相关解调结果AM相关解调结果AM包络解调结果DSBDSB结果滤波法产生SSB信号滤波法相移法产生SSB信号相移法FM调制时域图figure(1);dt=0.001;t=0:dt:1.5;am=15;fm=5;mt=am*cos(2*pi*fm*t);fc=50;ct=cos(2*pi*fc*t);kf=10;vt=cos(2*pi*fc*t+10*15*sin(2*pi*fm*t)/(2*pi*fm);subplot(3,1,1);plot(mt);axis(0,1500,-20,20);title(调制信号的时域图);subplot(3,1,2);plot(ct);axis(0,1500,-1,1);title(已调信号的时域图);FM调制频域图figure(2);am=15;fm=5;mt=am*cos(2*pi*fm*t);fc=50;ct=cos(2*pi*fc*t);kf=10;vt=cos(2*pi*fc*t+10*15*sin(2*pi*fm*t)/(2*pi*fm);subplot(2,1,1)Fs=20;T=1/Fs;N=1024;t=(0:N-1)*T;mt=am*cos(2*pi*fm*t);NFFT=N;Y=fft(mt,NFFT)/N;f=Fs/2*linspace(0,1,NFFT/2);Am=2*abs(Y(1:NFFT/2);plot(f,Am)title(调制信号频谱)xlabel(Frequency/Hz),ylabel(magnitude)subplot(2,1,2)Fs=200;T=1/Fs;N=1024;t=(0:N-1)*T;vt=cos(2*pi*fc*t+10*15*sin(2*pi*fm*t)/(2*pi*fm);NFFT=N;Y=fft(vt,NFFT)/N;f=Fs/2*linspace(0,1,NFFT/2);Am=2*abs(Y(1:NFFT/2);plot(f,Am)title(已调信号频谱)xlabel(Frequency/Hz),ylabel(magnitude)FM解调figure(3)dt=0.001;t=0:dt:1.5;am=15;fm=5;mt=am*cos(2*pi*fm*t);fc=50;ct=cos(2*pi*fc*t);kf=10;vt=cos(2*pi*fc*t+10*15*sin(2*pi*fm*t)/(2*pi*fm);subplot(3,1,1);plot(t,mt);title(调制信号时域图);subplot(3,1,2);plot(t,vt);title(已调信号时域图);vt1=vt;for i=1:length(t)-1 diff_vt1(i)=(vt1(i+1)-vt1(i)/dt;enddiff_vt2=abs(hilbert(diff_vt1);zero=(max(diff_vt2)-max(diff_vt2)/2;diff_vt3=diff_vt2-zero;subplo