mvsb.m

通信系统中实现残留边带调制

%显示模拟调制的波形及解调方法VSB
%信源
close all;
clear all;
dt = 0.001;          %时间采样间隔         
fm=5;                %信源最高频率
fc=20;               %载波中心频率
T=5;                 %信号时长
t = 0:dt:T; 
mt = sqrt(2)*( cos(2*pi*fm*t)+sin(2*pi*0.5*fm*t)  );  %信源

%VSB modulation
s_vsb = mt.*cos(2*pi*fc*t);
B=1.2*fm;
[f,sf] = T2F(t,s_vsb);
[t,s_vsb] = vsbpf(f,sf,0.2*fm,1.2*fm,fc);
figure(1)
subplot(311)
plot(t,s_vsb);hold on;     %画出VSB信号波形
plot(t,mt,'r--');          %标示mt的波形
title('VSB调制信号');
xlabel('t');

%VSB demodulation
rt = s_vsb.*cos(2*pi*fc*t);
%rt = rt-mean(rt);
[f,rf] = T2F(t,rt);
[t,rt] = lpf(f,rf,2*fm);

subplot(312)
plot(t,rt); hold on;
plot(t,mt/2,'r--');
title('相干解调后的信号波形与输入信号的比较');
xlabel('t')
subplot(313)
[f,sf]=T2F(t,s_vsb);
psf = (abs(sf).^2)/T;
plot(f,psf);
axis([-2*fc 2*fc 0 max(psf)]);
title('VSB信号功率谱');
xlabel('f');