fmdem.m

将音乐信号fm调制并解调

clear all;
clc;
[m,fs,bits]=wavread('C:\Documents and Settings\zhaoliang\桌面\weina\hujiaozhuanyi.wav') %读取音乐信号
len=size(m,1);
f=fs*(0:(len-1))/len;
figure(1);
subplot(2,1,1),plot(m);      %原始音乐信号的波形图
title('原始音乐信号的波形图');
y=fft(m,len);
subplot(2,1,2),plot(f,abs(y)); %原始音乐信号的频谱图
title('原始音乐信号的频谱图');
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%对音乐信号进行调制
z0=fmmod(m,70*10^3,20*10^4,15000);
figure(2);
subplot(3,1,1),plot(z0);
title('FM信号');
z1=diff(z0);
subplot(3,1,2),plot(z1);
title('微分后的FM信号');
%hilbert transform
z2=hilbert(z1);
k=z1.^2+z2.^2
z3=sqrt(k);
subplot(3,1,3),plot(z3);

%利用fmdemod函数进行解调
figure(3);
f=(0:length(fft(z0))-1)*(200*1000-1)/length(fft(z0));
subplot(2,1,1);plot(abs(fft(z0)));
title('调制后的频谱图');
z4=fmdemod(z0,70*1000,20*10000,15000);
f=(0:length(fft(z4))-1)*(200*1000-1)/length(fft(z4));
subplot(2,1,2);
plot(abs(fft(z4)));
title('解调后的频谱图');
sound(z4,17000,16);