MATLAB-使用fm解调器解码数据

Question

I am trying to extract a sinusoid which itself has a speed which changes sinusiodially. The form of this is approximately sin (a(sin(b*t))), a+b are constant.

This is what I'm currently trying, however it doesnt give me a nice sin graph as I hope for.

Fs = 100; % Sampling rate of signal
Fc = 2*pi; % Carrier frequency
t = [0:(20*(Fs-1))]'/Fs; % Sampling times
s1 = sin(11*sin(t)); % Channel 1, this generates the signal
x = [s1]; 
dev = 50; % Frequency deviation in modulated signal
z = fmdemod(x,Fc,Fs,fm); % Demodulate both channels.
plot(z);

Thank you for your help.

Answer 1

1. There is a bug in your code, instead of:

    z = fmdemod(x,Fc,Fs,fm); 

You should have:

z = fmdemod(x,Fc,Fs,dev); 

Also to see a nice sine graph you need to plot s1 .

It looks like you are not creating a FM signal that is modulated correctly, so you can not demodulate it correctly as well using fmdemod . Here is an example that does it correctly:

 Fs = 8000; % Sampling rate of signal
 Fc = 3000; % Carrier frequency
 t = [0:Fs]'/Fs; % Sampling times
 s1 = sin(2*pi*300*t)+2*sin(2*pi*600*t); % Channel 1
 s2 = sin(2*pi*150*t)+2*sin(2*pi*900*t); % Channel 2
 x = [s1,s2]; % Two-channel signal
 dev = 50; % Frequency deviation in modulated signal
 y = fmmod(x,Fc,Fs,dev); % Modulate both channels.
 z = fmdemod(y,Fc,Fs,dev); % Demodulate both channels.

If you find thr answers useful you can both up-vote them and accept them, thanks.