fredemod

clc;
clear all;
close all;
t=[0:0.001:2];
fm=5;
fc=100;
m=cos(2*pi*fm*t);
subplot(4,1,1);
plot(t,m);
title('Message Signal');
xlabel('Time');
ylabel('Amplitude');
c=sin(2*pi*fc*t);
subplot(4,1,2);
plot(t,c);
title('Carrier Signal');
xlabel('Time');
ylabel('Amplitude');
mf=15;
fm=sin((2*pi*fc*t)+mf.*sin(2*pi*fm*t));
subplot(4,1,3);
plot(t,fm);
title('Frequency Modulated Signal');
xlabel('Time');
ylabel('Amplitude');
x=diff(fm);
z=abs(x);
[b,a]=butter(10,0.056);
output=filter(b,a,z);
subplot(4,1,4);
plot(output);
title('Frequency de-Modulated Signal');
xlabel('Time');
ylabel('Amplitude');