FM_Mod

clc
clear all
close all

vm = input('Enter Amplitude (Message) = ');
vc = input('Enter Amplitude (Carrier) = ');
fM = input('Enter Message frequency = ');
fC = input('Enter Carrier frequency = ');
m = input('Enter Modulation Index = ');

t = [0:1/(100*fC):10/fM]; %10000 samples

msg = vm*cos(2*pi*fM*t);
subplot(4,1,1);
plot(t,msg); %plotting message signal
refresh;
xlabel('Time [s]');
ylabel('Amplitude [V]');
title('Message Signal waveform');
grid on;
axis tight

carrier = vc*sin(2*pi*fC*t);
subplot(4,1,2);
plot(t,carrier); %plotting carrier signal
xlabel('Time [s]');
ylabel('Amplitude [V]');
title('Carrier Signal waveform');
grid on;
axis tight

y = vc*cos(2*pi*fC*t+m*sin(2*pi*fM*t));

subplot(4,1,3);
plot(t,y); %plotting FM (Frequency Modulated) signal
xlabel('Time [s]');
ylabel('Amplitude [V]');
title('FM Signal waveform');
grid on;
axis tight


N = length(y);
fs = 100*fC; %50 mega samples per second
fnyquist = fs/2; %Nyquist frequency
X_mags = abs(fftshift(fft(y)));
bin_vals = [0 : N-1];
N_2 = ceil(N/2);
fax_Hz = (bin_vals-N_2)*fs/N;
subplot (4,1,4);
plot(fax_Hz(N_2:52000), X_mags(N_2:52000), '-r', 'LineWidth', 2 )
xlabel('Frequency [Hz]')
ylabel('Magnitude');
title('Double-sided Magnitude spectrum (Hertz)');
grid on
axis tight