plot_rows = 2;
plot_cols = 2;
t = 0:0.001:1500;
A = 1;
fc = 30;

%carrier
carrier = cos(2*pi*fc*t);
subplot(plot_rows,plot_cols,1);
plot(t,carrier);
xlim([0 20]);
ylabel('cos(t)');
xlabel('t');
title(sprintf('fc = %d',fc))


%m(t)
m =cos(pi*2*t);
subplot(plot_rows,plot_cols,2);
plot(t,m);
xlim([0 20]);
ylabel('m(t)');
xlabel('t');


%f_m
f_m = (A+m).*carrier;
subplot(plot_rows,plot_cols,3);
plot(t,f_m);
xlim([0 20]);
ylabel('f_m(t)');
xlabel('t');


%f_r
f_r = abs(f_m);
subplot(plot_rows,plot_cols,4);
plot(t,f_r);
xlim([0 20]);
ylabel('f_r(t)');
xlabel('t');

figure;
first = 25;
last = 37;
step = 1;
cols = 2;
rows = (last-first)/cols;

for RC = first:1:last;
  %h
  h = (1/RC).*(exp(-t./RC)).*(t>=0);

  %f_d
  f_d = (ifft(fft(h) .* fft(f_r))) - A;
  subplot(rows,cols,RC-first+1);
  plot(t,f_d - max(f_d)+3);
  xlim([0 20]);
  ylabel('f_d(t)');
  xlabel('t');
  title(sprintf('RC = %d',RC));



end