- white noise
- apply filter with the cutoffs both ends in the frequency domain
How do you add noise to an FM signal?
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This is Frequency modulation where
where
Question:
I have been able to modulate the message signal m(t) and demodulate it suing this code:
fc = 1000;
Ac = 5;
t0 = 0.2;
ts = 0.00000001;
fs = 1/ts;
t=[0:ts:t0];
m = 10*t.*(t>=0 & t<=0.1)+(2-10*t).*(t>0.1 & t<=0.2)+0.*(t>0.2);
u = Ac*modulate(m,fc,fs,'fm'); %% modulate the message signal
y = demod(u,fc,fs,'fm'); %% demodulate the message signal
y = y/(6.275*10^-5); %% scale the demodulated signal
figure(6)
subplot(2,1,1)
plot(t,m(1:length(t)));
title('Original Message signal m(t)')
xlabel('Time (s)')
ylabel('Amplitude')
subplot(2,1,2)
plot(t,y);
title('Demodulated Message Signal')
xlabel('Time (s)')
ylabel('Amplitude')
I now need to add noise to the signal according to the above formula of y(t) = u(t) + n(t)
where n(t) = nc(t).cos(2\pi fc.t) - ns(t).sin(2\pi fc.t)
How do I add this noise to u(t) using rand or randn ?
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Answers (2)
Hiro Yoshino
on 9 Sep 2020
You can check this up:
Basically you should follow this:
3 Comments
Hiro Yoshino
on 10 Sep 2020
I guess you should add noise before the command "modulation".
see:
it says demod works for the signal created by modulation.
Also this can be a help for you
Manuel A. Vázquez López
on 27 Mar 2021
Long time but...did you get to solve this? I'm facing a similar problem. I'm adding some Gaussian noise with standard deviation 1e-2, but that has a huge impact on the demodulated signal (and I was assuming FM should be fairly resilient to it).
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