What stage to add noise in FMCW radar system?

I want to add AWGN to a FMCW signal to observe how different SNR levels affect system performance (like range/velocity/DOA estimation). Do I add it directly to receiver end like:

% Let sig be the signal reflected from a target
sig2 = receiver(sig) + noise  % where receiver is the RX preamp object in the phased array toolbox

or do I add noise like this:

sig = sig + noise;
sig2 = receiver(sig);

I've tried both setups and I get different results, so I'm not sure what is correct.

Answer 1

[Honglei Chen]

The line

sig2=receiver(sig)

already adds noise to the signal and the noise power is determined by the parameters in receiver. So both options you listed will add additional noise to the signal.

HTH

Answer 2

[Naman Chaturvedi]

Hi Aimee,

The receiver receives the signal corrupted by noise and performs the estimation on the corrupted signal itself. So, the second way is the correct way to add the noise.

[Aimee Nogoy]

Hi Naman,

Thank you! Also, I forgot to mention I have an RX antenna array that involves the collector step. In this case, does the collector receive the corrupted signal or is it still done by the receiver preamp?