0
$\begingroup$

I have the transmitted pulse and the raw SAR image before range compression (dechirping). I understand the pulse compression its a convolution along the columns but I am not able to make it work. I've tried this:

   h_compressed = conv2(fliplr(conj(g)), 1, Dr, 'same');

Where g is the transmitted chirp and Dr is the raw SAR image.

Improve this question
$\endgroup$
6
  • $\begingroup$ Is this really a new question or just a slight variation to your previous question? You have reacted to none of the comments nor to the answer to that, so I'm slightly reserved about this question. $\endgroup$ – Marcus Müller Jan 4 '20 at 1:44
  • $\begingroup$ Correction: you did add a few interesting images (my browser had the last version of your question cached)! Anyways, "I am not able to make it work" isn't really a description of what goes wrong, and you should really clarify how this differs from your previous question, I think. $\endgroup$ – Marcus Müller Jan 4 '20 at 1:58
  • $\begingroup$ Yeah I think maybe my previous question was not clear enough so I updated it to this. It is still the same issue $\endgroup$ – Ben Romarowski Jan 4 '20 at 1:58
  • $\begingroup$ You should rather clear up your previous question, then, and tell the author of the answer you've gotten why her/his answer doesn't help you. $\endgroup$ – Marcus Müller Jan 4 '20 at 1:58
  • $\begingroup$ ok, do you know why this matched filter does not work tho? $\endgroup$ – Ben Romarowski Jan 4 '20 at 2:00
0
$\begingroup$

Dechirping is a bit different than matched filtering, but perhaps that not important here.

The code you have looks like it should work if the variables are as you describe. Here is a hypothetical example that range compresses an LFM pulse. The reflected signal from an actual target in the scene is a just a delayed version of the waveform, so it will just be a shifted version of what you get when you range compress the transmitted pulse itself:

Tp = 10e-6;              % Pulse length (s)
Brf = 200e6;             % Bandwidth (Hz)
fs = 1.2 * Brf;          % Sampling frequency (Hz)
Ns = ceil( Tp * fs );    % Number of samples per pulse

% Vector of time samples (s)
t = 1/fs * ( -Ns/2 : Ns/2 - 1 ).';

% The LFM waveform.
lfm = exp( 1j * pi * Brf / Tp * t.^2 );

% Matched filter the pulse.
rngcomp = conv2( flipud( conj( lfm ) ), 1, lfm );

% Display the magnitude of the IPR.
plot( 20*log10( abs( rngcomp ) ) );
Improve this answer
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.