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Author Topic: Using RMA algorithm with the data acquired via USB
Posts: 2
Post Using RMA algorithm with the data acquired via USB
on: December 17, 2013, 15:47


I built the small radar system with a PICmicro ramp generating and data logging circuit. I record the scattering data directly into MATLAB workspace.

My problem is that I couldn't use the RMA algorithm of Dr. Charvat's thesis with my data. I get the following error in MATLAB:

Error using griddedInterpolant
The point coordinates are not sequenced in strict monotonic

Error in interp1>Interp1D (line 335)
F = griddedInterpolant(X,V(:,1),method);

Error in interp1 (line 220)
Vq = Interp1D(X,V,Xq,method);

Error in rma_exp_m1 (line 180)
S_st(ii,:) = (interp1(Ky(ii,:), S_mf(ii,:), Ky_even));

IMO, probably I couldn't do the data conditioning properly.

As an example, I attached one of my recorded data. I moved the SAR system with 1cm increments for 91 positions. The frequency is swept with a center frequency of 2425E6 Hz and the BW is 221E6 Hz for each position. My ramp time is 180ms. The scattering data is recorded 145 times in a pulse. Hence the scattering matrix (S) is 91X145. How can I use RMA algorithm to obtain a SAR image using this data. Any help is greatly appreciated.

Thanks in advance.

Note: I couldn't attach the scattering data to the post hence shared the scattering file here:

Posts: 115
Post Re: Using RMA algorithm with the data acquired via USB
on: December 20, 2013, 09:01

Can you process the example data set that comes with the SAR MATLAB algorithm?

Here are several sample data sets with MATLAB algorithms to process. Scroll down to the coffee can files or give any of the others a try:

FYI, you can not mix data sets with algorithms, otherwise you have to change the Kr range over which data is interpolated.

Suggest you read the 'Range Migration Algorithm' chapter out of Spotlight Synthetic Aperture Radar, for more info.

Good luck!

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