read data from txt file and do FFT in matlab

Regarding you first comment, I modified a bit the code to display all data (i.e 4 chirps x 12 iterations = 48 chirps of 64 samples) . the plot below shows 48 traces that overlay quite well.

So I wonder what you want to do when you say you want to use all data - does it mean you average for each chirp accross the 12 iterations ?

C = readmatrix("data1.txt");
% all chirps data stored in one C matrix 
[m,n] = size(C);
% first rearrange data real / imag parts
data = real(C(:,1)) + j*imag(C(:,n));
% then remove NaN lines (correspond to lines with blanls or (:,:,:) text
data = data(~isnan(data));
% remove last line data ("193 end")
data(end) = [];
% this contains 4 chirps (1/2/3/4) of 64 samples each (complex data)
% this is repeated 12 times , so total amont of data is 4*64*12 = 3072
% samples
% % one single (first) iteration retrieval
% iter1_data = data(1:4*64);
% out_data = (reshape(iter1_data,64,4))';
% 
% % fft plot
% fft_mag = 20*log10(abs(out_data));
% figure(1),plot(1:64,fft_mag);
% title('FFT data block 1');
% ylabel('dB');
% legend('chirp 1','chirp 2','chirp 3','chirp 4')
% 
% all iterations retrieval
out_data = (reshape(data,64,4*12))';
% plot
figure(1),
subplot(2,1,1),plot(1:64,real(out_data));
ylabel('real part');
subplot(2,1,2),plot(1:64,imag(out_data));
ylabel('imag part');

Mathieu NOE 2021-2-24

hello

my previous answer was to show (see plot) that the 12 iterations of the 4 chirps give more or less the same results. The plot confirms that all 48 real traces overlay well , and so for the imaginary parts. But it is still unclear to me what you intend to do with the 12 iterations. I was thinking you wanted to do avearge of the 12 iterations , but maybe it's not right.

Huijie Zhang 2021-2-24

Thank you for your help at first.

I want to make the data to an array which size will be 4 by number of samples. For example, in this data1.txt, there are 12 sets of 4x64 complex number data. So I want to make the array to be size maybe 4x768. After doing 2D-FFT. In my understanding is that doing range-FFT along each row and doing doppler-FFT along each column.

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