Angle Doppler response using FFT

I m simulating a target at 45 degrees azimuth and with a certain doppler..I m using the following code to find angle doppler response...However, i get an error of 15 degrees in angle...

%% Beamforming and doppler processing

sigvol = zeros(fs*pri,128,128);

sigvol1 = sigvol;

tcsig1 = zeros(fs*pri,N,M);

for i = 1:300

temp1 = shiftdim(tsig(i,:,:));

temp2 = fftshift(fft(temp1,128,1),1); %% doppler processing

temp3 = fftshift(fft(temp2,128,2),2); %%beamforming

sigvol(i,:,:) =temp3 ;

end

ad = pow2db(abs(squeeze(sigvol(128,:,:))));

figure(2)

angle_axis = linspace(-90,90,128);

doppler_axis = -prf/2:prf/128:(prf/2)-(prf/128);

imagesc(angle_axis,doppler_axis,ad.');

colormap(jet)

colorbar

xlabel('Angle')

ylabel('Doppler')

Answer 1

[Honglei Chen]

I notice that you are using 128th range gate for plotting. Are you sure you have the correct target there? You can try to verify the result with what returned from phased.AngleDopplerResponse in Phased Array System Toolbox.

HTH

[ahmed hussain]

I have cross checked it with phased angle Doppler response..phased angle Doppler response gives the correct angle...however , the above code gives a bias of of 15 to 20 degrees