function [esti_ang_deg, P_FT, fft_ang_deg] = df_FFT_mar510(snapshot, NFFT, lambda_c, fft_ang, array_struct, Ntarget)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% Conventioanl Beamforming algorithm for df 
% Start : 23.08.25
% End   : 23.08.25
% developed by Kwanggoo Yeo
% 
% Description
%   - Input
%       - 1) snapshot [matrix], [-] : raw data(snapshot) for df 
%       - 2) test_ang_elev_deg [vector], [deg] : elevation angle grid for beamforming
%       - 3) test_ang_azi_deg [vector], [deg] : Azimuth angle grid for beamforming
%       - 4) lambda_c [scalar], [m] : wavelength of center frequency 
%       - 4) array_struct [struct], [-] : Structure containing virtual array information
%       - 5) Ntarget [scalar], [-] : The number of targets in snapshot
%
%   - Output
%       - 1) esti_ang_deg [matrix], [deg] : The estimated angles by CBF
%       - 2) P_CBF [matrix], [linear] : power spectrum of CBF
%
% History
% (23.08.25) Completed
%
% Referece
%   - 
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


Nsnap = size(snapshot, 2);

if isempty(fft_ang)
    fft_freq = -180 : 360/NFFT : (180 - 360/NFFT);
    fft_ang_deg = asind(fft_freq / 2 * lambda_c / array_struct.d_unit / 180);
end

% FFT spectrum
zero_padded_input = complex(zeros(NFFT, Nsnap));
zero_padded_input(flip(abs(array_struct.azi_eff_ch_loc))+1, :) = snapshot;

if Nsnap == 1
    %P_FT = abs((fftshift((1/Nsnap) * ((fft(zero_padded_input, NFFT)))').')).^2;
    P_FT = abs((((1/Nsnap) * ((fft(zero_padded_input, NFFT)))').')).^2;
else
    P_FT = abs((fftshift((1/Nsnap) * (sum(fft(zero_padded_input, NFFT),2))').')).^2;
end


[pks, pks_ang, ~, ~] = findpeaks(pow2db(abs(P_FT)), fft_ang_deg);
[~, order] = sort(pks, 'descend');
if isempty(pks)
    esti_ang_deg = nan;
else
    esti_ang_deg = pks_ang(order(1:Ntarget));
end
    

end