function [esti_ang_deg, P_CBF] = df_cbf(snapshot, test_ang_elev_deg, test_ang_azi_deg, lambda_c, 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
%   - 
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


% Spectrum
P_CBF = zeros(length(test_ang_elev_deg), length(test_ang_azi_deg));
for ang_elev_idx = 1 : length(test_ang_elev_deg)
    for ang_azi_idx = 1 : length(test_ang_azi_deg)
        sv = exp(-1i * 2 * pi / lambda_c * ( array_struct.azi_eff_ch_loc.' * array_struct.lambda_c * cosd(test_ang_elev_deg(ang_elev_idx)) * sind(test_ang_azi_deg(ang_azi_idx)) + array_struct.elev_eff_ch_loc.' * array_struct.lambda_c * sind(test_ang_elev_deg(ang_elev_idx))));         
        P_CBF(ang_elev_idx, ang_azi_idx) = abs((sum(sv'*snapshot))).^2;       
    end
end

if size(P_CBF, 1) == 1
    [pks, pks_ang, ~, ~] = findpeaks(pow2db(abs(P_CBF)), test_ang_azi_deg);
    [~, order] = sort(pks, 'descend');
    if isempty(pks)
        esti_ang_deg = nan;
    else
        esti_ang_deg = pks_ang(order(1:Ntarget));
    end
elseif size(P_CBF, 2) == 1
    [pks, pks_ang, ~, ~] = findpeaks(pow2db(abs(P_CBF)), test_ang_elev_deg);
    [~, order] = sort(pks, 'descend');
    if isempty(pks)
        esti_ang_deg = nan;
    else
        esti_ang_deg = pks_ang(order(1:Ntarget));
    end
else
    [pks, locs_x, locs_y] = peaks2(pow2db(abs(P_CBF)));
    [~, order] = sort(pks, 'descend');
    if isempty(pks)
        esti_ang_deg = nan;
    else
        esti_ang_deg = [test_ang_elev_deg(locs_x(order(1:Ntarget))).' test_ang_azi_deg(locs_y(order(1:Ntarget))).'];
    end
end

end