% function as_savefft_volts(fname_load,fname_save)
% David Cheung, 5/16/03
%
% Loads the specified corrected data set and generates
% the angular spectrum.  Saves the angular spectrum to
% the file specified.
%
% fname_load = filename to load
% fname_save = filename to save
%
% Assumes file loaded contains:
%   data3D_dB(x,y,freq) in dB, data3D_phase(x,y,freq) in rad
% Saves file containing:
%   as3D(x,y,freq) in linear power*m^2

% function as_savefft_volts(fname_load,fname_save)
fname_load = input('Please enter the file name to load \n','s');
fname_save= input('Please enter the file name to save\n','s');

% load data, convert to complex (voltage)
load(fname_load);  % data3D_dB data3D_phase
data3D_complex = 10.^(data3D_dB/20) .* exp(j*data3D_phase);
clear data3D_dB data3D_phase;

% perform 2D FFT
num_pts = size(data3D_complex,3);
for freq_index = 1:num_pts
  z = squeeze(data3D_complex(:,:,freq_index));
  as3D(:,:,freq_index) = fftshift(fft2(z));
end;

% save to specified file
save(fname_save,'as3D');  % as3D(x,y,freq)