Fourier Transform Of Fields

fft_fields.py

# May need to pad with zeros the input fields to FFT to get the 
# desired amount of frequency points. 
n_sample_points = 2 * int(n_freq_points/(max_freq - min_freq) * max_freq)

fft_field = abs(np.fft.fft(field, n=n_sample_points, axis=-1).real)
fft_field = fft_field[:, :, :fft_field.shape[-1]//2]
freqs = np.fft.fftfreq(n_sample_points, d=dt)[:(n_sample_points/2)]

# We are only interested on the frequencies inside the source bandwidth
mask = (freqs >= min_freq) * (freqs <= max_freq)
freqs = freqs[mask]
fft_field = fft_field[:, :, mask]