FFT Fourier -> Space

Use the 1D FFT > Advanced Settings > FFT Fourier -> Space menu option (FFTOUT GX) to transform data from the frequency domain back to the space domain.

FFT Fourier -> Space dialog options

Real component channel

Specify the real component channel.

Script Parameter: FFTOUT.R

Imaginary component channel

Specify the imaginary component channel.

Script Parameter: FFTOUT.I

Original data reference channel

Select the original space-domain reference channel.

Script Parameter: FFTOUT.REF

Output space domain channel

Specify the new space-domain output channel.

Script Parameter: FFTOUT.OUT

DC level multiple

Set the DC (zero wavenumber) level multiplier.

Default: 1.0 (no change)

Script Parameter: FFTOUT.DCMULT

Application Notes

Real and Imaginary Channels

  • The input real and imaginary channels should have been created from the reference channel using FFTIN GX. They may also originate from channels derived by FFTIN.

  • This method is useful for applying custom filters in the frequency domain. Use FFTIN GX to create frequency-domain real and imaginary channels, apply mathematical algorithms to these channels, and then use FFTOUT GX to convert the result back to the space domain.

  • A power spectrum can be calculated from the real and imaginary components using:

    Where r and i represent the real and imaginary channels, respectively.

DC Level Multiple

This parameter restores the trend removed by FFTIN GX. If the DC level changes after filtering, adjust this multiplier accordingly. The default value is 1.0, meaning no change. However, some filters applied to the real and imaginary channels may alter the DC level. In such cases, it is the user’s responsibility to set the correct DC level multiple. For example, a high-pass filter reduces the DC level to zero; therefore, the DC level multiple should be set to 0, and the trend will not be restored.

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