FFT Set Expansion Method

Use the 1D FFT > Advanced Settings > Set Expansion Method menu option (FFTSETEXTMD GX) to set 1D FFT extension fill method.

FFT Set Expansion Method dialog options

Expansion fill method

Select the extension fill method. (Default - Maximum Entropy) Options are: Maximum Entropy Constrained LP Script Parameter:FFTEXTFILL.METHOD

Application Notes

The padded segment will be interpolated by either the Maximum Entropy Prediction (MEP) method or the Constrained Linear Prediction (CLP) method.

The MEP (Maximum Entropy Prediction) method determines the spectral content or the preceding real data segment. It then predicts a data function that has the same spectral signature as the original data. As a result, the predicted data will not significantly alter the energy spectrum of the original data.

The CLP (Constrained Linear Prediction) method calculates a series of linear prediction coefficients based on a segment of real data and then uses these coefficients to recursively extrapolate the data. The nature of geophysical data with its wide range of distributions, generally, yields coefficients that produce a reasonable extrapolation. However, if the data contains un-damped oscillations, such as superimposed aircraft systematic noise, then CLP may produce an unstable outcome. An additional constrain on the calculation of the coefficients pushes the results back into the stable zone. The details of the CLP are outside the scope of this document. The avid reader can find further information in the reference below.

Reference