empymod.transform.fourier_fftlog(fEM, time, freq, ftarg)[source]

Fourier Transform using FFTLog.

FFTLog is the logarithmic analogue to the Fast Fourier Transform FFT. FFTLog was presented in Appendix B of [Hami00] and published at

This function uses a simplified version of pyfftlog, which is a python-version of FFTLog. For more details regarding pyfftlog see

Not the full flexibility of FFTLog is available here: Only the logarithmic FFT (fftl in FFTLog), not the Hankel transform (hankel_dlf in FFTLog). Furthermore, the following parameters are fixed:

  • kr = 1 (initial value)

  • kropt = 1 (silently adjusts kr)

  • dir = 1 (forward)

Furthermore, q is restricted to -1 <= q <= 1.

The function is called from one of the modelling routines in empymod.model. Consult these modelling routines for a description of the input and output parameters.


Returns time-domain EM response of fEM for given time.


Only relevant for QWE/QUAD.