empymod.transform.dlf(signal, points, out_pts, filt, pts_per_dec, kind=None, ang_fact=None, ab=None, int_pts=None)[source]

Digital Linear Filter method.

This is the kernel of the DLF method, used for the Hankel (hankel_dlf) and the Fourier (fourier_dlf) Transforms. See hankel_dlf for an extensive description.

For the Hankel transform, signal contains 3 complex wavenumber-domain signals: (PJ0, PJ1, PJ0b), as returned from kernel.wavenumber. The Hankel DLF has two additional, optional parameters: ang_fact, as returned from kernel.angle_factor, and ab. The PJ0-kernel is the part of the wavenumber-domain calculation which contains a zeroth-order Bessel function and does NOT depend on the angle between source and receiver, only on offset. PJ0b and PJ1 are the parts of the wavenumber-domain calculation which contain a zeroth- and first-order Bessel function, respectively, and can depend on the angle between source and receiver. PJ0, PJ1, or PJ0b can also be None, if they are not used.

For the Fourier transform, signal is a complex frequency-domain signal. The Fourier DLF requires one additional parameter, kind, which will be ‘cos’ or ‘sin’.