A tool for designing digital filters for the Hankel and Fourier transforms

What is it about?

The open-source code fdesign makes it possible to design digital linear filters for the Hankel and Fourier transforms used in potential-, diffusive-, and wavefield modeling. Digital filters can be derived for any electromagnetic method, such as methods in the diffusive limits (direct current, controlled-source electromagnetics) as well as methods using higher frequency content (ground-penetrating radar, acoustic and elastic wavefields). The direct matrix inversion method is used for the derivation of the filter values, and a brute-force inversion is carried out over the defined spacing and shifting values of the filter basis. Included or user-provided theoretical transform pairs are used for the inversion. Alternatively, one can provide layered subsurface models that will be computed with a precise quadrature method using the electromagnetic modeler empymod to generate numerical transform pairs.

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