A general and explicit formulation for wave digital filters with multiple/multiport nonlinearities and complicated topologies

Abstract

A general, explicit, and novel formulation for Wave Digital Filters (WDFs) with multiple/multiport nonlinearities is presented. It confronts graph-theoretic views of WDF structures (SPQR tree) with techniques from the nonlinear loop resolution literature (the K method) and a novel method for deriving scattering matrices (WDF adaptors) of arbitrarily complex topologies. It accommodates any number of memoryless nonlinearities with any number of ports each without requiring simplifying assumptions. A case study on the first clipping stage of the Big Muff Pi distortion pedal is presented. This circuit, with its multiple nonlinearities, multiport nonlinearity, and complicated topology, poses an intractable problem for state-of-the-art WDF methods. Hence, successful simulation of this circuit demonstrates the novelty and robustness of our framework.