Multi-port nonlinearities in Wave Digital Structures

Wave Digital Structures (WDS), with their inherent stability and robustness, would be particularly suitable for nonlinear (NL) circuit modeling in Virtual Analog applications, if it were possible for them to accommodate multi-port nonlinearities. In this work we present a method for modeling a rather general class of multi-port NL elements in the WD domain, which are obtained as the interconnection of linear and NL resistive bipoles. The method is based on a Piece-Wise Linear approximation of the individual nonlinearities that constitute the multi-port element. This method advances the state of the art as it enables the modeling of arbitrary interconnections between outer ports of the nonlinearity and individual ports of the local NL bipoles. As an example of application of the method, we show a WD implementation of a transformer-less ring modulator.