Nonlinear transient simulation of mixed EM/circuit-level system blocks

One of the most important challenges in nonlinear high-frequency circuit simulation is to incorporate linear, time-invariant circuit blocks described in the frequency-domain, within a separate set of nonlinear integro-differential equations in the time-domain describing semiconductor devices etc. Often the linear representation is derived from EM analysis. This paper reviews some existing approaches to this type of problem including those based on Vector Fitting and an approach based on a non-uniform discrete-time impulse response.