Contents I. Introduction
Over the last fifteen years, extended finite-difference time-domain (FDTD) formulations have been developed permitting the analysis of hybrid microwave circuits that include distributed and lumped components [1], [2]. In most cases, lumped components are incorporated into FDTD simulators by using equivalent circuit models. Unfortunately, in the case of active devices, most manufacturers provide only the -parameters of the device measured over the frequency band of interest under certain biasing conditions. Equivalent circuits are not easy to obtain and, moreover, some types of components are not even described reliably by such an approach. Therefore, the direct incorporation of circuits described by measured -parameters into FDTD simulators is of great interest.
