Time-varying (TV) materials have recently gained considerable attention for their ability to manipulate electromagnetic (EM) waves and improve the performance beyond the limits of conventional time-invariant materials. In addition, distributed TV capacitors are becoming more attractive to achieve particular effects. This work presents a systematic approach to modeling TV dielectrics by incorporating TV capacitors in the framework of the partial element equivalent circuit (PEEC) method. Thus, the standard formulation of the PEEC method is modified to include TV dielectrics and lumped elements for general 3D geometries directly in the time domain (TD). It is shown that this is possible through TV capacitances and voltage-controlled current sources. Four numerical examples validate the proposed approach.

Time-domain (TD) methods for the solution of Maxwell's equations are particularly appealing for their ability to provide the overall characteristics of an electrical system in a single simulation run. In many situations, such TD methods require computing the system's impulse response and using it in a convolution-based solver. In this work, we propose the evaluation of the scattering-parameters-type impulse response of partial element equivalent circuit (PEEC) models by firstly computing the scattering parameters pertaining to a unit-step excitation via the Numerical Inversion of Laplace Transform (NILT) technique, followed by recovering the corresponding impulse response. The accuracy and effectiveness of the advocated approach is validated by means of numerical experiments comparing its performance with that of more standard methods.