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.

Pulsed electromagnetic (EM) field signal transfer from a general EM source distribution to a transmission line (TL) is analyzed with the aid of Lorentz's reciprocity theorem. In this fashion, the transient voltage induced by the impulsive EM source is expressed through the EM fields as radiated by the TL. These transmitted EM fields are expressed in closed form using an analytical procedure that resembles the Cagniard-DeHoop (CdH) technique. The validity of the proposed reciprocity-based methodology is verified with the aid of an alternative analytical solution describing the EM field signal transfer excited by an impulsive vertical electric dipole (VED). Illustrative numerical examples are presented.