A Time-Domain Three-Dimensional Numerical Method for Comprehensive Common-Mode Analysis of Electric Circuits in Inhomogeneous Media

This article presents a numerical method to treat comprehensive common-mode (CM) signals in the time domain, which are electromagnetic noise sources in electrical and electronic devices. Electromagnetic potentials are a better choice to quantify the CM signals because we can easily extend the full-wave analysis of a multiconductor system. We start with the Maxwell equations in inhomogeneous media, which include conductors and dielectrics, and express the wave equations of the electromagnetic potentials. We also introduce a numerical method for the wave equations with lumped-parameter circuits by using the leap-frog scheme based on the central difference method. We calculate normal-mode (NM) and CM voltages in differential circuits with discontinuity and nonuniformity and conduct experiments by using the time-domain reflectometry method. The numerical results of the proposed method are compared with results from the finite-difference time-domain method and experiments for validation, observing conversions and reflections of NM and CM at discontinuities and nonuniformity, and show good agreements among these results.