Finite-Difference Analysis of EMP Coupling to Lossy Dielectric Structures

This article describes the 3-D EMP finite-difference time-domain computer code THREDE as generalized to calculate coupling to, and scattering from, lossy dielectric objects. The code primarily treats the scattered component of the electromagnetic fields (thus presuming linearity) and employs a radiating outer boundary. As sample scatterers, we use dielectric spheres of ϵ = 2ϵ0and 9ϵ0 illuninated by an EMP plane wave of double exponential profile. Comparitive calculations were made using the inverse-Fourier transform of the Rayleigh-Mie spherical-hannonic expansion solution-agreement of the two solutions is very good.