FDTD Time Domain Near- to Far-Zone Transformation Above a Lossy Dielectric Half-Space

Abstract

Near- to Far-zone transformations in the Finite-Difference Time-Domain (FDTD) method can be performed in either the time domain or in the freuency domain. For free space conditions, the time domain near- to far-zone transformation is generally much faster and more memory efficient to use, when we require results at a large number of frequency points at a small number of far-zone directions. However when a lossy dielectric half-space is present, representing the ground, the frequency domain transformation has been favored since the Green's functions involved are relatively simple to express the frequency domain compared with the efforts needed to transform the equivalent currents into the frequency domain. This paper describes a combined time and frequency domain near- to far-zone transformation above a lossy dielectric half-space, where it is not necessary to transform the equivalent currents into the frequency domain. This transformation is much faster than the pure frequency domain transformation and comparisons are made between the two different approaches. For validation purposes, scattering of a dihedral above a lossy dielectric half-space is considered.