Input impedance model for DE-based numerical simulations of radiation problems

The authors present a method to calculate the input impedance from time-domain DE (differential-equation)-based simulations of radiation problems. The method provides rigorous excitation of the antenna structure and extraction of impedance results with minimal additional computation. The method was applied to evaluate the change in input impedance of a VED (vertical electric dipole) source radiating in the presence of a lossy half space. For this application, the method can be considered as a numerical implementation of the classical analytic method described by J.R. Wait (1969). Reasonable agreement with the exact solution is obtained. The method was applied to numerical simulations based on the 3-D symmetric condensed TLM (transmission line matrix) model, and the TLM total/scattered field formulation.<>