Time and Frequency Bias in Extrapolating Wideband Responses of Resonant Structures

An improved technique is presented to extrapolate a wideband electromagnetic response of a resonant structure using only early-time and low-frequency computed data. The response is represented as a sum of weighted polynomials and pole terms. Previously, poles were estimated from early-time data. In this paper, poles are also estimated from low-frequency data and used to accurately extrapolate a response. A time or frequency bias is observed when estimating poles from either early-time or low-frequency data, respectively. It is shown that poles estimated from early-time and low-frequency data can be combined to reduce the amount of directly-computed data needed to accurately extrapolate a response. A genetic algorithm is used to select all necessary parameters and determine when enough data has been computed. The driving-point current of several resonant antennas and the electric field at a point outside of a metallic cavity are extrapolated.