Ultra-Wideband Antenna Development

Abstract : This report summarizes the results of a 1-year effort to investigate electromagnetic dispersion caused by finite electrical conductivity in ultra-wideband antennas. Integral equations are well-suited for antenna calculations, but numerical solutions of dispersive time-domain integral equations are extremely limited. The primary cause of this situation is the computational complexity, which increases by a factor or order N(sub t) (the number of time steps) for dispersive materials. We propose an efficient solution based upon surface impedance boundary conditions and upon a recursive evaluation of the time convolution integral that has a complexity increase on the order of log(N(sub t)). The numerical implementation of the efficient solution for a 2-dimensional planar transmission line is described in detail. Comparison of the efficient solution with the analytic solution of the same problem show good agreement in both time and frequency domains.