Comparison of time and frequency domain numerical modelling of outbound and local power from two perpendicularly oriented, electrically small TM dipoles

Abstract

Earlier work using the time dependent Poynting theorem has shown that the complete description of power in a multimodal radiation field requires the use of three numbers; two are sufficient only with a single modal field. Where three numbers are required it is not possible to correctly represent power as a complex number. In the common notation the third number is a suppressed phase angle; when multiple power fields are combined to form a single one it is essential to account for the suppressed phase angles. The differences in power calculations using the time and frequency domain power theorems are manifest in determination of the energy flow that remains local to the source, oscillating between the near field and source, which does not form part of the far field power. In this paper we numerically model, using commonly accepted frequency and time domain techniques, the simplest antenna design that clearly illustrates the differences between time and frequency domain representations of reactive power. We calculate and contrast the instantaneous and the steady-state far field and local powers emitted from two identical, perpendicularly oriented electrically small TM dipoles as a function of relative phase between the two dipoles. Copyright © 1999 John Wiley & Sons, Ltd.