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

Earlier work(1-3) 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 represen t power as a complex number. In the common notation the third number is a s uppressed phase angle; when multiple power fields are combined to form a si ngle one it is essential to account for the suppressed phase angles. The di fferences in power calculations using the time and frequency domain power t heorems are manifest in determination of the energy flow that remains local to the source, oscillating between the near field and source, which does n ot form part of the far field power. In this paper we numerically model, using commonly accepted frequency and t ime domain techniques, the simplest antenna design that clearly illustrates the differences between time and frequency domain representations of react ive power. We calculate and contrast the instantaneous and the steady-state far field and local powers emitted from two identical, perpendicularly ori ented electrically small TM dipoles as a function of relative phase between the two dipoles. Copyright (C) 1999 John Wiley & Sons, Ltd.