On the link between top-hat monopole antennas, disk-resonator diode mounts, and coaxial-to-waveguide transitions [and reply

Abstract

Francavilla et al. (1999) and Morgan and Schwering (1994) presented an analysis of a top-hat monopole antenna loaded with dielectric layers radiating above a conducting ground plane. In order to obtain a simplified solution to this rather complicated EM field problem, they introduce an upper ground plane that converts the original problem to the one of a monopole radiating in a parallel-plate radial guide, which is easier computationally to handle, provided that the upper ground plane is located a sufficient distance from the lower ground plane, the currents on the monopole and consequently the input impedance are approximately the same as for the original problem (with no upper conducting plane). The authors apply a field-matching method, in terms of radial harmonics in conjunction with a method of moments, to obtain field expansion coefficients in radial regions of the parallel-plate guide structure. Subsequently they obtain computer algorithms for calculating the input impedance of a top-hat monopole antenna in a parallel-plate waveguide. The present author notes that the problem of a top-hat monopole, as considered in Francavilla et al. and Morgan and Schwering is very similar to the problem of a disk-resonator diode mount as well as to the problem of a coaxial-to-waveguide transition with a disk-ended probe. Due to their different contexts, many antenna researchers overlooked the similarity of these problems. Hence the purpose of this communication is to highlight this oversight. Replies are given by Schwering and Morgan, and by Francavilla Bodner et al.