Flanged parallel-plate waveguide coupled to a conducting cylinder

Abstract

The characteristics of a flanged parallelplate waveguide coupled to a conducting cylinder are investigated in general. The parallel-plate guide opens, through a slot aperture in an infinite screen, into a semi-infinite half-space in which resides a perfectly conducting cylinder of arbitrary cross-section whose axis is parallel to that of the slot. The excitations considered for this structure are (a) a TEM wave in the guide and (b) a line source in the region exterior to the guide, which when sufficiently remote creates a local plane wave. Coupled integral equations for the aperture electric field (or equivalent magnetic current) and the cylinder current are derived from first principles and are solved numerically for cylinders of various cross-section, size and location relative to that of the slot aperture. From knowledge of aperture electric field and cylinder current, all other quantities of interest may be determined: voltage received in the guide, guide reflection coefficient and far-zone radiation. Data are presented that illustrate how the cylinder loads the guide, modifies its radiation pattern and serves as a shield for the aperture. From the data, one can assess the effectiveness of a conducting shield placed over, but not in contact with, the guide aperture.