Excitation Efficiency of Surface Waves over Corrugated Metal and Doubly Corrugated Metal and in Dielectric Slabs on a Ground Plane

摘要

Corrugated metal (and 'doubly corrugated metal') is an anisotropic boundary which supports only a hybrid surface wave mode in directions other than parallel or perpendicular to the corrugations. The mode phase velocity is a function of direction. To determine the excitation efficiency of these modes a three dimensional analysis is performed generalizing the results of Cullen and utilizing the author's previous work. The surface waves are shown to possess many of the properties of plane waves in a two dimensional anisotropic medium - notably that the energy propagation is radial and not generally normal to the wave fronts. Radial propagation, however, does not imply that the primary pattern of a feed and the resulting far pattern of the surface wave are the same. The hybrid plane wave component of the spectrum of the source which propagates in a direction psi parallel to the ground plane with the natural surface wave phase velocity of the boundary in this direction is observed in the far field in a direction phi not generally equal to psi. Moreover the excitation efficiency is not independent of psi. Therefore, the possibility of focussing by an anisotropic boundary remains