DIFFRACTION BY A WIDE APERTURE IN AN ANISOTROPIC MEDIUM

Abstract

Two-dimensional scattering of a plane electromagnetic wave by an aperture in a conducting screen immersed in an anisotropic medium, such as a magnetically gyrotropic plasma, is considered. With the aperture edge, or its tangent, parallel to the gyrotropic axis, the E-polarized field of the wave is unaffected by the anisotropy and attention is confined to the H-polarized field. From the asymptotic form of the exact solution for half-plane diffraction, a coefficient is extracted and the geometrical theory of diffraction used to derive expressions for singly and first-order multiply scattered fields of a slit and, for normal incidence, of a circular aperture. Far-field diffraction patterns of a normally incident wave are shown of slits with ka ranging from 3 to 8, where k is the propagation constant in the medium and 2a is the slit width, for various degrees of anisotropy. The patterns indicate an enhancement in the forward direction for a highly anisotropic surrounding medium. While the phase of the patterns is asymmetrical about the forward direction, their amplitude is not, in contrast with results obtained from approximate solutions for radiation from a small aperture.