Scattering from an infinite slit in a thick conducting screen

Abstract

Electromagnetic wave scattering of three-dimensional oblique incidence on a slit in a thick conducting screen is studied. The electromagnetic wave is decomposed into TE- and TM-mode representation. The Fourier-transform and the mode-matching technique are used to obtain simultaneous equations. The simultaneous equations are solved to represent the scattered and transmitted fields in series forms which are amenable to numerical computation. The integral in simultaneous equation is expanded into pole and branch-cut contribution for efficient numerical computation. An approximate high-frequency solution for transmission is obtained in closed-form. The numerical computations are performed to illustrate the slit scattering behavior in terms of slit size, incident angle and frequency. Several results of radar cross section (RCS), radiation pattern, and transmission coefficient are compared with measurements or results obtained by other methods. The transmission coefficient is critically dependent on the cutoff frequencies of the modes and on the width of the slit, which causes strong resonances, whereas the far-field patterns are influenced by the width, especially at oblique incidence. Typical diffraction patterns of scattered and transmitted fields are presented to illustrate their behavior.