Plane wave diffraction by a terminated, semi-infinite parallel-plate waveguide with three-layer material loading

Analysis of the scattering from open-ended metallic waveguide cavities is an important subject in radar cross section (RCS) reduction studies. This problem serves as a simple model of duct structures such as jet engine intakes of aircraft and cracks occurring on surfaces of general complicated bodies. Some of the cavity diffraction problems have been analyzed thus far using various analytical and numerical methods. However, it appears that the solutions due to these methods are not uniformly valid for arbitrary cavity dimensions. Kobayashi and Sawai (1992) and Koshikawa and Kobayashi (1993) considered a finite parallel-plate waveguide with a planar termination at the open end as an example of simple two-dimensional cavity structures, and analyzed rigorously the plane wave diffraction using the Wiener-Hopf technique, where the efficient approximate solution is obtained which is valid as long as the cavity depth is not too small compared with the wavelength. In the present paper, as a related two-dimensional problem, the authors analyze the diffraction of a plane wave by a material-loaded cavity formed by a semi-infinite parallel-plate waveguide with an interior planar termination. The method of solution is again based on the Wiener-Hopf technique, and both E and H polarizations are considered. Since there are no essential differences on the solution technique between E and H polarizations, analytical details are presented only for the E-polarized case. Numerical examples are given for both polarizations.<>