PLANE-WAVE DIFFRACTION BY AN OPEN-ENDED PARALLEL PLATE WAVE-GUIDE CAVITY

The diffraction of a plane electromagnetic wave by an open-ended parallel plate waveguide cavity with a planar termination is rigorously analyzed for the E-polarized case using the Wiener-Hopf technique. Introducing the fourier transform for the unknown scattered field and applying boundary conditions in the transform domain, the problem is formulated in terms of the simultaneous Wiener-Hopf equations, which are solved via a factorization and decomposition procedure. The solution is exact but formal since branch-cut integrals with unknown integrands and an infinite number of unknowns are involved. Approximation procedures based on rigorous asymptotics are further presented and the approximate solution to the Wiener-Hopf equations is derived. The scattered field inside and outside the cavity is evaluated by taking the inverse Fourier transform and applying the saddle point method of integration. Based on these results, numerical computations of the bistatic scattered pattern as well as the radar cross section have been carried out for various physical parameters, and the scattering characteristics of the cavity are discussed in detail. Some comparisons with existing methods are also given and the validity of those methods is discussed.