Uniform asymptotic theory of diffraction by a curvelinear impedance wedge

Abstract

Ray-based uniform asymptotic methods are now widely used for electromagnetic modeling of diffraction processes on microwave, both in conjunction with various numerical methods, and independently. The most commonly used among them and the simplest one is the uniform geometrical theory of diffraction (UTD). The main disadvantage of this method is low accuracy (/spl sim/k/sup -1/2/, where k is the wavenumber). The other asymptotic methods, such as conventional uniform asymptotic theory (UAT), theoretically allow to compute any higher order terms by means of the asymptotic calculation of the fields in integral form. Though, such a calculation for the terms O(k/sup -1/2/) is hardly realizable because of their great complexity. In the present work UAT field is obtained from the exact solution of Helmholtz's equation in a small vicinity of the edge. This allows to obtain initial conditions for the edge wave calculation and excitation coefficients for the surface waves in more efficient way than the asymptotic calculation of the integral expressions.