An asymptotic result for the diffraction of plane waves propagating along a cylindrically truncated flat surface

An asymptotic result is obtained for evaluating the diffraction of a plane wave incident along a perfectly conducting fiat surface toward a drop in this surface. This drop is formed with a convex cylinder smoothly joined to the fiat section, thus creating a discontinuity in curvature at the join. The asymptotic result is also useful for analyzing the radiation of a source mounted on the fiat section of the conducting surface. Unlike a previously available solution which still requires a fair amount of numerical evaluation using a hybrid approach combining the moment method with the geometrical theory of diffraction, the computation of this asymptotic result is simple and efficient. Since this result is expressed in the simple format of the geometrical theory of diffraction, it is easily applied to solving more complicated diffraction problems. An application is found in the aperture-matched horn designs.