Diffraction coefficients for a curved edge with soft and hard boundary conditions

Diffraction of high-frequency electromagnetic fields are very important from both the theoretical and engineering points of view. Generally, asymptotic methods are preferred for the solution of diffraction problems because rigorous analysis is generally impossible. In the paper the diffraction of whispering gallery modes by the edge of a conducting spherical reflector with soft and hard boundary conditions are considered separately, where the incident modes are assumed to be present in the concave side of the reflector. The analysis has been done for the special case (ka) ≫ 1 by using the locality principle of the GTD (geometrical theory of diffraction). The results are expressed in the GTD form and various coefficients for the determination of edge-excited rays and surface ray fields are extracted. It is concluded that these coefficients can be used for the determination of diffracted rays and surface ray fields excited by apertures on arbitrarily curved surfaces. These coefficients are not valid in the transition regions, but they reveal the effect of surface curvature on diffraction phenomenon.