INCREMENTAL DIFFRACTION COEFFICIENTS FOR SOURCE AND OBSERVATION AT FINITE DISTANCES FROM AN EDGE

Recently, an incremental theory of diffraction (ITD) has been introduc ed which provides a self-consistent, high-frequency description of a w ide class of scattering phenomena within a unified framework, Explicit expressions of the incremental diffracted field contributions have be en obtained for a plane-wave illumination of wedge-shaped configuratio ns and observation points at a finite distance from the incremental po int. In this paper, this method is extended to treat the case when bot h the source and the observation point are at finite distance from the local incremental point along the edge, To this end, a spectral-domai n approach is used to derive a spectral-integral representation for th e incremental field contribution, The latter is asymptotically evaluat ed to find high-frequency closed-form expressions which are uniformly valid at any incidence and observation aspects, including caustics and shadow boundaries of the corresponding ray-field description. The exp ressions of the incremental diffraction coefficients explicitly satisf y reciprocity. Numerical results are presented and compared with those obtained from different techniques.