Elimination of Fictitious Penetrating Rays from PO and Hybridization with AFIM

Abstract

Physical optics(PO) is an approximation method for high-frequency scattering and diffraction problems. But PO fields are inaccurate in the shadow region where the source is screened by the scatterer. Two key factors of the error for PO are (i) edge diffraction coefficients and (ii) existence of fictitious penetrating rays. The correction with respect to the former has been extensively investigated by many author using the ray techniques such as GTD, UTD and UAT. On the other hand, the latter was identified recently by the authors. This paper proposes a novel PO-based calculation procedures named PO-AF and PTD-AF, where PO and Aperture Field Integration Method (AFIM) are merged with the help of special elementary diffraction coefficients. These can uniformly cover whole the angular region and only the error factor (ii) is removed in PO-AF while both of (i) and (ii) are removed in PTD-AF. The theoretical backgrounds of PO currents are discussed in terms of field equivalence theorem and visualization of EM waves. Then new methods are proposed and their validity is numerically demonstrated for 2-D scattering problems of a strip, a corner reflector and a cylinder of circular arc.