Novel interpretation of physical optics errors, fictitious penetrating rays and corrections by hybrid use of PO and AFIM

Abstract

Novel interpretation of the physical optics (PO) is discussed and two mechanisms are identified as the error factors, that is, (1) errors in diffraction coefficients and (2) fictitious penetrating raysll]. Based upon these observations, new methods named PO-AF and PTD-AF are proposed which eliminate the fictitious penetrating rays from PO and PTD, respectively.The accuracy is confirmed numerically for corner reflectors and circular arc reflectors. 2PO approximation is generally inaccurate in the shadow region, in which the direct incident waves from the source are screened by the scatterer. In correction of PO errors, most of works were directed to factor (l), which cause the perturbation in the edges; PTD was improved about factor (1) by GTD diffraction coefficients. The effect of t,b: fictitious peiictrating rays (2), which is named to be based upon intensive interpretation of the rays cmanating from invisible edges, has liardly at all been discussed and evaluated in detail. The purpose of this study is to extract the niechanisni of the generation of the fictitious penetrating rays and to correct PO by removing them Firstly, PO currents are decomposed into two currents, whicli are the scts of equivalent currents in the aperture field integration method (AFIM) for reflection and shadow waves (Table 1).Extract t h e mechanism of P O errors AFIM+ and AFIM-currents form respectively the shadow by canceling the dircct incident waves and the reHection from the scatterer[2]. AFIM+ currents do not radiate the scattering fields from the inncr edges in terms of field equivalence theorem. AFIM-currents. on the other hand, causes the radiation from the invisible edges, that is the fictitious penetrating rays, as if they are generated by images corresponding to the reflections.