Equivalence of physical optics and aperture field integration method for reflectors approximated by polyhedra

Abstract

The equivalence of physical optics (PO) and the aperture field integration method (AFIM) in the full 360/spl deg/ angular region of reflector antennas is discussed from two viewpoints. One is how to approximate the equivalent surface currents and the other is how to select the integration surface. The former was already discussed by Oodo and Ando (see IEEE AP-S Int. Symp., p.66-9, 1994), which pointed out that the equivalent currents (I,M) on the integration surface should consist of not only the geometrical optics (GO) reflected fields (E/sup n/,H/sup r/) by the reflector but also the incident fields (E/sup i/,H/sup i/) from the feed, namely I=n/spl circ//spl times/(H/sup i/+H/sup r/), M=(E/sup i/+E/sup r/)/spl times/n/spl circ/(1), where n/spl circ/ is the outer unit vector normal to the integration surface. On the other hand, the method of selecting the integration surface was discussed only for parabolic reflectors. In such a case, a simple aperture which caps the reflector is the integration surface needed for the equivalence of PO and AFIM. We discuss the effects of the integration surface in the AFIM applied for strip reflectors, corner reflectors and parabolic reflectors approximated by polyhedra. Numerical comparisons between the PO and AFIM using various kinds of integration surfaces for the reflectors are demonstrated and the effects of the integration surface are shown. This paper deals with only 2-D models, but the discussion can be extended to 3-D cases. The equivalent currents are used in all the calculations.