Equivalence of physical optics and aperture field integration method for parabolic reflectors with offset feeds

This paper discusses the equivalence of physical optics (PO) and the aperture field integration method (AFIM) for the full pattern prediction of parabolic reflectors with offset feeds. In the calculation of the AFIM, there are two important procedures for obtaining the scattered fields. The first one is how to choose the surface of integration. The second one is how to approximate the equivalent currents on the surface of integration. This paper also discusses a polyhedron approximated reflector. For the former model, good agreement between PO and AFIM in the full angular region is numerically shown provided the equivalent currents on the aperture capping the reflector are determined by the incident fields and the geometrical optics (GO) reflected fields. For the latter model, it is shown that the use of simple aperture is not enough for the full angular equivalence to PO. For such a reflector, the surface of integration which caps the conducting element should be assigned separately for each conducting element. The AFIM which adopts the proper integration surface predicts the perfectly identical patterns to those by PO.