Equivalence of physical optics and aperture field integration method in the full pattern analysis

Physical optics (PO) and the aperture field integration method (AFIM) are high frequency approximation methods which are widely used for the analysis of reflector antennas. For an offset reflector, PO predicts asymmetric far field patterns in the offset plane, while AFIM in choosing the integration plane normal to the boresight direction always predicts symmetric patterns which are generally inaccurate. AFIM, however, in choosing the integration plane that caps the reflector predicts fields similar to those of PO within the first few sidelobes. In previous discussions, only the component which is reflected from the reflector is used as the equivalent currents in AFIM. In the present paper, the authors extend the equivalence of PO and AFIM to the whole observation angle. In view of the field equivalence theorem, the equivalent currents in AFIM consist of both the incident and the reflected fields. The authors numerically demonstrate that the far fields from the above AFIM excellently agree with the PO fields even in back observation angles. The equivalence is also discussed analytically in terms of high frequency approximation.<>