PO and PTD analyses of offset reflector antenna patterns

The maximum angle at which the physical optics (PO) formulation for offset reflector antenna problems is derived. Obliquely incident plane-wave diffraction by a flat plate is first discussed to demonstrate the accuracy of physical theory of diffraction (PTD) and to establish the method predicting the PO error in the offset plane. Then it is applied to the reflector antennas, and the PO error is expressed as functions of only the offset angle and observation angle. A variety of numerical results for actual offset reflectors shows the validity of these expressions.<>