Observation-point-dependent blocking shadows on a reflector antenna

The authors present efficient algorithms that can be incorporated in a physical-optics integration to account for migrating feed- and observation-point-dependent geometrical shadows caused by obstacles in the aperture of a reflector antenna with the feed under focused or scanned conditions. The expressions involve only addition and multiplication of simple low-order polynomials and hence do not introduce expensive overhead into the numerical integration. Obstacle shapes considered are disks, polygons, cylinders, and polyhedrons. Some appropriate diffraction corrections are presented which are compatible with the blocking algorithms