Analysis of near-field Cassegrain reflector: plane wave vs. element by element approach

The authors outline how to calculate the pattern of a near-field Cassegrain reflector (NFCR) using a more exact element-by-element approach. Each element in the feed array is considered individually and its diffraction pattern calculated from the subreflector using the geometrical theory of diffraction (including uniform theories at the shadow boundaries). The field contributions from all elements are superimposed at the curved main reflector surface, and a physical-optics integration is performed to obtain the secondary pattern.>