Forward radiation from axially symmetric reflector antennas

The fields radiated from focus-fed symmetric reflector antennas in the vicinity of forward axial direction are determined by a series representation of the physical optics integral. The considered feeds have cosine-tapered patterns with different tapers in
E
- and
H
-planes. The influence of feed pattern asymmetry, subreflector blockage, feed taper, focal distance to diameter (
f/D
) ratio and the reflector size on the performance parameters of paraboloidal, Cassegrain, near-field Cassegrain, and corresponding Gregorian antennas is investigated. Design curves are presented to predict the performance parameters of the considered antennas.