Side-fed offset cassegrain antennas with 18????18?? field of view: An efficiency comparison using surface area efficiency criterion

Calculated performance of side-fed offset Cassegrain antennas (SFOCAs) with two different feed arrangements and two different subreflector sizes is investigated and compared in this paper. Antennas under investigation have 70 wavelength circular apertures (1° beamwidth) and operate over a conical FoV of 18°×18°. The efficiency investigation and comparison are performed using the novel surface area efficiency (SAE) criterion that was introduced as an additional criterion for comparison of efficiencies of the dual-reflector antennas with big subreflectors in addition to the classical aperture efficiency (AE) criterion. Using SAE criterion for beams located at the edge of FoV, it is shown that in the case of the simplified feeds arrangement within a plane array oversizing of the subreflector dimensions is much more effective than comparable increasing of the surface area of the whole AS with the standard subreflector size. In the case of the feeds with optimal positions and orientations this benefit is negligible. Designed SFOCA with an oversized subreflector within the whole FoV of 18°×18° has SAE better than 25% (AE > 50%) for the simplified feed positions within a plane array and SAE better than 32% (AE > 65%) in the case of the feeds with optimal positions and tilt angles.