A COMPARISON OF REFLECTOR ANTENNA DESIGNS FOR WIDE-ANGLE SCANNING*

Conventional reflector antennas are typically designed for up to S O beamwidths scan. In this paper we try to stretch this scan range to some +300 beamwidths. We compare six single and dual reflector antennas. It is found that a symmetrical parabolic reflector with f/D=2 and a single circular waveguide feed has the minimum scan loss (only 0.6 dB at 80=8", or a 114 beamwidths scan). The scan is achieved by tilting the parabolic refletor by an angle equal to the half-scan angle. The f/D may be shortened if a cluster 7 to 19 elements instead of one element is used for the feed. The cluster excitation is adjusted for each new beam scan direction to compensate for the imperfect field distribution over the reflector aperture. The antenna can be folded into a Cassegrain configuration except that, due to spillover and blockage considerations, the amount of folding achievable is small