Computation and optimization of beam efficiencies for reflector antennas

The difficulties of numerically computing beam efficiency for reflector antennas are identified along with possible remedies. Beam efficiencies are shown for some typical reflector antennas with circular open-waveguide feeds. The optimization of beam efficiency by a feed cluster is presented. It is shown that for highly tapered patterns, an integration over the first few sidelobes is sufficient for roughly obtaining the total far-field power. Beam efficiency is maximized by a highly tapered aperture distribution and so must be balanced against aperture efficiency. In general a smaller f/D ratio produces a higher beam efficiency since the spillover loss is lower. Beam efficiency is calculated as a function of feed radius (related to edge taper) and scan angle. It is concluded that use of a cluster feed can improve beam efficiency when the beam is scanned.<>