An offset spherical reflector antenna for small earth stations

The design of an offset spherical reflector antenna for a fixed-beam earth station is described. Diagrams of Cassegrain and Gregorian offset spherical reflector antennas are presented. The function of the subreflector is discussed. The cross-polarization of the antenna is examined. The relation between subreflector size and the length/diameter ratio and efficiency is studied. The first sidelobe radiation patterns for the Cassegrain and Gregorian antennas are predicted using methods of physical optics and a feed model corresponding to an appropriate corrugated hot flare angle.