Radiation-pattern control of Cassegrain antennas

Using the results of a theoretical analysis of the radiation pattern of Cassegrain antennas, the paper discusses the requirements imposed by the most recent Consultative Committee on International Radio (CCIR) recommendations for the maximum-allowable sidelobe level applicable to earth-station antennas with D/¿ > 150 (D being the diameter of the main reflector). Also considered are the requirements of smaller antennas, and a possible sidelobe level response for D/¿ < 150 is suggested. Although the analysis explicitly considers axisymmetric configurations, the results have been extended to embrace the radiation characteristics of offset geometries. This permits the indication of when it is preferable and sometimes necessary to employ the offset configuration.