Average Pattern and Beam Efficiency Characterization of Reflector Antennas with Random Surface Errors

Abstract

Random errors on a reflector surface will result in antenna gain loss, beam efficiency reduction, and sidelobe level degradation. In this study, an improved mathematical model is presented for handling correlated random surface errors. The average power patterns of arbitrarily distorted antennas are determined by performing a complete numerical integration. Furthermore, in the case of a parabolic reflector antenna with random surface errors that have relatively short correlation length, the effective aperture distribution parameters, Be and p_e, can be defined and analytically derived. Numerical data for a parabolic reflector antenna with dimensions recommended by a recent NASA study are generated to investigate the effects of uniform and linear random surface errors on power pattern, boresight gain loss, and beam efficiency. The results properly characterize the pattern degradation and the beam efficiency reduction as a function of random surface errors. For high beam efficiency and low sidelobe specifications, the acceptable tolerance on the surface errors becomes more stringent. Several charts on the beam efficiency are presented as general guidelines to be used by the designers of large reflector antennas.