Shielding of single- and double-reflector earth station antennas: a near- and far-field approach

This paper describes the off-axis radiation pattern calculation of a Cassegrain antenna system with prescribed geometrical parameters, in the absence and presence of a (hypothetical) half-plane obstacle located either in the near or far field of the antenna. The attenuation caused by the obstacle as a function of antenna orientation and position is calculated and presented. The results for the halfplane shielding of the double-reflector system are compared with those obtained for a single-reflector antenna system shielded by the same obstacle. Three different, but related, approaches for calculating the additional propagation loss are presented and compared. It is found that the proposed near-field approach gives the best overall results