Horn subreflector blockage effects in the analysis of earth station antenna sidelobe performance

An efficient method of analysis for the combined configuration of a horn and a subreflector that efficiently accounts for the mutual blocking effects is formulated by means of a near-field spherical-wave expansion of the fields on a sphere that encloses the physical apertures of the horn and the subreflector. The method also allows for mutual interaction effects between horn and subreflector if desired. The radiation patterns have been measured inside an anechoic chamber at a distance of 5.6 m from the centre of the sphere enclosing the horn-subreflector configuration. The radiation patterns of the same configuration have been predicted using a computer program developed by the authors. The measured and predicted results show excellent agreement, particularly, with respect to the mutual blockage effects and the horn spillover.<>