Feed Scattering in Primary-Fed Reflector Antennas

This paper presents a method to improve the calculation of the directivity and the radiation pattern of a primary-fed reflector antenna, by including the contribution due to multiple reflections between the feed and the reflector. These multiple reflections are controlled by introducing a feed scattering pattern, which is the scattered field from the feed when illuminated by a plane wave. The method is applied to a reflector with a self-supported dipole-feed, showing good agreement with both the measurements and a moment method solution of the complete antenna including the feed as well as the paraboloidal reflector. The results show that the multiple reflections may have stronger effect on the directivity and the cross-polar sidelobe level than the centre blockage has.