Shaped reflector and multi-feed paraboloid-a comparison

The last decade has seen dramatic changes in the evolution of shaped reflector technology. Many implementations of this technology have been used for generating shaped contour beams on many satellites: single offset reflector, dual gridded reflector and dual reflector. Shaped reflectors have replaced multi-feed reflectors as the primary design for single beam applications in many of these satellites due to lower weight, lower feed spillover and lower loss associated with a single feed design. However when multiple beams have to be generated from a single antenna, a multi-feed paraboloid with individual beam-forming networks for each beam is the obvious choice. While the principal advantage of both of these antenna systems mentioned above are well understood, a detailed comparison of the performance characteristics and radiation mechanisms of the two antenna types have not been presented in the literature. This paper presents such a comparison between the two with reference to the following characteristics: (a) directivity performance; (b) feed complexity and losses; (c) aperture fields; and (d) sidelobe performance.