A far field wavelet expansion for the synthesis of contoured-beam array-fed reflector antennas

This work is concerned with the design of "contoured-beam" antennas (also known as "shaped-beam" antennas) as used in satellite communication systems, i.e. antennas having the main beam shaped so that its footprint on ground closely follows the contour of specific geographical regions (e.g. Europe or the U.S.), with the objective of maximizing the radiation efficiency and reducing interferences with neighbouring regional systems. The reference solution for this work are "array-fed" reflectors, i.e. antennas fed by an array of horns or equivalent radiating elements, each producing a "component" beam toward a different direction upon reflection on the reflection dish. The idea behind this work is to find an efficient representation of the desired radiation pattern that concentrates the field information relevant to the design task in few, suitably constructed functions; if properly coded, this enables synthesis algorithms to converge faster. The proposed approach exploits the properties of the multi-resolution (MR) representation. We have generated a wavelet system suitable to the coverage problem of present interest. In this paper we consider array-fed offset reflector antennas. Two very different synthesis techniques are considered as application examples of the devised pattern representation: 1) a simple (and fast) field synthesis projection method; and 2) a power synthesis via an optimization based on a genetic algorithm (GA)