Feed optimization in multi-feed antennas

The problem of attaining close beam spacing and high crossover levels in multi-beam antennas is discussed with attention directed toward the mutual effects of the several feeds. A series of measured curves is used to present the mutual coupling effects on the primary feed patterns. The measured data is used to show that all values of feed dimensions are not equally attractive, and that particular ranges of values of feed dimensions may be used to obtain optimum performance from the antenna. It is further shown that the existence of preferred ranges in the feed dimensions carries implicitly the existence of preferred ranges of F/D. Nomograms are presented which aid in the evaluation of crossover levels and permit the rapid choice of the optimum F/D. In the design of monopulse radars, radio astronomical interferometers, and multi-beam radars, it frequently becomes necessary to place several feed devices about the focus of a parabolic reflector. These feed devices interact with one another, giving rise to secondary pattern effects which may or may not be to the overall advantage of the antenna system. The object of this paper is to illustrate the manner in which a judicious choice of antenna parameters may be made in order to take advantage of these phenomena.