RGA-based Pattern Optimization For Hybrid Antennas

Demand for reflector antennas for use in modern applications such as radars, radio astronomy, microwave communications, satellite communications, and the like has resulted in the development both of sophisticated reflector antenna configurations and synthesis techniques. In this paper, the physical optics (PO) method based on the surface current integration is determined as the research method after comparison of some analytical methods, and the real-coded genetic algorithm (RGA) is established as a candidate for solving the synthesis problems of hybrid reflector/ array antennas.The main work is shown as follows:?First of all, hybrid offset parabolic reflector/ array antennas with a 7-element or a 19-element cluster feed are analyzed to form basic multi-beam.Secondly, a 7-element cluster feed with optimized excitation coefficients instead of a single feed is used to improve the beam scanning performance as the feed moves away from the focal point of the offset parabolic reflector. Also, the feed excitation coefficients are optimized for hybrid offset parabolic reflector/ array antennas with 19-element feed cluster to produce different shaped beams.Thirdly, the surface of the offset shaped reflector is represented by a set of orthogonal global expansion functions (the Jacobi-Fourier expansion), and the sensitivity of the reflector shape and performance to the variation of the surface expansion coefficients is studied for the single-fed offset shaped reflector antenna in order to determine the bounds of the coefficients to be optimized.Finally, we shape the reflector surfaces of the single-fed offset reflector antennas and simultaneously adjust the reflector surfaces and the feed array excitation coefficients of the hybrid offset shaped reflector/ array antennas to produce contoured patterns with maximum mean gain or desired field distribution inside a given area.