Radiation pattern control by subreflector shaping

Several design examples of shaped dual offset reflector antennas for shaped beam applications have been presented. In these designs, radiation control was obtained by simultaneously shaping both reflectors or shaping only the main reflector while the subreflector is an offset portion of a conventional conical surface (ellipsoid or hyperboloid). In both cases, crosspolarization is reduced by adjusting the relative position of the offset reflectors. We follow an alternative way by exploring the possibilities of using the dual offset configuration with a shaped subreflector and a parabolic main reflector, in order to obtain shaped beams or an increased efficiency of the focused beams. The shaping technique is briefly outlined and results confirming the performance improvement due to the subreflector shaping are shown. Significant results for elliptical beam coverage are also presented.