Multiple reflector system with dielectric support webs and foam body

Claim 1

An antenna structure comprising: a primary reflector having a reflective surface which is shaped as a surface of revolution about an axis, said axis being the axis of said primary reflector, said reflector surface being supported on a foam body, and having an opening through said primary reflector and said foam body on said axis; a subreflector having a reflective surface which is a surface of revolution about a second axis, with said two axes positioned substantially colinear, said subreflector positioned with respect to said opening in said primary reflector such that radiation reflects on both said primary reflector and said subreflector; at least three slots in each of said primary reflector and said subreflector, said slots lying substantially on planes passing through said axis of said primary reflector, with respective ones of said slots in said subreflector lying on the same plane through said primary reflector axis as respective ones of said slots in said primary reflector, said slots in said primary reflector extending into said foam body; a plurality of support webs of low loss dielectric material between said reflectors for maintaining said subreflector at a substantially fixed distance away from said primary reflector and for maintaining said axes so that they lie substantially together, said support webs being of substantial width in a direction normal to said axes and substantially thin in a direction circumferential to said axes, and having a width to thickness ratio between about 7 and about 100, the thickness of said webs being on the order of between 0.001 and 0.007 times the aperture diameter where the diameter of said primary reflector is the aperture diameter of said antenna, said support webs being mounted in said slots.