A new minimum blocking condition including subreflector and quadrupod shadow for the design of dual reflector systems

Earlier minimum blocking conditions (MBC´s) for paraboloidal reflector antennas formulated by Hannan and Gillitzer did not take into acount the significant blocking contribution of the shadow of the legs supporting the feed or subreflector. A numerical-integration study to determine conditions under which the combined blocking shadow of the subreflector and its supports are minimized is described. Two types of MBC´s are found: one which is based on the sidelobe level-more important in radioastronomy (polarization measurements)-and a second type which is related to the aperture efficiency (directivity)-more important for spectroscopy and telecommunications. Both MBC´s are compared and it is shown that they are only slightly different from each other.