ELECTRONICALLY SCANNED CASSEGRAIN ANTENNA WITH FULL APERTURE SUBREFLECTOR/RADOME

摘要

A Cassegrain antenna system includes a flat dielectric plate radome having a thickness of one-half wavelength at a frequency of operation. The plate has an electrically conductive grid disposed on an inside surface thereof to permit perpendicularly polarized energy rays to pass there-through. A parabolic twist reflector is spaced from the radome, and includes a dielectric substrate having a thickness equivalent to one- quarter wavelength at a frequency of operation and having formed on an interior surface thereof an array of conductive strips oriented by 45 degrees relative to the incident ray polarization. A conductive ground layer is formed on an exterior surface of the substrate, wherein radiation reflected by the ground layer and passing through the dielectric substrate is shifted by 180 degrees in phase and is rotated in polarization when combined with energy reflected from the conductive strip array by 90 degrees relative to radiation incident on the twist reflector. The reflected energy from the polarization twist reflector is again reflected, this time by the grid formed on the radome surface, to a focal region. An RF housing with a plurality of RF feed elements is located at the focal region and are respectively spaced by a single beamwidth.