Patent ID: 7236681

Claim:
A feed assembly for use in establishing a communications link with a first satellite, in an antenna that has a reflector with a non-circular profile, the feed assembly being field-switchable between circularly polarized and linearly polarized operating modes, the feed assembly comprising: (a) a feed horn comprising: a circular waveguide section having opposite first and second ends; a corrugated waveguide section having a wall encircling a longitudinal axis of the feed horn; and a conical waveguide section connected between the corrugated waveguide section and the first end of the circular waveguide section; wherein an inner surface of the wall of the corrugated waveguide section defines a circular cross-section at a narrow end of the corrugated waveguide section adjacent to the conical waveguide section, the inner surface progressively widening to a non-circular cross-section at an opposite wide end of the corrugated waveguide section, the inner surface of the wall defining a plurality of concentric circumferential grooves spaced along the longitudinal axis of the feed horn, the grooves each having a depth defined in a thickness of the wall of the corrugated waveguide section, the depths of the grooves varying such that the grooves progressively transition from substantially circular at the narrow end of the corrugated waveguide section to substantially non-circular at the wide end of the corrugated waveguide section, such that the grooves compensate for distortions caused to circularly polarized signals propagating through the feed horn by the non-circular shape of the reflector; and (b) a polarizer rotatably coupled to the second end of the circular waveguide section such that the polarizer is rotatable with respect to the feed horn between first and second orientations displaced 45° apart, the polarizer being structured and arranged in the first orientation to be substantially transparent to a linearly polarized signal propagated through the assembly, and in the second orientation to impart right or left handedness to a circularly polarized signal propagated through the assembly.