Offset-fed multi-beam tracking antenna system utilizing especially shaped reflector surfaces

TLDR: In this article, a reflector antenna system suitable for ground stations used in communication with geostationary satellites is described, and a novel method for shaping subreflectors using the ratios of ray lengths squared and variable focal lengths is applied in the optimally tilted offset geometry results in almost uniform aperture power distributions.

Abstract: A reflector antenna system is described suitable for ground stations used in communication with geostationary satellites. Dual beams or multi-beams can be directed at several satellites spaced angularly from 5° to 20° apart and these beams are scanned by feed motion keeping a single main reflector surface fixed. Offset feed geometry is used for low aperture blocking and shaping of subreflectors and main reflector results in very high aperture efficiencies, low sidelobes and symmetric low cross-polarization patterns needed for satellite links. A novel method for shaping subreflectors using the ratios of ray lengths squared and variable focal lengths is applied in the optimally tilted offset geometry results in almost uniform aperture power distributions. A new general procedure for shaping doubly curved surfaces intercepting a known population of rays such that these rays are focused to a point or reflected in a given direction is used to shape the main reflector for elimination of aperture phase errors and to shape a second subreflector which focuses perfectly to the apex of a second feed horn.