Multi-band ring focus dual reflector antenna system

1. Statement of the Technical Field A ring focus antenna and method of using same. The ring focus antenna can have a main reflector of revolution shaped as a non-regular paraboloid about a boresight axis of the antenna. A sub-reflector/feed pair is provided comprising a sub-reflector of revolution shaped as a non-regular ellipsoid having a ring-shaped focal point about the boresight axis. A feed element is installed at a feed element location separated spaced from a vertex of the sub-reflector on the boresight axis of the antenna. The main reflector is adapted for operation with multiple sub-reflector/feed pairs having a coupled configuration, and multiple sub-reflector/feed pairs having a decoupled configuration (i.e. classical optical dual reflector system). The main reflector is operable at a plurality of spectrally offset frequency bands. For example, the antenna can be designed for operation over C-band, X-band, Ku-band, and Ka-band.