Millimetre-wave aerials for full illumination radars

The constraints for the considered antennas are discussed. The constraints may be met by the use of horn antennas or systems fed by horn antennas. Antenna types used include diagonal, Potter, and scaler horns and both Cassegrain and front-fed paraboloids. The diagonal horn is basically a smooth transition from waveguide of circular cross-section to waveguide possessing a square cross-section. Cassegrain and front-fed paraboloids have been produced for use at frequencies up to 80 GHz with either Potter or scalar horn feeds. A series of lensed antennas have been produced to operate at 80 GHz, 140 GHz, and 280 GHz. Attention is given to a Potter horn with circular polarizers and rotary joints, designed to operate at 140 GHz.