Design of offset double torus dual-beam antenna by minimizing aperture mapping distortion

Dual-beam earth station antennas which track two satellites simultaneously have been developed for the Japanese public telecommunication network systems. The dual-beam earth station antenna is an offset double torus antenna with two auxiliary-reflectors that can be used for the 30/20 GHz band and has a good commercial record of performance. The authors describe a reflector system design scheme that minimizes the aperture mapping distortion of an offset double torus antenna with two auxiliary-reflectors. In order to achieve higher aperture efficiency and higher XPD (cross polarization discrimination), the double torus configuration is optimized and the transformation of nondistorted mapping is applied to all reflectors including the two auxiliary-reflectors. The relation between the antenna geometrical parameters and the distortion of aperture mapping is studied. The validity of this design scheme is verified by the experimental results gained from a fabricated offset double torus dual-beam antenna operating in the 14/12 GHz band