A design method of an offset trireflector antenna whose main reflector is of an offset parabola type with high efficiency and low cross polarization characteristics

A design method is developed for a high efficiency and low cross polarization offset tri-reflector antenna made of an offset parabolic main reflector and two shaped reflectors. In this method, the main reflector is an offset parabola while the #2 reflector corresponding to a subreflector and the #1 reflector as the focussing reflector are shaped by a method using reflector shaping functions. Further, the reflector system is selected as an initial value such that a low cross polarization characteristic is obtained after reflector shaping. As a method for determination of such initial values, a new reflector configuration transformation method is developed. Those design methods are applied to an offset tri-reflector antenna with an aperture diameter of 250 wavelengths. Validity of the design is confirmed by a numerical calculation. (C) 2000 Scripta Technica, Electron Comm Jpn.