This paper presents a novel technique to improve the cross-polarization and the beam efficiency of an offset parabolic reflector antenna used for space borne radiometric applications. A special multi-mode primary feed (tri-mode conjugate matched feed) is used to illuminate the offset parabolic reflector antenna. The simulated data on the radiation characteristics of the offset parabolic reflector antenna with a matched feed has been compared with that of a conventional Potter horn. It is observed that the tri-mode feed suppress the unwanted high cross-polarization of an offset reflector antenna and improves the beam efficiency.
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