Study On Offset Reflector Antenna

High gain antenna is required in the long distance communications and high resolution radar applications in which reflector antenna is the most widely used one. The Ku-band offset reflector antenna is studied in this paper so that the antenna could achieve the electrical performance characteristics of high gain, low sidelobe and low cross polarization.Firstly, the basic concept and the configuration of reflector antenna are introduced in this article. And then some commonly used methods such as GO, GTD and PO etc are discussed. The properties of the feed used in the antenna simulation are described, and the radiation field based on the methods of physical optics is derived.Secondly, the single offset reflector antenna and dual offset reflector antenna are studied and designed. In the first place, two single offset reflector antennas of different sizes are designed. The selection methods for each parameter are introduced to determine the final size of the antennas. The results of simulation and the tested patterns are given. The good performance characteristics of high gain and low sidelobe are obtained. But due to the structural asymmetry of the single offset reflector antenna, cross polarization is too high when working in linear polarization, which could not meet the requirements. In order to solve this problem, the dual offset reflector antenna is studied and designed in this paper. The design methods of dual offset reflector antenna meeting the conditions of zero-cross polarization and minimum spillover are highlighted in this article. A Gregorian-type dual offset reflector antenna is designed to obtain the antenna efficiency of 72%, and the cross polarization is greatly reduced.Finally, the shaped design of dual offset reflector antenna is studied. Using the MATLAB software as simulation and optimization tool, the surfaces of the dual offset reflector antenna are represented by a set of orthogonal global expansion functions. By optimizing the coefficients of the basis functions, the shaped design of dual offset reflector antenna is realized and the electrical performance characteristics of high efficiency and good sidelobe envelope are obtained.