Research On Multi-beam Design Method Of On-board Large Aperture Reflector Antennas

With the requirements of miniaturization and light weight of ground handheld terminals,real-time changes in service distribution,and frequency reuse,on-board large aperture multibeam reflector antennas have been widely used in satellite communication systems.Multi-beam design,as the key technology of the satellite-borne large-aperture multi-beam reflector antenna,has an important impact on the communication performance of the satellite and plays a key role.Firstly the concept of field matching was used to derive the relationship between the reflecting surface aperture field,the focal plane field and the feed array aperture field in the incoming and outgoing states in this thesis,enabling the rapid calculation of the feed excitation coefficients and the analysis of the feed array design and optimisation based on the feed array muzzle field distribution.Secondly,the configuration of the reflecting surface was analysed and designed in this thesis.Ellipsoidal and hyperbolic surfaces are used as reflector devices in single offset reflector antennas,and the scanning characteristics of the two reflectors are compared.Compared with the parabolic surface,it can avoid the blockage of beam formation by the platform to a certain extent and improve the flexibility of beam formation,while obtaining better scanning characteristics,which is of certain reference value in engineering applications.Thirdly,the scanning characteristics of the feeder array in the case of defocusing and the relationship between transverse defocusing and longitudinal defocusing in obtaining the optimum scanning gain was investigated by using the conjugate matching method in this thesis.This relationship is also used to design a curved feeder array,which is able to obtain a high scanning gain.Finally,an optimization by using an adaptive array signal processing algorithm was proposed in the thesis.The excitation coefficients of the feeder array are quickly calculated using the eigen-decomposition of the correlation matrix.Compared to conventional algorithms,this method does not require any target values to be set,and the placement of sampling points minimally affects the calculation results,saving a lot of time and effort,and obtaining a high signal-to-noise ratio.