Research On Multi-beamforming Technology Of Satellite Mobile Communication Systems

As an important means to realize mobile communication,satellite communication technology plays a more and more important role in the field of communication.Multibeam antenna technology as one of the key technologies of next-generation satellite communication system has become a research hotspot in recent years.Multi-beam satellite systems use multiple spot beams to cover the entire service area,similar to the the cellular system on the ground,can effectively achieve frequency reuse,thus it can increase system throughput;through using spot beams to cover the ground,system provides higher EIRP and G/T values for the service area,which is conducive to the miniaturization of terrestrial terminals.By adjusting beam pointing neatly,beam reconstruction can be done as needed to improve the flexibility of the system.In order to develop our country's space communication technology and establish a new generation of satellite mobile communication network,there is a need to investigate multi-beam technology in-depth.At first,the key technologies involved in multi-beam satellite mobile communication systems are studied by analyzing the status quo inland and abroad combined with existing systems.The multi-beam satellite systems are analyzed via three aspects: system architectures,antenna types and beamforming methods.The advantages and disadvantages of different technologies are compared.The development trend of multi-beam technology is analyzed according to existing systems.It provides a theoretical reference for selecting the direction of developing multi-beam satellite systems.Then,based on the previous analysis,the multi-beamforming algorithms using in satellite are studied,a variable step size LMS algorithm(KBLMS)based on Kalman estimation is proposed based on the classical algorithm.This algorithm uses the excellent characteristics of Kalman filter to obtain the step size,which is changed with the sampled signal in the process of weights iteration.Compared with the traditional algorithm,the new algorithm can achieve a great improvement in the convergence rate and the residual under the premise that the computational complexity is not high.Finally,considering multi-beam satellite mobile communication systems are often faced with sudden business,the beamforming technology of hotspot beam is studied.Firstly,the existing beamforming schemes are analyzed and compared.Then,inspired by the LMS algorithm,a "staring beamforming" algorithm based on gradient idea is proposed.The algorithm can adjust the weights of antenna array so that the satellite can cover the specific users or regions continuously,so that the system can deal with the emergent business effectively.