Research On Beamforming Technology In Ultra-Large-Scale Array Antenna Terahertz Systems

With the advent of the 6G(6th Generation Mobile Networks),the amount of wireless communication data would grow explosively,and Terahertz communication technology has become the key technical to support such large capacity.However,considering the great path loss in terahertz band,it is necessary to use large-scale array antenna system to provide antenna gain and beam gain.At the same time,with the increasing scale of array antenna and the extremely small wavelength of terahertz band,large-scale array antenna terahertz system is very easy to be involved in the near-field.The spherical wavefront characteristic of near-field communication makes the channel matrix more complex,and the beamforming technology of large-scale array antenna is more difficult to solve;In addition,the ultra-high density of communication equipment access makes the communication environment more complex,and the interference between terminal devices is more likely to occur.6G would require more stringent spatial focusing of beamforming.Therefore,aiming at the problem of large-scale array antenna terahertz beamforming,this thesis proposes to adopt the frequency offset-phased two-dimensional beamforming technology to realize the angle-distance spatial focusing characteristics of the beampattern,and this thesis finds that terahertz large-scale phased array has spatial focusing characteristics at the near field;At the same time,this thesis uses the analytical method to establish an analytical model for frequency offset-phased two-dimensional beamforming.The model accurately and intuitively explains the state of beamforming in angle-distance space,and uses the analytical model to analyze the characteristic of beampattern.In this thesis,a flexible and controllable beamforming technology is proposed by using frequency offset-phased technology.The specific research contents and innovations of this thesis are as follows:1.A unified analytical model of near-field and far-field for terahertz large-scale array antenna beamforming is establishedIn order to characterize the spatial focusing characteristics of terahertz large-scale array antenna frequency offset-phased beamforming technology better,this thesis proposes an analytical model of the transmitted beam in the angle-distance space,and proves that the transmitted beam is focused as an ellipse in the angle-distance space.The data simulation results show that the model accurately and intuitively describes the spatial focusing characteristics of the beam.In addition,through the analytical model,it is proved that the beam of terahertz large-scale array phased array can show spatial focusing characteristics in the near field;By simplifying the spherical wavefront to plane wavefront,a more simplified analytical model of far-field large-scale array antenna is obtained in this paper.2.Frequency offset-phased beamforming technology is used to realize flexible and controllable beamformingAccording to the unified analytical model of near-field and far-field of terahertz large-scale array antenna beamforming established in this thesis,the spatial coverage characteristics of the transmitted beam are fully analyzed,and by adjusting the frequency offset,the beam can be controlled flexibly according to the range coverage requirement.This method is also an analytical method.Compared with the traditional optimization method and numerical method,this method shows better characteristics in algorithm complexity.