Research On Beamforming Techniques Using Uniform Circular Arrays

With the rapid development of global communications services,the demand for faster and better communications services is becoming more and more urgent.The smart antenna has the advantage of flexibility,antijamming and high system capacity.Uniform circular antenna array,as a special structure of smart antenna,is centrosymmetric.Compared with other array structures,uniform circular antenna array has a larger coverage area,strong flexibility and adaptability.Therefore,uniform circular antenna array has been widely and deeply researched,which has already become an important future direction of development of communication services.Beamforming technology mainly includes two fields which includes direction-of-arrival(DoA)estimation and beamforming.Because of the objective existence of mutual coupling.The performance of DoA estimation and beamforming has been severely degraded.To address this problem,two existing mutual coupling compensation schemes have been introduced.However,these two schemes are very limited.Therefore this thesis proposes appropriate and effective solutions.On the one hand,Low-complexity MUSIC(multiple signal classification)algorithm for DoA estimation has been proposed in this paper.This modified algorithm not only accurately estimates the DoA,but also significantly reduce the computations.Simulation results and practical implementation show that the proposed MUSIC algorithm achieves lower complexity and similar resolution compared with the traditional MUSIC method.On the other hand,a novel particle swarm optimization(PSO)algorithm for beamforming has been proposed in the presence of mutual coupling.This algorithm first designs the fitness function for PSO algorithm based on Equivalent Isotropic Radiated Power(EIRP)and proposes a null-steering control to suppress interference.Compared with the traditional beamforming algorithms based on ideal patterns,the proposed algorithm significantly reduces the impact of mutual coupling,raises the EIRP of systems and suppresses interference.Therefore it is very attractive for practical realization.This paper mainly studies practical problems,and presents specific and effective solutions,which have high practical value in engineering.