Study Of Beam-Forming Method Based On Time-reversal Algorithm

By controlling the array topology and the amplitude and phase distributions of the feed terminals,the requirements for the radiation pattern of antenna array,such as covering a specific area,suppressing the interference at the specific direction and beam steering,can be easily realized.Therefore,the beamforming method is very important during the design process of antenna array.However,the traditional frequency domain method can only be applied to certain types of antenna array,and suffers from the complicated process and the huge requirements for computing resources.In this thesis,based on the time revesal algorithm and the multi-beam superposition theory,we propose a novel broadband time domain beam forming method that avoid all the above mentioned defects of the traditional methods.The most important features of this method are its ability of solving wide band problems and achieving shaped beam for arbirty array structures.This method has great convenience in dealing with the problem of beam forming of the antenna array with the characteristics of broadband,irregular arrangement and strong coupling effects.The major works and contributions of the author are as follows:1.The basic concept of time reversal theory in electromagnetic system is introduced.The method of time revesal beam steering used to realize single beam scanning is presented.Meanwhile,the method is analyzed by using the antenna reciprocity theorem.Finally,the beam forming technique based on time revesal algorithm and multi-beam superposition theory is proposed.2.The validity of the proposed method is demonstrated by example of a linear dual-polarized magneto-electricity dipole array for radio base stations of mobile communication systems.The whole processes,including main beam tipping,main beam cosecant-square distribution,upper sidelobe suppression and zero point filling are described in details,which show in solving the broadband problem.3.We apply this method to achieve the shaped beam of a special designed subarray,and then,use this subarray as radiating element to construct the planar phased array with wide scanning angle.This example mainly demonstrates the ability of beamforming for the complicated antenna array with tightly-coupled elements.The proposed method provides a new idea for extending the scanning angle of the planar phased array.