Research On Mutual Coupling Compensation Technology Of 5G Miniaturized Base Station Antenna

With the development of mobile communication network towards 5G,Massive MIMO has been applied to mobile communication system as core technology.Lots of antenna elements are been integrated to form massive antenna array in this technology,in order to make the use of the limited time and frequency resources.But because of the limited occupied space of array in practical application,the miniaturization of base station antenna has become inevitable trend.The small array element spacing of miniaturized array leads to the strong mutual coupling.It affects the antenna performance directly and has become a burning issue that how to achieve mutual coupling compensation on the basis of the miniaturization of array.Therefore,we study on the technology of mutual coupling compensation.The main researches are as follows:1.After analyzing the model of array signal and the mechanism of mutual coupling,we study a self calibration algorithm which named joint estimation of DOA and coupling matrix.This method simplifies the form of coupling matrix according to the characteristic of mutual coupling and separates the coupling matrix and direction vector by transform formula.The good results of the mutual coupling compensation and the direction finding are verified by the simulation experiments of uniform linear array,uniform circular array and uniform rectangular array.2.For solving the issue of low resolution of joint algorithm,we use a uniform linear array with polarization microstrip antennas to analyse the influence factors of resolution,and then propose a method for joint estimation of DOA and coupling matrix based on linear prediction which has higher resolution.This method augments array aperture virtually and calculates coupling matrix by virtual array.Use this coupling matrix as initialization matrix of joint estimation algorithm to loop iterate.A uniform linear array with eight dipoles is used to carry on the simulation experiments.The results prove that this method could achieve mutual coupling compensation,in addition,improve the resolution of the algorithm.3.A new wide-band mutual coupling compensation in digital domain method is proposed.In this method,wide-band time domain signal transforms frequency domain signal by FFTand achieve mutual coupling compensation in frequency domain.This method calculates coupling calibration matrix by element pattern reconstruction method to calibrate the effect on coupling.According to a characteristic that element patterns change little in a small frequency range,the bandwidth of the array is divided into several small frequency bands with equal bandwidth.Signals use the same coupling calibration matrix to achieve mutual coupling compensation within each small band,and these coupling calibration matrices make up wide-band mutual coupling compensation network.This method achieves mutual coupling compensation of wide-band array,at the same time reduces the measurement steps of antennas and the computation of the algorithm.A designed 5G base station antenna is used to carry on the simulation experiments for this method.The mutual coupling compensation effect of single frequency point and the feasibility of algorithm in wide-band case are verified.The results prove the effectiveness of wide-band mutual coupling compensation by this method.