Research On Broadband Dual Polarization Compact MIMO Antenna For Wireless Communication

Multiple Input Multiple Output(MIMO)antennas can improve the channel capacity and transmission efficiency of a system by using multiple antenna units.However,as the number of antenna units increases,the space occupied by multiple antenna units also increases,leading to a growing demand for compact MIMO antennas.However,the coupling between compactly arranged MIMO antenna units increases,which affects communication quality.Therefore,it is of great research value to maintain high isolation between antenna units while compactly arranging them.Compared with single-polarized base station antennas,dual-polarized base station antennas can reduce the number of antennas and significantly improve communication efficiency in the same area.Therefore,dual-polarized antennas are almost always used as base station antennas in practical applications.Based on these,the thesis mainly studies the decoupling methods of compact dual-polarized base station MIMO antennas.The research content of the thesis is as follows.Firstly,the research background of compact MIMO antennas is introduced,and the decoupling methods of MIMO antennas are presented from two aspects: decoupling of single-polarized antennas and decoupling of dual-polarized antennas.Then,the basic knowledge of MIMO technology and the principles of decoupling surface and neutralization line are introduced.Based on these,a broadband ±45° dual-polarized folded dipole antenna is designed.The operating bandwidth of the antenna is 3.3GHz-3.8GHz,and the radiation patch size is 0.295 ×0.295(which is the air wavelength at 3.55GHz).Furthermore,it is composed of four single-unit MIMO antennas with a unit spacing of 0.4.In order to reduce the coupling between units,a composite decoupling surface is designed,including two layers of dielectric plates with printed metal and two layers of dielectric plates without printed metal.This structure is mainly used to reduce the coupling between the co-polarization ports of the MIMO antenna,but it also has a certain effect on reducing the coupling between the cross-polarization ports.In order to reduce the coupling between the crosspolarization ports,a U-shaped neutralization line is designed.In order to further reduce the coupling,metal isolation walls are added between the units.The port isolation was further improved through a metal isolation wall.By loading the above decoupling structure onto the four-unit MIMO antenna at the same time,a compact,broadband,and high-isolation four-unit ±45° dual-polarized MIMO antenna is designed.In the frequency band of 3.3GHz-3.8GHz,the reflection coefficient of all ports is less than-11 d B,the isolation between the cross-polarization ports is greater than 22 d B,and the isolation between the co-polarization ports is greater than 26 d B,and the envelope correlation coefficient(ECC)between all ports is less than 0.0019.Finally,the four-unit dualpolarized MIMO antenna is processed and tested,and the excellent performance of the antenna is verified.