Researches On Compact Planar MIMO Antenna With Low Coupling

With the gradual commercialization of the 5G mobile communication technology,wireless communication technology is developing in the trend of high speed and large capacity.As one of the core technologies of the 5G mobile communication technology,the multiple-input multiple-output(MIMO)technology can effectively improve the spectrum utilization and greatly increase the information transmission rate,channel capacity and transmission reliability without additional bandwidth and transmitting power.As an important part of the MIMO technology,the MIMO antenna has received extensive attention and research in recent years.With the development of miniaturized mobile communication terminal equipment,the requirements for compactness of the terminal antennas are becoming stricter.However,when the spacing between the elements of a MIMO antenna is too small,a strong electromagnetic coupling effect will occur,which may seriously affect the performance of the MIMO antenna.Therefore,the focus of the study of compact MIMO antennas is on reducing the coupling between the MIMO antenna elements.In this thesis,various decoupling technologies are studied,such as defective ground structure,neutralization line,resonator structure,extended ground structure,and so on.Based on the above decoupling technologies,several low-coupling dual-frequency microstrip MIMO antennas and low-coupling planar ultra-wideband(UWB)MIMO antennas are proposed.Firstly,this paper describes the research background and significance of MIMO antennas,and analytically summarizes the mainstream technologies to reduce the mutual coupling of MIMO antenna arrays.After that,the basic antenna theory is briefly introduced,including the main electrical parameters for measuring antenna performance and the related knowledge about MIMO antennas and electromagnetic mutual coupling.Secondly,the mutual coupling suppression of compact dual-band microstrip MIMO antenna is studied based on the defective ground structure and neutralization line.By studying the filtering characteristics of the defective ground structure,a low-coupling microstrip MIMO antenna with a defective ground structure is designed.Then,the effect of neutralization line on reducing the coupling of MIMO antenna is studied,and a low-coupling compact dual-frequency microstrip MIMO antenna with neutralization line is proposed.The simulation results show that both the defective ground structure and the neutralization line can effectively reduce the coupling between the elements of compact dual-band microstrip MIMO antenna.Finally,this paper studies the decoupling problem of UWB MIMO antennas and several low-coupling compact UWB MIMO antennas are proposed.One is a low-coupling compact UWB MIMO antenna based on the ground slots and branch.Studies have shown that the etched ground slots and loaded ground branches can effectively improve the isolation between array elements.In addition,this paper also presents several low-coupling compact planar UWB MIMO antennas based on a variety of decoupling technologies such as extended ground structure,resonator structure,and polarization diversity.The measured results are in good agreement with the simulation results,which proves the effectiveness of the above methods in the suppression of wideband mutual coupling.