Research And Design Of Dual-band MIMO Antennas With Low Coupling

With the rapid development of wireless system,the design of wireless communication system has put forward higher requirements,including more wireless spectrum resources,higher data transmission rate,better service quality and greater channel capacity.In recent years,the multiple-input multiple-output(MIMO)technology,as an effective means to meet these requirements,has received extensive attention and research.With the development trend of miniaturization of wireless communication equipment,the design of the MIMO antenna,as an important part of wireless communication system,is more compact.However,the smaller the interval between the MIMO antenna elements,the stronger the mutual coupling will be,which in turn deteriorate the performance of the MIMO antenna.Therefore,aiming at suppressing coupling between the compact MIMO antenna elements,this thesis studies the decoupling technology of defective ground structure,ground branches,parasitic structure and resonator structure,and finally four low-coupling dual-frequency MIMO antennas based on the above technologies are proposed.Firstly,this thesis describes the research background and significance of MIMO antenna,and summarizes the main methods used for MIMO antenna decoupling.Then,the basic theoretical knowledge of antenna is briefly introduced,including the main electrical parameters to measure the performance of the antenna,the MIMO technology the mutual coupling of MIMO antenna,and other related knowledge.Secondly,this thesis studies the mutual coupling suppression of the compact dualfrequency monopole MIMO antenna based on the loading of the ground branch and the parasitic structure.By slotting on the ground,loading the ground branches and loading the metal strip between the two antenna elements,a compact 2-port dual-frequency monopole MIMO antenna is proposed.Then,the effects of polarization diversity and resonator structure on reducing the coupling of MIMO antenna are studied,and a lowcoupling compact 8-port dual-frequency monopole MIMO antenna based on polarization diversity and resonator structure is proposed.Both simulation and measurement results show that the above decoupling techniques can effectively reduce the mutual coupling between the dual-frequency monopole MIMO antenna elements.Finally,this thesis studies the decoupling of dual-frequency microstrip MIMO antennas,and two low-coupling dual-frequency microstrip MIMO antennas are proposed.One antenna is based on the etched H-shaped defective ground structure and the resonator structure.Another one is based on the defective ground structure and the parasitic structure.Research shows that the etched defective ground structure and loaded parasitic resonator structure effectively improve the isolation between the dual-frequency MIMO antenna elements.The test results are in good agreement with the simulation ones,which proves that the above method can effectively reduce the coupling between dual-frequency microstrip MIMO antenna elements.