| Along with the continuous development of communication technology,MIMO array antenna has been widely used in mobile terminal to meet the high-speed and large-capacity communication needs.In mobile terminal for 5G applications,the number of MIMO antennas has doubled or even increased,which makes the problem of antenna coupling between antennas more serious than before.In order to overcome this problem,based on decoupling technologies,this thesis presents three high isolation MIMO antenna arrays,which cover Sub-6G frequency band.The main research work of this thesis includes the following aspects:1.Based on Shannon theory,the relationship between MIMO channel capacity and the design of MIMO antenna is analyzed by simulation experiments.It mainly includes the relationship between channel capacity and envelope correlation coefficient,the relationship between channel capacity and isolation.The experimental results show that the MIMO channel capacity increases with the decrease of envelope correlation coefficient,and the growth rate is decreasing;and the MIMO channel capacity increases with the increase of isolation.2.Based on bending monopole antenna,a high isolation MIMO antenna array is designed with decoupling ground branch in this thesis.Under the condition of ensuring good decoupling effect in the 3.3GHz-3.6GHz working frequency band,the new 2.4GHz-2.7GHz working frequency band is obtained for the MIMO antenna element adjacent to the decoupling structure.The antenna realizes dual frequency characteristics,and the low frequency band of antenna also has high isolation.The traditional decoupling structure can only realize the decoupling in single frequency or multi frequency band.Without changing the structure of MIMO antenna element,this decoupling structure introduces inductivity into the impedance matching of low frequency band by the branches,which makes the antenna realize the multi frequency performance,and provides the new decoupling structure design idea for the actual engineering design.3.Based on F shape bent monopole antenna,a dual-frequency high-isolation MIMO antenna array is designed with Y shape grounded parasitic branches in this thesis.The two deformed branch arms of the F shape bent monopole antenna control two working frequency bands,and the Y shape grounded parasitic branch can absorb the coupling current generated by the antenna in different frequency bands.By loading Y shape decoupling stubs between two monopole antennas,the antenna isolation in the two frequency bands is improved at the same time,and a single antenna block is obtained.By analyzing the different layouts of multiple antenna blocks on the terminal platform,the MIMO antenna array with high isolation is finally obtained.4.Based on antenna pattern diversity,a MIMO antenna array with high isolation is designed in this thesis.The MIMO antenna element takes a coupled monopole antenna and has the advantage of simple structure.By setting the antenna feeding point reasonably,the far-field pattern of the antenna is shifted,and avoid cross-over phenomenon.Because no decoupling structures such as parasitic patches and ground gaps are loaded,the MIMO antenna array has high isolation while ensuring high antenna radiation efficiency. |
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