| China has realized the large-scale commercial use of 5G in 2020,which will bring more convenience to users.In order to meet the needs of 5G systems,Multiple-Input Multiple-Output(MIMO)antenna systems are widely applied.However,due to the increase in communication standards,antennas need to cover as many different communication standards as possible,and mobile terminal space is usually limited.Therefore,how to achieve the high-isolation performance of closely spaced multi-band antennas has become a key,the problem has been studied in this paper,and the main innovative research content is as follows:1.The multi-band antennas based on 5G mobile communication band are studied.In order to design a multi-band antenna with simple structure and convenient adjustment,a simple multi-band method of loading multiple branches is chosen.A circular radiation patch and U-shaped antenna branch are loaded in the antenna to excite the resonant bands at 3.5 and 4.85 GHz,respectively.By changing the size of radiation patch and U-shaped antenna branch to adjust the deviation of two resonant frequencies,respectively.The two resonant bands of the proposed antenna are 3.35-3.61 and 4.78-5.02 GHz.Then,in order to cover the band of 5G mobile communication at 2.6 GHz,a parasitic element is loaded on the back of the dual-band monopole antenna.This method does not increase the size of antenna.As a result,the size of the optimized tri-band monopole is 29 mm*30 mm*1.524 mm,which completely covers the 5G mobile communication frequency band(Sub-6 GHz).2.A 5G dual-band high-isolation dual port common ground monopole antenna is studied.Firstly,the coupling interference of the lower band is reduced by loading the defected ground structure(DGS)and the ground branches.Then a T-shaped parasitic element is loaded between the two dual-band antenna elements to suppress the influence of electromagnetic interference coupling at the higher band.The two bands of the designed antenna are 3.409-3.601 and 4.76-5.04 GHz.After decoupling,the isolations of the proposed antenna at 3.5 and 4.85 GHz are-29 and-41.4 dB,respectively.Finally,the effectiveness of the decoupling structure is well proved by the simulation of the surface current distribution.Besides,the spacing between antennas is reduced by 38.7%.Compared with before decoupling,the isolations of the proposed antenna at 3.5 and 4.85 GHz are increased by 15.5 and 31.4 dB,respectively.The envelope correlation coefficient(ECC)in the two frequency bands is less than 0.005,meeting the requirements of MIMO terminal system.What more,the designed structure is simple and convenient for integration and processing.3.A plane multi-port multi-band common ground closely spaced high-isolation MIMO antenna is studied.As the electromagnetic interference of ground surface wave,DGS is etched to extend the current path and reduce the port-to-port coupling.Two ground branches are loaded on the ground plane as reflecting plates to suppress and reflect the coupling between the two parasitic elements.For suppressing the interference of space radiated waves,a novel non-connected neutralization structure is loaded on the microstrip lines of two monopole antennas.Different parts of the new structure can be activated resonance at different frequencies to obtain good isolation and impedance matching.Compared with the traditional neutralization line,the novel non-connected neutralization structure solves the shortcoming of narrow-band decoupling and has practical application significance.Finally,the high-isolation MIMO antenna achieves tri-band of 2.5-2.7,3.26-3.83,and 4.73-4.97 GHz(S11&S22<-10 dB,S12&S21<-25 dB).The results show that the designed MIMO antenna can cover the whole 5G band(Sub-6 GHz)and has good isolation characteristics,which can well meet the requirements of 5G applications. |
PDF Full Text Request