| The fifth generation wireless system(5G)has obvious improvement in channel capacity,delay,throughput and other aspects,and its data transmission rate can reach hundreds of times of 4G.With the rapid development of 5G technology,the application of 5G will penetrate into all aspects of our lives and promote the transformation of digitization.At present,the commercial application of 5G spectrum in mobile terminal is mainly concentrated in sub-6 GHz band,and the application in millimeter wave band is not yet ripe for it.Due to the requirement of high transmission rate of 5G and the size limitation of mobile terminal,5G terminal antennas must have the characteristics of wide band,miniaturization and high channel capacity.Multipleinput multiple-output(MIMO)technology is one of the key technologies of 5G terminal antenna,which can make highly use of the spatial resources within the terminal equipment,increase the channel capacity and the communication quality of the system greatly without increasing the spectrum resources and the transmit power of antenna.Therefore,combining MIMO technology with terminal antenna design,and based on the research of the background and current situation of MIMO antenna,the advantages of MIMO system,and the key technologies of MIMO terminal antenna,two design schemes of MIMO terminal antenna applied to 5G sub-6 GHz band are proposed.First of all,for China’s spectrum schematization in 5G sub-6 GHz frequency band,a dualband 8-element MIMO antenna based on metal frame is proposed.By slotting the metal frame in place,two parallel radiation branches are formed and simultaneously fed by a T-shaped coupling strip,so that two resonant modes are excited and a compact size is obtained.The proposed antenna can cover the frequency bands of 3300-3600 MHz and 4800-5000 MHz,and the isolation is greater than 14 d B without additional decoupling structure.At the same time,as a key factor to assess the diversity and the multiplexing of MIMO antenna,the envelope correlation coefficient(ECC)of the proposed antenna is also studied,the simulated and measured ECCs between the antenna elements are lower than 0.1,which shows good performance in diversity and multiplexing of the MIMO antenna.The antenna is simple in structure and easy to be fabricated,and it obtains the merits of miniaturization and highisolation.Then,to achieve the full coverage of sub-6 GHz band,a broadband and miniaturized 8-element MIMO antenna is proposed.By slotting the metal plate in ground and introducing Lshaped strip,and then employing T-shaped coupling strip as feeding structure,the MIMO antenna with three resonant modes is obtained.The impedance bandwidth of the antenna is from 3.3 to 6 GHz(S11 <-6 d B),the measured isolation of the antenna is greater than 11 d B without any additional decoupling structure,and the efficiency of the antenna is higher than 55%.Furthermore,the ECC between any two elements is less than 0.1.Finally,the influence of human hands on the MIMO antenna’s radiation performance is investigated,the simulated results show that the presence of human hands has a slight impact on the radiation performance of a few antenna elements,while the overall operation status of the MIMO antenna is acceptable. |
PDF Full Text Request