| With the implementation and use of 5G communication systems and the growth of global mobile data services,the communication spectrum below 6 GHz has become increasingly crowded.Therefore,the development of millimeter-wave antenna system has become a key issue in the next step of 5G system development.Millimeter wave antenna has the advantages of light weight,small size,narrow beam,good directivity and stable propagation.Therefore,this paper mainly designs and studies millimeter-wave antenna applied to 5G frequency band.In this paper,two kinds of slot antennas working in the 26.5 GHz are designed and different feeding modes are selected,starting from the slot antennas in the millimeter wave frequency band.Based on two kinds of slot antennas,a two-port antenna element with orthogonal polarization is designed.The U-shaped slot can improve the bandwidth of the antenna.The designed antenna element has a high isolation of-40 d B and a continuous-10 d B bandwidth of 1300 MHz in millimeter wave frequency band.The antenna has good directional characteristics.Gain is very important for millimeter-wave antenna.In this paper,the surface of antenna element is covered with metasurface,and the average gain of antenna is increased from 4 d Bi to 7 d Bi.The designed antenna unit has a good scattering coefficient,bandwidth,directivity and gain,and can be used for 5G mobile communication in millimeter-wave band.Then,based on the designed antenna unit,an eight-port MIMO antenna system is designed to maximize the size advantage of millimeter-wave antenna and further improve the information transmission rate of antenna.The designed eight-port MIMO antenna has a size of 100×60mm~2,which meets the size of modern smart phones.The MIMO antenna has the same bandwidth and gain as the antenna unit,while maintaining a high isolation degree of-37 d B.The envelope correlation coefficient between each port is less than 0.2 required by the communication system.The designed eight-port MIMO antenna has a channel capacity of 35 bps/Hz in the operating frequency band,which is less different from the theoretical value.Finally,the performance of the designed MIMO antenna under actual conditions is simulated and analyzed.After loading the smartphone shell and human body,the performance of the antenna will be changed to a certain extent,in which the antenna gain is increased to 9 d Bi due to the reflection effect of the LCD shield,with an isolation degree of-30 d B.After loading the hand model,most ports still have radiation efficiency of more than 40%.The SAR value of the antenna for the human body is also less than 2W/kg,which meets the requirements of the antenna system for mobile devices.The millimeter-wave frequency antenna designed in this paper meets the design requirements in terms of bandwidth,isolation degree,efficiency,gain and human radiation,and can be used as one of the choices of 5G millimeter-wave antenna. |
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