Research And Design Of Compact Wideband MIMO Antennas With High Isolation

Multiple Input Multiple Output(MIMO)technology is a spatial diversity technique that uses multiple antenna elements transceiver at the same time to decompose a communication channel into multiple non-interfering parallel sub-channels,which can effectively improve the resource utilization rate and reliability of wireless communication system.It has broad application prospect in 5G/6G mobile communication,high-performance broadband communication network and large-scale communication with integration of heaven and earth.However,in order to greatly improve the wireless communication quality,MIMO antenna design needs to simultaneously solve the problem of miniaturization and high isolation,and it needs to consider how to make multiple antennas work well in a small space.The small spacing between antenna elements will lead to the increase of electromagnetic coupling between MIMO antenna elements and affect the communication quality.In this context,this paper takes compact wide-band MIMO antenna as the research object,and the decoupling technique of this kind of antenna is studied deeply.The work carried out and the main progress made in this paper include:Firstly,the theoretical basis of MIMO antenna design is analyzed from the channel model of MIMO system and the mutual coupling mechanism of MIMO antenna,and three key parameters describing MIMO antenna performance indexes are discussed.Secondly,typical array antenna decoupling techniques are systematically studied for both compact and wide-band MIMO antennas.On this basis,the decoupling methods of the compact wide-band MIMO antenna are studied,and finally two high-isolation MIMO antennas are designed by using two different decoupling methods.A decoupling method for multi-port compact microstrip quasi-Yagi MIMO antenna is proposed.The structure and working principle of yagi antenna,microstrip yagi antenna and microstrip quasi-yagi antenna derived from integrated microstrip form are analyzed.This paper proposes a decoupling method combining pattern diversity and defected ground structure,the design of compact microstrip quasi-Yagi MIMO antenna structure evolvement process is mainly introduced.On the basis of realizing the pattern diversity,the defected ground structure is further loaded,and the method will be migrated and verified on two-port,three-port and four-port MIMO antenna.Finally,the three antennas are processed and measured,and the measured data agree well with the simulation results.In the whole frequency bandwidth(5.5-6.1 GHz),the isolation between microstrip quasi-Yagi MIMO antenna elements is greater than 25 d B,the gain is greater than 8 d Bi,and the variation range of gain is less than 1 d Bi.In the proposed method,the pattern diversity is realized by using the directors of the microstrip quasi-Yagi antenna itself,and the defected ground structure is placed outside the element and its size is significantly reduced compared with the traditional structure,which provides a new idea for the design of compact and miniaturized directional MIMO antenna.A decoupling method of compact ultra-wideband MIMO antenna based on loading resistance and patch is proposed.The principle and structural characteristics of Vivaldi antenna and antipodal Vivaldi antenna are analyzed.Taking the evolution of antipodal Vivaldi antenna element and four-port MIMO antenna structure as the main line,a series of electromagnetic control measures such as etching rectangular slots on the radiation plates,loading absorption resistance and parasitic rectangular patch,and parasitic elliptical patch in the center of the opening slot are integrated.The performance indexs and current distribution of antipodal Vivaldi antenna element and four-port MIMO antenna are compared and analyzed.Finally,the antenna element and MIMO antenna are processed and measured,and the measured data agree well with the simulation results.The working bandwidth is nearly 20 octave bands,and the isolation is greatly improved,with a maximum increase of 20 d B.The gain is more than 4 d Bi in the band from 1 to 16 GHz,and more than 10 d Bi in the band greater than 3 GHz.The proposed antenna has the advantages of compact structure,simple form,lower cutoff frequency,high isolation,higher average gain and stronger direction in the bandwidth range,which is of great significance for the design of compact ultra-wideband MIMO antennas.