Research On Decoupling Method Between Adjacent Elements In MIMO Patch Antenna

With the advent of the age of 5G communication,and due to the increasing scarcity of spectrum resources,MIMO(Multiple-Input Multiple-Output)technology has become a key technology of 5G because of its ability to improve the spectrum utilization and channel capacity of the system.However,on the premise of miniaturization of communication system,MIMO technology will form strong mutual coupling among antenna elements in a limited space due to the use of multiple antennas,which will worsen the performance of antennas.As a result,how to improve the isolation between antenna units effectively is a difficulty that must be solved.On the other hand,in terms of the forms of antennas,microstrip patch antennas have been widely researched and applied due to their advantages of low profile,light weight,simple manufacturing and easy integration.Considering the advantages and considerable application requirements of MIMO technology and microstrip patch antennas comprehensively,this article mainly focuses on studying the decoupling method between adjacent elements in the patch antenna arrays.The specific research contents of this article are as follows:1.Firstly,the research status of MIMO antennas decoupling is summarized to determine the research contents and significance of this paper.It mainly includes:analyzing the working mechanism of microstrip patch antennas and decoupling methods that can lay a theoretical foundation for the subsequent decoupling researches.Summarizing and evaluating the advantages and disadvantages of these decoupling methods which have been published,a decoupling scheme with simple structure and superior performance is proposed on this basis.2.A self-decoupling method for single frequency MIMO patch antenna is designed based on the inset-fed structure.An inherent weak-field area is exactly created on the ground near the patch antenna,and the mutual coupling strength between adjacent units can be effectively reduced if putting another antenna element in the weak-field area strategically.On the basis of it,in order to improve the isolation between the adjacent antenna units furtherly,the C-slots are etched on the patches to suppress the mutual coupling of space waves.In order to verify the above scheme,a dual-unit MIMO patch antenna with an operating frequency of3.6 GHz has been designed,and its relative bandwidth is 3.15%.The edge-to-egde distance between adjacent elements is 0.03 ?₀?and the isolation is greater than 20 dB within working bandwidth,a peak isolation level of 45 dB between adjacent antenna elements can be achieved at the central operating frequency,it proves that the self-decoupling method can significantly improve the isolation between closely placed antenna elements.3.A new low-profile decoupling scheme suitable for dual-band MIMO patch antennas is proposed.The decoupling structure based on the proposed scheme is mainly composed of the defective ground structure(DGS)and the metal branches with shorting pins,the mutual coupling through surface wave on the ground plane is suppressed by DGS and the coupling through surface wave on the substrate is decoupled by means of introducing metal branches with shorting pins.To verify the scheme above,a dual-unit MIMO patch antenna with operating frequencies of 3.04 GHz and 4.24 GHz is designed,and the edge-to-edge distance between adjacent elements is 0.13₀?(where₀?is the wavelength at the operation frequency of3.04 GHz).After introducing the decoupling structure,the isolation is improved from 9.1 dB to 20.2 dB at the center frequency of low band and the isolation is improved from 16.8 dB to42.1 dB at the center frequency of high band,which means a considerable coupling reduction of 11.1 dB and 25.3 dB has been achieved,respectively.In addition,the coupling coefficient is able to be reduced below-20 dB at each band.It indicates that the combined decoupling structure proposed in this article can effectively improve the isolation between adjacent dual-band antenna elements.