Research On MIMO Filtering Antenna Based On Couping Matrix

The rapid development of wireless communication makes the channel resource become more and more tense,forcing the MIMO communication technology of WiFi and LTE to develop rapidly.MIMO technology provides spatial channel diversity through multiple transceiver antennas,which improves communication quality and speed,but it must depend on the low correlation of MIMO antennas.However,the limited size of mobile communication equipment limits the distance between antennas,resulting in strong coupling between antennas,that is,and greater correlation.The method of solving this MIMO interconnect problem is usually to use the space decoupling or the network decoupling.On the other hand,the design of the filtering antenna can improve the frequency selectivity of the antenna and further enhance the channel resource utilization.However,the MIMO filtering antenna combined with two technologies has not been reported,the reason is that the MIMO filtering antenna not only to solve the coupling between the antennas,but also to achieve a specific transfer function,so that the entire antenna design is very complex.Moreover,blind direct simulation and optimization is difficult to find the best results,it is not possible to determine whether a physical structure meets the design requirements at the beginning of the antenna design.It is necessary to propose a system design method,which can realize MIMO decoupling and filtering characteristic antenna structure in principle.In this paper,we use the coupling matrix theory of filter to model the MIMO filtering antenna and analyze the coupling matrix form of the equivalent circuit of the MIMO filtering antenna.In addition,we put forward the structure of the resonantor-coupled MIMO filtering antenna,and theoretically prove the absolute decoupling ability of the structure and the feasibility of realizing the specific filtering response.Based this mothed,realize MIMO decoupling and complete filtering at the same time.The main research contents are as follows:(1)Analysis of MIMO equivalent circuit based on coupling matrix.In this paper,the equivalent circuit model of MIMO is constructed by coupled resonators,and is expressed by coupling matrix.The coupling coefficients are helpful to show the mutual coupling of MIMO antennas from the coupling strength of the resonator.The MIMO equivalent circuit model based on coupling matrix adds new ideas and methods to the design of MIMO decoupling network.(2)MIMO decoupling technology based on coupling matrix.A simplified model of the MIMO equivalent circuit with coupling matrix is presented,and the equivalence between the two circuit models is validated.On the basis of the simplified form of the MIMO equivalent circuit,the order of the N+2 order coupling matrix is reduced,and a network topological which can be used for MIMO decoupling is realized by the similarity transformation of the matrix.(3)Synthesis of MIMO filtering antennas based on coupling matrix.The equivalent model of MIMO filtering antenna is formed by adding the resonator at the back end of the antenna by using the simplified form of the MIMO equivalent circuit model,and the coupling matrix is extracted.This paper analyzes the possibility of several network topologies of MIMO filtering antenna decoupling,and analyzes,simulates and verifies it in detail.