Mutual Coupling Reduction Of Compact MIMO Array With Defected Ground Structure And Resonator

The rapid development of mobile communication technology makes the spectrum resources becoming scarce, and then how to improve the utilization of spectrum resources and the rate and quality of information transmission become hot research topics. Multiple input multiple output(MIMO) technology can improve channel capacity and transmission reliability without the increase in transmission bandwidth and transmitting power. In recent years, with the development of integrated circuits, the increasing integration of wireless terminal blocks makes the size of RF transreceiver smaller and smaller, which results in miniaturized compact antenna array. However, there is serious mutual coupling in multi-antenna array for the RF terminals with limited space, which may cause significant effects on the performance of the array. The purpose of this thesis is to study how to reduce the mutual coupling of compact MIMO antenna array based on defected ground structures(DGS) and resonators. Novel structures are proposed and studied in details for mutual coupling reduction of compact MIMO array.Firstly, the thesis introduces the background of mobile communication technology and MIMO antenna, then summarizes the progress of decoupling of MIMO antenna array in recent years. Furthermore, the basic theory of antennas, coupling theory and MIMO technology are briefly explained.Then, the study of mutual coupling reduction for compact MIMO antenna arrays utilizing the defected ground structure is presented. With the understanding of their operating mechanism, the single- and dual-frequency split ring resonator DGSs are proposed and optimized based on parametric study. Taking microstrip array and monopole array as examples, the performances of the arrays with and without DGS are compared. The results show that the proposed DGSs can effectively reduce the mutual coupling of compact antenna array. In addition, the equivalent circuit of the dual-frequency DGS is proposed, which is validated by the results of circuit simulation and electromagnetic simulation.Finally, the performance of resonators in mutual coupling reduction is studied. A U-shaped microstrip resonator and an H-shaped microstrip resonator are designed and analysed. The H-shaped resonator works at dual frequencies. To reduce the mutual coupling effect, the proposed microstrip resonators are implemented between the elements of E-plane and H-plane microstrip arrays, respectively. By comparing the results of array performance with and without microstrip resonators, it is concluded that the resonators can be used in mutual coupling reduction of compact array. Lastly, the equivalent circuit of the dual-frequency H-shaped resonator is proposed. The result of circuit simulation agrees well with that of electromagnetic simulation.