Enhancing MIMO Antenna Isolation Characteristic by Manipulating the Propagation of Surface Wave

Multiple-input multiple-output (MIMO) antennas have been a mainstream technology in fifth generation (5G) communications. However, strong mutual coupling between both adjacent and nonadjacent elements is inevitable, especially among highly integrated devices. In this paper, a slit embedded mushroom electromagnetic bandgap structure (EBG) is primarily proposed to suppress the propagation of surface wave between antenna elements. Subsequently, complementary split-ring resonators (CSRRs) are periodically arranged in two sides of the ground to steer the surface wave. By effectively utilizing the unusual electromagnetic property of EBG and CSRR to manipulate the propagation of surface wave, the mutual coupling between antenna elements has immensely alleviated. Finally, an H-shape defected ground structure (DGS) is introduced to reinforce decoupling effect. In order to validate the feasibility of the design principle, a prototype of the proposed antenna has been fabricated and measured. Measured results demonstrate that the decoupling concept in this paper is reasonable and approximately 12 dB reduction of mutual coupling is realized.