Isolation Enhancement Techniques for MIMO Antenna: A Review

The Multiple-Input-Multiple-Output (MIMO) antenna is currently used in wireless communication application such as Bluetooth, Wi-Fi, Wi-Max, WLAN and UWB. This antenna has lot of advantages such as large data capacity, beam steering and diversity. However, isolation between antenna elements should be higher for a better performance of the MIMO antenna. Therefore, isolation enhancement is one of the research areas where work is evolving. A number of techniques are available such as ground plane defected structure (DGS), Periodic Electromagnetic Band Gap (EBG) structure, slot and stub, neutralization line, metamaterial, complimentary split ring resonator, cylindrical dielectric resonator and decoupling network. Techniques such as Genetic algorithm and Partial swarm optimization are also used to improve the isolation in the digital domain. By implementing the above techniques, isolation of more than 20dB is possible. In this paper isolation improvement techniques are compared on the basis of different design parameters. MIMO antennas are designed with multiband features, compactness of size, and higher isolation between antenna elements for use in wireless communication systems. This review paper will help in future designs of massive MIMO antenna for base stations.