A review on different techniques of mutual coupling reduction between elements of any MIMO antenna. Part 1: DGSs and parasitic structures

This two-part article presents a review of different techniques of mutual coupling (MC) reduction. MC is a major issue when an array of antennas is densely packed. When the separation between the antennas is <λ
0
/2, i.e., half of the free-space wavelength, the antenna parameters suffer from the surface wave, and the space wave coupling effect between the antenna elements. To reduce the MC influence, several techniques have been discussed in the scientific literature. This part of the review paper will discuss strategies: antenna placement and orientation approach, Defected Ground Structures (DGSs), slots/slits-etching approach, protruding ground stub structures, and parasitic elements/structures. This article concludes with feasibility, applications, and comparison of the techniques mentioned above. Simultaneously, the applications and possibilities of the remaining methods are discussed in part two of the article.