Review of isolation enhancement with the help of theory of characteristic modes

Multiple-input-multiple-output (MIMO) antennas performance can be degraded due to the poor isolation between the MIMO antenna elements. In this paper a review of the different isolation enhancement schemes available in the literature is presented. Empirically the isolation between the antennas can be improved by placing the antenna as far as possible and it can be enhanced further by introducing different isolation enhancement schemes. Theory of characteristic modes (TCM) was recently proposed that had useful benefits. TCM was also used to enhance the isolation. This papers will also focus on the different approaches of TCM, to enhance the isolation.