Isolation enhancement of MIMO system using metamaterial zeroth-order resonant antennas

In this paper, a MIMO antenna system consisting of two types of MTM (Metamaterial) ZOR (Zeroth-Order Resonant) antennas is proposed and its performances are evaluated in terms of isolation between antenna elements and envelope correlation between the two radiation patterns. The resonant frequency of the each antenna element is 2.22 GHz. The isolation of the proposed MIMO antenna is 28.2 dB at 2.22 GHz and the envelope correlation is 0.0002. Owing to these relatively good performances, each antenna may be regarded to operate almost independently. Furthermore, the sizes of the proposed antenna elements are significantly small due to the use of ZOR antennas. The ENG (Epsilon-NeGative) ZOR antenna size is 16.5× 7.1 mm (0.121× 0.052 λ at 2.2 GHz) and the MNG (Mu-NeGative) ZOR antenna size is only 7.5× 7.1 mm (0.055× 0.052 λ at 2.2 GHz). These results are also compared with those of other representative MIMO antennas.