A broadband metamaterial superstrate based MIMO antenna array for sub-6 GHz wireless applications

Abstract

A circularly polarised Multi-Input Multi-Output (MIMO) array antenna integrated with the metamaterial superstrate is proposed and developed. The proposed antenna configuration includes a substrate and superstrate, featuring a 2x2 array MIMO setup on the substrate, and a metamaterial layer configuration setup on the superstrate. Although use of metamaterial superstrate enhances the antenna performance, an air gap between the substrate and superstrate is introduced to further enhance the performance. This proposed antenna configuration significantly broadened the impedance bandwidth to 24.3 % (2.9–3.7 GHz), a substantial improvement compared to the MIMO antenna alone, which achieved only 2.85 % (3.46–3.56 GHz). Furthermore, it substantially increased the axial ratio bandwidth to 17.7 % compared to only 0.86 % of MIMO itself. Additionally, the peak realized gain increased from 2.5 dBic to 11.5 dBic. Operating effectively within the 2.9–3.7 GHz frequency range, the proposed antenna achieves port isolation < -30 dB between its ports making it suitable for MIMO applications. The proposed antenna occupies a volume of 1.4 λ x 2.8 λ x 0.09 λ excluding the connectors.