Metamaterial loaded highly isolated tunable polarisation diversity MIMO antennas for THz applications

This article investigates the designing of tunable laterally and orthogonally placed MIMO antennas with enhanced isolation for THz applications. The tunability is achieved by varying the chemical potential of trapezoidal graphene-based patches loaded over the metallic patch antennas. Mutual coupling between the laterally placed MIMO antennas is mitigated by the use of defected ground structures. In the first design, a cross-shaped stub emanating out from a square shaped slot has been introduced in the ground plane for improving the isolation between the unloaded antennas without degradation of their impedance bandwidth. Introduction of a trapezoidal graphene patch over the antennas in the second design aids in conceiving tunable mutual coupling reduction. The mutual coupling has been reduced by deployment of a T-shaped stub arising from a square shaped slot in the ground plane. Orthogonally placed antennas, when separated by reflective metamaterial walls or planar metallic parasitic strip, result in improved isolation between the antennas in the frequency band of 1.6 to 3.0 THz. This configuration aids in achieving polarization diversity. A maximum isolation of 38 dB is achieved which is the highest as compared to the reported MIMO antenna designs. The envelope correlation coefficient, channel capacity loss and mean effective gain of the proposed graphene loaded antennas are within acceptable limits. The field results with several analytical results are presented for justification. The development aspect of these types of antennas has also been discussed.