Design and Analysis of a Hybrid Circularly Polarized Multi-Band MIMO Antenna for Sub 6 GHz Applications

In this article, a hybrid circularly polarized Multiple-Input Multiple-Output (MIMO) antenna for multi-band operation from 2.3 to 9.2 GHz with an impedance bandwidth of 7 GHz is proposed and investigated experimentally. The designed MIMO antenna model has a compact size of 20mm×40mm×1.6mm on the FR-4 substrate. The microstrip feed of the proposed slot antenna consists of a tapered structure, and the radiating element consists of the inverted L- shaped slots, which were opened on both sides of the radiating elements to introduce notches at the sub-6 GHz frequencies. L-shaped stubs are also introduced on another side of the substrate in the common ground plane to attain high isolation between the radiating elements of the proposed antenna. In the operating band from 2.3 to 9.2 GHz, isolation of less than -20 dB is achieved by the proposed model. The performance of the circularly polarized MIMO antenna in terms of RHCP and LHCP radiation patterns, axial ratio, surface current distributions, isolation between the ports, diversity gain (DG), envelope correlation coefficient (ECC), total active reflection coefficient (TARC), and peak gain are studied and presented in this work. The obtained characteristics of the proposed antenna make it suitable for sub-6-GHz frequency applications.