A Compact Wideband Circularly Polarized MIMO Antenna with Polarization Diversity

A compact multi-input multi-output (MIMO) antenna system composed of two circularly polarized antennas with opposite rotational directions is proposed. The antenna system consists of two E-shaped patch antennas and employs the shorting wall (SW) and the metasurface for decoupling. Simulation results show that the operational bandwidth, where $S_{11}$ is less than $\mathbf{- 1 0} \mathrm{dB}$ and the axial ratio is less than 3 dB, is $15.5 \%$ ($5.31-6.20 \mathrm{GHz}$). The isolation $\left(\mathrm{S}_{21}\right)$ is better than 23 dB, the antenna envelope correlation coefficient (ECC) is less than 0.0015, and the antenna gain is 5.5 dBi.