Design of Self-Decoupled Circularly Polarized MIMO Dielectric Resonator Antenna Arrays Based on Polarization Orthogonality

The E-plane- and H-plane-coupled linearly polarized (LP) multi-input–multi-output (MIMO) dielectric resonator antenna (DRA) arrays are investigated. It is found that by adjusting the dimensions of DRA, the $E$ -field of the coupled element can be made out of phase with that of the excited element for both arrays. Based on this discovery, a self-decoupled circularly polarized (CP) MIMO DRA array is devised based on the polarization orthogonality of the coupled and excited DRAs. Without using any additional decoupling structure, the array can achieve either an extremely low coupling level of about −45 dB within a bandwidth of 10% or a broad decoupling bandwidth of 20.1% with a coupling level of about −27 dB by simply adjusting the antenna dimensions. Furthermore, a four-element MIMO array is proposed, yielding a 6.7% operating bandwidth with $\vert \text{S}_{11}\vert < -10$ dB, $\vert \text{S}_{21}\vert < -20$ dB, and AR < 3 dB. The universality of the proposed decoupling method is, therefore, verified.