A Self-Decoupling Method for MIMO Linear and Planar Dielectric Resonator Antenna Arrays Based on Transmission Characteristics of Feeding Structure

In this article, a novel self-decoupling method for the multi-input multi-ouput (MIMO) dielectric resonator antenna (DRA) arrays is investigated. This method is based on the transmission characteristics of the conformal strip that feeds the DRA. It is found that when the strip-fed DRA operates in the higher order mode, e.g., TE ₁₁₃ mode, the $E$ -field coupled to the metal strip of the adjacent passive DRA presents a standing-wave distribution. By appropriately adjusting the dimensions of the feeding strip, the $E$ -field can form a node with zero amplitude at its bottom where a coaxial probe is connected, preventing the energy from getting into the receiving port and hence achieving a high isolation level without requiring any extra decoupling structure. This self-decoupling method is applicable not only to 1-D H- and E-plane coupled MIMO linear arrays but also to 2-D MIMO planar arrays. To verify its feasibility, a prototype of $2\times $ 2 MIMO planar DRA array is simulated, processed, and tested. The results show that a usable bandwidth ( $\vert \text{S}_{\mathrm {ii}}\vert < -10$ dB and $\vert \text{S}_{\mathrm {ij}}\vert < -20$ dB) of 10.8% is achieved, and the maximum isolation is over 40 dB within the passband.