Broadband Dielectric Resonator Antenna Array With Enhancement of Isolation and Front-to-Back Ratio for MIMO Application

Dielectric resonator antenna (DRA) arrays with enhanced isolation and front-to-back ratio (FBR) are proposed in this letter. Specifically, each DRA element is mounted on a small and separated ground plane; all the DRA elements (with small ground planes) share a large common ground plane. Each DRA element is excited by two differential probes at its edges. The DRA element in its {\boldsymbol{TE}}_{{\boldsymbol{\delta }}11}^{\boldsymbol{x}} mode is equivalent to a magnetic dipole. Meanwhile, the differential probes also excite electric current on the small grounds that can be viewed as an electric dipole. The equivalent magnetic and electric dipoles are orthogonal, behaving like a magnetoelectric dipole (ME-dipole). By properly adjusting the small ground planes' size and their height above a sizeable common ground plane, a broadside unidirectional radiation pattern with low backward radiation is realized; moreover, the small ground structures can provide neutralization paths to counteract the original coupling waves. A 1 \times 4 single-polarized DRA array is designed, fabricated, and measured. Measurements align well with the simulations, demonstrating significant isolation and FBR improvements compared with the conventional DRA array. The proposed array has about 20% relative bandwidth.