Performance Improvement of Multiband MIMO Dielectric Resonator Antenna System With a Partially Reflecting Surface

This letter presents a novel partial reflector surface structure to improve the isolation and correlation coefficient values between cylindrical dielectric resonator antennas (cDRAs) for multiband multiple-input-multiple-output (MIMO) applications. To achieve multiband characteristics, three different groups of cDRA are proposed to cover 5.2, 5.5, and 5.8 GHz bands, respectively. Each group has two cDRAs. Thus, three groups (i.e, six cDRA) are placed at the top of the substrate and each cDRA is excited using a coplanar waveguide-fed conformal strip-line. To achieve improved isolation, three different phase gradient frequency selective surfaces (FSSs) are designed, which operate at 5.2, 5.5, and 5.8 GHz bands, respectively. This phase-gradient FSS is utilized as a superstrate above each group of the DR elements. As a result, two different far-field patterns are achieved from each group of antenna elements, which deliver improved isolation as well as low field correlation. This exclusive technique offers more than 12 dB of enhancement in the isolation values and more than 70% improvement in the envelope correlation coefficient values, thus guaranteeing improved MIMO performance.