Isolation and Bandwidth Enhancement in Compact CP MIMO DRA in H-Plane Using Z-Shaped Strip

In this letter, we investigate the use of decoupling structure to improve isolation and bandwidth in a multiple-input- multiple-output (MIMO) dielectric resonator antenna (DRA). The MIMO antenna consists of two identical DRAs that are fed by the same rectangular slots to excite the fundamental mode (TE111). In total, two annular vias are inserted in each DRA to realize circular polarization at this mode. Moreover, the annular vias create quasi hybrid mode (HEM11 delta) in the DRA. Vertical and Z-shaped strips are printed on the adjacent walls of DRAs for isolation purposes, in which the Z-shaped strips are coupled with the annular vias to realize the circular polarization at the HEM(11 delta )mode. Thus, improved bandwidth and isolation are achieved without occupying additional space. A prototype was fabricated and measured, which showed an overlapping 3 dB axial ratio bandwidth (ARBW) of 13.8% (2.7-3.1 GHz) with an isolation of 20 dB across the bandwidth, keeping the interelement spacing of 0.03 lambda(0). The measured radiation patterns were in agreement with simulated results in phi, = 0(degrees)(xz-plane) and phi, = 90(degrees)(yz-plane) planes, achieving a peak right-handed circularly polarized gain of 4.3 dBi for a single port.