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

Abstract

This study investigates the used 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 (TE<inline-formula><tex-math notation=LaTeX>$_{111}$</tex-math></inline-formula>). Two annular vias are inserted in each DRA to realize circular polarization at this mode. Moreover, the annular vias create quasi-hybrid mode (HEM<inline-formula><tex-math notation=LaTeX>$_{11\delta }$</tex-math></inline-formula>) 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 coupled with the annular vias to realize the circular polarization at the HEM<inline-formula><tex-math notation=LaTeX>$_{11\delta }$</tex-math></inline-formula> mode. Thus, improved bandwidth and isolation are achieved without occupying additional space. A prototype was fabricated and measured, which showed an overlapping 3 dB ARBW of 13.8% (2.7–3.1 GHz) with an isolation of 20 dB across the bandwidth, keeping the inter-element spacing of 0.03<inline-formula><tex-math notation=LaTeX>$\lambda _{0}$</tex-math></inline-formula>. The measured radiation patterns were in agreement with simulated results in <inline-formula><tex-math notation=LaTeX>$\phi =0$</tex-math></inline-formula><inline-formula><tex-math notation=LaTeX>$^\circ (xz-plane)$</tex-math></inline-formula> and <inline-formula><tex-math notation=LaTeX>$\phi =90$</tex-math></inline-formula><inline-formula><tex-math notation=LaTeX>$^\circ (yz-plane)$</tex-math></inline-formula> planes, achieving a peak right-handed circularly polarized (RHCP) gain of 4.3 dBi for a single port. IEEE