Millimeter-Wave Co-Polarized Self-Decoupled Substrate-Integrated Dielectric Resonator Antennas for In-Band Full-Duplex and MIMO Systems

Millimeter-wave (mm-wave) co-polarized self-decoupled substrate-integrated dielectric resonator antennas (SIDRAs) are investigated. A dual-port design is first studied which employs the loading effect of the feeding probe to modify the E-field distributions of the dielectric resonator (DR) $ {\text {TE}}_{{3}\delta {1}}^{y}$ mode. The interaction between the probe-loaded and DR modes results in the formation of a quasi-fundamental mode ${\text {TE}}_{{1}\delta {1}}^{y}$ and a weak field region at the coupled port, leading to stable radiation patterns for each port with high port isolation. Additionally, metal vias is used to surround the DR to reduce cross-polarization. Also, the metal vias form electric walls which can reduce the DR size effectively. A hole is introduced at the center of the DR to further enhance the isolation. Based on the dual-port antenna element, a $2\times 3$ -port multiple-input multiple-output (MIMO) array with a center-to-center distance of $0.49\lambda _{0}$ is developed. To improve isolation between adjacent elements, a leaky wave decoupling structure and two strips are introduced, increasing the isolation by 11 dB. Both the antenna element and the MIMO array were fabricated to validate the designs. Experimental results indicate that the −10-dB impedance bandwidth and isolation level of the dual-port antenna element are 6% and 24.4 dB, respectively. For the $2\times 3$ -port MIMO array, the −10-dB bandwidth and isolation level are 5% and 20 dB, respectively. Stable radiation patterns with low cross-polarization levels are obtained for each port. Our designs feature a simple structure using a single substrate only, with the design methodology extendable to larger MIMO arrays.