Design of MIMO Antennas With DRAs and a Dual-Function Decoupling/Radiating Monopole Antenna

For the first time, a dual-function monopole antenna (MA) is proposed in this article for radiating as an independent antenna and for decoupling dielectric resonator antennas (DRAs) simultaneously. For the
${H}$
- and
${E}$
-plane-coupled
$1 \times 2$
DRAs, two decoupling posts can be inserted into the interface of the DRAs, with out-of-phase and in-phase currents on the posts, respectively. To obtain antenna function, the two posts can be connected together to form a pair of MAs, with common-mode and differential-mode excitations for the
${H}$
- and
${E}$
-plane cases, respectively. High isolations can be obtained between the DRAs and the MA due to the current orthogonality between the decoupling and radiating functions. To verify the design philosophy, both the
${H}$
- and
${E}$
-plane prototypes are designed, fabricated, and measured, with reasonable agreement observed. All of the measured isolations, average realized radiation efficiencies and envelope correlation coefficients (ECCs) are higher than 18.9 dB, higher than 75%, and lower than 0.03. These high-isolation, high-efficiency, and low-correlation designs can be useful for multiple-input and multiple-output (MIMO) application scenarios.