A Metasurface-Based MIMO Antenna With Compact, Wideband, and High Isolation Characteristics for Sub-6 GHz 5G Applications.

A compact metasurface (MS) based MIMO antenna with wideband operation and high isolation characteristics is proposed for sub-6 GHz applications. A single element is constructed by a slot coupled with $2\times $ 2 unit cells MS. For mutual coupling suppression, the MS of each MIMO element is grounded at proper positions by metallic vias. Compared to other reported designs, the proposed antenna possesses several unique features including a simple decoupling method with no extra space requirement, compact size, and wideband operation. For verification, the measurements have been implemented on a fabricated prototype with overall dimensions of $0.85\lambda _{c} \times 0.48\lambda _{c} \times 0.03\lambda _{c}$ ( $\lambda _{c}$ is the free-space wavelength at center operating frequency) and the center-to-center element spacing of $0.43\lambda _{c}$ . The measured results indicate that the proposed design has a wide operating bandwidth of 15% ( $3.7-4.3$ GHz) with high isolation of better than 25 dB. In addition, the measured maximum gain is about 4.1 dBi, and good diversity performance is also achieved. The proposed MIMO antenna is a potential candidate for 5G applications operating at the NR77 band.