Isolation Enhancement of a Metasurface-Based MIMO Antenna Using Slots and Shorting Pins

In this paper, a metasurface-based multiple-input multiple-output (MIMO) antenna with high isolation between antenna elements is presented. The main patch radiator is sandwiched between a metasurface and a ground plane to achieve performance enhancement. The fabricated single element antenna has a compact size of $0.85\lambda _{0} \times 0.85\lambda _{0} \times 0.038\lambda _{0}$ . The antenna exhibits a wideband operational bandwidth from 3.27 to 3.82 GHz for $\vert \text{S}_{11}\vert < -10$ , which corresponds to a fractional bandwidth of 15.5%. Moreover, stable radiation patterns with a peak gain of 8.1 dBi are also achieved across the operating band. The proposed single element antenna is characterized for $2 \times 2$ MIMO system by translating each antenna element orthogonal to each other. A decoupling structure consisting of slots and metallic strip with shorting pins is used to improve the isolation between the MIMO elements. The shorting pins connect the metallic strips (located between MIMO elements) on the metasurface and ground plane. These slots on ground plane and shorting pins affect the electromagnetic field distribution and consequently reduce the mutual coupling. The fabricated MIMO antenna has a compact size of $1.75\lambda _{0}\times 1.75\lambda _{0} \times 0.038\lambda _{0}$ . The proposed 4 port ( $2\times 2$ ) MIMO antenna provides 15.9% of 10 dB impedance bandwidth from 3.3 to 3.87 GHz with a peak gain of 8.72 dBi. Moreover, the proposed MIMO antenna offers excellent diversity performance, isolation between antenna elements is very high (>32dB), ECC is lower than 0.001, and diversity gain is 9.99 dB very close to the ideal value of 10dB. Owing to these features, the proposed MIMO antenna can be a good candidate for 5G Sub-6 GHz (n78 band) smart devices and sensors.