Metasurface Loaded Closely Spaced Shared Radiator 4-port MIMO Antenna with Dual-Radiation Performance

A slot-based configured closely spaced shared radiator was utilized to serve as 4-port mutiple-input-multiple-output (MIMO) antenna. Two distinct slots cavity were used to excite the radiating patch. The center-fed elliptical closed slot cavity provides magnetic field coupling while the open-ended diagonal slots provides electric field coupling. The induced coupling effect effectively improve the boresight radiation gain by top loading a metasurface layer. With the aforementioned design configuration, the proposed antenna asserts dual-radiation characteristics for $\varphi=0^{0}$ and $\varphi=90^{0}$ radiation planes. With the shared footprint, the antenna achieves better port isolation of $\gt18 \mathrm{~dB}$ and the 10-dB impedance matching was improved by arranging the unit pixels of metasurface spacing. The prototype fabricated antenna of dimension $60 \mathrm{~mm} \times 60 \mathrm{~mm} \times 3.1 \mathrm{~mm}$ was validated to operate from (4.31 - 5.85) GHz with $30.3 \% 10-\mathrm{dB}$ IBW with maximum realized gain of 8.28 dBi. The performance merits shows its viability for Super-high frequency (SHF) applications.