Dual-band compact high isolation array antenna design loaded with metasurface

In order to reduce the coupling between very small distance multiple-input multiple-output (MIMO) antennas, an extremely compact dual-band MIMO patch antenna with resonant frequencies of 2.45 GHz and 3.5 GHz is designed. The MIMO antenna consists of two symmetrical double-slot U-slot patch antennas with an edge-to-edge distance of 0.5 mm (0.004λ₀, λ₀ is the free space wavelength at a center frequency of 2.45 GHz). Double-layer wire cut pairs of different widths are used as metasurface elements, which are compact and can significantly reduce the coupling between antenna elements. Through simulation and measurement, in the antenna operating frequency band 2.4–2.5 GHz and 3.4–3.6 GHz range, the isolation between the units can be increased to more than 30 dB, and the impedance of the two antenna ports is well matched, at the same time, the total efficiency in the low frequency band is increased by about 9%, and the envelop correlation coefficient (ECC) between the two antennas is reduced from 0.33 to 0.01 at 2.45 GHz, at 3.5 GHz, it drops from 0.09 to 0.006, which has good radiation performance.