Dual-Band Metasurface-Based Closely Packed Antennas by Controlling Surface Wave Propagation

In this letter, a dual-band metasurface (MS)-based slot antenna with bidirectional and unidirectional radiation patterns is proposed. The MS is simultaneously used to reduce mutual coupling for the closely packed antenna system. The proposed antenna is a single-layer coplanar waveguide (CPW)-fed slot antenna integrated with an MS-based superstrate. The lower band and the higher band are generated by the slot and the MS, respectively, which yields the advantages of independent and flexible frequency control. The impedance matching bandwidths (|S₁₁| < –10 dB) are 3.44–3.54 GHz (a relative bandwidth of 2.9%) and 4.38–5.84 GHz (28.6%). Bidirectional and unidirectional radiation patterns are obtained in the two bands, respectively. Moreover, a 2 × 1 edge-to-edge closely packed (∼0 space) dual-band antenna array is proposed by simply reusing the MS for multiple-input–multiple-output (MIMO) systems. Over 18.3 and 19.7 dB isolations are obtained by suppressing the surface wave in the lower band and steering the radiation pattern in the higher band. The proposed antennas can find applications in dual-band MIMO and 5G communication systems.