A Hybrid Technique for Mutual Coupling Reduction in a Compact Dual-Band Millimeter-Wave MIMO Antenna

This letter reports a hybrid approach employing metallic vias and metasurface for mutual coupling reduction in a multiple-input--multiple-output (MIMO) antenna at millimeter-wave frequencies. Initially, a dual-band coaxial-fed antenna, operating at 27 GHz and 28 GHz, is designed using modified K-shaped patch arms with a tapered profile which is then used to develop a four-element dual-band MIMO array. Subsequently, metallic vias are incorporated to suppress surface wave-induced coupling. Finally, metasurface slab is integrated to mitigate near-field interactions. The proposed design achieves impedance bandwidths of 26.75 GHz to 27.28 GHz and 27.77 GHz to 28.19 GHz, with coupling levels below 30 dB, and broadside radiation patterns with respective peak gains of 6.52 dBi and 6.74 dBi. Furthermore, the proposed design exhibits an envelope correlation coefficient of less than 0.05 for isotropic and less than 0.25 for Gaussian environments. An excellent agreement between the experimental and simulation results validate the proposed design approach.