Dual-band MIMO antenna with spline patch and metamaterial superstrate for 5G/Wi-Fi applications

Abstract A novel dual-band MIMO antenna operating in the n78 5G and 5.2 GHz Wi-Fi bands is presented in this work. The initial design employs a Catmull–Rom spline-shaped patch with a smaller Catmull–Rom spline slot defected ground structure. To achieve dual-band operation with wideband characteristics, additional features such as a crescent patch and Koch snowflake fractal patch were incorporated. The desired response was finally realized by introducing a second-generation Apollonian geometry-inspired metamaterial superstrate above the basic antenna. Both the antenna and the superstrate were fabricated on an FR-4 substrate of dimensions 58 mm ×58 mm. The fabricated single-element antenna exhibited wideband performance, achieving 977 MHz (3333–4310 MHz) in the 5G band, covering both n78 and n79, with a minimum reflection coefficient( S 11 ) of –36.2 dB at 3.97 GHz, and 818 MHz (5033–5851 MHz) in the Wi-Fi band with a minimum S 11 of –23.66 dB at 5.45 GHz. The same configuration was extended to a two-port MIMO antenna, which achieved a bandwidth of 744 MHz in the n78 5G band with a minimum S 11 of –37.81 dB at 3.3 GHz, and 766 MHz in the 5.2 GHz band with a minimum S 11 of –32 dB at 5.62 GHz, along with a peak gain of 8.32 dBi. The fabricated MIMO antenna exhibited excellent isolation (>28 dB), diversity gain close to 10 dB, ECC below 0.003, TARC below –10 dB across the operating bands, and CCL below 0.25 bps Hz −1 . These results confirm that the proposed antenna provides robust dual-band performance with superior MIMO characteristics, making it a strong candidate for modern wireless systems requiring simultaneous 5G and Wi-Fi connectivity.