The presented work describes the four-port multiple-input multiple-output (MIMO) antenna designed on Rogers substrate with a thickness of 0.787 mm. The core of the MIMO antenna includes a hexagonal-patch etched by a rectangular slot and an etched hexagonal-ring in full-ground, which are printed on opposite surfaces, generating measured millimeter-wave (mmWave) bandwidth of 26.45 GHz-29.27 GHz and 37.04 GHz-39.12 GHz. The dielectric material is micromachined, and the four-port radiating elements maintain isolation of more than 20.0 dB with an overall size of 17.0 mm × 22.0 mm × 0.787 mm. The novel 11 × 11 hexagonal-ring frequency-selective-surface (FSS) is placed below the MIMO antenna, enhancing the peak-gain by 5.16 dBi with a size of 42.50 mm × 42.50 mm printed on Rogers5880 0.787 mm thickness. The MIMO antenna also features good diversity-performance with ECC mmWave-FSS 9.995 dB, TARC mmWave-FSS < −4.76 dB, and CCL mmWave-FSS < 0.30 b/s/Hz. The cumulative features with dual millimeter wave bands, enhanced peak-realized gain, suppressed back-lobe radiations, and good diversity performance make the proposed MIMO antenna loaded with FSS suitable for 5G, satellite-communication, IoT, and smart cities applications. The MIMO antenna loaded with FSS is also subjected for SAR analysis for input power of 50 mW and 500 mW.
Sharma et al. (2026) studied this question.