Ultrathin dual-band metalens integrated with Huygens’ metasurface and Fresnel zone plate

In this article, an ultrathin dual-band metalens is proposed for Internet of Things (IoT) applications in sub-6 GHz and millimeter-wave (mmW) 5G/6G networks. The hybrid metalens, which integrates a Huygens' metasurface and a Fresnel zone plate (FZP) lens, is designed to achieve Huygens' resonance at mmW bands (28 GHz) and partial reflectivity for sub-6 GHz waves (5.8 GHz) with an ultrathin thickness of 1.5 mm. This configuration enables dual-mode operation, where a focused lens is built for high-efficiency mmW beamforming, and a Fresnel zone plate (FZP) lens is formed for sub-6 GHz waves. By incorporating an aperture-shared feed antenna that co-locates a mmW patch radiator and a sub-6 GHz slot resonator within the same compact structure, the design achieves an exceptionally low profile. Experimental results demonstrate high gains of 16.2 dBi at 5.8 GHz and 29.9 dBi at 28 GHz, along with a compact profile of 0.14<i>λ</i>_h (wavelength at 28 GHz) and an <i>F/D</i> ratio of 0.25. The proposed metalens offers a scalable strategy for IoT communications, enabling reliable connectivity and high-speed backhaul for data aggregation and distributed networks in smart cities.