High-Transmission Ultrathin Huygens' Metasurface with 360° Phase Control by Using Double-Layer Transmitarray Elements

Metasurfaces, which are planar surfaces or interfaces constructed by placing subwavelength scatterers into a two-dimensional array pattern, have attracted much attention in recent years. However, it has been shown that transmission-type metasurfaces without vias are hard to simultaneously achieve high transmission and 360 degrees phase control when the number of cascaded layers is less than three. An ultrathin Huygens' metasurface composed of only double-layer transmitarray elements without vias is proposed to achieve both high transmission (-2.5-dB criteria) and 360 degrees phase control. Benefiting from the antisymmetric design of the double-layer transmitarray element, the proposed Huygens' metasurface excites both electric and magnetic dipole resonances with mutual interference, allowing the realization of high transmission and 360 degrees phase control at the same time, which cannot be fulfilled by symmetric unit structures. Based on the ultrathin Huygens' metasurface, a high-gain transmitarray antenna is designed, fabricated, and measured, which can achieve high aperture efficiency up to 61.04% with a very small thickness of only 0.033 wavelengths at a microwave frequency of 13 GHz.