Ultrathin Huygens Transmitarray With High Transmission Efficiency for Single-Layer Metalens Antenna Applications

In this letter, an ultrathin polarization-converting transmissive Huygens element is proposed by achieving nearly 100% transmission efficiency for circularly polarized (CP) incident waves. The element consists of a single-layer dielectric substrate with a thickness of only 0.03$\lambda _{0}$ and asymmetric S-shaped patches located on both sides. By utilizing surface currents flowing in the reverse direction of the upper and lower patches to form a magnetic dipole, while generating an electric dipole in the orthogonal direction, the electromagnetic response satisfies the Huygens resonance requirement, which makes the transmitarray extremely highly efficient for transmission. The independent regulation of the CP beam and $\text{360}<^>{\circ }$ phase coverage can be flexibly achieved by adjusting the rotation angle of the element. The designed element is experimentally integrated to form a metalens antenna to generate a directional beam with high gain and low sidelobes. The measured results show the achieved peak gain of 24.4 dBi at 9.8 GHz with a peak aperture efficiency of 51.3%, which well demonstrated the advantages of low profile, high efficiency, and easy integration of the designed transmitarray structure. Above all, the proposed metalens antenna exhibits superiority for further being applied in device-to-device satellite communications.