Design of a High-frequency Dual-polarized Metalens Antenna

Abstract

Throughout the project, a low profile, high gain, dual-polarized, broadband gradient refractive index (GRIN) lens antenna is proposed for 5G communication (24-28GHz). The proposed design consists of a feeding antenna and a novel three-layers stacked, planar lens based on high refractive-index metasurfaces. The unit cell of the core layer, composed of bi-layer square copper foil with a rhombus hole, provides a wide range of refractive index variation of about 4.79 (2.08 to 6.78). To deal with the wave impedance mismatching between the core layer and the free space, two impedance matching layers sandwiched with the core layer are introduced to enhance the antenna efficiency, providing the lower refractive index variation range of 1.43 (1.24 to 2.62). The pattern of either Core layer or impedance matching unit cell is x- and y-symmetric for adapting the dual-polarized wave propagating in the z-direction, and thus a thin lens with an overall thickness of 0.32𝜆0, where 𝜆0 is the free-space wavelength at 26 GHz. For realizing the performance of the proposed GRIN metalens antenna, a dual-polarized, wideband Magneto-Electric dipole (ME dipole) with adequate isolation and high gain, which is about -30dB between two input ports and 9.7dBi respectively, is introduced as a feeding source antenna. The simulated results demonstrated a wide impedance bandwidth of 40%, high gain up to 20dBi, and high isolation of -30dB over the operating frequency. Furthermore, the lens exhibited the enhancement of the radiation characteristics, where its sidelobe level is less than -20dB and the cross-polarization level is better than -30dB.