Ka‐band 1‐bit ultra‐thin reflective metasurface for generating vortex beams based on wideband polarization converter

Abstract

A 1-bit ultra-thin (~λ/12) reflective metasurface is proposed to generate vortex beams, whose mechanism of realizing 1-bit phase quantization is based on wideband polarization converter (PC). A diamond-shaped patch is studied as the unit cell of PC, which has the properties of high polarization conversion transmission efficiency, simple structure, wideband, and ultra-thin. By employing the proposed PC and its mirror image, a stable 180° phase shift is realized over the bandwidth of 18–36 GHz. Phase distributions of vortex beams with different modes and the corresponding radiation patterns are calculated and simulated. Reflective metasurface employing the proposed unit cells are arranged according to the calculated phase distribution, and the microstrip quasi-Yagi antenna is used as the feed antenna to illuminate the metasurface to generate vortex electromagnetic waves. A prototype is fabricated and measured, verifying that vortex beams can be generated flexibly by the proposed design. The measured gain of the vortex beams reaches to 19.5 dBi with the narrow divergence angle of ±4°. The proposed 1-bit measurface is compact, ultra-thin and offers a new possibilities for vortex beams generation.