Beam-Scanning Reflectarray With Switchable Polarization Based on Liquid Crystal at Millimeter Wave

This study presents a design for a millimeter-wave reflectarray (RA) with simultaneous polarization and beam direction control. A dual-polarized unit cell (UC) based on liquid crystal (LC) material is proposed and an RA is designed accordingly. The UC comprises a back-plate reflector, a double slot-loaded ground plane, and two rectangular patches. The LC material is used between the patches and the common slot-loaded ground plane. By illuminating the UC with a slant polarization, the wave decomposes into two components, and by applying a proper voltage to each patch, the polarization and beam direction can be manipulated. A $10\times 10$ RA has been fabricated and measured. The horn feed illuminates the RA with a fixed linear polarization, and four types of polarization are generated with a 70° and 100° scanning range in the E- and H-planes, respectively. The measured 3-dB gain bandwidth is 6% and the axial ratio (AR) bandwidth is 5% with around 15% aperture efficiency (AE).