A 2-Bit Millimeter-Wave Reconfigurable Folded Reflectarray Antenna With Electronically Tunable Liquid Crystal for IoV Sensing and Communication

This article proposes a novel millimeter-wave liquid-crystal (LC)-based reconfigurable folded reflectarray antenna (RFRAA) tailored for Internet of Vehicles (IoV) sensing and communication. It offers 2-D beam scanning capabilities. The RFRAA consists of a reflectarray (RA), a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times 2$ </tex-math></inline-formula> feeding array, and a polarization-selective surface (PSS). The unit cell of the RA is designed using a slot-coupled patch array with a cross-shaped slot. The differential-driven structure and meandered microstrip line are added into the unit cell. They produce a 90° polarization rotation of the reflected wave relative to the incident wave and provide phase compensation for in-phase radiation. LC substrate is injected into the unit cell and can adjust the phase delay of the meandered microstrip line to meet the beam scanning. To minimize cross-polarization, an array of metallic strip along x-axis is employed as the PSS, it can only transmit x-polarized wave. A prototyped RFRAA with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$15\times 15$ </tex-math></inline-formula>-unit cells is fabricated and measured. The RFRAA achieves 2-D beam steering within ±60° in both the E-plane and H-plane. It demonstrates a peak aperture efficiency (AE) of 29.6% at 24 GHz and a height-to-dimension (H/D) ratio of 0.29. These features make it a promising candidate for IoV sensing and communication applications.