A Reconfigurable Reflectarray Antenna With an 8 μm-Thick Layer of Liquid Crystal

This article demonstrates an electronically scanned reflectarray antenna based on liquid crystal (LC). The LC-based reflectarray element was designed as a periodically loading of parallel H-shaped polygons on two metal layers. To realize a tunable reflection phase and reduce the inhomogeneity effect of LC, an 8 mu m-thick LC layer was designed as a varactor rather than a substrate. In simulations, the adjustable reflection-phase range of the proposed element was 180 degrees in the frequency band 21-21.5 GHz. The design concept was verified on a reflectarray prototype containing 26 rows of the basic elements. In addition, a 32-channel control circuit was designed and fabricated for biasing. The measured results confirmed a tunable phase range of 150 degrees at 23.8 GHz. The disagreements between the simulated and measured results are discussed, and a test process is proposed. As a proof of concept, the main beam was steered to 0 degrees, -40 degrees, and -60 degrees in one plane. The result confirmed the high beam-steering capability of the proposed reflectarray with measured gains above 18 dB at 23.8 GHz. This work provides useful references for the design and measurement of LC-based reflectarray antennas.