A Dual-Polarized Reconfigurable Reflectarray With a Thin Liquid Crystal Layer and 2-D Beam Scanning

A novel approach for dual-polarized liquid crystal (LC) unit cell design is introduced, allowing significant thickness reduction of an LC layer without compromising its loss and phase shift. For each unit cell, LC is used for a tunable superstrate between a cross patch above and a square patch below. The square and cross patches are coupled through two slots for each polarization. By changing the voltage applied to the square and cross patches, the LC in-between varies the resonant frequency and phase of the unit cell to realize 2-D beam steering.
$10\times 10$
dual-polarized reflectarray (RA) with
$30\,\mu \text{m}$
(
$0.0028 \lambda$
) and
$4\,\mu \text{m}$
(
$3.73\times 10 ^{-4}\lambda$
) thick LC layers are simulated in the 28 GHz band, where the aperture efficiencies (AE) are 25.3% and 22.5%, respectively. As a proof of concept, the dual-polarized RA with
$30\,\mu \text{m}$
thick LC is fabricated manually and measured at 28.5 GHz. A measurement technique is proposed to obtain the phase curves of the RA and reduce the effect of fabrication errors. With the imperfect manual fabrication, the RA still achieves the measured realized gain of 14.6 dBi corresponding to 12.5% AE. Besides, ±45° beam steering is demonstrated in the 2-D plane for both polarizations.