An electrically tuned phase shifter based on the single slot unit cell and liquid crystal for a reconfigurable reflectarray antenna was presented. The simulation and measured results obtained at the F-band were used to demonstrate that the dielectric properties of a nematic state liquid crystal could be exploited to realize a slot unit cell phase shifter for the reconfigurable reflectarrays antennas. By reducing the inhomogeneous of the external electric field in the liquid crystal layer, a lower control voltage and improved model accuracy was obtained. In the experiments test, the achieved saturation bias voltage (10 V) was smaller than the previously reported structure, and the phase shift of the reflectarray greater than 300° was achieved in the frequency range 121.5–126 GHz. The maximum phase shift of 306° occurred at 124.5 GHz.

This paper introduces a tunable metamaterial absorber (MA) based on polymer network liquid crystal (PNLC) in the terahertz (THz) frequency band. Under the optimal polymerization condition, through electrical control of the orientation of the PNLC embedded in the frequency selective surface, the resonant frequency of the absorber can be tuned from 416.5 to 405.0 GHz, corresponding to fractional frequency bandwidth of 2.8%. The experimental results show that the proposed MA based on the PNLC offers an adjustment time of 10 ms and recovery time of 85 ms, which is significantly faster than the tunable metamaterial devices based on conventional nematic liquid crystal (LC).

This paper introduces a compact dual-circularly polarized (DCP) reflectarray antenna with independent focus and beam directions for satellite communication. The reflectarray employs semicircle strip elements with slots on their diameters, which facilitates adjusting the opening direction and slot width, providing hybrid phase shift, and controlling the focus and beam directions of the reflectarray independently. The mechanism for the hybrid phase is analyzed using the linear polarization scattering matrix. The achieved reflectarray can provide independent left-hand circularly polarized (LCP) and right-hand circularly polarized (RCP) beams in the ±20° range. The profile of the single-layer reflect plane is 0.136 λ ₀ , and the focal length to diameter ratio (F/D) of the compact reflectarray is 0.5. The reflectarray prototype is designed, fabricated, and measured. The experimental results show that the peak gain of the reflectarray is 21.3 dBic at -20° under RCP excitation and 20.1 dBic at 20° under LCP excitation, respectively. The measured 1dB Gain and 2dB axial ratio (AR) bandwidth are 10.6% (9.75-10.8 GHz) and 5.9% (9.75-10.35 GHz) with LCP helix and RCP helix antenna excitation respectively. The proposed compact dual-circularly polarized reflectarray antenna could be an alternative for satellite communication.

In the previous work, two new nematic liquid crystal (NLC) mixtures, E7-2 and S200-2, were produced by adding eight LC monomers to two commercial LCs S200 and E7, respectively. At λ = 589 nm, the birefringence (Δn) characteristics of the two LC nematic mixtures E7-2 (Δn = 0.260) and S200-2 (Δn = 0.298) are greater than those of the commercial LC E7 (Δn = 0.224) and S200 (Δn = 0.266). The properties (T_N-I, ε_//, Δɛ, K₁₁, and K₃₃) of these four NLCs were measured. A double-layer metal loop arrays modulation structure based on metamaterial (MM) metal–dielectric–metal (MDM) was designed and fabricated for use in the THz frequency range. The results show that the LC mixtures E7-2 and S200-2 have greater modulation depth (MD) and less modulation insertion loss (IL) than E7 and S200 at THz frequencies. The results show that LC mixtures have significant potential for designing active tunable LC-based devices in the THz and visible light range.

This study presents an independent dual-circularly polarized RFID tag and introduces a method for measuring the incident angle between the RFID tag and the reader. The tag, constructed with hybrid phase shift elements, possesses the capability to convert and independently control dual-circular polarization. The reflection from left-handed circularly polarized (LCP) waves exhibits a higher monostatic Radar Cross Section (RCS) than those from right-handed circularly polarized (RCP) waves within a certain angle range. The monostatic RCS difference between LCP and RCP depends on the tag incident angle, varying in magnitude as the angle changes. Therefore, the tag's incident angle can be obtained by comparing the measured difference with theoretically predicted values. A nine-element RFID tag was designed, fabricated, and its performance validated through experiments. Experimental results confirmed significant distinguishability between the scattered LCP and RCP monostatic RCS patterns, aligning with simulated predictions. The proposed tag incident angle measurement method requires only a single RFID tag and a single reader. Additionally, the method is compatible with conventional positioning methods and can serve as an alternative method to enhance stability.

This paper presents a dual circularly polarized encoding terahertz tag utilizing linked-semi-ellipses elements. The proposed design achieves broadband 2-bit polarization encoding in terahertz frequency bands through independently controlling dual circularly polarized phases with linked-semi-ellipses elements. The tag simultaneously possesses two key functionalities: circular polarization conversion and circular polarization encoding, which enhance its resilience to environmental influences. Simulations demonstrated the polarization conversion rates exceeding 80% across 0.42–0.53 THz with reflected RCS from tag achieved −51.7 dB·m² and a 3 dB beamwidth of ±22°. The tag achieves broadband 2-bit circular polarization encoding and attains a 23.6% relative bandwidth. The circular polarization encoding method enhances stability in metal-rich environments and offers substantial potential for diverse practical applications, including indoor positioning, logistics tracking, and object identification.