We propose an F-band phase shifter based on the nematic liquid crystals (NLCs). The proposed phase shifter is formed by a voltage-controlled cavity through introducing an NLC layer between a dipole structure array and a metal floor. Under the action of electric field, the orientation of the NLC molecules will be deflected. We adjust the resonant frequency and phase of the reflected electromagnetic (EM) wave by tuning the permittivity. The transmission characteristics and the LC parameters are calculated and analyzed for EM waves within the frequency range from 85 to 115 GHz. The LC-based device with a 30 × 30 array of two parallel unequal dipoles is printed on a quartz substrate, with 4 cm × 4 cm area and 490 µm thickness. The experimental results show that phase shift of zero to 350.7 • is achieved at 104.2 GHz by changing the applied bias voltage on the LC layer from 0 to 20 V. Considering the anisotropy and inhomogeneity of the LC, an improved electrification model is established and compared with the test results. The proposed phase shifter is expected to find several applications in millimeter wave and terahertz reconfigurable antenna systems.

This study investigated a novel electronically controlled two-dimensional beam-scanning reflective array antenna (reflectarray), which uses nematic liquid crystals. A double-dipole resonance structure is used as the phase-shift unit for the reflectarray for the required phase compensation. The simulation shows that, for about 7 GHz bandwidth of the phase shift range, over 360 • can be achieved at the F-band. In addition, a novel wiring scheme is proposed to reduce the adverse effect of the biasing line on the phase-shift performance and simplify the manufacturing process. A simulation of the designed 39 × 39 reflectarray shows that the maximum beam steering range, maximum gain, and side-lobe level at 115 GHz are 20 • , 16.55 dBi, and −8.4 dB, respectively.

In this work, we propose a liquid crystal (LC)-based double-dipole phase shifter. By manipulating the electric field, we change the resonant frequency and phase of the electromagnetic wave by deflecting the orientation of LC molecules. We made the LC-based device with a 30 × 30 array of two parallel unequal dipoles on a Quartz substrate. The substrate has an area and thickness of 4 × 4 cm 2 and 480 µm, respectively. The experimental results show that the phase shift of 0 • -385.4 • is achieved at 94 GHz by changing the applied bias voltage on the LC layer from 0 V to 8.4 V. The phase shift is greater than 360 • in the range 91.75-94.85 GHz. When the LC molecules are most significantly affected by the electric field, the maximum precision of phase shift is 4.08 • with a bias voltage of 2 mV.

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