Abstract
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 $30\times 30$ array of two parallel unequal dipoles is printed on a quartz substrate, with 4 cm $\times {4}$ cm area and $490~\mu \text{m}$ 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.
Highlights
Over the past few years, the ever increasing applications of terahertz (THz) wave in aerospace, bio-sensing, wireless telecommunications, imaging, biomedicine and other fields have attracted extensive attentions [1]–[4]
We have proposed a tunable THz phase shifter based on the nematic liquid crystals (NLCs)
A phase tuning mechanism is achieved by applying different bias voltages, regulating the effective permittivity of the liquid crystals (LCs) layer
Summary
Over the past few years, the ever increasing applications of terahertz (THz) wave in aerospace, bio-sensing, wireless telecommunications, imaging, biomedicine and other fields have attracted extensive attentions [1]–[4]. Several THz devices have been proposed such as modulators [6], filters [7], absorbers [8] and phase shifters [9]. A variety of controllable phase shifting technologies have been proposed, including MEMS [11], flexible film metamaterials [12], ferroelectric films [13] and liquid crystals (LCs) [14]. Among these technologies, LCs are widely concerned for their excellent permittivity and wide tuning range in the THz band [15]
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