Tunable Liquid Crystal Based Phase Shifter With A Slot Unit Cell For Reconfigurable Reflectarrays

Terahertz research and application are rapidly development over the pase 20 years,especially in the are of communication,undamaged test and imaging.The electronically scanned reconfigurable reflectarray antenna with the properties of high gain,fast modulation,beamscanning and beam synthesis has been widely researched.The dielectric of Liquid crystal(LC)controled by the voltage is suitable for the design of reconfigurable reflectarray antenna in THz frequency.The paper concentrate on the LC-based reflectarray anteena in Terahertz and a series of optimized and improved designs.In this paper,the RLC equivalent module and parameter extract process in high loss are presented to analysis the parameter of LC-based reflectarray unit-cell in THz band.The influence of metal loss and dielectric loss in the unit-cell are investigated and the reflection phase will rapidly vary in a narrow band with the loss exceeds.The simulation and measurement result indicate that the high-loss lead to phase varied phenomenon and full absorption.The slot-structure specificed used for LC-base phase shifter is proposed for solving the insufficient coverage of resonance laye.The less coverage will lead to inhomogenuiouse distribution of LC molecule,edge effect and the increase of saturated voltage.A single slot LC-based phase shifter unit-cell is designed.Experiment result identified that the single slot unit-cell has the abiliy of reflection phase lineable varied 300°and saturated voltage less than 10 V in 100 ? 130 GHz.A trislot structure LC-based phase shifter is designed to extend working band and phase shift.Simulation result identified with the dielectric of LC varied in the range of 2.47-3.26 the phase shift is greater than 360°with 375-387 GHz working band.Gate electrode is integrated onto the LC-based phase shifter to provide horizontal static electric field to full-electronic control liquid crystal.For a single slot structure,the proposed element provides a phase range greater than 180° in the freuquency band from 111.2 to 117.8 GHz.Low loss phase shifter is achived by using impedance matching?It operates from 376 to 401 GHz with S11 >-4dB.A controllable phase shift of 200°over all working frequency is realized.The three-slot LC-based antenna has been simulated to provide beam scanning capabilities over a wide angular range,a large bandwidth and reduced Side-Lobe-Level.Simulated radiation patterns show that the antenna generates an electronically steerable beam in one plane over an angular ange of 30 in the frequency of 380 GHz.The Side Lobes Level is lower than 10 dB for all the scan angles.