Research Of Fully Electronically Controlled Terahertz Phase Shifter Based On Liquid Crystal

Terahertz(THz) science and technology has been recognized as the foundation of the next generation of IT technology.It has attracted the attention of scientists from all over the world.In recent years,many companies have developed many related commercial products.THZ technology continuous to develop rapidly.It is currently gradually transitioning from a basic science to practical engineering in areas like communication,industrial production,medical testing,environmental monitoring,and safety inspection.The antennas are likely the most important component in THZ communication,detection,and imaging systems.There exists currently no practical THz phased array antenna for the 0.1-1 THz band.An important factor for the development of THz phased array antennas is their potential high-performance,easy implementation,and availability of low-cost THz phase shifters.The main content of this paper is as follows:The design principle of a microstrip half-wave dipole patch was analyzed using a transmission-line model.According to Babigne’s principle,the design method for a slot resonant unit cell based on liquid crystal(LC)was proposed.The numerical calculations and experiments verified the tunable electromagnetic characteristics of the metal-dielectric-metal(MDM)structure based on the slot unit cell and LC.According to the radiation principle of the slot unit cell,an LC-based slot phase shifter,which operates at 128 GHz,is designed.The experimental results show that the phase shifter generated a phase shift greater than 290° for the frequency range 124-128 GHz.The maximum phase shift(296°)occurred at 124.5 GHz.Based on the resonant structure of the phase shifter,a fully electronic phase shifter,based on a LC and comb electrodes,is designed.The ground plane of a traditional LC device is replaced with a combed electrode to form the lateral electric field.Both aligning of the direction in the initial state and the recovery of LC molecules are controlled by the external electric field.This avoids the free relaxation time of the LC molecules.The experimental results show that,by adjusting the voltage of the voltage-variable electrodes,the completely electronically-controlled phase shifter produced a maximum phase shift of 189.2° at 114.9GHz.In order to explore the characteristics of the LC-based slot unit cell in THz band,an LC-based THz phase shifter,operating at 387 GHz,was proposed.The tolerance of the proposed phase shifter is analyzed by exploring the sensitivity of the resonant frequency with respect to the size of the resonant unit cell.The experimental results show that the proposed phase shifter generated a phase shift greater than 180° in the frequency range379.5-398.5 GHz.The maximum phase shift(242.1°)occurred at 390.6 GHz.Then,the metallic ground plane is replaced with comb electrodes with different grating constants.To improve the simulation accuracy,the phase shifter was accurately modeled by analyzing the electrostatic field distribution inside the LC layer.Finally,the effect of the comb electrodes with different grating constants on the tuning ability of the LC devices was discussed.