Electrically Tunable Phase Shifter With Improved Phase-Shifting Capability Based on Liquid Crystal
Qipeng Wang, Zhiguo Su, Shunli Li, Yue Su, Hongxin Zhao, Xiaoxing Yin
Abstract
An electrically tunable phase shifter with improved phase-shifting capability per wavelength is proposed based on liquid crystal (LC). The proposed LC phase shifter is constructed by an inverted microstrip line with defected ground structures (IMSL-DGSs) and two novel transition structures. Different from the conventional LC phase shifter, the characteristic impedance of the IMSL-DGSs phase shift part is not restricted to 50 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> for fully exploiting its phase-shifting capability. The impedance mismatch from the feeding parts to the phase shift part is tackled by the transition structures. To verify the proposed LC phase shifter, a prototype is fabricated and measured. The measurement results demonstrate that a phase shift of 401°, high phase shift per wavelength of 365°/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> , and excellent figure-of-merit (FoM) of 67°/dB at 15 GHz are achieved. Besides, good impedance matching and low insertion loss are realized between 9 and 15 GHz.