Comparative Analysis of Liquid-Crystal Driving between the Grounded-Coplanar Waveguide and the Floating-Electrode-Free Coplanar Waveguide in Liquid-Crystal Phase Shifters

We studied the effectiveness of the conductor-backed design on implementing the liquid-crystal phase shifter (LCPS) over the floating-electrode-free (FE-free) design at 28 GHz. We compared and analyzed the LC driving characteristics under the same cell gap thickness (= 50 μm), characteristic impedance (= 50 Ω), and the physical length. This work can be thought of as a comparison between the in-plane-switching mode and quasi-electronically controlled birefringence mode of the liquid-crystal display. We verified that the conductor-backed design is adequate for designing the LCPS in terms of the driving voltage, response time, and tuning range. These analyzed results will help design more efficient passive phase shifter using LCs.1