Enhanced Performance of Continuously Variable Phase Shifters Using Liquid Crystals in Corrugated Oversized Substrate Integrated Waveguides

This work presents a continuously variable SIW phase shifter based on liquid-crystal technology with a maximized figure of merit and adequate biasing. The proposed design operates efficiently within the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$30-40 \text{GHz}$</tex> range, using corrugated SIW with intrinsic DC blocking to enable electric polarization of the liquid crystal mixture. The oversized version of CSIW is used to increase the propagation constant and reduce the loss, allowing a higher figure of merit and compact size. The phase shifter was successfully fabricated and characterized with performance metrics compared to existing solutions. The phase shifter can be continuously tuned up to 300 degrees, with an insertion loss ranging from 2.5 to 4.5 dB. The results demonstrate a competitive figure of merit of 120 to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$67^{\circ} / \text{dB}$</tex>, showcasing the potential of this approach for next-generation millimeter-wave applications.