Benchmarking Frequency-Time Domain Performance of Tall-Electrode Coplanar Waveguide Phase Shifters in Liquid Crystals up to 40 GHz for 5G Subsystem

Tall-electrode coplanar waveguide (CPW) structures have garnered limited attention in microwave and millimeter-wave applications due to their inherent manufacturing challenges - such as the requirement for heavy copper cladding - and their deviation from conventional planar integration paradigms, which favor ultra-thin metallization. However, in the context of liquid crystal (LC)-based symmetric CPW phase shifters, tall electrodes offer a critical advantage: enhanced phase tuning range per unit length. This improvement arises from the increased height of the LC-filled coplanar gaps between electrodes, which amplifies the volumetric influence of the tunable LC dielectric anisotropy. Moreover, taller electrodes mitigate fringing field effects, further optimizing device performance. Despite these benefits, tall-electrode CPW phase shifters face significant challenges when integrated into packaged systems, particularly due to geometric discontinuities at connector interfaces. These discontinuities introduce impedance mismatches, leading to elevated return loss, radiation loss, and potential degradation of the phase tuning enhancement. To systematically evaluate this trade-off and identify key design vulnerabilities, this study presents a comprehensive numerical analysis of an LC-based tall-electrode CPW phase shifter operating up to 40 GHz. The investigation employs two distinct full-wave electromagnetic simulation methodologies - a time-domain solver and a frequency-domain solver - to cross-validate the results and ensure robustness. This dual-solver approach not only enhances the reliability of the findings but also provides insights into solver-specific artifacts and computational efficiencies. The study benchmarks both frequency-domain and time-domain performance metrics, including insertion loss, return loss, and phase tuning efficiency, offering a holistic assessment of tall-electrode CPW phase shifters for high-frequency applications.