Tackling Differential Phase Shift Peaking and Degradation of Liquid Crystal Integrated Delay Line Phase Shifters with Barrel Plated Shut Micro-vias Across 1 GHz to 67 GHz

Liquid crystal (LC)-loaded reconfigurable passive wideband transmission line components (e.g., phase shifters) have found a home in feeding laboratory-grade phased array beam steering research that is not stringently requiring the system footprint and tuning speed. To widen their commercial application landscape, using vias for multi-layer components’ integration into the system in low loss and reduced footprint is highly desirable. However, in wave-guiding circuits operating at millimeter-wave to optical frequencies, vias introduce a significant source of non-uniformity in liquid crystal-based devices. This study identifies a newly observed perturbation in the differential phase shift (DPS), adding to the previously reported surge in insertion loss caused by via-related effects. Two designs of LC-based phase shifters of an identical inverted microstrip-typed LC-accommodating structure but with diverse heights of barrel-plated filled vias (0.787 mm vs. 0.127 mm) are numerically compared across 1 GHz to 67 GHz. With the same LC-tunable length, the reduction of vias’ height not only yields a compact solution but also enhances the DPS by 30% (featuring suppressed peaking and enhanced linearity), reduces the return loss by 11%, and mitigates the radiation loss by 24%. These findings highlight the critical need for advanced design and optimization strategies to mitigate the adverse electromagnetic impacts of micro vias, thereby preserving the performance and reliability of LC-based phase-modulating components for bandwidth-intensive 5G-and-beyond networks.