Employing Open/Short Via-Hole to Control the Coupling Coefficient for LTCC Bandpass Filters

In this letter, the multilayered bandpass filter (BPF) is synthesized with the assistance of via-holes. By controlling the coupling coefficient with open or short via-hole, the transmission zero can be shifted to lower or higher passband skirt. Theoretical analysis and design procedures are provided. The prototypical low-temperature co-fired ceramic BPFs are fabricated and measured as well. In addition, comparisons of simulated results and experimental data are shown. Good match validates the proposed filter.