A High Q-Factor Hybrid Resonator Integrated Bandpass Filter with Shielding Case

This paper presents a second-order bandpass filter using novel hybrid resonator which composed of a mi- crostrip line and a short-circuit coaxial line, has greatly utilization of space in the shielding box of RF module and easy inte- gration with other microstrip planar printed circuits. Additionally, the unloaded quality factor of the proposed resonator Q = 455, shows a high value in comparison to the conventional microstrip resonator. Furthermore, by employing source-load cou- pling and mixed electromagnetic coupling scheme, two adjustable transmission zeros separate on each side of passband are generated to enhance the selectivity and the out-of-band rejection simultaneously. The measured results are in good agreement with theories and simulations.