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Abstract
A fourth-order dual-band microstrip band-stop filter is proposed in this paper. Folded stepped impedance resonators are implemented as well as capacitive gap and inductive grounded via, thus the dual-band performance can be obtained in merely one resonator. Besides its compact size, simplicity, and good spurious band suppression, the filter also features its excellent mid-band rejection and skirt characteristic which is achieved by four reflection zeros adjacent to the dual resonating frequencies. Controllable response of filter is realized by tuning of gap capacity and via inductance, and the theory is verified by both simulation and experimental results that agree well with each other.
Acknowledgments
This work was supported in part by NSFC (No. 60901022), in part by RFDP (No. 20090185120005), and in part by the Fundamental Research Funds for the Central Universities (No. ZYGX2010J021).