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Abstract
A novel dual-mode dual-band bandpass filter design is introduced by virtue of modified ring resonator. According to qualitative analyses on the field distributions of a conventional ring resonator, T-junctions are utilized instead of ring transmission lines to control the frequency ratio of passbands. Meanwhile, each individual passband is formed using a pair of degenerate modes of the same order resonance. Stepped-impedance perturbations are adopted to split the degenerate modes and control the bandwidths. A design example is given to validate the design approach. The measured results agree well with the performances predicted by analyses.
Acknowledgment
This work was supported by the National Natural Science Foundation of China under National Outstanding Young Scientist Award No. 60788402, Grant No. 60976067, and Grant for Youths No. 61006031/F040204, and Fundamental Research Funds for the Central Universities (Wuhan University) under No. 3101033.