Progress In Electromagnetics Research C
ISSN: 1937-8718
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By K. Deng, J. Z. Chen, B. Wu, T. Su, and C.-H. Liang

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In this paper, a miniaturized wideband bandpass filter utilizing a square ring resonator and loaded open-stubs is proposed. One pair of bent open-stubs characterized as perturbations is installed outside the diagonal corners of the ring, and another pair of loaded open-stubs is added inside the ring resonator. By stretching the perturbation stubs more than half-wavelength of the ring, three pairs of degenerated modes in a ring are split for wideband operation. The first two split modes form the dominant passband. Meanwhile, the loading effect introduced by the loaded open-stubs could move the third split mode into the dominant passband, at the same time, an additional transmission zero is generated by the loaded open-stub, which improves the skirt selectivity. Due to the applying of the perturbation stubs as long as more than half-wavelength, this kind of wideband microstrip ring resonator filter occupies a smaller size than those conventional ones that based on ring resonator. To verify the mechanism above, a wideband bandpass filter centered at 3.5 GHz is designed, implemented, and fabricated. Measured results of experimental circuit show good agreement with simulated responses.

K. Deng, J. Z. Chen, B. Wu, T. Su, and C.-H. Liang, "Miniaturized Wideband Bandpass Filter Utilizing Square Ring Resonator and Loaded Open-Stub," Progress In Electromagnetics Research C, Vol. 39, 179-192, 2013.

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