Novel compact parallel-coupled microstrip bandpass filters with lumped-element K-inverters |
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Authors: | Yo-Shen Lin Chi-Hsueh Wang Chao-Huang Wu Chun Hsiung Chen |
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Affiliation: | Dept. of Electr. Eng., Nat. Taiwan Univ., Taipei, Taiwan; |
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Abstract: | Novel compact parallel-coupled microstrip bandpass filters are proposed by using additional lumped inductors to realize K-inverters between coupled-line sections to achieve an equivalent to the quarter-wavelength (/spl lambda//4) resonator filters. As a result, the filter order can be doubled without increasing the circuit area, and no repeated passband is observed at twice the center frequency. In addition, by introducing the cross-coupling effect, two transmission zeros at upper and lower stopbands may be created. Simple equivalent-circuit models are also established as effective design tools. Specifically, several compact fourth-order microstrip bandpass filters with good stopband rejection are implemented and carefully examined. |
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