PIER Letters
Progress In Electromagnetics Research Letters
ISSN: 1937-6480
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By K. C. Lee, H. T. Su, and M. K. Haldar

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Step-by-step procedures for designing a third order bandpass filter and a sixth order bandpass filter using a triple-mode resonator are described in this paper. The triple-mode resonator is a square open-loop resonator with an open circuited stepped-impedance stub and a grounding via located at the symmetrical plane of the resonator. The equations for approximating the resonant frequencies of the resonator are obtained from odd- and even-mode analysis. To design a filter, first, the theoretical resonant frequencies for the filter are calculated. Then the basic dimensions of the resonator are approximated using the equations. The filter layouts are fine-tuned by simulation and verified by experiment to conclude the paper. The first spurious response occurs at about 3 times the center frequency of the first passband in both filters. The simulated and measured results are in good agreement.

K. C. Lee, H. T. Su, and M. K. Haldar, "Compact Microstrip Bandpass Filters Using Triple-Mode Resonator," Progress In Electromagnetics Research Letters, Vol. 35, 89-98, 2012.

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