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ABSTRACT In this letter, a new coupling configuration of the stepped-impedance resonator (SIR) has been presented to design dual-passband filters with the small circuit size. We design the filter with higher selectivity based on SIR direct-coupling, input, and output external quality factors. Through resonance characteristics of a SIR, the second resonant frequency can be tuned by adjusting structure parameters. The agreement between measured results and full-wave simulation prediction validates the feasible configuration of the proposed filters. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2514-2517, 2013 [ABSTRACT FROM AUTHOR]

In this article, a new configuration of higher selectivity bandpass filter using miniature open-loop stepped-impedance resonator (SIR) is designed and fabricated. The central frequency of the filter is 2.45 GHz and the bandwidth is 8%. Using miniature open-loop SIR resonator, we design filter based on cross-coupling and input and output external quality factor. A single transmission zero is realized by the cross-coupling in the structures, which can improve the skirt selectivity of the filter. The circuit size of a miniature open-loop SIR bandpass filter reduces to 50% of the square open-loop resonator bandpass filter. The results of measurements are in good agreement with the full-wave simulation results. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1167-1170, 2012 [ABSTRACT FROM AUTHOR]