Miniature bandpass filters with stepped‐impedance resonators

Abstract

Abstract 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