Compact dual‐band bandpass filter based on stepped impedance resonators and T‐shaped line

A compact dual-band bandpass filter (BPF) realized with stepped impedance resonators (SIR) and T-shaped line is proposed in this article. By appropriately selecting the impedance ratio of the SIR, a passband around at 5.4 GHz can be achieved by the second harmonic frequency of the SIR. In addition, a T-shaped line is used to replace the quarter-wavelength line between the two SIRs, and another passband at 2.45 GHz is realized between the transmission zeros created by the central open stub of the T-shaped line and the fundamental frequency of the SIR. Moreover, the transmission zeros created by the central open stub and SIR could also be used to improve the skirt selectivity of the proposed BPF. Good agreement can be observed between the measured and simulated results, demonstrating the validity of the design strategies. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2721–2724, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25599