A compact quad‐band band‐pass filter using novel stub‐loaded SIR structure

A compact quad-band band-pass filter (BPF) based on a novel stub-loaded step-impedance resonator (SL-SIR) is analyzed and designed in this article. The proposed SL-SIR, which is found to have the advantages of introducing four narrow passbands and providing more degrees of freedom to adjust the resonant frequencies, is investigated by using even/odd mode analysis. A prototype of a quad-band BPF centerd at 1.5, 2.5, 3.5, and 5.2 GHz is designed and fabricated. The simulated and measured results are in good agreement with each other. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:538–542, 2014