Design of tri‐band microstrip BPF using SLR and quarter‐wavelength SIR

A tri-band microstrip bandpass filter (BPF) with compact size and high selectivity is presented by using the stub-loaded resonator (SLR) and quarter-wavelength stepped-impedance resonator (SIR). The quarter-wavelength SIR is designed for the first and third passband and the SLR mainly controls second passband performance, so three passband frequencies can be flexibly tuned. Because of the intrinsic characteristics of the resonators and source-load coupling, multiple transmission zeros can be created to improve the selectivity. Finally, a tri-band BPF prototype located at 0.98 GHz (FRID application), 3.6 GHz (Wimax application), and 5.8 GHz (WLAN application) is designed. Measurement results agree well with the full-wave EM simulated results. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:212–215, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27247

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