Miniaturized dual‐band bandpass filter based on stepped impedance resonators

Abstract

ABSTRACTIn this article, we developed a dual‐band band‐pass filter (DB‐BPF) based on stepped impedance resonators (SIRs) using coupled feeding lines input and output ports. The developed filter allows the adjustment of the frequency and the bandwidth of the upper band (3.8 GHz) and the lower band (2.4 GHz). The transmission coefficients of the DB‐BPF are improved by maximizing the coupling between the SIRs. Furthermore, the capability of the rejection band is increased and the insertion losses between the two pass‐bands are reduced. The experimental results for the insertion loss (S21) and the return loss (S11) of the lower band (2.4 GHz) were1.0 and 2.0 dB, respectively while the insertion loss and return loss for the upper band (3.8 GHz) were 23 and 25 dB, respectively. The 3 dB fractional bandwidths obtained for both bands were about 200 MHz and four transmission zeros around the passband edges were created to improve the selectivity of the DB‐BPF. The overall size of the DB‐BPF was also reduced significantly. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:1116–1119, 2017