Compact dual-band bandpass filter (BPF) with wide and narrow bands simultaneously is presented. By using the stepped impedance resonators (SIRs) in multilayered structure, the dual-band responses with wide and narrow bands simultaneously can be obtained. The filter has 3-dB fractional bandwidths (FBWs) of 45% and 10% for 2.4 GHz and 5.2 GHz, respectively. The circuit size is compact due to the multilayered structure. Moreover, multi-path propagation inside the multilayered structure generates transmission zeros at each skirt of the passbands for improving the passband selectivity. Measured results of the filter are in good agreement with the full-wave electromagnetic (EM) simulation.
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