A novel microstrip dual-band bandpass filter (BPF) by coupling a stub-loaded hairpin resonator and two stub-loaded uniform impedance resonators (UIRs) is proposed. First, a open-ended stub is tap-connected to a meandering UIR at its centre, and these two stub-loaded meandering UIRs are further placed at symmetrical locations with respect to a stub-loaded hairpin resonator. Secondly, by introducing two parallel coupled lines at the two sides of the stub-loaded hairpin resonator, a dual-band BPF with two passbands at 2.4 GHz and 5.2 GHz is constructed. Finally, a prototype filter is designed and fabricated, and its measured results are provided to verify the predicted dual-band filter design.
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