Compact dual-band bandpass filter using coupled three-line microstrip structure with open stubs

Abstract—This paper presents a novel dual-band bandpass filter (DBBPF). Three open-stubs have been attached to a symmetrical coupled three-line microstrip structure. By implementing Richards’ transform and Kuroda's identities, a compact DBBPF is obtained from a third-order prototype bandpass filter (BPF). A wideband DBBPF with central frequencies of 1.57-GHz (GPS) and 5.25-GHz (ISM) is designed and fabricated. The measured results agree well with the simulations.