Dual-wideband bandpass filter based on a dual-stubs loaded half-wavelength resonator

A compact dual-wideband bandpass filter (BPF) is proposed by using dual-stubs loaded λ/2 resonator (DSLR). The resonance of the DSLR is investigated by using the even-/odd-mode analysis method. As the length of the stubs increases, the second and third resonant frequencies are coalesced. So when the DSLR is employed to design a dual-band BPF, the first three resonant frequencies are used to build up the first passband, and the fourth and fifth resonant frequencies will form the second passband. Meanwhile, the two passbands can be adjusted by tuning the parameters of the DSLR. To verify the design concept, one dual-wideband BPF has been designed, fabricated, and measured. Good agreement is observed between measured and simulated results.