Design of compact dual-band bandpass filter using dual-mode stepped-impedance stub resonators

A dual-band bandpass filter (BPF) using a novel stepped-impedance stub resonator (SISR) is presented. The proposed SISR is found to have the advantage that the even-mode resonant frequencies can be flexibly controlled, whereas the odd-mode resonant frequencies are fixed. Based on the proposed SISR, a dual-band filter is implemented by tuning its geometric parameters. To improve the selectivity, a filter with four transmission zeros on either side of both passbands is designed by introducing a 0 degrees feeding structure. A prototype of a dual-band BPF centred at 1.84 and 2.65 GHz has been designed and fabricated. The measured results validate the full-wave EM simulated results.