Design of Triple-band Bandpass Filter Using Trn-section Stepped-Impedance Resonators

On the basis of tri-section stepped-impedance resonator (SIR), a novel triple-band bandpass filter (BPF) is presented, which has a triple-band feature of three passbands at desired frequencies and high out-of-band suppression. The new coupling scheme at the input and output can improve the performance of the BPF, and the hairpin structure helps to reduce the size. A microstrip filter was designed and simulated, proving the concept in an excellent way. The prototype of the BPF achieved insertion loss of 2.2, 1.8 and 1.7 dB at 1.0, 2.4, 3.6 GHz, respectively.