2.44/5.25 GHz dual-band pass filter using l/4 stepped-impedance resonators for WLAN applications

A novel dual-band pass filter (DBPF) is accomplished using 1/4 stepped impedance resonators (SIRs) with low insertion loss, covering the frequency range of both 2.40~2.48 GHz and 5.15~5.35 GHz, which are the operating frequencies of IEEE 802.11 a/ g, respectively. Additionally, a new frequency transformation is applied to evolve the general design formulas of DBPF. The derived DBPF topology is then simplified with the aid of J-inverters, in which only J inverters and paralleled LC resonators corresponding to the 1/4 SIRs are involved. Finally, the filter is fabricated easily using distributed elements and the measurement is in a good agreement with the simulation.