A Highly Compact Sext-band Bandpass Filter with Simple Structure and Wide Bandwidth

A highly compact sext-band bandpass filter (BPF) is investigated in this paper, which adopts quad-section stepped impedance resonators (SIRs) along with a series of multiple open stubs. This quad-section SIRs are constructed by tri-section SIR loaded L-shaped resonator. To achieve compact size, the filter utilizes tri-section SIR and is embedded in the double L-shaped resonators. Aseries of multiple open stubs are introduced to improve fractional bandwidth and the return loss. A sext-band BPF centering at 1.12, 2,12, 2,78, 5,59, 6.59 and 8.97 GHz has been designed and fabricated. This highly compact sext-band with wide bandwidth and simple structure is constructed on Rogers 4350 with a dielectric constant of 3.66 and a height of 0.508mm. The overall size of the fabricated filter is 0.15λ g × 0.16λ g . Good agreements are observed between the simulated and measured results.