A novel dual-band bandpass filter using stub-loaded resonators

A novel compact dual-band bandpass filter using novel stub-loaded resonators(SLRs) is proposed in this paper. The proposed dual-band bandpass filter comprises two folded mirror-symmetry SLRs, the open stub loaded inside the open loop in the paper is bifid and folded to increase the length of the stub- loaded line for increase the tuning range of even-mode frequency without a size increase. Two paths of coupling for the two resonators exist, by introducing zero-degree feed line structure and spur-line, A filter with six transmission zeros is designed, greatly improve the selectivity.