A novel dual-band step-impedance filter with tunable transmission zeros

A novel dual-band step-impedance bandpass filter for multimode wireless LANs is presented, which has a dual-band feature of two passbands at desired frequencies and high out-of-band suppression generated by tunable transmission zeros which are given by incorporating step-impedance resonators with special input/output (I/O) ports. The location of transmission zeros can be chosen at any desired frequencies.