Novel filters based on hybrid structure of coaxial resonator and evanescent mode waveguide with loaded posts

A novel hybrid bandpass filter based on coaxial resonator and evanescent mode waveguide(EMW) with loaded posts is presented. The coaxial resonators are directly coupled to the EMW with posts through air windows. The fundamental TEM mode of the coaxial resonator and the evanescent mode of the EMW constructing the passband of the filter, while the staggered spurious modes of the coaxial rsonator and EMW are suppressed each other to improve the stopband. A four-order bandpass filter is designed fabricated and measured, with good selectivity and wide stopband.