A new class of pseudo-elliptic waveguide filters using resonant posts

In this paper a new class of very simple waveguide filters composed of solely cylindrical posts having the same diameter is presented. In such filters a resonator composed of two cylindrical metal posts placed in antipodal position is used to create band-pass filtering functions having transmission zeros. In particular the first two resonant modes have been exploited: the mode resonating at the higher frequency is used to obtain the pass-band, while that resonating at lower frequency is used as a nonresonating mode and exploited to obtain transmission zeros. The design of multiple cavity filters is presented along with the experimental results of a 4^th order filter having 2 transmission zeros.