New Triple-Resonance Configurations Using Stubbed Waveguide Dual-Mode Cavities

This paper presents new configurations of stubbed waveguide cavities for the realization of pseudo-elliptic and self-equalized filters. The basic structure consists of a main TE102/TE201 dual-mode cavity which is loaded with a pair of waveguide stubs. The two-stub arrangement can be seen as a TM110 mode cavity which is embedded into the main dual-mode cavity. By properly setting the polarization of the stubs with respect to the main cavity, as well as finely adjusting the difference between the lengths of the stubs, triple-resonance structures with selected topologies and controllable coupling mechanisms can be implemented. The resulting 3rd order filtering functions comprise 3 poles and 2 zeros, the latter being either group delay equalization zeros or finite frequency transmission zeros depending on the polarization of the stubs. The experimental results of a 5th order filter with 2 finite frequency transmission zeros validate the new configuration.