A New Microstrip Directional Filter Configuration Composed by Hybrid-Mode Resonators

The design, fabrication and experimental test of a microstrip two-pole directional filter based on a new approach consisting of hybrid-mode resonators is presented in this paper. The use of hybrid even-mode and odd-mode resonators allows the structure to be composed by two stages having bandstop filter behavior, and following a symmetrical configuration, which in turn makes it easier to design and adjust while keeping low dimensions. The proposed filter is designed to operate over the uplink channel of the 1.8 GHz band used for mobile communications with a 4 % bandwidth.