A New Dielectric-Loaded Dual-Mode Cavity for Mobile Communications Filters

A new dielectric loaded cavity structure for dual-mode filters suitable for cellular-radio base stations is presented. The cavity exhibits high unloaded Q-factor, wide spurious-free operating window and possibility of tight coupling either to input or between the dual-mode resonances. Experimental results, on a four-pole filter with an asymmetric transmission zero, confirm the validity of the proposed resonator for realizing transmit filters for UMTS cellular-radio base stations.