Dual-Frequency Combline Resonators for Four-Port Bandpass Filters

This paper presents a new dual-frequency coaxial cavity resonator and its potential in the implementation of a new class of four port filters that provide cost and volume efficient solutions for emerging multiband base transceiver stations (BTS). The proposed concept delivers in a single physical structure two virtually independent bandpass filters without significant sacrifices in design or manufacturing complexity as well as performance. This is achieved by introducing within a single cavity two coaxial stubs for two independent frequency bands. Experimental results on a fabricated prototype demonstrate the validity of the concept and the potential of its implementation.