Band-pass filter including resonance elements coupled by a coupling line and a by-pass coupling line

摘要

A band-pass filter which includes a plurality of dielectric coaxial resonators which are arranged in a parallel relation and extending axially in the same direction, and have respective coupling terminals inserted therein, and a dielectric substrate formed, on its first surface, with a plurality of coupling electrodes for connecting the respective coupling terminals. The coupling electrodes on the first surface of the dielectric substrate have an inductance element between them for connecting at least two coupling electrodes to each other. Confronting electrodes facing the coupling electrodes are formed on the other surface of the dielectric substrate to from a capacitance bypass circuit. The inductance element may be a printed circuit on the dielectric substrate or an air-core coil. The air-core coil may be located either adjacent the first surface of the substrate, or away from the substrate between the resonators.