Patent ID: 6023207
Filing Date: 2000-02-08
Classification: H01P

Abstract:
A dielectric filter comprising:a dielectric ceramic block having an outer conductive layer formed on an outer peripheral surface;three or more dielectric coaxial resonators provided in parallel to each other on a dielectric ceramic block, each said resonator including (a) a through hole provided to be extended from one end surface to the other end surface opposite to said one end surface of the dielectric ceramic block and (b) an inner conductive layer provided on an inner surface of the through hole for forming a resonance conductor, each of said resonance conductors having one end connected to the outer conductive layer to form a short-circuit end and the other end separated from said outer conductive layer to form an open-circuit end;electromagnetic field coupling input/output terminals provided on said dielectric ceramic block, with which outermost resonators of said dielectric coaxial resonators are electromagnetically coupled; andat least one counterbore provided on the open-circuit end of the resonance conductor of at least one dielectric coaxial resonator other than the outermost dielectric coaxial resonators electromagnetically coupled with said input/output terminals for extending the resonant length of that dielectric coaxial resonator, each said counterbore including (a) a conductive layer on an inner wall thereof which is connected to the associated resonance conductor, and (b) having a diameter larger than that of the resonance conductor of each of the dielectric coaxial resonators.