JPS6460005A - Branching filter - Google Patents

Abstract

PURPOSE:To make the titled branching filter smaller, to lower the costs of it, and to prevent the decrease of a Q due to a copper loss by including the capacity of a branching filter circuit into the input capacity of a dielectric filter. CONSTITUTION:A filter N125 for transmission and a filter N226 for receiving mounted on a substrate 20 are composed of a homogeneous dielectric of a single body, connected with plural dielectric resonators 27 and 34 consisting of a cylindrical central conductor built in the dielectrics at a prescribed interval and the central conductors of the respective dielectric resonators 27 and 34, provide capacity elements 28 and 35 for coupling, and provide input/output capacity elements 31, 32, 37 and 38 between the dielectric resonators 27 and 34 on both sides and input/output terminals. Further, the capacity of the branching filter circuit is included in the input capacity of the dielectric filters 25 and 26. Thus, the multiplexer is made smaller, its costs are lowered, and the decrease of the Q is prevented.