| 摘要 |
A dielectric filter which corrects the mismatch of the resonance frequencies of resonators formed by internal conductors between a balanced terminal side and an unbalanced terminal side of the filter, and which is capable of easily obtaining a predetermined external coupling capacitance. Also, a dielectric duplexer, and a communication apparatus having the filter are obtained. Inside a dielectric block, a plurality of internal-conductor holes have different cross-sectional sizes, in which both ends thereof are open and internal conductors are formed on the inner surfaces. Also, the outer surface of the dielectric block is formed with an external conductor over four surfaces, but not on the opening surfaces of both ends of the internal-conductor holes. A pair of balanced terminals are coupled to the ends of one of the internal conductors, and an unbalanced terminal is coupled to one of the end portions of another internal conductor. An external-conductor-removed section may also be formed in a portion in the vicinity of the end portion of the other internal conductor. In this manner, the dielectric filter is formed.
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