Dielectric filter, composite dielectric filter, duplexer, and communication apparatus

摘要

There is provided a dielectric filter comprising: a dielectric block (1); a plurality of resonance-line holes (2a; 2b; 2c) aligned therein; a resonance line (5a; 5b; 5c) disposed on an inner surface of each of the resonance-line holes (2a; 2b; 2c); and an outer conductor (3) disposed on an outer surface of the dielectric block (1); wherein one end of the resonance-line hole (2a; 2b; 2c) is a short-circuited end; a sectional area of at least one of the resonance-line holes (2a; 2b; 2c) is changed at a predetermined portion; the predetermined portion of at least one of the resonance-line holes (2a; 2b; 2c) is set to be different from that of the other of the resonance-line holes (2a; 2b; 2c) along to the axial direction of the resonance-line hole and at a side opposed to the adjacent resonance-line hole. According to the above structure, the coupling between specified resonance lines (5a; 5b; 5c) among the adjacent resonance lines can be independently determined without changing a pitch Po for aligning the resonance-line holes (2a; 2b; 2c).