Dielectric filter, dielectric duplexer, and communication apparatus

A dielectric filter comprising:

• a dielectric block;
• a plurality of inner-conductor holes each having an inner-conductor disposed on an inner surface thereof provided in the dielectric block;
• an external conductor disposed on the outer surface of the dielectric block;
• and
• input-output electrodes disposed on the outer surface of the dielectric block and capacitance-coupled to respective inner-conductors;
• wherein each of the inner-conductors has an open end at at least one opening surface of the corresponding inner-conductor hole or in the vicinity of the opening surface;
• each of the inner-conductor holes opposed to the input-output electrodes has a stepped portion to define a first inner-conductor hole portion and a second inner-conductor hole portion divided thereby;
• and
• the first inner-conductor hole portion has the open end and is located closer to the input-output electrode than the second inner-conductor hole portion;
• the respective first inner-conductor hole portions of the inner-conductor holes opposed to the input-output electrodes having first corresponding longitudinal axes which define a first longitudinal plane, each of said first corresponding longitudinal axes being parallel to said first longitudinal plane;
• the respective second inner-conductor hole portions of the inner-conductor holes opposed to the input-output electrodes having second corresponding longitudinal axes which define a second longitudinal plane, each of said second corresponding longitudinal axes being parallel to said second longitudinal plane;
• said first and second planes being spaced apart along a thickness direction of the dielectric block so that said axes of said first and second inner-conductor hole portions are in different respective longitudinal planes.