Characteristic adjusting method for dielectric filter using a grinding

Abstract

A method of adjusting characteristics of a dielectric filter having integral electromagnetic shielding, the dielectric filter comprises a dielectric body having an outer surface including first and second end surfaces and side surfaces extending between the first and second end surfaces; an external conductor disposed on the outer surface of the dielectric body and providing integral electromagnetic shielding of the dielectric filter; at least one hole extending through the dielectric body between the first and second end surfaces; a respective pair of internal conductors provided in the at least one hole and conductively connected to the external conductor at respective ends of the hole, a respective non-conductive portion in the hole being spaced from both ends and thereby separating the pair of internal conductors and defining a respective capacitance between the pair of internal conductors; and signal input and output electrodes provided on the outer surface of the dielectric body and electrically isolated from the external conductor. According to the method, a portion of the dielectric material is removed, for example by grinding, to form the respective non-conductive portion in the hole. The hole may have a changing diameter along its length, due to a hollow formed in one end surface, the non-conductive portion being adjacent to the hollow; or due to a narrowed throttle portion formed at or near the end surface, the non-conductive portion being formed on the throttle portion. Alternatively, the hole may have a substantially constant cross-section, and the non-conductive portion may be substantially flush with the inner surface of the hole. The dielectric body may be regular in shape or may have a side surface with portions spaced from the resonator hole by different respective distances.