Dielectric filter having interstage coupling using adjacent electrodes

Claim 1

A dielectric filter comprising: at least two dielectric resonators, each dielectric resonator including: a dielectric base body including first, second, third and fourth side surfaces and first and second end surfaces, wherein a through hole is provided to extend from the first end surface to the second end surface, along a central axis of the dielectric base body, to define an inner surface thereof; an outer conductor located on the first, second, third and fourth side surfaces, wherein the outer conductor covers the entire first and second side surfaces and covers a portion of the third and fourth side surfaces, thereby leaving an uncovered portion of the third side surface that is adjacent to an uncovered portion of the fourth side surface, and wherein the uncovered portions of the third and fourth side surfaces are adjacent to the first end surface and respectively extend across a corresponding width of the third and fourth side surfaces; an inner conductor located on the inner surface of the dielectric base body; a connection conductor located on the second end surface of the dielectric base body, wherein the connection conductor connects the inner conductor to the outer conductor; an interstage coupling electrode located on the uncovered portion of the third side surface, wherein an area of the uncovered portion of the third side surface extends in three directions from the interstage coupling electrode and separates the interstage coupling electrode from the outer conductor and the second and fourth side surfaces; and an input/output coupling electrode located on the uncovered portion of the fourth Side surface, wherein an area of the uncovered portion of the fourth side surface extends in three directions from the input/output coupling electrode and separates the input/output coupling electrode from the outer conductor and the first and third side surfaces; wherein the dielectric resonators are connected with each other in such a manner that the outer conductor of a first one of the dielectric resonators is electrically connected to the outer conductor of a second one of the dielectric resonators.