Dielectric filter having coupling windows between resonators, and transceiver using the dielectric filter

Abstract

A dielectric filter in which both the resonant frequency of each resonator and the degree of coupling between resonators can be adjusted independently. The dielectric filter includes at least first and second dielectric blocks, each having a through bore extending between first and second end faces thereof and a plurality of side surfaces extending between those end faces. Substantially all of the faces of the dielectric blocks, including the bore, are covered with a conductive film to define a first dielectric resonator whose electric energy component varies in the direction of an axis of the through bore. A first coupling electrode is formed, isolated from the conductive film, on at least one and preferably bridging between two of the side surfaces of the first dielectric block for coupling an input signal applied thereto to the first dielectric resonator. A second coupling electrode is formed, isolated from the conductive film, on a second one of the side surfaces of the first dielectric block in a location wherein the electric energy component in the first dielectric block is at a relatively high level so that electric energy in the first dielectric block exits the first dielectric block via the second coupling electrode. The second dielectric block has a first side surface which abuts the second side surface of the first dielectric block. A third coupling electrode is formed on the first side surface of the second dielectric block at a location corresponding to the second coupling electrode such that electric energy leaving the first dielectric block via the second coupling electrode enters the second dielectric block via the third coupling electrode and sets up an electromagnetic field in the second dielectric block whose electric energy component varies in the direction of the through bore of the second dielectric block. A fourth coupling electrode is formed on at least one and preferably bridging between two of the surfaces of the second dielectric block at a location where the resonant electric energy component in the second dielectric block is relatively high such that electric energy in the second dielectric block leaves the dielectric block via the fourth coupling electrode.