Abstract: A band rejection filter includes at least of two dielectric resonators and an inductor. Each dielectric resonator is composed of a dielectric base formed as a rectangular prism and having a penetrating hole in a central portion, an inner conductive layer arranged on an inner side surface of the dielectric base, an outer conductive layer arranged on an outer side surface of the dielectric base, a connecting conductive layer arranged on one end surface of the dielectric base to connect the outer conductive layer and the inner conductive layer, an outer conductor layer cut-out groove formed on the outer side surface of the dielectric base, and an independent coupling electrode surrounded by the outer conductor layer cut-out groove on the dielectric base. The inductor connects the independent coupling electrode of the dielectric resonators, and the outer conductive layers of the dielectric resonators are connected with each other.

Abstract: A dielectric filter comprises a pair of dielectric resonators 11 and 12, which have outer conductors 11c and 12c formed with cutouts 11k and 12k, respectively. Interstage coupling electrodes 11f and 12f are provided within the region of these cutouts 11k and 12k, so that the electrodes 11f and 12f do not contact with the conductors, such as outer conductors 11c, 12c and the inner conductors 11d, 12d. The dielectric resonators are connected in such a manner that these electrodes 11f and 12f are brought into contact with each other. Furthermore, input/output coupling electrodes 11g and 12g are provided within the region of the cutouts 11k and 12k. Then, by connecting the electrodes 11f and 12f, it becomes possible to provide a dielectric filter which is compact in size and capable of reducing the number of parts and, therefore, cheap in cost.

Abstract: A filter device for a transmitter-receiver antenna includes a transmission side filter having resonators and a reception side filter having resonators. Each of the transmission side resonators has a first characteristic impedance ratio other than one. On the other hand, each of the reception side resonators has a second characteristic impedance ratio being set to a value which prevents spurious resonance of the reception side filter at an integral multiple of a fundamental resonance frequency of the transmission side filter, so as to avoid the situation where spurious components increase at the above-noted integral multiple in a frequency characteristic of the transmission side filter being affected by a frequency characteristic of the reception side filter.

Abstract: A dielectric filter including a plurality of coaxial type dielectric resonators having outer conductors and inner conductors is arranged so that the outer conductors are connected to each other. Also included in the dielectric filter are central conductors arranged to be brought into contact with the inner conductors of said plurality of coaxial type dielectric resonators and a dielectric substrate having thereon a plurality of substrate conductors whose number at least corresponds to the number of the plurality of coaxial type dielectric resonators, and input/output terminals provided on said dielectric substrate. The central conductors are respectively coupled to the substrate conductors provided on the dielectric substrate and inductance elements are connected to the substrate conductors which are positioned at both sides.

Abstract: A coaxial dielectric resonator for use at high frequency. The outer or inner peripheral surface of a tubular dielectric member is stepped so as to provide a greater suppression of spurious resonance. The dielectric member has a prism-shaped outer configuration so as to provide a high Q value, as well as improved space factor.