1. Field of the Invention
The present invention relates to dielectric filters of the type including a plurality of dielectric resonators.
2. Related Art
A dielectric filter of the type referred to above is shown in
In the dielectric filter of
In conventional dielectric filters such as that shown in
In view of the foregoing, an object of the present invention is to solve the aforementioned problem caused by the outer conductor being present between the input-output terminals. A further object of the present invention is to provide a dielectric filter which has broadband filter characteristics.
In order to achieve the above objects, there is provided, in accordance with the present invention, a dielectric filter including: a dielectric block having end and side surfaces; a plurality of resonators provided in the dielectric block in parallel with each other, each of the resonators comprising an inner conductor on a wall surface of a through-hole extending from a first end surface of the dielectric block to a second end surface of the dielectric block opposite the first end surface; and an outer conductor on the end and side surfaces of the dielectric block except for the first end surface, the inner conductor provided on the wall surface of each through-hole and the outer conductor provided on the circumferential surface of the dielectric block being connected together so that the second end surface serves as a short circuit end surface, and the first end surface serves as an open end surface, and the dielectric filter further comprising: a pair of input-output terminals disposed on one side surface of the dielectric block such that the input-output terminals are located adjacent to the open end surface at respective positions corresponding to open ends of two of the resonators; insulating sections disposed on the one side surface in such a manner that each insulating section isolates a corresponding one of the input-output terminals from the outer conductor formed on the one side surface of the dielectric block; and a further section without a conductor thereon for controlling filter characteristics of the dielectric filter, the further section being disposed on the one side surface between the input-output terminals, and extending over a predetermined distance along the insulating sections from an edge between the one side surface and the open end surface.
Preferably, the further section for controlling the filter characteristics of the filter has dimensions such as to prevent magnetic field coupling between the resonators.
In one embodiment of the present invention, the further section is formed through removing, by cutting away or the like, a part of the outer conductor formed on the one side surface of the dielectric block.
Further features and advantages of the present invention will be set forth in, or apparent from, the detailed description of preferred embodiments thereof which follows.
Preferred embodiments of the present invention will now be described with reference to the accompanying drawings,
An outer conductor 4 serving as a ground or earth conductor is formed on the side surfaces 1c, 1d, 1e, and 1f of the dielectric block 1. As shown in
A pair of input-output terminals 7a and 7b are formed on the side surface 1c of the dielectric block 1. The input-output terminals 7a and 7b are insulated from the outer conductor 4 by “conductor-absent” sections, i.e., insulating sections 8a and 8b wherein no conductor is present.
The input-output terminals 7a and 7b may be formed by two methods. In the first method, during formation of the outer conductor 4 on the side surface of the dielectric block 1, the input-output terminals 7a and 7b are formed through screen printing, while the areas corresponding to the insulating sections 8a and 8b are masked. In the second method, after formation of the outer conductor 4 on the side of the dielectric block 1, portions of the outer conductor 4 corresponding to the insulating sections 8a and 8b which define the input-output terminals 7a and 7b, are cut away or otherwise removed by use of an appropriate cutting or grinding means such as a laser trimmer or a sand blasting unit.
One input-output terminal 7a is capacitively connected with the inner conductor 3a via the dielectric block 1, and in a similar manner, the other input-output terminal 7b is capacitively connected with the inner conductor 3b via the dielectric block 1. The overall filter device is connected to an electrical path or connection in such a manner that one of these input-output terminals 7a and 7b serves as an input terminal, and the other one serves as an output terminal, so that electrical connection of the high-frequency dielectric filter is established.
A key feature of the dielectric filter of the present invention will next be described.
As shown in
Exemplary specific dimensions of the thus-formed dielectric filter shown in
Although the aforementioned embodiments of the present invention are directed to three-stage dielectric filters for high-frequency use having three dielectric resonators, the present invention can also be applied to two-stage dielectric filters for high-frequency use having two dielectric resonators as well as to dielectric filters for high-frequency use having four or more stages.
As has been described hereinabove, the dielectric filter according to the present invention includes a dielectric block having side and end surfaces; a plurality of resonators provided in the dielectric block in parallel to each other, each resonator comprising an inner conductor on a wall surface of a through-hole extending from a first end surface of the dielectric block to a second end surface of the dielectric block opposite the first end surface; and an outer conductor on the side and end surfaces of the dielectric block except for the first end surface, the inner conductor on the wall surface of each through-hole and the outer conductor on the side and end surfaces of the dielectric block are connected with each other so that the second end surface serves as a short circuit end surface, and the first end surface serves as an open end surface. A pair of input-output terminals are provided on a side surface of the dielectric block such that the input-output terminals are located adjacent to the open end surface at respective positions corresponding to open ends of two of said resonators. Insulating sections are provided on the side surface in such a manner that each insulating section isolates corresponding one of the input-output terminals from the outer conductor formed on the side surface of the dielectric block. A conductor-absent section for controlling the filter characteristics of the dielectric filter, i.e., a section wherein no conductor is present, is provided on the side surface so as to be located between the input-output terminals, the conductor-absent section extending from an edge between the side surface and the open end surface, along the insulating sections, over a predetermined distance. As discussed above, with this construction, a dielectric filter is provided which has broadband characteristics and in which magnetic field coupling is prevented.
Although the invention has been described above in relation to preferred embodiments thereof, it will be understood by those skilled in the art that variations and modifications can be effected in these preferred embodiments without departing from the scope and spirit of the invention.
Number | Date | Country | Kind |
---|---|---|---|
2002-094658 | Mar 2002 | JP | national |
Number | Name | Date | Kind |
---|---|---|---|
5218329 | Vangala et al. | Jun 1993 | A |
5506554 | Ala-Kojola | Apr 1996 | A |
5652555 | Tada et al. | Jul 1997 | A |
5831495 | Hino | Nov 1998 | A |
6235341 | Hino | May 2001 | B1 |
6504455 | Toda et al. | Jan 2003 | B2 |
6680661 | Hiroshima et al. | Jan 2004 | B2 |
20020022948 | Okada et al. | Feb 2002 | A1 |
Number | Date | Country |
---|---|---|
1 098 384 | May 2002 | EP |
2 359 420 | Aug 2001 | GB |
2 374 985 | Oct 2002 | GB |
2 382 234 | May 2003 | GB |
110340708 | Dec 1999 | JP |
2001284905 | Oct 2001 | JP |
Number | Date | Country | |
---|---|---|---|
20030184414 A1 | Oct 2003 | US |