JP3468193B2 - Dielectric filter - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric filter used for a mobile communication base station such as a mobile phone, a broadcast radio wave transmitting station, and the like. FIG. 2 is a bird's-eye view of a conventional dielectric filter. Here, a TE mode dielectric filter is shown as an example of the dielectric filter. A cavity 52 in which a dielectric resonator 51 is provided is connected in a predetermined number of stages to form a filter. The dielectric resonator 51 has an inner surface having a high conductivity A through a pedestal 53 made of alumina or the like.
It is installed at the center of a cavity 52 plated with g or the like. An adjacent dielectric resonator has a coupling window 5 at its center.
4 are separated by a cavity partition wall 55 plated with Ag or the like having high conductivity. An input signal 56 is incident on an input stage cavity 58 via a coupling probe 57, and excites a resonance mode unique to the cavity. The standing wave excited in the input stage cavity 58 is coupled to the adjacent cavity 52 via the coupling window 54 to excite a predetermined resonance mode. Similarly,
The modes connected to the cavities connected to each other are coupled via the coupling window, and a predetermined standing wave is generated as a whole. [0004] The standing wave excited in the output stage cavity 59 is emitted to the outside as an output signal 61 via a coupling probe 60. By adjusting the coupling degree of the coupling probes 57 and 60 and the coupling window 54 between the cavities to a predetermined strength, for example, only signals within a predetermined frequency bandwidth are passed, and signals of other frequencies are suppressed. A filter function can be provided. The degree of coupling can be controlled by the length / position / shape of the coupling probe, the size / shape / position of the coupling window, or the length / position / insertion direction of the coupling adjusting screw 62. Particularly, in order to increase the size of the coupling window, it is necessary to cut the cavity partition wall 55. [0005] In general, the filter housing 63 is composed of i) A
l, cutting of metal blocks such as brass and SUS, i
i) Same sheet metal working, iii) Same die casting. In consideration of cost, dielectric filters used in mobile communication base stations, broadcast radio transmission stations, and the like require i
i) Sheet metal processing is often used. The dielectric resonator 51, the pedestal 53 and the housing bottom 6
4 is fixed by bonding with an adhesive. The filter housing 63 includes a housing body 65 and a housing lid 66. The casing body 65 is manufactured by integral processing in i) and iii). In ii), a plurality of sheet metals are assembled and screwed or welded, or silver brazed or soldered to obtain mechanical strength and tolerance. Further, in order to suppress unnecessary radiation of electromagnetic waves to the adjacent cavities or the outside of the filter, the gaps are electrically connected by welding or filling with silver wax, solder, or the like. The casing body 65 and the casing lid 66 are screwed to the side edge 67 and brought into close contact. On the other hand, the coupling probes 57 and 60 are electrically connected to the coaxial connector 68 by soldering or the like, and have mechanical strength. [0012] The conventional dielectric filter has the following problems. First, there is a problem in filter characteristics. 2. Description of the Related Art In a base station filter for a mobile communication system, etc., as much as possible attenuation and as steep attenuation as possible are required in a stop band near a pass band. Further, the transfer characteristic is not flat in the pass band but rises to the right, and the loss at the low band side at the end of the pass band is larger than that at the high band side. [0014] Second, there is a problem of ii) cost reduction in manufacturing a filter by sheet metal processing. Conventionally, to form a single coupling window 54, a cavity partition 55
Was constructed by assembling two sheet metals. FIG. 3 shows a conceptual diagram thereof. In this case, the number of components required for forming the cavity partition wall is two per coupling window, which is a problem in reducing member costs and assembly costs, and improving assembly accuracy and reliability. Third, in order to increase the degree of coupling, it is necessary to cut the cavity partition walls plated with Ag or the like having a high conductivity. However, since the cut surface has no plating, the conductivity of the cavity partition walls deteriorates. , Increasing the filter loss. Fourth, there is a problem in increasing the speed and cost of the assembly tact of the dielectric resonator. Positioning of dielectric resonator and housing bottom 64
The use of screws and the like for fixing to the cavity causes metal projections to be formed on the inner wall of the cavity, which causes a decrease in the Q value of the cavity. In addition, it is necessary to drill a screw hole in the pedestal, which hinders cost reduction. Become. On the other hand, with respect to the positional accuracy of the dielectric resonator, there has been a demand for a method of simply and accurately fixing the dielectric resonator at a predetermined position only for elements directly connected to the filter characteristics such as the degree of coupling. Fifth, there is a problem in that reliability is reduced due to unnecessary radiation from a gap between the housing body and the housing lid. Conventionally, the casing body 65 and the casing lid 66 are screwed together at the side edge 67 to achieve close contact, but a small gap is inevitably formed, and unnecessary radiation may leak from the gap. Was. Sixth, there is a problem in mechanical strength of the coupling probe holding mechanism. Conventionally, the coupling probes 57 and 60 are held at a predetermined position by soldering to the coaxial connector 68. However, torque is applied due to vibration during transportation and the like, and the coupling probes 57 and 60 rotate from a predetermined angle, and There is a possibility that the degree of change may occur or a short circuit may occur with the inner wall of the cavity. Means for Solving the Problems To solve the above problems, the present invention is characterized by having the following configuration. (1) The input / output probe is brought close to the coupling window, and the input / output signal is coupled to the adjacent cavity. Embodiment 1 FIG. 1 shows a dielectric filter according to a first embodiment of the present invention. Is shown. The present invention is an example of a receiving filter for a mobile communication base station, in which six TE mode dielectric resonators are connected. Six stages of cavities are provided in the housing body 1 via Ag-coated cavity partitions 3 to constitute a filter. The coupling probes 9 and 10 are installed close to the coupling windows 2 and 15, respectively, as shown. The input signal is coupled via the coupling probe 9 to excite a predetermined resonance mode in the cavity 13. The standing wave excited in the cavity 13 is coupled to the adjacent cavity 14 via the coupling window 2 to excite a predetermined resonance mode. Similarly, the modes connected to the cavities connected to each other are coupled via the coupling window, and a predetermined standing wave is generated as a whole. In the present invention, since the coupling probe 9 is disposed close to the coupling window 2, the input signal is
Not only 3 but also the cavity 14 is slightly coupled to perturb the standing wave of the entire filter. Similarly, the coupling probe 10 on the output side is also slightly coupled with the coupling window 15, and perturbs the standing wave of the entire filter. For comparison, FIG. 3 shows a conventional dielectric filter. As is apparent from the figure, in the conventional dielectric filter, the coupling probes 9 and 10 are separated from the coupling windows 2 and 15, respectively, and the input and output signals hardly directly couple to the cavities 14 and 16. FIG. 4 shows the pass characteristics of a prototype dielectric filter of the present invention and the pass characteristics of a conventional dielectric filter. As is clear from FIG. 4, in the dielectric filter of the present invention, a pole appears near the high frequency side of the pass band, and a steep attenuation characteristic can be obtained. Further, flat characteristics can be obtained in the pass band, and the insertion loss in the high band increases, but the insertion loss in the low band decreases, and the insertion loss in the entire pass band decreases. The same effect can be obtained even if one of the binding probes 9 and 10 is separated from the binding window 2 or 15. (Embodiment 2) FIG. 5 is a bird's-eye view of a dielectric filter according to a second embodiment of the present invention. The casing body 1 is made of, for example, a 1 mm thick SUS sheet metal plated with Ag. The coupling window 2 is formed with a gap between the case wall 4 and the Ag-plated cavity partition wall 3. FIG. 6 shows a conceptual diagram of a conventional housing assembly process, and FIG. 7 shows a conceptual diagram of a housing assembly process of the present invention. 7, a cavity 6 is formed at a predetermined position so that the cavity partition wall 3 and the cavity partition wall 5 are fitted to each other at right angles. These were fitted and fixed to the housing bottom 7 by welding.
As a fixing method, screwing, silver brazing, soldering or the like may be used. As shown in FIG. 5, the coupling window 2 is provided between each stage.
Was formed with a gap between the housing wall 4 and the cavity partition wall 3. The width of the gap was designed so as to have a coupling degree suitable for obtaining desired filter characteristics. The dielectric resonator 8 and the coupling probes 9 and 10 were arranged in the cavity, and finally, the housing cover 11 was screwed to complete. The fine adjustment of the degree of coupling was performed by adjusting the amount of insertion of the coupling adjusting screw 12 into the coupling window. According to the present invention, the number of components required for forming the cavity partition wall is reduced from two conventionally per coupling window to one. As a result, while reducing material costs and assembly costs,
Reliability can be improved. When the characteristics of the filter according to the present invention were evaluated, it was possible to obtain characteristics equivalent to those of the conventional filter having a coupling window at the center of the cavity partition wall in terms of both insertion loss and out-of-band attenuation. In the above embodiment, the coupling window is provided using the gap between the housing wall and the cavity partition wall.
As shown in the above, a cavity partition having a hole or a part missing may be used. FIG. 9 is a view in which the cavity partition walls 5 are cut in order to strengthen the coupling between the dielectric resonators 8.
The cut surface is plated with Ag and the SUS sheet metal is exposed. By coating this with solder, the conductivity of the cavity partition wall surface is increased, and the loss of the filter can be improved. (Embodiment 3) FIG. 10 shows a third embodiment of the present invention.
1 is a sectional view of a dielectric filter according to an embodiment. At the center of the housing bottom 7, a circular counterbore 22 having a depth of 1 mm for fitting a cylindrical or columnar pedestal 21 and defining the position of the dielectric resonator 8 is provided. The dielectric resonator 8 adhered concentrically and the pedestal 21 made of alumina or the like are fixed along the counterbore 22 so as to be accurately and speedily positioned. You can now do. If the inner diameter of the counterbore 22 is within approximately +0.5 mm and -0.01 mm of the diameter of the pedestal 21, the dielectric resonator can be simply set at a predetermined position without affecting the filter characteristics. Was completed. It goes without saying that the present invention has the same effect as described above, even if the pedestal has another shape such as a prismatic shape, for example, if the counterbore is formed in a shape suitable for it. (Embodiment 4) FIG. 11 is an overhead view showing a dielectric filter and a method of manufacturing the same according to a fourth embodiment of the present invention. Dielectric resonator 8 and pedestal 21
Is defined at the center of the cavity, three M2s are placed in the housing bottom 7 at a position where the vertices of the triangles form an equilateral triangle and whose center of gravity coincides with the center of the housing bottom 7.
Screw holes 23 are provided. When the dielectric resonator 8 and the pedestal 21 are fixed to the cavity, the pedestal 21 with the adhesive is first attached to the screw 24 with the screw 24 mounted in the screw hole 23 and the projection 25 formed. Stick along. After the adhesive is dried, the screw 24 is removed from the screw hole 23 again. By taking the above assembling process, the dielectric resonator can be accurately and quickly positioned. By attaching a metal adhesive tape 26 or the like to the screw holes 23 from the outside,
The leakage of radio waves to the outside was shielded. In the above embodiment, three screw holes 23 are provided, but the same effect can be obtained with only two screw holes. (Embodiment 5) FIG. 12 is a bird's-eye view of a dielectric filter according to a fifth embodiment of the present invention. Al
A counterbore 32 having a depth of 1 mm is provided on a side edge 31 of the housing wall 4 having a thickness of 5 mm of the housing body portion 1 formed by the cutting process. The conductive rubber 33 is provided therein. The housing cover 11 is screwed to the housing body 1 in which the dielectric resonator is provided, and the filter housing 34 is completed. According to the structure of the present invention, the housing body 1 and the housing lid 11 can be brought into electrical close contact with each other, and unnecessary radiation to the outside can be reliably prevented. In the above embodiment, an example was described in which the casing 1 was formed by cutting.
Alternatively, a similar effect was obtained in a case formed by sheet metal processing. The material loaded into the counterbore 32 is a conductive rubber 3
In addition to 3, the same effect was obtained with a metal net or metal foil. Further, in this embodiment, an example is shown in which the counterbore is provided on the side edge 31 of the housing wall 4, but the counterbore is provided on the side of the housing lid 11 on the side of the housing lid 11. The same effect can be obtained without any problem even if it is provided at a position opposing to 31. (Embodiment 6) FIG. 13 is an overhead view of a dielectric filter according to a sixth embodiment of the present invention. The coupling probe 9 made of φ2 copper wire whose surface used for input / output coupling is Ag-plated is electrically connected to the coaxial connector 41 by soldering. The coupling probe 9 is fixed to the housing wall 4 via a reinforcing plate 42 made of a low-loss glass / epoxy insulating material. A hole is formed in the center of the reinforcing plate 42, and a copper foil bonding portion 43 is provided around the hole. Binding probe 9
Are soldered to the bonding portion 43 and fixed to the reinforcing plate 42. The reinforcing plate 42 is bonded to the housing wall 4 with an adhesive. By using the reinforcing plate 42 of the present invention, the mechanical strength of the holding mechanism of the coupling probe 9 is improved, and the problem of rotation of the coupling probe due to vibration during transportation, which has been a problem to be solved conventionally, is eliminated. (Embodiment 7) FIG. 14 is a bird's-eye view of a dielectric filter according to a seventh embodiment of the present invention. The coupling probe 9 used for input / output coupling is electrically connected to the coaxial connector 41 by soldering. The coupling probe 9 is fixed to the housing wall 4 via a fixing jig 44 made of a low-loss glass / epoxy insulating material. By using the fixing jig 44 of the present invention,
The mechanical strength of the holding mechanism of the coupling probe 9 has been improved, and the problem of rotation of the coupling probe due to vibration during transportation, which has been a problem to be solved conventionally, has been eliminated. By using the present invention in a dielectric filter, (1) a filter having a steep attenuation characteristic can be easily obtained. (2) The transmission characteristics of the pass band can be made flat, and low loss can be realized. (3) The number of cavity partition wall parts is reduced,
Cost reduction can be realized. (4) The positioning of the resonator can be performed simply and accurately, and the characteristics and mass productivity can be improved. (5) It is possible to prevent unnecessary radiation from leaking from the gap at the screwed portion of the housing, thereby improving reliability. (6) The seismic resistance and reliability of the input / output coupling probe can be improved. The effect was obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a dielectric filter according to a first embodiment. FIG. 2 is a diagram showing a conventional dielectric filter. FIG. 3 is a diagram showing a conventional dielectric filter. FIG. 5 is a diagram showing the pass characteristics of the dielectric filter of the first embodiment and the conventional dielectric filter. FIG. 5 is a diagram showing the dielectric filter of the second embodiment. FIG. 6 is an assembly process of the conventional dielectric filter. FIG. 7 is a conceptual view of an assembling process of a dielectric filter according to a second embodiment. FIG. 8 is a view showing a cavity partition wall of the second embodiment. FIG. 9 is a cutaway view of a cavity partition wall of the second embodiment. FIG. 10 is a diagram illustrating a dielectric filter according to a third embodiment; FIG. 11 is a diagram illustrating a dielectric filter according to a fourth embodiment; FIG. 12 is a diagram illustrating a dielectric filter according to a fifth embodiment; 13 is a diagram showing a dielectric filter according to a sixth embodiment. FIG. 14 is a seventh embodiment. [Description of reference numerals] 1,65 Casing body 2,5,54 Coupling windows 3,5,55 Cavity bulkhead 4 Casing wall 6 Groove 7,64 Casing bottom 8, 51 Dielectric resonators 9, 10, 57, 60 Coupling probe 11, 66 Casing lid 12, 62 Coupling adjustment screw 13, 14, 16, 52 Cavity 19 Cavity partition wall cutting surface 21, 53 Base 22, 32 Counterbore 23 Screw Hole 24 Screw 25 Projection 26 Metal adhesive tape 31, 67 Side edge 33 Conductive rubber 34, 63 Filter housing 41, 68 Coaxial connector 42 Reinforcement plate 43 Adhesive part 44 Fixing jig 56 Input signal 58 Input stage cavity 59 Output stage Cavity 61 output signal

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshio Ishizaki 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Toshito Tachibana 55-12 Osumihama, Kyotanabe, Kyoto Prefecture Nitto Matsushita Electric Inside (72) Inventor Toshiaki Nakamura 55-12 Osumihama, Kyotanabe, Kyoto Prefecture Inside Matsushita Nitto Denki Co., Ltd. (72) Inventor Kunihiko Minami 55-12 Osumihama, Kyotanabe, Kyoto Prefecture Inside Matsushita Nitto Electric ( 56) References JP-A-2000-31706 (JP, A) JP-A-2001-127502 (JP, A) JP-A-2000-13107 (JP, A) Japanese Utility Model Application Sho 62-68303 (JP, U) (58) Field (Int.Cl. ⁷ , DB name) H01P 1/20 H01P 1/205

Claims (1)

(57) [Claim 1] A cavity having a dielectric resonator disposed inside a housing having a low-resistance inner wall, and a cavity partition having a partially opened coupling window are provided. In the dielectric filter connected by a predetermined number of stages, at least one of the coupling probes provided in the cavity of the input / output stage is adjacent to the coupling window, and couples the input / output signal with the adjacent cavity , The dielectric probe to which the coupling probe is coupled
A dielectric filter, wherein the vibrator forms a band-pass filter.