JP2003152401A - Dielectric filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an abrupt attenuation characteristic of a dielectric filter in the vicinity of a band and. reduce the number of cavity partition components to cut down the cost. SOLUTION: An input/output probe is disposed close to a coupling window enough to couple input/output signals with adjacent cavities, the cavity partition between the adjacent connected cavities is composed of a single metal plate, and the coupling window is composed of a gap between the cavity partition disposed in contact with one side wall and the opposite wall.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric filter used in a mobile communication base station such as a mobile phone or a broadcast radio wave transmitting station.

[0002]

2. Description of the Related Art FIG. 2 shows an overhead view of a conventional dielectric filter. Here, a TE mode dielectric filter is shown as an example of the dielectric filter. A cavity 52 having a dielectric resonator 51 provided therein is connected by a predetermined number of stages to form a filter. The dielectric resonator 51 has an inner surface having a high conductivity A via a pedestal 53 made of alumina or the like.
It is installed in the center of the cavity 52 plated with g. The adjacent dielectric resonator has a coupling window 5 at its center.
They are separated by a cavity partition wall 55 provided with 4 and plated with Ag having high conductivity.

The input signal 56 is incident on the input stage cavity 58 via the coupling probe 57 and excites a resonance mode specific to the cavity. The standing wave excited in the input stage cavity 58 is coupled with the adjacent cavity 52 through the coupling window 54 to excite a predetermined resonance mode. Similarly,
The modes that are connected to the cavities that are connected to each other are coupled through the coupling window, and a predetermined standing wave is generated as a whole.

The standing wave excited in the output stage cavity 59 is emitted to the outside as an output signal 61 via the 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 at other frequencies are suppressed. It can have a filter function. 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. In particular, in order to increase the size of the coupling window, it is necessary to cut the cavity partition wall 55.

The filter housing 63 is generally i) A
Cutting of metal block such as l, brass, SUS, i
It is formed by i) same sheet metal processing, and iii) same die casting. Considering cost, dielectric filters used in mobile communication base stations, broadcast radio wave transmission stations, etc.
i) Sheet metal working is often used.

[0006] Dielectric resonator 51, pedestal 53 and housing bottom 6
4 are fixed by adhering with an adhesive.

The filter housing 63 is composed of a housing body portion 65 and a housing lid portion 66.

The casing body portion 65 is manufactured by integral processing in i) and iii).

In ii), a plurality of sheet metals are assembled and screwed, welded, silver brazed, soldered or the like to obtain mechanical strength and tolerance. Furthermore, in order to suppress unnecessary radiation of electromagnetic waves to the adjacent cavity or the outside of the filter, the gap is electrically connected by welding or filling with silver wax, solder or the like.

The housing body portion 65 and the housing lid portion 66 are screwed to the side edge portion 67 so as to be in close contact with each other.

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. In a mobile communication system base station filter or the like, a large attenuation amount and a steepest attenuation characteristic 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.

The second problem is ii) cost reduction in filter manufacturing by sheet metal working. Conventionally, in order to form one 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 parts required for forming the cavity partition wall is two per one coupling window, which is a problem in reducing member cost, assembling cost, and assembling accuracy / reliability.

Thirdly, in order to increase the degree of coupling, it is necessary to cut the cavity partition wall plated with Ag or the like having high conductivity, but the conductivity of the cavity partition wall deteriorates because the cut surface is not plated. , Increase the filter loss.

The fourth problem is to increase the speed and cost of the dielectric resonator assembling tact. Positioning of dielectric resonator and housing bottom 64
Use of screws, etc. for fixing to the inner wall will form a metal protrusion on the inner wall of the cavity, which will be a factor of lowering the Q value of the cavity, and it will be necessary to machine screw holes in the pedestal and prevent cost reduction. Become. On the other hand, as for 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 an element that is directly connected to a filter characteristic such as coupling degree.

Fifth, there is a problem that reliability is deteriorated due to unnecessary radiation from the gap between the casing body and the casing lid. Conventionally, the housing body portion 65 and the housing lid portion 66 are screwed to each other at the side edge portion 67 to be in close contact with each other, but there is a possibility that a slight gap is inevitably generated and unnecessary radiation may leak to the outside. It was

The sixth problem is the mechanical strength of the combined probe holding mechanism. Conventionally, the coupling probes 57 and 60 were held at a predetermined position by soldering with the coaxial connector 68, but torque is applied due to vibration during transportation and the coupling probes 57 and 60 are rotated from a predetermined angle to couple them. There is a risk that it may change in degree and may short-circuit with the inner wall of the cavity.

[0020]

In order 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 to couple the input / output signal with the adjacent cavity.

(2) The cavity partition wall between adjacently connected cavities is made of a single metal plate. Further, the coupling window is formed by a gap between the cavity partition wall arranged in contact with one side wall and the side wall facing each other.

(3) The cutting surface is covered with solder.

(4) A counterbore for positioning the dielectric resonator is provided on the inner surface of the cavity. Alternatively, a protrusion for position regulation is provided. The fitting tolerance is 0.5 mm or less.

(5) A counterbore is provided on the edge of the housing wall or the housing lid, and conductive rubber or a metal net is placed in the counterbore and screwed.

(6-1) The root of the input / output coupling probe is
It is fixed to the cavity via the reinforcing plate.

(6-2) The input / output coupling probe is fixed to the cavity via a jig having a high Q insulation property.

[0028]

(First Embodiment) FIG. 1 shows a dielectric filter according to a first embodiment of the present invention. The present invention is an example of a reception 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 through Ag-plated cavity partition walls 3 to form a filter. The coupling probes 9 and 10 are installed close to the coupling windows 2 and 15, respectively, as shown. The input signals are 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 with the adjacent cavity 14 through the coupling window 2 to excite a predetermined resonance mode. Similarly, the modes that are connected to the cavities that are connected to each other are coupled through the coupling window, and a predetermined standing wave is generated as a whole.

In the present invention, since the coupling probe 9 is arranged in the vicinity of the coupling window 2, the input signal is the cavity 1
Not only 3 but also some coupling with the cavity 14 gives a perturbation to the standing wave of the entire filter. Similarly, the coupling probe 10 on the output side is also slightly coupled to the coupling window 15 to perturb 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 are hardly directly coupled to the cavities 14 and 16.

FIG. 4 shows the pass characteristics of the prototype dielectric filter of the present invention and the pass characteristics of the 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. Also, flat characteristics can be obtained in the pass band, and the insertion loss on the high band side increases, but the insertion loss on the low band side decreases, and the insertion loss on 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.

(Second Embodiment) FIG. 5 shows an overhead view of a dielectric filter according to a second embodiment of the present invention.

The casing body 1 is made of, for example, Ag-plated SUS sheet metal having a thickness of 1 mm. The coupling window 2 is formed by leaving a gap between the housing wall 4 and the Ag-plated cavity partition wall 3.

FIG. 6 shows a conceptual diagram of a conventional casing assembling process, and FIG. 7 shows a conceptual diagram of the casing assembling process of the present invention. In FIG. 7, the cavity partition wall 3 and the cavity partition wall 5 are orthogonal to each other, and a groove 6 is formed at a predetermined position so as to fit each other. These were fitted and welded and fixed to the bottom 7 of the housing.
Of course, screwing, silver brazing, soldering or the like may be used as the fixing method.

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 widths of the gaps were designed so that the degree of coupling was suitable for obtaining the desired filter characteristics.

The dielectric resonator 8 and the coupling probes 9 and 10 were placed in the cavity, and finally the housing lid 11 was screwed to complete the process. The fine adjustment of the coupling degree was performed by adjusting the insertion amount of the coupling adjusting screw 12 into the coupling window.

According to the invention of the present application, the number of parts required for forming the cavity partition wall can be reduced to one from the conventional two for one coupling window. As a result, the material cost and the assembly cost are reduced, and the assembly accuracy and
It has become possible to improve reliability.

When the characteristics of the filter of the present invention were evaluated, it was possible to obtain the same characteristics in insertion loss and out-of-band attenuation as compared with the conventional filter having a coupling window at the center of the cavity partition wall.

In the above-mentioned embodiment, the coupling window is provided by utilizing the gap between the housing wall and the cavity partition wall.
As described above, a cavity partition wall with a hole or a part thereof may be used.

FIG. 9 is a view in which the cavity partition wall 5 is cut in order to strengthen the coupling between the dielectric resonators 8.
The cutting surface is Ag-plated 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.

(Third Embodiment) FIG. 10 shows a third embodiment of the present invention.
3 is a cross-sectional view of the dielectric filter according to the embodiment of FIG. A circular counterbore 22 having a depth of 1 mm is provided at the center of the housing bottom portion 7 for fitting a cylindrical or cylindrical pedestal 21 to define the position of the dielectric resonator 8.

The dielectric resonator 8 bonded concentrically and the pedestal 21 made of alumina or the like are arranged along the countersink 22 and fixed therein, so that the dielectric resonator can be positioned accurately and speedily. You can now do.

If the inner diameter of the counterbore 22 is within approximately +0.5 mm and -0.01 mm as compared with the diameter of the pedestal 21, the dielectric resonator can be easily defined at a predetermined position without affecting the filter characteristics. I was able to. Needless to say, even if the pedestal has another shape such as a prismatic shape, the present invention has the same effect as described above if the counterbore has a shape adapted to the shape.

(Fourth Embodiment) FIG. 11 is a bird's-eye 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 in the center of the cavity, the housing bottom part 7 has three M2 at a position where the centers of the two parts form a regular triangular vertex and the center of gravity thereof coincides with the center of the housing bottom part 7.
Screw holes 23 are provided.

When fixing the dielectric resonator 8 and the pedestal 21 to the cavity, the pedestal 21 with the adhesive is first attached to the screw hole 23 with the screw 24 attached to the screw 24. It adheres along with. After the adhesive has dried, the screw 24 is removed from the screw hole 23 again. By taking the above assembling process, the dielectric resonator can be positioned accurately and speedily. About the screw hole 23, by attaching a metal adhesive tape 26 or the like from the outside,
We have blocked the leakage of radio waves to the outside.

In the above-mentioned embodiment, the screw holes 23 are provided at three places, but the same effect can be obtained by only two places.

(Embodiment 5) FIG. 12 shows an overhead 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 portion 31 of a casing wall 4 having a thickness of 5 mm of the casing body portion 1 formed by the cutting process. A conductive rubber 33 is arranged therein. The housing cover 11 is screwed to the housing body 1 in which the dielectric resonator is arranged, and the filter housing 34 is completed.

With the configuration of the present invention, the housing body 1 and the housing lid 11 can be electrically brought into close contact with each other, and unnecessary radiation to the outside can be reliably prevented.

In the above-mentioned embodiment, the example in which the casing body portion 1 is cut is described.
Alternatively, the same effect was obtained in a case made by sheet metal processing. Further, the material to be loaded in the counterbore 32 is the conductive rubber 3
In addition to 3, a metal net or a metal foil had the same effect.

In the present embodiment, an example in which the counterbore is provided on the side edge 31 of the housing wall 4 has been shown, but the counterbore is the side edge of the housing wall 4 on the housing lid 11 side. Even if it is provided at a position facing 31, the same effect can be obtained without any problem.

(Sixth Embodiment) FIG. 13 shows an overhead view of a dielectric filter according to a sixth embodiment of the present invention. The coupling probe 9 made of a copper wire of φ2, the surface of which is used for input / output coupling and which is plated with Ag, 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 adhesive portion 43 and fixed to the reinforcing plate 42. The reinforcing plate 42 is adhered 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 for the coupling probe 9 is improved, and the problem of rotation of the coupling probe due to vibration during transportation, which has been a conventional problem, is eliminated.

(Embodiment 7) FIG. 14 shows an overhead 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 for 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 in the past, has been eliminated.

[0058]

By using the present invention in a dielectric filter, (1) it is possible to easily obtain a filter having a steep attenuation characteristic.

(2) The transfer characteristic of the pass band can be flattened, and low loss can be realized.

(3) The number of cavity partition wall parts is reduced,
Cost reduction can be realized.

(4) Positioning of the resonator can be performed easily and accurately, and the characteristics and mass productivity can be improved.

(5) Unnecessary leakage of radiation from the clearance between the housing screwing portions can be prevented and the reliability is improved.

(6) The seismic resistance and reliability of the input / output coupling probe can be improved. The effect was obtained.

[Brief description of 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. 4 is a diagram showing pass characteristics of the dielectric filter of the first embodiment and a conventional dielectric filter.

FIG. 5 is a diagram showing a dielectric filter according to a second embodiment.

FIG. 6 is a conceptual diagram of an assembly process of a conventional dielectric filter.

FIG. 7 is a conceptual diagram of an assembling process of the dielectric filter according to the second embodiment.

FIG. 8 is a diagram showing a cavity partition wall according to a second embodiment.

FIG. 9 is a cut surface view of a cavity partition wall of the second embodiment.

FIG. 10 is a diagram showing a dielectric filter according to a third embodiment.

FIG. 11 is a diagram showing a dielectric filter according to a fourth embodiment.

FIG. 12 is a diagram showing a dielectric filter according to a fifth embodiment.

FIG. 13 is a diagram showing a dielectric filter according to a sixth embodiment.

FIG. 14 is a diagram showing a dielectric filter according to a seventh embodiment.

[Explanation of symbols]

1,65 Case body part 2,15,54 coupling window 3,5,55 Cavity partition 4 housing wall 6 grooves 7,64 bottom of chassis 8,51 Dielectric resonator 9,10,57,60 Binding probe 11,66 Case cover 12,62 coupling adjustment screw 13,14,16,52 cavity 19 Cavity bulkhead cutting surface 21,53 pedestal 22,32 counterbore 23 screw holes 24 screws 25 protrusions 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

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toru Yamada             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Toshio Ishizaki             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Minato Tachibana             55-12 Ohsumihama, Kyotana-shi, Kyoto Prefecture Matsushita Nitto             Denki Co., Ltd. (72) Inventor Toshiaki Nakamura             55-12 Ohsumihama, Kyotana-shi, Kyoto Prefecture Matsushita Nitto             Denki Co., Ltd. (72) Inventor Kunihiko Minami             55-12 Ohsumihama, Kyotana-shi, Kyoto Prefecture Matsushita Nitto             Denki Co., Ltd. F term (reference) 5J006 HC04 HC12 HC23 HC26 JA01                       JA13 JA15 LA25 LA26 NA01                       ND05 PA01

Claims (3)

[Claims] 1. A dielectric in which a cavity in which a dielectric resonator is disposed inside a housing having an inner wall surface with low resistance is connected by a predetermined number of steps through a cavity partition wall having a partially open coupling window. In the filter, the cavity partition wall between adjacently coupled cavities is composed of a single metal plate. 2. The dielectric filter according to claim 1, wherein the coupling window is formed by a gap between a cavity partition wall provided in contact with one side wall and a facing side wall. 3. The dielectric filter according to claim 1, wherein the cavity partition wall is plated, and a cutting surface obtained by cutting the cavity partition wall is covered with solder.