JPH10190313A - Surface mounted dielectric filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dielectric filter for which the process of putting a shield member on a filter part is extremely easy, the dispersion of characteristics between filters is eliminated and the characteristics of the filter are excellent. SOLUTION: For this filter, to the filter part 1 for which dielectric resonators 10a and 10b whose one end face is turned to an open end face are joined through the one side face, the shield member provided with a side wall plate 22 for covering the upper surface of the filter part 1 and at least the open end face is attached. Then, at the side wall plate 22 of the shield member for covering the open end face of the filter part 1, the projection part 23 of the projection amount of 0.1-0.4mm on an inner side abutted to the joined part of the open end faces of the dielectric resonators 10a and 10b joined with each other is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric filter which is easy to assemble and suitable for surface mounting.

[0002]

2. Description of the Related Art As a filter such as a high-frequency band-pass filter and an antenna filter of a communication device, a surface mount type dielectric filter which can be directly mounted on a printed wiring board is frequently used.

[0003] A through-hole is formed in a prism-shaped dielectric block from one end face to the other end face of the dielectric block,
An inner conductor made of a conductive film is formed on the inner wall surface of the through-hole, and a dielectric resonator formed by forming an outer conductor formed of a conductive film on the other end face and four side faces of the dielectric block. JP-A-6-268412 and JP-A-6-268412 disclose a filter in which a pair of side surfaces are in contact with and joined to each other, and the joint side surface portion achieves the coupling capacitance component of two dielectric resonators. -303006,
JP-A-7-154105, JP-A-6-112704
JP-A-4-150101, JP-A-5-17570
No. 4 has been proposed.

Such a dielectric filter is disclosed in Japanese Unexamined Patent Publication No.
Using a dielectric substrate having a capacitance component for achieving coupling between the dielectric resonators outside the filter unit in which the dielectric resonators disclosed in FIG. Connect the dielectric resonator and the dielectric substrate,
Unlike a dielectric filter which is joined between the dielectric resonators via a coupling capacitor, the entire dielectric filter can be made compact.

[0005]

In the above-described dielectric filter, although the filter portion itself can be made compact, on the contrary, since the dielectric substrate is used, the space between the shield case and the filter portion is reduced. A relatively wide gap is formed, and a stray capacitance component generated between the open end face, which is one end face of each dielectric resonator, and the shield case is generated. As a result, the characteristics of the dielectric filter are largely changed.

In each of the above prior arts, there is no reference to the relationship between the filter section and the shield case.

The inventor of the present invention has been devised in view of the above-described problems, and has as its object the purpose of covering a filter portion with a shield case very simply and reducing variations in characteristics between filters. An object of the present invention is to provide a surface-mount type dielectric filter which can simultaneously suppress the third harmonic which is not preferable for the characteristics of the filter.

[0008]

According to the present invention, a through hole is formed in a prismatic dielectric block from one end face to the other end face of the dielectric block, and a conductive film is formed on an inner wall surface of the through hole. For the inner conductor, a plurality of dielectric resonators each having an outer conductor made of a conductive film formed on the other end face and each side face of the dielectric block, one side face of each dielectric resonator is a mounting bottom face. A filter member joined to each other on the other side, and a shield member having a ceiling flat plate covering the top surface of the dielectric resonator constituting the filter portion and a side wall plate covering one end surface of each dielectric resonator. Is a surface-mount type dielectric filter. The side wall plate of the shield member is formed with a protrusion having a protrusion amount of 0.1 to 0.4 mm, which is in contact with one end face of the dielectric resonator to be joined.

[0009]

According to the present invention, a projection that contacts the open end face of each dielectric resonator is formed on the side wall plate that covers the open end face of each dielectric resonator of the shield member. Therefore, when the filter portion is formed and this filter portion is covered with the shield member, the protrusion amount of the protrusion between the open end face of each dielectric resonator of the shield member and the side wall plate (0.1-0. 4mm)
Can define the interval.

In other words, positioning of the shielding member on the filter portion becomes very simple, and variations among the dielectric filters can be suppressed.

Further, the distance between the open end face of each dielectric resonator and the shield member is 0.1 to 0.4 mm corresponding to the amount of protrusion.
Therefore, the electromagnetic wave component that is to be coupled outside the open end face of the dielectric resonator is immediately absorbed by the shield member, and the third harmonic unnecessary for the filter characteristics is obtained. Can be suppressed.

Thus, it is possible to obtain a filter characteristic having a predetermined filter characteristic stabilized at the resonance frequency of each dielectric resonator adjusted before assembly.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is an external perspective view of the surface-mounted dielectric filter of the present invention, FIG. 2 is a bottom view of the surface-mounted dielectric filter, FIG. 3 is a side view, and FIG. b)
1 is an external perspective view of a dielectric resonator used in the present invention.

The surface mount type dielectric filter of the present invention comprises a filter unit 1 formed by joining a plurality of dielectric resonators 10a and 10b, and a shield member 2 covering the filter unit 1.

The filter section 1 is constituted by, for example, two dielectric resonators 10a and 10b being joined to each other via respective joining side surfaces.

The shield member 2 is made of a metal member and has a flat ceiling portion 21 which is in close contact with the upper surface of the filter portion 1.
And a side wall plate 22 that covers at least the open end face side of the filter portion 1, and has, for example, an L-shape in a side view as shown in FIGS. 1 and 3.

The dielectric resonators 10a and 10b correspond to FIG.
(A) As shown in (b), a dielectric block 11 made of a rectangular dielectric ceramic and this dielectric block 1
A through-hole 12 penetrating one end face (hereinafter, referred to as an open end face) and the other end face (hereinafter, referred to as a short-circuit end face) is formed. In the figure, the vicinity of the opening on the open end face side of the through hole 12 has two steps.

The through hole 1 of such a dielectric block 11
An inner conductor 13 of a conductor film formed by a plating method or a thick film method is formed on the inner wall surface of the dielectric block 1.
An outer conductor 14 of a conductor film formed by a plating method or a thick film method is formed on one short-circuit end face and four side faces. Of the four side surfaces, in particular, the side that becomes the mounting bottom surface of the filter is the mounting bottom surface a, the side surface that is bonded to the adjacent dielectric resonator is the bonding side surface b, the side surface that faces the mounting bottom surface a is the upper surface c, The side surface facing the side surface b is referred to as a terminal side surface d. That is, in the filter unit 1 of FIGS. 1 to 3, the dielectric resonators 10a and 10b are substantially flush with the mounting bottom surface a and the upper surface c, and the bonding side surfaces b of the dielectric resonator 10a are electrically conductively bonded. Join each other through the material.

Bonding side surface b of dielectric resonators 10a and 10b
The rectangular coupling windows 16a, 1b are exposed at a predetermined length in the longitudinal direction of the dielectric block 11 from a ridge line portion with the open end surface and a predetermined width of the ridge line portion with the open end surface.
6b are formed.

The rectangular coupling windows 16a, 16b are
The two dielectric resonators 10a and 10b are joined together to form an effective coupling window having a predetermined shape.
Further, an L-shaped terminal electrode 15 is formed to extend over the terminal side surfaces d and the mounting bottom surface a of the dielectric resonators 10a and 10b. Around the terminal electrode 15, a region that is electrically separated from the outer conductor 14 is formed.

The filter unit 1 includes the above-described dielectric resonator 10
A junction side b of the dielectric resonator 10b is joined to the junction side b of the dielectric resonator 10b via a conductive adhesive such as solder.
At this time, it is important that the conductive adhesive does not flow to the area of the coupling windows 16a and 16b and does not cause a change in the actual area of the coupling window 16.

As described above, for example, when two dielectric resonators 10a and 10b are connected, in the filter unit 1,
Inner conductor 13 and outer conductor 14 of dielectric resonators 10a and 10b
, An LC resonance equivalent circuit is formed. In addition, a capacitance component is generated via the coupling windows 16a and 16b on the joint side surfaces of the two dielectric resonators 10a and 10b. Furthermore, a capacitance component is generated between the inner conductor 13 and the terminal electrode 15 within one dielectric resonator, for example, 10a.

The capacitance component between the inner conductors 13 of the adjacent dielectric resonators 10a and 10b is
a and 10b, and the band characteristics are determined by the degree of coupling. Further, the capacitance component between the terminal electrode 15 and the inner conductor 13 becomes an input / output capacitance component.

Thus, the two dielectric resonators 10a,
The predetermined filter characteristics of the filter unit 1 are obtained by controlling the resonance characteristics and the degree of coupling of 10b.

The filter member 1 is covered with a shield member 2. The shield member 2 ensures that the outer conductors 14 of the two dielectric resonators 10a and 10b are set to the ground potential, and suppresses fluctuations in filter characteristics due to external noise.

To ensure that the outer conductors 14 of the two dielectric resonators 10a and 10b are at the ground potential, the ceiling member 21 of the shield member 2 is connected to the respective dielectric resonators 10a and 10b.
To the outer conductor 14 on the upper surface c via a conductive adhesive such as solder. In addition, in order to suppress a change in filter characteristics due to external noise, the open end face where the surface of the dielectric block 11 is exposed is covered with the side wall plate 22.

In the present invention, in order to stabilize and improve the filter characteristics and to simplify the assembling process, the filter 1 (two dielectric resonators 10a, 1a) is provided on the inner surface of the side wall plate 22.
0b), a projection 2 having a predetermined projection amount Δd in contact with the open end face
3 are provided.

More specifically, the projection 23 abuts on the junction of the two dielectric resonators 10a and 10b or near the junction. As a result, the protrusion amount Δ of the protrusion 23 is provided between the side wall plate 22 of the shield member 2 and the open end face of the filter 1.
A gap corresponding to d will be provided. The protrusion amount Δd of the protrusion 23 is 0.1 to 0.4 mm.

The projections 23 of the side wall plate 22 can be easily formed by press working simultaneously with mechanical working such as bending of a metal flat plate material to be the shield member 2.

Next, the assembly process of the present invention will be briefly described.

First, a predetermined dielectric ceramic material is press-formed so as to form a dielectric block 11 having a predetermined shape, and fired. Further, the shield member 2 having the above-described structure is prepared.

Next, the inner wall surface, the short-circuit end surface, and the four side surfaces of the through hole 12 of the dielectric block 11 are plated with, for example, a plating method.
Conductive film is selectively applied by thick film method and inner conductor 1
3, outer conductor 14, coupling windows 16a, 16b, terminal electrode 15
To form Thereafter, a part of the open end face of the dielectric resonator and a part of the outer conductor 14 are ground and removed to adjust the resonance frequency.

Next, the adjacent dielectric resonators 10a, 10a
b) and cream solder is applied to the inner surface of the ceiling plate 21 of the shield member 2 and the ceiling plate 2 of the shield member 2
1 and the side wall plate 22 are connected to the respective dielectric resonators 10a, 1
The dielectric resonators 10a and 10b are brought into contact with the protruding portions 23 while arranging them so as to form a ridge line between the open end face of Ob and the upper surface c.

In this state, the shield member 2 and the two dielectric resonators 10a and 10b are put into a reflow furnace, and the abutting portions of the dielectric resonators 10a and 10b with the joining side surfaces b and b and the dielectrics The contact portions between the upper surfaces c, c of the body resonators 10a, 10b and the ceiling flat plate 21 of the shield member 2 are joined. The shield member 2 includes dielectric resonators 10a, 1
Since the holding pieces 24, 24 sandwiched inside through the outer conductor 14 of the terminal side surface d of the terminal 0b are formed, the joining between the dielectric resonators 10a and 10b can be reliably performed, and the two dielectric resonators 10a The projecting portion 23 of the side wall plate 22 can be located at the joint of the open end surfaces of the side walls 10b and 10b.

In the above assembly, the positional relationship between the shield member 2 and the dielectric resonators 10a and 10b is determined based on the corner between the ceiling flat plate 21 and the side wall plate 22. Since the arrangement is performed, the longitudinal displacement of the dielectric resonators 10a and 10b does not occur. In addition, since each of the dielectric resonators 10a and 10b is sandwiched from the terminal side surface d on which the terminal electrode 15 is formed, no displacement occurs in the width direction of the dielectric resonators 10a and 10b. Further, since the protruding portion 23 abuts on the joints at the open end faces of the dielectric resonators 10a and 10b, the gap Δd between the open end face and the side wall plate 22 is kept constant.

Accordingly, the assembly process is greatly simplified. What is important here is that the filter unit 1
The distance between the open end faces of the dielectric resonators 10a and 10b and the side wall plate 22 can be set to a constant gap Δd corresponding to the amount of protrusion of the protrusion 23. Even if the conductive protrusion 23 contacts the filter unit 1, this contact portion is substantially adjacent to the dielectric resonators 10a and 1a.
0b, which is the position where the outer conductor 14 is originally formed, the fluctuation of the filter characteristics can be suppressed even if the projection 23 which is a conductive member abuts on this portion.

The protrusion amount of the projection 23 is 0.1 to 0.4 mm
The gap between the open end face of each of the dielectric resonators 10a and 10b and the side wall plate 22 can be made uniform with an extremely narrow 0.1 to 0.4 mm.

This gap Δd is extremely narrow, 0.1 to 0.4.
By maintaining mm, the filter characteristics are improved.

Generally, two dielectric resonators 10a, 1
0b is coupled between the inner conductors 13, 13 of the two dielectric resonators 10a, 10b by the coupling windows 16a of the joining side surfaces b, b.
16b. That is, inside the dielectric resonators 10a and 10b, both the dielectric resonators 10a and
0b has been combined.

However, actually, the openings of the inner conductors 13 exposed on the open end face are coupled to each other via the stray capacitance outside the open end face.

As in the present invention, the dielectric resonators 10a and 10a, 1
Since the shield member 2 of the ground potential exists on the open end face of Ob with a gap of about 0.1 to 0.4 mm,
In order to immediately set the stray capacitance component generated outside the open end face to the ground potential, the two dielectric resonators 10a,
The coupling of 10b can be performed only inside the dielectric resonators 10a and 10b, and the degree of coupling as designed can be achieved. The protrusion amount of the protrusion 23, that is, the gap Δd between the open end faces of the dielectric resonators 10a and 10b and the side wall plate 22
Is set to 0.1 to 0.4 mm.
The protrusions 23 formed by mechanical processing are loosened, and the side walls 2 are formed on the open end faces of the dielectric resonators 10a and 10b.
2 substantially comes into surface contact. If the side wall plate 22 of the ground potential comes into surface contact with the open end surface, the electrically operated outer conductors 14 substantially increase, and the filter characteristics greatly fluctuate.

When the distance becomes 0.4 mm or more, the inner conductors 13 and 1 of the adjacent dielectric resonators 10a and 10b are removed.
The gap between the three ends is also connected to the outside of the open end face, so that the characteristics are deteriorated.

The present inventor has found that the dielectric resonators 10 adjacent to each other
Variations in characteristics due to the distance between the open end faces a and 10b and the side wall plate 22 were examined.

As the filter section 1, the shape of the dielectric block 11 constituting the two dielectric resonators is 2 mm in cross section.
2 mm, length 4.6 mm, cross section 2 mm x 2 mm
A through hole 12 having a diameter of 0.6 mm is formed at the center of the surface of the dielectric block as the inner conductor 13, outer conductor 14, and terminal electrode 15.
Electrolytic plating Cu and 2.5 μm electrolytic plating Ag were applied and formed.

As a product of the present invention, 0.2 mm
The shield member 2 formed with the projection 23 is used. still,
As a comparative product, a shield member having a 0.5 mm protrusion on the side wall plate 22 was used.

Then, the above-described dielectric resonators were joined together to form a 1.9 GHz band dielectric filter.

The thus-prepared product of the present invention and the comparative product were used at a frequency of 1.5 GHz to 6.5 GHz.
The attenuation characteristics were measured. The characteristic diagram is shown in FIG.

In FIG. 5, the solid line indicates the characteristics of the product of the present invention, and the dotted line indicates the difference between the characteristics of the comparative product and the characteristics of the product of the present invention.

As is clear from FIG. 5, the comparative product has a characteristic in which the amount of attenuation extremely deteriorates near 5.7 GHz, which is three times the center frequency of 1.9 GHz of the dielectric filter. That is, in the present invention, even in a frequency range higher than 2.2 GHz, a stable attenuation amount, for example, 20
dB, whereas in the comparative product, 5.
In the vicinity of 7 GHz, for example, it is on the order of 10 dB.

As described above, according to the present invention, the protrusion 23 having a predetermined height is formed on the side wall plate 22 of the shield member 2 which covers the open end face of each dielectric resonator. By arranging the open end faces of the body resonators in contact with each other, the assembly process can be performed very easily, and the flicker between the filters is suppressed. In this case, unnecessary characteristics can be suppressed, and the filter characteristics become very stable.

In the above-described embodiment, the configuration of the filter unit 1 has been described in the case where the two simplest dielectric resonators are joined, but three or more dielectric resonators may be joined. Absent.

Further, the shape of the inner conductor of the dielectric resonator is formed in two steps at the opening on the open end face side and on the inner wall surface of the through hole having a uniform diameter. Various shapes are possible in consideration of the degree of bonding between adjacent dielectric resonators and the input / output capacitance between the inner conductor and the terminal electrode.

For example, as shown in the vertical sectional view of the dielectric resonator shown in FIG.
The opening diameter of the through hole 12b on the short-circuit end face side is made small, for example, 0.6 mm, and the opening diameter of the through-hole 12b on the short-circuit end face side is made small, for example, 0.6 mm. It may be a shape in which the groove 12d is formed.

Further, a capacitance intermediate electrode 17 which is electrically independent of the outer conductor 14 may be formed in the coupling window 16.

[0055]

According to the present invention, a predetermined amount of protrusion is formed on the side wall plate of the shield member covering the open end face of each dielectric resonator, and this protrusion and the open end face of each dielectric resonator are applied. It was placed in contact. As a result, the assembling process can be performed very easily, and the flapping between the filters can be suppressed. In particular, by setting the protrusion amount to 0.1 to 0.4 mm, components that are bonded to each other on the open end face side of the dielectric resonator can be absorbed by the shield member.
On the filter characteristics, it is possible to suppress deterioration of attenuation in a high frequency region, for example, in the vicinity of the third harmonic frequency, and the filter characteristics are also very stable.

[Brief description of the drawings]

FIG. 1 is an external perspective view of a surface mount type dielectric filter of the present invention.

FIG. 2 is a bottom view of the surface mount type dielectric filter of the present invention.

FIG. 3 is a side view of the surface mount type dielectric filter of the present invention.

FIGS. 4A and 4B are external perspective views of a dielectric resonator used in the surface mount type dielectric filter of the present invention.

FIG. 5 is a characteristic diagram illustrating characteristics of a dielectric filter.

FIG. 6 is a longitudinal sectional view of another dielectric resonator used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Filter part 10a, 10b ... Dielectric resonator 2 ... Shield member 22 ... Side wall plate 23 ... Projection part

Claims (1)

[Claims] 1. A through hole penetrating from one end surface of the dielectric block to the other end surface of the prismatic dielectric block, and an inner conductor made of a conductive film is formed on an inner wall surface of the through hole by the dielectric block. A plurality of dielectric resonators each having an outer conductor made of a conductive film formed on the other end face and each side face of the same are joined to each other on the other side face such that one side face of each dielectric resonator is a mounting bottom face. And a shield member having a ceiling flat plate covering the upper surface of each dielectric resonator constituting the filter unit and a side wall plate covering one end surface of each dielectric resonator. A surface mount type dielectric, wherein a protrusion having a protrusion amount of 0.1 to 0.4 mm is formed on a side wall plate of the shield member so as to be in contact with one end face of the dielectric resonator to be joined. filter.