JP2778432B2 - Dielectric filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric filter mounted on a communication device such as a portable telephone or a radio telephone.

[0002]

2. Description of the Related Art A conventional dielectric filter will be described below.

FIGS. 4 and 5 are a perspective view and an exploded perspective view showing a conventional dielectric filter, respectively. 4 and 5, reference numerals 1 and 2 denote dielectric resonators, and reference numerals 1a and 2a denote dielectric substrates each formed of a dielectric material. Dielectric substrates 1a and 2a are provided with through holes 1b and 2b, respectively. Outer conductors 1c and 2c are provided on the outer peripheral portions of the dielectric substrates 1a and 2a, respectively.
b and 2b are provided with inner conductors 1d and 2d, respectively.

Further, outer conductors 1c and 2c and inner conductors 1d and 2d
Are provided on one end face of each of the dielectric substrates 1a and 1b. Also, the three outer surfaces of the dielectric substrates 1a and 2a do not come into contact with other outer conductors, so that the electrodes 1f and 2f for interstage coupling and the electrodes 1g and 1 for input / output coupling are provided.
h, 2g, and 2h. Further, the inter-stage coupling electrodes 1f, 2f and the outer conductors 1i, 2i are electrically and mechanically joined to each other by a conductive joining material such as cream solder to form a two-stage filter.

[0005]

However, in the above-mentioned conventional configuration, the bandwidth of the filter is determined by the size (coupling capacitance) of the area of the inter-stage coupling conductor. It is difficult to realize a wide-band filter because the area of the conductor for connection cannot be increased, and if the area of the inter-stage coupling conductor is increased, the resonance frequency of the resonator increases, and when the filter is formed, the shape increases. There was a problem.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a dielectric filter which is small in size, can have a wide band, and is excellent in mass productivity.

[0007]

In order to achieve the above object, according to the first aspect of the present invention, the outer surface of the prismatic dielectric substrate is provided.
The outer conductor, inner conductor,
A connecting conductor is provided for each, and a second
Non-contact with outer conductor by providing one notch
And the first cutout is made of a dielectric substrate.
It was provided over the two outer surfaces of the body. Invention according to claim 2
Then, in claim 1, the bonding electrode is brought into contact with the outer conductor.
So that the second notch is not formed on the two outer surfaces of the dielectric substrate.
Provided across. According to the third aspect of the present invention,
And the bonding electrode extends over the two outer surfaces of the dielectric substrate.
Provided. In the invention according to claim 4, in claim 1,
The surface of the dielectric substrate was roughened. In the invention according to claim 5,
Was further subjected to an etching treatment.

[0008]

According to the first aspect of the present invention, an electrode for interstage coupling is provided.
Is not surrounded on all sides by the outer conductor,
The capacitance between the can be reduced and the broadband filter
Reduce the capacitance between the outer conductor and
Can be reduced and the central conductor, etc., can be omitted.
Can be. According to the invention of claim 2, the connection electrode and
The electrodes formed on the circuit board are
When joining by joining, the connecting electrode and outer conductor by the joining material
Electrical connection with the battery can be prevented. According to the invention of claim 3
The connection surface of the dielectric filter with the circuit board.
The poles can be extended. According to the fourth aspect of the present invention, the relatively formed
Small-area connection and interstage coupling electrodes and dielectric substrate
The joint strength of the body can be improved. Claim 5
In the invention described above, there is no change in the adhesion to the surface of the dielectric substrate.
The substance can be removed.

[0009]

1 and 2 are a perspective view and an exploded perspective view, respectively, showing a dielectric filter according to an embodiment of the present invention. 1 and 2, reference numerals 11 and 12 denote dielectric resonators, respectively. Hereinafter, the structure of the dielectric resonator will be described using the dielectric resonator 11. BaO-TiO _{2-
Nd 2 O 3, BaO-TiO} 2, ZnO 2 -SnO 2 -Ti
O ₂ , BaO—Sm ₂ O ₃ —TiO ₂ , Ln ₂ O ₃ —BaO—
Dielectric substrate 11 made of a dielectric material such as TiO ₂
a is provided with a through hole 11b.

At this time, the outer shape of the dielectric substrate 11a is rectangular, and the through-hole 11b is formed in a cylindrical cross section.
An outer conductor 11c is provided on an outer surface of the dielectric substrate 11a, and an inner conductor 11c is provided on an inner surface forming the through hole 11b.
d is provided. The outer conductor 11c and the inner conductor 11d are connected by a connecting conductor 11e provided on one end surface. A cutout 11k is provided on the open end 11j side of the outer surface 11i of the four outer surfaces of the dielectric substrate 11a so that the dielectric substrate 11a is exposed.

Further, an electrode 11f for interstage coupling is provided on the open end 11j side of the outer surface 11l which is in contact with the outer surface 11i and is perpendicular to the outer surface 11i, and the electrode 11f is in contact with the outer conductor 11c. It is provided in a notched groove 11o provided on the outer side surface 11l so as not to be disturbed.

Further, the open ends 1 of the outer surfaces 11m and 11n
On the 1j side, and over the respective surfaces, electrodes 11g and 11h for input / output coupling are provided.
g and 11h are on the outer surface 1 so as not to contact the outer conductor 11c.
It is provided in a cutout groove 11p provided over 1m and 11n.

The dielectric resonator 12 has substantially the same configuration as the dielectric resonator 11. That is, the dielectric substrate 12a,
Through-hole 12b, outer conductor 12c, inner conductor 12d, connecting conductor 12e, interstage coupling electrode 12f, input / output coupling electrode 12g, 12h, outer surface 12i, 121, 12m, 12
n, open end 12j, notch 12k, notch groove 12o, 1
It is composed of 2p. The portions of the dielectric resonator 11 and the dielectric resonator 12 corresponding to the alphabets (for example, the dielectric base 11a and the dielectric base 12a) have substantially the same configuration. The reason why the dielectric resonators are described as having substantially the same configuration is that the dielectric resonator 11 and the dielectric resonator 12 have a mirror-symmetric relationship with each other, as can be seen from FIG. Therefore, the formation positions of the electrodes 11f, 11g, 11h and the electrodes 12f,
Care must be taken in the formation positions of 12g and 12h.

When the dielectric resonator 11 and the dielectric resonator 12 are joined to each other with cream solder or the like while the inter-stage coupling electrode 11f and the electrode 12f are opposed to each other, the electrodes 11g, 11h and 12g, 12h face the same plane.

This is because these dielectric resonators 1
This is because 1 and 12 have a mirror-symmetrical relationship with each other.

The outer conductors 11c, 12c and the inner conductor 11
d, 12d, connecting conductors 11e, 12e electrodes 11f, 12
f, electrodes 11g, 11h, 12f, 12g (hereinafter, these films are collectively referred to as conductive films) are each formed of a thin film made of a conductive material such as copper or silver, and have a thickness of 5 μm. It is formed so that it is about. In this embodiment,
Although the conductor film is composed of one layer, it may be composed of two or more layers. Further, the film thickness was set to about 5 μm, but the film thickness must be appropriately determined depending on the conditions of use of the filter and the like.

FIG. 3 shows a notch 11 according to an embodiment of the present invention.
9 is a graph showing the relationship between the inter-stage coupling degree K according to the size of the area S of k and 12k (the area indicated by Z1 × Z2 in the figure).

As can be seen from FIG. 3, notches 11k and 12k
Increases, the degree of inter-stage coupling K also increases.
Further, the degree of inter-stage coupling K can be increased as compared with the conventional example, and a wideband filter can be configured.

Hereinafter, a method of manufacturing the dielectric filter having the above configuration will be described. First, raw materials (Ba
O, TiO ₂ , Nd ₂ O _3, etc.) are mixed in a predetermined amount, and this mixture is mixed using a mill or the like. Next, the mixture is granulated by adjusting the particle size and adding a binder using a spray dryer or the like. Next, the granulated product is formed into a predetermined shape by using a dry press, and the formed product is placed in a firing furnace at 130 ° C.
Sintering is performed at a temperature of 0 ° C. to 1400 ° C. to produce a cylindrical dielectric substrate 11a. Next, a conductor film is formed on the dielectric substrate 11a. First, in the case of forming a conductive film, there are various forming methods.

First, as a first method, a case where copper is used as a material forming a conductive film will be described. Dielectric substrate 11
The surface of a is roughened by a barrel polisher or a blasting device, and thereafter, the dielectric substrate 11a is subjected to an etching treatment to adjust the surface roughness of the dielectric substrate 11a to about 5 μm to 9 μm. At this time, for example, HF-
HNO ₂ type is used. Next, after sensitizing the entire surface of the dielectric substrate 11a using stannous chloride or the like, palladium as a catalytic metal is adhered to the entire surface, and a resist film is formed on a part of the dielectric substrate 11a. I do.

That is, the portion of the dielectric substrate 11a to which the conductor film must not adhere (the notch 11k, the notch 1
1o, a part to be the notch groove 11p). The resist film is formed by applying a resist ink on the dielectric substrate 11a using a printing technique, a transfer technique, or the like, and drying and curing the applied resist ink. Next, a thin first copper film is formed on the dielectric substrate 11a thus processed by using an electroless copper plating method. At this time, the first copper film is selectively formed only on the portion where the resist film is not formed.

Next, a second copper film is formed on the first copper film by electrolytic copper plating.
Are laminated to form a conductor film. At this time, the conductor film is 5
It is formed to have a thickness of about μm. Finally, the resist film is dissolved with a solvent or the like to form an electrode. In this manufacturing method, the resist film is formed by applying a resist ink to a predetermined position of the dielectric substrate 11a by printing and then drying and curing the resist ink, but there is also a method of using a photosensitive resist as the resist. That is, after a catalytic metal such as palladium is adhered to the dielectric substrate 11a, a photosensitive resist is applied to the entire surface of the dielectric substrate 11a and is exposed to light to cure only a predetermined portion of the photosensitive resist. Then, a portion where the photosensitive resist has not been cured is washed away with a developer to form a predetermined electrode.

As another method, an Ag paste is applied to the entire surface of the dielectric substrate 11a by printing or dipping, dried, and then subjected to a heat treatment at a temperature of 800 ° C. to 900 ° C. so that the conductive film is made of a dielectric material. It may be formed on the entire surface of the base 11a. Further, after the formation of the entire surface conductor film, unnecessary portions of the conductor film may be removed by using an etching technique such as chemical etching or dry etching to form a predetermined electrode.

As another method, after a conductive film is formed on the entire surface of the dielectric substrate 11a, a cutting process, a laser process, or the like is performed to physically remove the conductive film, thereby forming a predetermined electrode.

The dielectric resonator 11 and the dielectric resonator 12 constructed as described above are joined so that the electrodes 11f and 12f face each other, and the outer conductors 11c and 12c are joined by cream solder or the like. The electrode 11f and the electrode 12f are respectively bonded by a bonding material such as cream solder.

In this embodiment, the notches 11k, 12k
Although notches are provided as shown in FIG.
k may be formed so as to reach at least the open end m.
Further, in the present embodiment, the notch portions 11k and 12k are provided in the dielectric resonators 11 and 12, respectively, but may be provided in at least one of the dielectric resonators.

[0027]

According to the first aspect of the present invention, a prismatic dielectric is provided.
Outer conductors on the outer surface, inner surface, and one end surface of the body
Body, inner conductor, connecting conductor, and a dielectric substrate
By providing a first notch on the outer surface of the
An interstage coupling electrode is provided so as to be in non-contact, and the first notch
Part is provided over the two outer surfaces of the dielectric substrate.
Therefore, the capacitance between the inter-stage coupling electrode and the outer conductor can be reduced.
Can increase the degree of coupling between stages,
Broadband filters can be manufactured. Moreover, the central conductor etc. are omitted
It is possible to reduce the size of the filter because it can be omitted
And the number of parts is reduced, improving productivity,
Moreover, it is advantageous in cost. With the invention according to claim 2
Does not contact the bonding electrode with the outer conductor in claim 1.
The second notch to the two outer surfaces of the dielectric substrate
Formed on the connection electrode and the circuit board
The joined electrodes with a joining material such as solder
The electrical connection between the connection electrode and the outer conductor
Characteristics, and the filter itself is completely functional.
Inconveniences such as inoperability can be reduced. Claim
In the invention according to claim 3, in claim 2, the bonding electrode is also provided.
The provision over the two outer surfaces of the dielectric substrate
Connection electrode on the joint surface of the dielectric filter with the circuit board.
The electrodes on the circuit board and the connection electrodes can be
Because it can actually contact, it is possible to improve the mountability
You. According to a fourth aspect of the present invention, in the first aspect, the dielectric
Due to the roughened surface of the body substrate, a relatively formed surface
Connecting electrode and interstage coupling electrode with small product and dielectric substrate
Connection electrode because the bonding strength of
Can be prevented from peeling off, and characteristic deterioration can be prevented.
Even if the formation area of the inter-step coupling electrode becomes very small,
Sufficient bonding strength can be obtained, and filter size can be reduced.
realizable. In the invention according to claim 5, the invention according to claim 4
In addition, by performing further etching treatment,
Removal of alterations adhering to the surface of the substrate
Therefore, deterioration of the Q value of the filter can be prevented.

[Brief description of the drawings]

FIG. 1 is an overall perspective view of a dielectric filter according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view showing a dielectric filter according to one embodiment of the present invention.

FIG. 3 is a graph showing a relationship between the area S of a notch and the degree of inter-step coupling K in one embodiment of the present invention.

FIG. 4 is a perspective view showing a conventional dielectric filter.

FIG. 5 is an exploded perspective view showing a conventional dielectric filter.

[Explanation of symbols]

11, 12 Dielectric resonator 11a, 12a Dielectric substrate 11b, 12b Through hole 11c, 12c Outer conductor 11d, 12d Inner conductor 11e, 12e Connecting conductor 11f, 11g, 11h, 12f, 12g, 12h Electrode 11i, 11l, 11m , 11n, 12i, 121, 1
2m, 12n Outer surface 11j, 12j Open end 11k, 12k Notch 11o, 11p, 12o, 12p Notch groove

Continuation of front page (56) References JP-A-64-37101 (JP, A) JP-A-4-150101 (JP, A) JP-A-4-126404 (JP, A) (58) Fields investigated (Int .Cl. ⁶ , DB name) H01P 1/20-1/219 H01P 7/00-7/10 H01P 5/08

Claims (5)

(57) [Claims] A cylindrical prismatic dielectric substrate; an outer conductor provided on an outer surface of the dielectric substrate; an inner conductor provided on an inner surface of the dielectric substrate; A connecting conductor provided on one end face of the body base for connecting the outer conductor and the inner conductor, an open end provided on the other end face of the dielectric base body, and a first outer face of the dielectric base body First on
By providing the interstage coupling electrode provided in a non-contact manner with the outer conductor by providing the notch portion, and providing the second notch portion on the second outer surface opposite to the first outer surface. Having a connection electrode provided in a non-contact manner with the outer conductor,
The first notch and the second notch are not continuous, and the first notch reaches the open end, and the first notch is the first outer surface. a pair of third dielectric resonators extended to an outer surface adjacent to each of the second outer surface and said pair of dielectric resonator
Dielectric filter according to claim <br/> that electrically connecting the vessel respective interstage coupling electrodes to each other. 2. The second cutout has a first outer surface and a second outer surface.
To the outer conductor on the fourth outer side adjacent to each side
Dielectric filter according to claim 1, characterized in that it. 3. A connection across the first outer surface and the fourth outer surface.
3. The dielectric filter according to claim 2, further comprising an electrode for use . 4. A dielectric filter according to claim 1, characterized in that facilities the roughening treatment to the dielectric substrate. 5. The method according to claim 1, wherein the surface of the dielectric substrate is roughened.
The dielectric filter according to claim 4 , wherein a ching process is performed .