JPH07312505A - Dielectric filter - Google Patents

Abstract

PURPOSE:To obtain the dielectric filter with excellent characteristic, quality and yield in the manufacture at a low cost by forming uniformly an inner conductor film on the entire face of a hole with a bottom of the dielectric filter. CONSTITUTION:An L-shaped notch 10 is provided in a dielectric block 1 to form an inner conductor 11 by applying, e.g. chemical copper plating or the like on the entire inner wall face of a hole 2 with a bottom made nearly from a short-circuit end face 4 leading to an open end face 3 of the dielectric block 1. The air having been stayed in the inside of the hole 2 with bottom is exhausted easily externally and the inner conductor 11 is formed, in which the entire inner wall face of the hole 2 with bottom and chemical copper plating or the like is uniformly applied to the entire inner wall face of the hole 2 with bottom.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a dielectric filter used in a high frequency band such as a microwave region, and more particularly to a dielectric filter having an input / output coupling structure.

[0002]

2. Description of the Related Art Conventional multistage resonator filters using a microwave dielectric ceramic such as barium titanate have the advantages of low loss and large permittivity and can be miniaturized. It is widely used in mobile communication devices in the microwave band. The technique relating to such a dielectric filter is generally an inner conductor formed on the entire inner wall of a plurality of bottomed holes tuned to a quarter wavelength at predetermined intervals in a dielectric block having a substantially rectangular parallelepiped shape. Is provided and the axial centers of these inner conductors are arranged in parallel with each other and coupled, and the input / output coupling capacitance generated between the inner conductors is utilized.

An equivalent circuit of these dielectric filters is shown in FIG.
FIG. 10 and FIG. 11 show a perspective view and a sectional view of a conventional dielectric filter.

In FIGS. 10 and 11, 1 is a dielectric block, 2 is a hole formed in a bottomed shape, 3 is an open end face, 4 is a short-circuited end face, and 5 is generally outside the dielectric block 1. An outer conductor formed by depositing a conductor film such as electrolytic copper plating, 6
Is a tuning frequency correction capacitor formed between the bottom surface of the bottomed hole 2 and the outer conductor 5, and 7 is an input / output terminal having a terminal electrode disposed at a predetermined position of the impedance of the inner conductor 11. 8 is a conductor film peeling portion separating the input / output terminal 7 from the outer conductor 5, 9 is an input / output terminal hole connected to the bottomed hole 2 by a connecting conductor, and 11 is electroless copper plating similar to the outer conductor 5. It is an inner conductor formed by applying a conductor film such as.

The input / output terminals 7 are located on two adjacent sides of the short-circuited end face 4, and are guided from the predetermined positions of the impedance of the inner conductor 11 to the outer side of the dielectric block 1 by the input / output terminal holes 9 to form the outer conductor. It is installed insulated from conductor 5 by conductor film isolation 8. The inner conductor 11 is connected to the capacitor 6 for correcting the tuning frequency.

The dielectric filter formed in such a structure as described above has an equivalent circuit as shown in FIG. Then, the operation of a general dielectric filter will be described with reference to the equivalent circuit of FIG. First, the dielectric filter is composed of the inner conductor 11, the outer conductor 5 and the capacitor 6 as described with reference to FIGS. 1 and 2, and the inner conductor 11, the outer conductor 5 and the capacitor 6 form a resonance portion. For example, these two resonating parts are respectively referred to as 15a and 15b.
By arranging in parallel with each other, capacitive and inductive coupling characteristics can be obtained between the two resonance parts 15a and 15b. Then, this coupling characteristic is
It is output from the input / output terminal 7 to the outside through the input / output hole 9 connected to a predetermined position of the impedance of a and 15b.

[0007]

However, in the structure of such a conventional dielectric filter, since it is necessary to form the capacitor 6 on the open end face 3 side, the bottomed hole 2 is formed. Then, the inner conductor 11 must be formed on the entire inner wall of the bottomed hole 2 so that the bottom surface of the bottomed hole 2 and the open end face 3 face each other. The inner conductor 11 is generally formed by depositing electroless copper plating or the like on the entire inner wall of the bottomed hole 2. The work for depositing the electroless copper plating or the like on the inner wall of the bottomed hole 2 is performed while expelling the air contained in the bottomed hole 2.

However, since the work involved depositing electroless copper plating or the like from the inlet direction where the air in the bottomed hole 2 was expelled, the air contained in the bottomed hole 2 was completely removed. I couldn't get through. Then, electroless copper plating or the like was applied while the air remained in the bottomed hole 2. Therefore, electroless copper plating or the like was not uniformly applied to the entire inner wall of the bottomed hole 2. As described above, in the above-described conventional dielectric filter, it is difficult to uniformly form the inner conductor 11 formed by depositing electroless copper plating or the like on the entire inner wall of the bottomed hole 2. It was Therefore, the performance of the dielectric filter, for example, the variation of the pass characteristic or the attenuation characteristic is greatly varied, and the quality yield is lowered in manufacturing.

Therefore, the object of the present invention was made in view of the above-mentioned circumstances, and the inner conductor 11 formed by depositing electroless copper plating or the like on the entire inner wall of the bottomed hole 2 is made uniform. The purpose is to form.

[0010]

In order to solve the above-mentioned problems, the dielectric filter according to the present invention is characterized in that, in claim 1, a dielectric block having a substantially rectangular parallelepiped shape is bottomed from one end surface to the other end surface. A plurality of holes that are bored in the hole and are arranged with their axes parallel to each other, an inner conductor that is attached to the inner wall of the holes, and an outer conductor that is attached to the outer surface of the dielectric block. In the dielectric filter, a communication hole communicating with the hole is provided from the outer surface of the dielectric block near the bottom surface of the hole.

In claim 2, referring to claim 1,
A terminal electrode insulated from an outer conductor is provided on a side surface of the dielectric block, and a connection conductor connecting the terminal electrode and the inner conductor is provided.

In claim 3, referring to claim 1 or claim 2, a corner portion in which the communication hole is formed by the other end surface of the dielectric block of the outer conductor and the upper surface of the outer conductor. In the above, the opening cross section that is commonly opened in the vicinity of the bottom surface of the plurality of holes is opened by an L-shaped notch.

In claim 4, referring to claim 1 or claim 2, the communication hole is provided at a corner formed by the other end surface of the dielectric block and a side surface adjacent to the other end surface. The bottom surface of the hole is formed so as to penetrate through the upper surface side of the outer conductor and the lower surface side of the outer conductor and open.

In claim 5, referring to claim 1 or claim 2, the side surface side of the corner portion where the communicating hole is formed by the other end surface of the dielectric block and the side surface of the outer conductor. And is a through hole that penetrates the vicinity of the bottom surface of the hole.

In the sixth aspect, referring to the first or second aspect, the communication hole has a corner portion formed by the other end surface of the dielectric block and the upper surface of the outer conductor, on the upper surface side. And is a through hole that penetrates the vicinity of the bottom surface of the hole.

[0016]

The above technical means operates as follows. When the inner conductor is formed on the entire inner wall of the bottomed hole by electroless copper plating or the like, the bottomed hole is formed by providing a communication hole communicating from the outer conductor toward the bottom surface of the bottomed hole. The air contained in the hole is expelled to the outside, and electroless copper plating or the like is uniformly applied to form the inner conductor.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION A dielectric filter according to the present invention is a filter having a quarter wavelength, and the structure of the present invention will be described below with reference to the drawings. 1 and 2 are a first embodiment of the present invention, FIGS. 3 and 4 are a second embodiment of the present invention, and FIGS. 5 and 6 are a third embodiment of the present invention. 7,
FIG. 8 shows a fourth embodiment of the present invention, and shows a perspective view and a sectional view of a dielectric filter, respectively.

In these figures, the same parts as those of the conventional example and the first to fourth embodiments of the present invention are designated by the same reference numerals and the description thereof will be omitted. The first to fourth embodiments of the present invention are remarkably different from the conventional example in that a communication hole communicating from the outside of the dielectric block 1 toward the bottom surface of the bottomed hole 2 is provided. The different structures are different.

First, the first embodiment will be described with reference to FIGS. 1 and 2. The dielectric block 1 is provided with the above-described communication hole as an L-shaped notch 10. The L-shaped notch 10 communicates with the bottomed hole 2 from the corner where the open end surface 3 of the dielectric block 1 and the upper surface are adjacent to the bottomed hole 2 near the bottom. The opening cross-section opened at is open at an L-shaped notch. The L-shaped notch 10 has a notched end 12 which is not coated with a conductor film and is a non-conductor in which the dielectric is exposed.

Next, a second embodiment of the present invention will be described with reference to FIGS.
Describing with reference to the above, the above-mentioned communication hole is provided in the dielectric block 1 as the L-shaped missing portion 16. The L-shaped missing portion 16 is formed by opening the bottomed hole 2 toward the vicinity of the bottom surface of the bottomed hole 2 from each corner where two side surfaces are adjacent to the open end surface 3 of the dielectric block 1. In order to communicate with each other, the upper surface side of the outer conductor 5 and the lower surface side of the outer conductor 5 are penetrated and cut out and opened. And L
As in the first embodiment of the present invention described above, a conductor film is not applied to the end portion of the cut portion 12 where the character-shaped missing portion 16 is missing, and a non-conductor in which the dielectric is exposed is formed.

Next, a third embodiment of the present invention will be described with reference to FIGS.
In the dielectric block 1, the above-mentioned communication hole is provided as the opening hole 13. And this opening hole 13
Are located on two adjacent side surfaces of the short-circuited end surface 4 of the dielectric block 1, respectively, and communicate with the bottomed hole 2 from the corner near the open end surface 3 toward the bottom surface of the bottomed hole 2. The structure is provided with holes. In this case, the periphery 14 of the opening 13 is not coated with a conductor and is a non-conductor with the dielectric exposed.

FIGS. 7 and 8 show a fourth embodiment of the present invention. The difference from the third embodiment of the present invention described above is that the opening provided in the third embodiment of the present invention described above. The holes 13 are transferred to the corners on the open end face 3 side of the upper surface adjacent to the open end face 3. Also in this case, similarly, the periphery 14 of the opening hole 13 is not coated with a conductor film and is a non-conductor in which the dielectric is exposed.

In the above-described structure, when the inner conductor 11 is formed by depositing electroless copper plating or the like on the entire inner wall of the bottomed hole 2, the bottomed hole 2 enters the inside of the bottomed hole 2. The air is expelled to the outside from the L-shaped cutout portion 10 and the opening hole 13 which are communicated between the bottom surface of the bottomed hole 2 and the outer conductor 5. Therefore, electroless copper plating or the like is uniformly applied to the entire inner wall of the bottomed hole 2, so that the inner conductor 1 is evenly formed.
1 can be formed. Incidentally, FIG. 1, FIG. 2 and FIG.
The installation positions of the L-shaped cutout portion 10 and the opening hole 13 described with reference to FIG. 8 may be moved to the bottom surface side of the dielectric block 1 facing each other.

[0024]

As described above, according to the present invention, since the opening hole communicating with the outer conductor is provided near the bottom surface of the bottomed hole, the entire inner wall of the bottomed hole is For example, when the inner conductor is formed by depositing electroless copper plating or the like, the air contained in the bottomed hole is easily expelled to the outside from the opening. Therefore, since electroless copper plating or the like is uniformly applied to the entire inner wall of the bottomed hole, the inner conductor can be uniformly formed. Therefore, the non-uniformity of the inner conductor is eliminated, and the performance of the dielectric filter, such as the cutoff of the pass characteristic and the attenuation characteristic, is improved. Further, it is possible to obtain the effect that the quality yield is improved in manufacturing and an inexpensive dielectric filter can be provided.

[Brief description of drawings]

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

FIG. 2 is a sectional view of a dielectric filter according to the first embodiment of the present invention.

FIG. 3 is a perspective view of a dielectric filter according to a second embodiment of the present invention.

FIG. 4 is a sectional view of a dielectric filter according to a second embodiment of the present invention.

FIG. 5 is a perspective view of a dielectric filter according to a third embodiment of the present invention.

FIG. 6 is a sectional view of a dielectric filter according to a third embodiment of the present invention.

FIG. 7 is a perspective view of a dielectric filter according to a fourth embodiment of the present invention.

FIG. 8 is a sectional view of a dielectric filter according to a third embodiment of the present invention.

FIG. 9 is an equivalent circuit diagram of a dielectric filter.

FIG. 10 is a perspective view of a conventional dielectric filter.

FIG. 11 is a cross-sectional view of a conventional dielectric filter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dielectric block 2 Bottomed hole 3 Open end surface 4 Short-circuited end surface 5 Outer conductor 6 Capacitor part 7 Input / output terminals 8, 14 Conductive film peeling part 9 Input / output terminal hole 10 L-shaped notch part 11 Inner conductor 12 Cutting Part 13 Opening holes 15a, 15b Resonant part 16 L-shaped missing part

Claims (6)

[Claims] 1. A plurality of holes, each of which is formed in a bottomed shape from one end surface to the other end surface of a substantially rectangular parallelepiped dielectric block, and whose axes are arranged parallel to each other, and an inner wall of the holes. A dielectric filter comprising an attached inner conductor and an outer conductor attached to an outer surface of the dielectric block, wherein the outer surface of the dielectric block is in communication with the hole near the bottom surface of the hole. A dielectric filter having holes. 2. The dielectric according to claim 1, wherein a terminal electrode insulated from an outer conductor is provided on a side surface of the dielectric block, and a connection conductor connecting the terminal electrode and the inner conductor is provided. Body filter. 3. The communication hole is at a corner formed by the other end surface of the dielectric block of the outer conductor and the upper surface of the outer conductor, and is commonly provided near the bottom surfaces of the plurality of holes. 3. The dielectric filter according to claim 1 or 2, wherein the opened cross section has an L-shaped cutout. 4. The communicating hole is at a corner formed by the other end surface of the dielectric block and a side surface adjacent to the other end surface, and the upper surface side of the outer conductor is near the bottom surface of the hole. 2. The dielectric filter according to claim 1, wherein the outer conductor is cut off and opened through the lower surface side of the outer conductor. 5. A through hole which is located on the side surface side of a corner portion formed by the other end surface of the dielectric block and the side surface of the outer conductor and which penetrates the vicinity of the bottom surface of the hole. The dielectric filter according to claim 1 or 2, wherein 6. A through hole which is located on the upper surface side of a corner portion formed by the other end surface of the dielectric block and the upper surface of the outer conductor, and through which the communication hole penetrates near the bottom surface of the hole. The dielectric filter according to claim 1 or 2, wherein