JPH1051206A - Dielectric filter and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dielectric filter whose characteristics is easily designed and whose metallic die is used in common. SOLUTION: Two non-through-holes 11 are formed to a dielectric block 10, an entire surface of the dielectric block 10 is covered with electrodes 12, and the two non-through-holes 11 are used for inner conductors of two coaxial resonators. An opening side of the non-through-holes 11 is regarded as a short- circuit end 15 of the resonator, and a face opposite to the short-circuit end 15 is regarded as an open end 16. Furthermore, two separate input/output terminals 13 are formed to the electrode of an outer circumferential face of the dielectric block, and non-forming part of a conductor 14 is provided to part of the outer conductor of the dielectric block 10. The non-forming part 14 is formed thin and long, so that the non-forming part 14 of the conductors is placed in the vicinity of the short-circuit end 15 of the resonator and orthogonal to the lengthwise direction of the resonator inner conductor.

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 for radio communication in a high frequency band, and more particularly to a non-through-hole monolithic filter in which a portion of a conductor covering a surface of a dielectric block has no conductor. And implements the filter characteristics and adjusts the filter characteristics.

[0002] The present invention relates to a technique in which a hole formed in a dielectric block is not limited to a non-through hole or a through-hole. I may mention only.

[0003]

2. Description of the Related Art A conventional technique will be described with reference to the drawings. As a conventional example of a monolithic dielectric filter, FIG. 10 shows a monolithic filter in which two non-through holes are formed. Two non-through holes 11 in the dielectric block 10
Is formed, and the entire surface of the dielectric block is covered with the electrode 12, and the two non-through holes 11 can be regarded as inner conductors of the two coaxial resonators. Dielectric block 1
The input / output terminals 13 are formed separately on the electrode 12 on the outer peripheral surface of the reference numeral 0. The electrodes 12 are mounted on a wiring board or the like so as to be at the ground potential, and the characteristics are measured between the input / output terminals 13. Then, it functions as a bandpass filter composed of two resonators.

[0004] The dielectric filter is used for radio communication in a high frequency band and the like, and is often used mainly for mobile phones and cordless phones. However, the frequency band to be used and the required characteristics differ depending on the system, so that the dielectric filter needs to realize the characteristics according to the system to be used. FIG. 11 shows the characteristics of the filter shown in FIG. The portion indicated by A is the pass band of the band-pass filter, and the pass bandwidth requires a frequency band suitable for the system to be used.

FIG. 13 shows the characteristics of a dielectric filter in which two through holes are formed in a dielectric block.

[0006]

In the method of manufacturing a dielectric filter shown in FIG. 10, a dielectric material powder is press-molded by a compacting die, the formed press body is sintered, and then the surface is pressed. In general, metallization is performed.

The characteristics of a dielectric filter having a monolithic structure are determined by the shape of a dielectric block, the shape of input / output terminals, and a dielectric material. In addition, since the input / output terminals and conductors inside the resonator required for the circuit configuration are capacitively coupled to each other, even if the shape is partially changed to change some of the characteristics, it will affect various parts. Greatly changes the characteristics of the entire filter. For this reason, even when it is desired to change only a part of the filter characteristics, it is necessary to review the entire filter structure.

An example in which a part of the filter characteristic is changed will be described with reference to FIGS. In the filter characteristics shown in FIG. 11, the portion A is a pass band,
When changing the passband, it is necessary to adjust the coupling between the input / output terminal and the conductor in the resonator, and at the same time, to adjust the coupling between the resonators.

One of the methods for changing the strength of the coupling is to change the distance between the electrodes. For example, in the case of adjusting the coupling between the input / output terminal and the conductor in the resonator in the dielectric filter shown in FIG. 10, it is necessary to change the distance between the electrodes to change the coupling strength. It is necessary to change the thickness of the dielectric between the inner conductors.
This is the same when adjusting the coupling between the resonators. In order to realize this, it is necessary to change the shape of the dielectric block, and as a means, it is necessary to change the shape of the die used for press molding, or to cut the dielectric block by additional processing .

[0010] One of the methods for changing the coupling strength is to change the electrode area. In the case where the coupling is adjusted by changing the electrode area, when the coupling between the input / output terminal and the conductor in the resonator is strengthened, the area of the input / output terminal electrode may be increased, but when the coupling between the resonators is adjusted. However, since it is necessary to increase the electrode area by changing the conductor diameter in the resonator, it is necessary to change the shape of the die used for press molding.

FIG. 12 shows frequency characteristics when only the area of the input / output terminal electrodes is increased in order to increase the pass band width. Although the coupling between the input / output terminal and the conductor in the resonator has been strengthened by increasing the electrode area, the coupling between the resonators has not changed, so that the overall balance is poor and the filter characteristics are degraded. In this state, if the coupling between resonators is strengthened, ideal filter characteristics will be obtained, but in order to do so, it is necessary to change the shape of the dielectric block.

In a dielectric filter in which two through holes are formed in a dielectric block, in order to widen a pass band,
FIG. 14 shows frequency characteristics when only the input / output terminal electrode area is increased.

As described above, in a dielectric filter having a monolithic structure, a structural change is necessary to change the filter characteristics, and it is difficult to make a design change. Therefore, in order to overcome the drawbacks, an object of the present invention is to provide a dielectric filter in which characteristics can be easily designed and a mold can be shared as compared with a conventional dielectric filter.

[0014]

The present invention employs the following means to solve the above-mentioned problems.

(1) A dielectric filter in which a plurality of non-through holes are formed in a dielectric block, and the entire surface including the inner surface of the non-through hole is covered with a conductor except for a region around an input / output terminal. A dielectric filter, wherein a non-formed portion of a conductor is provided on a part of an outer peripheral surface of the dielectric block among the conductors.

(2) The non-formed portion of the conductor is arranged on the outer peripheral surface of the dielectric block in the direction orthogonal to the longitudinal direction of the non-through hole, near the non-through hole opening surface of the dielectric block. The dielectric filter according to (1), wherein:

(3) The dielectric filter according to (1), wherein the coupling between the resonators is adjusted by changing the size of the non-formed portion of the conductor.

(4) After covering the entire surface except the area around the input / output terminal with the conductor, a non-formed portion of the conductor is formed to adjust the filter characteristics. A manufacturing method of the dielectric filter according to the above.

(5) A plurality of through-holes are formed in the dielectric block, and the entire area including the inner surface of the through-hole except for a region around the input / output terminals and a partial region for forming a resonator open end. A dielectric filter, the surface of which is covered with a conductor, wherein a non-formed portion of the conductor is provided on a part of the outer peripheral surface of the dielectric block among the conductors.

(6) The non-formed portion of the conductor is arranged on the outer peripheral surface of the dielectric block, in a direction perpendicular to the longitudinal direction of the through hole, near the through hole opening surface of the dielectric block. The dielectric filter according to the above (5).

(7) The dielectric filter according to (5), wherein the coupling between the resonators is adjusted by changing the size of the non-formed portion of the conductor.

(8) After covering the entire surface except the area around the input / output terminal with the conductor, a non-formed portion of the conductor is formed, and the filter characteristics are adjusted. A manufacturing method of the dielectric filter according to the above.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention performs filtering by a surface mount type dielectric filter composed of a single dielectric block in a mobile communication radio such as a portable telephone or a digital cordless phone.

Embodiments of the present invention will be described in detail in the section of Examples.

[0025]

FIG. 1 shows a dielectric filter in which two non-through holes are formed in a dielectric block according to a first embodiment of the present invention.
Two non-through holes 11 are formed in the dielectric block 10,
The entire surface of the dielectric block 10 is covered with the electrode 12, and the two non-through holes 11 can be regarded as inner conductors of two coaxial resonators. Here, the opening side of the non-through hole can be regarded as the short-circuit end 15 of the resonator, and the surface facing the short-circuit end 15 as the open end 16. Further, two input / output terminals 13 are formed separately on the electrode 12 on the outer peripheral surface of the dielectric block 10, and a conductor non-forming portion 14 is formed on a part of the outer peripheral conductor of the dielectric block 10. Is provided. In the case of the first embodiment shown in FIG. 1, the position of the non-formed portion 14 of the conductor provided on the outer peripheral surface conductor is near the short-circuited end of the resonator and is elongated so as to be orthogonal to the longitudinal direction of the conductor in the resonator. Is formed.

Referring to FIGS. 1 to 6 showing the first to third embodiments of the present invention, in a dielectric filter having the same shape of a dielectric block and an input / output terminal (both are non-through holes),
A change in characteristics depending on the size of the non-formed portion of the conductor will be described.

FIG. 2 shows the frequency characteristics of the dielectric filter having the shape shown in FIG. Pass bandwidth is 130 [MHz]
It has become about. The loss in the pass band is constant, and it can be said that the coupling strength between the conductors in the resonator is ideal compared to the coupling strength between the input / output terminals and the conductor in the resonator. Can be said to be an ideal waveform. At this time, the length L of the non-formed portion of the conductor provided on the outer circumferential surface conductor is 1 [mm] width, and is the same length (L = P) as the inner conductor pitch P of the resonator.

Next, a dielectric filter having the same shape as that of the dielectric filter shown in FIG. 1 is added to a dielectric filter having the same shape as the dielectric filter shown in FIG. The second aspect of the dielectric filter of the present invention in which the length L is 1 [mm] width and is half the length (L = P / 2) of the inner conductor pitch P
FIG. 3 shows an embodiment, and FIG. 4 shows frequency characteristics at that time. In the characteristics of FIG. 4, the pass band is narrow and the loss is not constant. This is because the strength of the coupling between the resonators is smaller than the coupling between the input / output terminal and the resonator. That is, it can be said that the coupling between the resonators is reduced by reducing the size of the non-formed portion of the conductor provided on the outer peripheral surface conductor.

Further, a dielectric filter having the same shape as the dielectric filter shown in FIG. 1 except for the non-formed portion of the conductor provided on the outer conductor is provided with a size of the non-formed portion of the conductor provided on the outer conductor. The length L is 1 [mm] width and the inner conductor pitch P is 1.5.
FIG. 5 shows a third embodiment of the dielectric filter of the present invention having twice the length (L = 1.5 P), and FIG. 6 shows the frequency characteristics at that time. In the characteristics shown in FIG. 6, the pass band is widened, a depression is formed in the band, and the loss is not constant. this is,
This is because the coupling strength between the resonators is greater than the coupling between the input / output terminal and the resonator. That is, it can be said that the coupling between the resonators is increased by increasing the size of the non-formed portion of the conductor provided on the outer peripheral surface conductor.

From these facts, it can be understood that the provision of the non-formed portion on the outer peripheral surface of the dielectric filter makes it possible to adjust the coupling strength between the conductors in the resonator. The magnitude of the coupling strength changes in synchronization with the size of the non-formed portion of the conductor. 1 to 6 show the results of changing the size of the non-formed portion of the conductor formed at a fixed distance from the short-circuit end face and changing the length while keeping the width constant. Experiments have also confirmed that even when the size of the non-formed portion of the conductor is changed in the longitudinal direction of the conductor in the resonator, the coupling between the conductors in the resonator changes. However, the change amount of the coupling strength was larger when the size of the non-formed portion of the conductor was changed in the direction orthogonal to the longitudinal direction of the conductor in the resonator.

Next, characteristics of the dielectric filter in which the coupling between the resonators is changed by changing the size of the non-formed portion of the conductor, when the size of the input / output terminal electrode is adjusted will be described.

As a conventional example, the filter shape shown in FIG. 10 has the same shape as the dielectric block shown in FIG. However, the size of the input / output terminal electrode is adjusted to the strength of the coupling between the conductors in the resonator, and this size is smaller than the input / output electrode of the dielectric filter shown in FIG. I have. FIG.
FIG. 1 shows the dielectric filter characteristics of FIG.
The attenuation in the passband is constant, and is ideal as a bandpass filter. The pass bandwidth at this time is 100
[MHz].

When this is compared with the filter characteristics shown in FIG. 2, a difference of 30 [MHz] occurs in the pass band width.
In the conventional filter shown in FIG. 10 and the filter according to the first embodiment of the present invention shown in FIG. 1, the working dielectric blocks have the same shape. In other words, even if a dielectric block having the same shape is used, the strength of the conductor coupling in the resonator can be adjusted by the metallization forming method, so that a dielectric filter having different characteristics can be realized. I have.

For the same reason, the filter characteristics shown in FIGS. 4 and 6 also become ideal if the size of the input / output electrode is adjusted. In the case of the filter according to the second embodiment of the present invention shown in FIG. 3, if the area of the input / output electrode is reduced,
A filter having a characteristic having a narrower pass bandwidth than the filter characteristic of FIG. 2 of the first embodiment of the present invention is completed. In the case of the filter according to the third embodiment of the present invention shown in FIG. 5, if the input and output electrodes are enlarged, the dielectric filter has a wider pass band compared with the filter characteristics of the first embodiment of the present invention shown in FIG. Is completed.

As a method of forming the non-formed portion of the conductor in a part of the outer conductor, a method of cutting the surface such as a laser beam machine or sand blast is used, but not only the electrode layer but also the dielectric is cut at the same time. No effect is seen on the characteristics.

Further, even in the conventional dielectric filter shown in FIG. 10 having no conductor non-formed portion, if the conductor non-formed portion is formed as a post-processing for adjustment, the frequency characteristic at that time can be improved. Changes gradually in synchronization with the area of the non-formed portion of the conductor, so that a highly accurate dielectric filter can be manufactured.

Next, a description will be given of each dielectric filter in which two through holes are formed in the dielectric block according to the fourth to sixth embodiments of the present invention. These are different from the respective structures of FIGS. 1, 3 and 5 showing the first to third embodiments only in that the non-through holes 11 are replaced with through holes, respectively, and the other points are the same. .

FIGS. 7 to 9 show the frequency characteristics of the dielectric filters of the fourth to sixth embodiments, respectively.

[0039]

As described above, according to the present invention, even when the shape of the dielectric block is kept constant, the resonator is formed by providing a portion of the outer conductor on which the conductor is not formed. It is possible to change the magnitude of the intercoupling. Therefore, when the adjustment is performed simultaneously with the size of the input / output terminal electrodes, dielectric filters having various characteristics can be realized with the dielectric blocks having the same shape only by changing the metallization method of the dielectric blocks.

In the case of changing the characteristics of the conventional monolithic filter, it was necessary to change the shape of the dielectric block. Therefore, it was difficult to change the design. However, according to the present invention, the characteristics are different. Many types of dielectric filters can be manufactured at low cost, and a surface-mounted dielectric filter that can be easily designed and developed and can use a common mold can be realized.

[Brief description of the drawings]

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

FIG. 2 is a graph showing frequency characteristics of the 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 graph showing frequency characteristics 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 graph showing frequency characteristics of a dielectric filter according to a third embodiment of the present invention.

FIG. 7 is a graph showing frequency characteristics of a dielectric filter according to a fourth embodiment of the present invention.

FIG. 8 is a graph showing frequency characteristics of a dielectric filter according to a fifth embodiment of the present invention.

FIG. 9 is a graph showing frequency characteristics of a dielectric filter according to a sixth embodiment of the present invention.

FIG. 10 is a perspective view of a conventional dielectric filter in which two non-through holes are formed in a dielectric block.

FIG. 11 is a graph showing 1 of frequency characteristics of a dielectric filter in which two non-through holes are formed in a conventional dielectric block.

FIG. 12 is a graph showing a frequency characteristic 2 of a dielectric filter in which two non-through holes are formed in a conventional dielectric block.

FIG. 13 is a graph showing 1 of frequency characteristics of a dielectric filter in which two through holes are formed in a conventional dielectric block.

FIG. 14 is a graph showing a frequency characteristic 2 of a dielectric filter in which two through holes are formed in a conventional dielectric block.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Dielectric block 11 Non-through hole 12 Electrode 13 I / O terminal 14 Non-forming part of conductor 15 Short-circuit end 16 Open end A Passband L Length of non-forming part of conductor P Inner conductor pitch

Claims (8)

[Claims] 1. A dielectric filter in which a plurality of non-through holes are formed in a dielectric block, and a whole surface including an inner surface of the non-through hole is covered with a conductor except for a region around an input / output terminal. A dielectric filter, wherein a non-formed portion of the conductor is provided on a part of an outer peripheral surface of the dielectric block among the conductors. 2. The method according to claim 1, wherein the non-forming portion of the conductor is arranged on an outer peripheral surface of the dielectric block in a direction orthogonal to a longitudinal direction of the non-through hole and near a non-through hole opening surface of the dielectric block. 2. The dielectric filter according to claim 1, wherein: 3. The dielectric filter according to claim 1, wherein the coupling between the resonators is adjusted by changing the size of the non-formed portion of the conductor. 4. The filter characteristics are adjusted by covering the entire surface of the input / output terminal except for the area around the input / output terminal with the conductor, and then forming a non-formed portion of the conductor.
A manufacturing method of the dielectric filter according to the above. 5. A plurality of through holes are formed in a dielectric block, and the entire surface including the inner surface of the through holes except for a region around an input / output terminal and a partial region for forming an open end of a resonator. A dielectric filter comprising a conductor covered with a conductor, wherein a portion of the conductor that is not provided with a conductor is provided on a part of an outer peripheral surface of the dielectric block. 6. The non-formed portion of the conductor is disposed on the outer peripheral surface of the dielectric block, in a direction orthogonal to the longitudinal direction of the through hole, near the through hole opening surface of the dielectric block. The dielectric filter according to claim 5, wherein 7. The dielectric filter according to claim 5, wherein the coupling between the resonators is adjusted by changing the size of the non-formed portion of the conductor. 8. The filter according to claim 5, further comprising: forming a non-formed portion of the conductor after covering the entire surface except for a region around the input / output terminal with the conductor to adjust a filter characteristic.
A manufacturing method of the dielectric filter according to the above.