JPH1197904A - Dielectric filter and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a dielectric filter easy to design and capable of using a metallic mold in common and easily changing filter characteristics by forming the non-formation of a conductor at one part of a conductor covering the surface of a dielectric block. SOLUTION: In this dielectric filter 1, two non-through holes 11 are formed in a dielectric block 10, and the whole surface of the dielectric block 10 is covered with an electrode 12. The non-through holes 11 can be considered as inner conductors 11a of two co-axial resonators. The opening face side of the non-through holes 11 can be considered as a short-edge 15 of a resonator, and a face opposite to this short-circuit edge 15 can be considered as an open edge 16. Two separated input and output terminals 13 are formed on an electrode 12 on the outer peripheral face of the dielectric block 10. A conductor non- formation part 14a is formed at one part of the opening face of the non-through hole 11. The position of the conductor non-formation part 14a is present between the two non-through holes 11. Thus, connection between resonators can be adjusted by changing length L of the conductor non-formation part 14a.

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 dielectric filter having a non-through hole monolithic structure and a method of manufacturing the same.

[0002]

2. Description of the Related Art A dielectric filter is used for radio communication in a high frequency band or the like, and is mainly used for a portable telephone, a cordless telephone or the like in many cases. However, the frequency band used and the required characteristics differ depending on the system, so that the dielectric filter needs to realize characteristics suitable for the system used.

A conventional technique will be described with reference to the drawings. As a conventional example, FIG. 10 shows a dielectric filter having a monolithic structure in which two non-through holes are formed.

In FIG. 10, a dielectric filter 1 has two non-through holes 11 formed in a dielectric block 10, and the entire surface of the dielectric block except for the periphery of an input / output terminal 13 is covered with an electrode 12. ing. Also, two non-through holes 11
Can be regarded as inner conductors 11a of two coaxial resonators.

The electrode 12 on the outer peripheral surface of the dielectric block 10 is formed with two input / output terminals 13 separated from each other on opposing surfaces. When the characteristics are measured between the input / output terminals 13, the device functions as a band-pass filter including two resonators.

A method of manufacturing the dielectric filter 1 is generally such that a dielectric material powder is press-molded with a compacting die, and the formed pressed body is sintered, so that the surface is metallized. It is a target.

The characteristics of the monolithic dielectric filter are determined by the shape of the dielectric block, the shape of the input / output terminals, and the characteristics of the dielectric material. Also, since the input / output terminals and conductors inside the resonator required for the circuit configuration are electrically coupled to each other, even if the shape of some of them is changed to change And it 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 structure of the filter.

FIG. 11 shows frequency characteristics of a conventional dielectric filter. The portion indicated by A in FIG. 11 is the pass band of the band-pass filter, and the pass band requires a frequency band that matches the system used.

Next, 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.
Is a pass band, but when the pass bandwidth is changed, it is necessary to adjust the coupling between the input / output terminal 13 and the inner conductor 11a of 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, FIG.
In the dielectric filter 1 shown in FIG.
When adjusting the coupling between the inner conductor 11a of the resonator and the inner conductor 11a of the resonator, the distance between the electrodes can be changed to change the strength of the coupling. It is necessary to change the thickness.

This is the same when adjusting the coupling between the resonators. To achieve this, it is necessary to change the shape of the dielectric block. As a means,
It is necessary to change the shape of the mold used for press molding or to cut the dielectric block by post-processing.

One of the methods for changing the strength of coupling is to change the electrode area. When adjusting the coupling by changing the electrode area, the input / output terminals 13
When the coupling between the resonator and the inner conductor 11a of the resonator is strengthened, the area of the input / output terminal 13 may be increased, but when the coupling between the resonators is adjusted, the diameter of the inner conductor 11a of the resonator is changed and the electrode is changed. It is necessary to increase the area. As a means for this, it is necessary to change the shape of a mold used for press molding.

FIG. 12 shows filter characteristics when only the area of the electrode of the input / output terminal 13 is increased in order to increase the pass band width. By expanding the electrode area, the coupling between the input / output terminal 13 and the inner conductor 11a of the resonator is strengthened.
Since the resonator-to-resonator coupling has not changed, 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. However, in order to achieve this, it is necessary to change the shape of the dielectric block.

FIG. 13 shows the characteristics of a dielectric filter in which two through holes are formed in a dielectric block. FIG. 14 shows the frequency characteristics of this dielectric filter when only the electrode area of the input / output terminal is increased in order to increase the pass band width.
It was shown to.

[0017]

As described above,
In the case of changing the filter characteristics of a monolithic dielectric filter, it is necessary to change the structure of the filter itself. However, it is difficult to change the design, which involves changing the mold, costs, time, and the like.

Accordingly, an object of the present invention is to provide a dielectric filter which is easier to design, can use a common mold, and can easily change the filter characteristics, as compared with a conventional dielectric filter. And

[0019]

SUMMARY OF THE INVENTION The present invention relates to a mobile communication radio such as a mobile phone or a digital cordless phone.
Filtering is performed by a surface mount type dielectric filter composed of a single dielectric block. Further, the present invention is to form a non-formed portion of the conductor on a part of the conductor covering the surface of the dielectric block, thereby realizing the filter characteristics and adjusting the filter characteristics. In addition, the present invention is a technology regardless of whether the hole formed in the dielectric block is a non-through hole or a through-hole, but in the following description, matters common to both are described only for the non-through-hole. .

That is, according to the present invention, a part of a non-through hole opening surface in which a plurality of non-through holes are formed from one surface of a dielectric block toward an opposing surface and a region around an input / output terminal are removed. A dielectric filter in which the entire surface including the inner surface of the non-through hole is covered with a conductor.

Further, the present invention is the above dielectric filter, wherein a conductor-free portion which is not covered with the conductor on the opening surface of the non-through hole is arranged between the non-through holes.

Further, the present invention is the above dielectric filter, wherein the coupling between resonators is adjusted by changing the size of the non-conductor-formed portion.

Further, according to the present invention, there is provided a method of manufacturing a dielectric filter according to the present invention, wherein the conductor-free portion is formed after covering the entire surface except for the area around the input / output terminal, and the filter characteristics are adjusted. It is.

The present invention also relates to a part of a through hole opening surface in which a plurality of through holes are formed from one surface of a dielectric block, a region around input / output terminals, and a part for forming a resonator open end. A dielectric filter in which the entire surface including the inner surface of the through hole except for the region is covered with a conductor.

Further, the present invention is the above dielectric filter, wherein a conductor-free portion not covered with a conductor on the opening surface of the through hole is arranged between the through holes.

Further, the present invention is the above dielectric filter, wherein the coupling between the resonators is adjusted by changing the size of the non-formed portion of the conductor.

Further, according to the present invention, the conductor-free portion is formed after covering the entire surface except for a region around the input / output terminal and a partial region for forming the resonator open end with the conductor. And a method for manufacturing the dielectric filter for adjusting the filter characteristics.

[0028]

Embodiments of the present invention will be described below.

First, a first embodiment of the present invention will be described.

FIG. 1 shows a dielectric filter 1 in which two non-through holes 11 are formed in a dielectric block according to a first embodiment of the present invention. In FIG. 1, a dielectric filter 1 includes:
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. The non-through hole 11 can be regarded as the inner conductor 11a of the two coaxial resonators.

Here, the open surface side of the non-through hole 11 is the short-circuited end 15 of the resonator, and the surface facing the short-circuited end 15 is the open end 1.
6 can be considered. The electrode 12 on the outer peripheral surface of the dielectric block 10 is provided with two separated input / output terminals 13. Further, a part of the opening surface of the non-through hole 11 has a conductor non-formed portion 14 a Is provided. The position of the conductor non-forming portion 14 a provided on the non-through hole opening surface 17 is between the two non-through holes 11.

FIG. 2 shows the frequency characteristics of the dielectric filter. In FIG. 2, the width of the pass band A is 100 MHz.
It has become about. The loss in the pass band A is substantially constant, and the strength of the coupling between the inner conductors 11a of the resonator is ideal compared to the strength of the coupling between the input / output terminal 13 and the inner conductor 11a of the resonator. It can be said that there is. This can be said to be an ideal waveform for a bandpass filter. At this time, the length L of the conductor non-formed portion 14a provided on the non-through hole opening surface 17
Has the same length (L = φ) as the diameter φ of the inner conductor 11 a of the non-through hole 11.

Next, a second embodiment of the present invention will be described.

As shown in FIG. 3, the dielectric filter according to the second embodiment of the present invention uses the conductor non-forming portion 14b provided on the non-through hole opening surface 17 to form the dielectric filter shown in FIG. A dielectric filter having the same shape as the filter, and the non-through hole opening surface 1
7, the length L of the non-conductor portion 14b is longer than the diameter φ of the non-through hole, and L> φ.

FIG. 4 shows the frequency characteristics of the dielectric filter according to the second embodiment. In FIG. 4, pass band A
Has a narrower bandwidth than the pass band of the dielectric filter of the first embodiment, and the loss is not constant. This is because the strength of the coupling between the inner conductors of the resonator is smaller than the coupling between the input / output terminals and the inner conductor of the resonator. That is, it can be said that the coupling between the resonators is reduced by increasing the size of the non-conductive portion 14b provided on the opening surface 17 of the non-through hole.

Next, a third embodiment of the present invention will be described.

As shown in FIG. 5, the dielectric filter according to the third embodiment of the present invention uses the conductor non-forming portion 14c provided on the non-through hole opening surface 17 to form the dielectric filter shown in FIG. A dielectric filter having the same shape as the filter, and the non-through hole opening surface 1
7, the length L of the non-conductor portion 14c is shorter than the diameter φ of the non-through hole, and L <φ.

FIG. 6 shows the frequency characteristics of the dielectric filter according to the third embodiment. In FIG. 6, pass band A
Although the bandwidth becomes wider as compared with the pass band of the dielectric filter of the first embodiment, the band is depressed in the band and the loss is not constant. This is because the coupling strength between the inner conductors of the resonator is larger than the coupling between the input / output terminal and the inner conductor of the resonator. That is, it can be said that the coupling between the resonators is increased by reducing the size of the conductor non-formed portion 14c provided on the opening surface 17 of the non-through hole.

From these facts, it can be understood that the provision of the non-conductor portion on the opening surface of the non-through hole of the dielectric filter makes it possible to adjust the coupling strength between the inner conductors of the resonator. Then, the magnitude of the coupling strength changes in synchronization with the size of the non-formed portion.

In the first to third embodiments,
Near the center between the two non-through holes 11, two non-through holes 1
The results obtained by changing the length while keeping the width constant in the direction orthogonal to the straight line connecting the center points of No. 1 are shown. Also, the conductor non-formed portion 1
4a, 14b, and 14c, the size of the two non-through holes 11
It has been confirmed by experiments that the coupling between the inner conductors 11a of the resonator changes even when the direction is changed in a direction parallel to the straight line connecting the center points of. However, the result that the amount of change in the coupling strength is larger when the size of the conductor non-formed portions 14a, 14b, and 14c is changed in a direction perpendicular to a straight line connecting the center points of the two non-through holes 11 is larger. Has become.

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

The shape of the conventional dielectric filter shown in FIG. 10 is the same as that of the dielectric block shown in FIG. 1, although no conductor-free portion is provided on the non-through hole opening surface 17. However, the size of the input / output terminal electrodes is adjusted to the strength of the coupling between the inner conductors 11a of the resonator, and the size of the input / output terminal electrodes 13 of the dielectric filter shown in FIG.
It is larger than that.

FIG. 11 shows the frequency characteristics of the dielectric filter of FIG. 10. The attenuation in the pass band A is constant, and is ideal as a band-pass filter.
The width of the pass band A at this time is about 130 MHz.

Comparing this with the frequency characteristic (FIG. 2) of the dielectric filter shown in FIG.
Hz difference occurs. In other words, even when the dielectric blocks having the same shape are used, the coupling between the inner conductors 11a of the resonator can be achieved by the metallization forming method when the input / output terminals 13 are formed.
In addition, since the coupling strength between the input / output terminal 13 and the inner conductor 11a of the resonator can be adjusted, it is possible to realize a dielectric filter having different characteristics.

For the same reason, the frequency characteristics of the dielectric filters according to the second and third embodiments of the present invention shown in FIG. 4 and FIG. It becomes ideal filter characteristics. That is, in the case of the dielectric filter according to the second embodiment of the present invention shown in FIG. 3, if the area of the input / output terminal electrode 13 is reduced, the characteristic having a narrower pass bandwidth than the frequency characteristic shown in FIG. The dielectric filter is completed.

In the case of the dielectric filter according to the third embodiment of the present invention shown in FIG. 5, if the input / output terminal electrode 13 is enlarged, the frequency characteristic shown in FIG. 2 of the first embodiment of the present invention can be obtained. As a result, a dielectric filter having a characteristic having a wider pass band width is completed.

As a method of forming the non-conductor-formed portion in a part of the opening surface of the non-through hole, a method of cutting the surface of the electrode (conductor) using a laser machine, sand blast, or the like is used.
Even if not only the electrode layer but also the dielectric is cut at the same time, there is almost no effect on the characteristics.

Further, even in the conventional dielectric filter shown in FIG. 10 having no conductor-free portions, if the conductor-free portions 14a, 14b, and 14c are formed as post-processing, the frequency characteristics at that time can be improved. , Conductor non-forming portions 14a, 14b, 1
Since it gradually changes in synchronization with the area of 4c, a highly accurate dielectric filter can be manufactured.

In order to realize a dielectric filter having a narrow pass band, both the coupling between the inner conductors of the resonator and the coupling between the input / output terminal electrode 13 and the inner conductor 11a of the resonator must be reduced. In order to reduce the coupling between the inner conductors 11a, it is necessary to increase the inner conductor pitch. In the case of the conventional dielectric filter having no conductor-free portion shown in FIG. 10, when the pitch of the inner conductors 11a is increased to reduce the coupling between the inner conductors 11a, the outer diameter of the dielectric block becomes larger. Would.

However, in the case of the dielectric filter according to the present invention shown in FIG. 1, even if the shape of the dielectric block 10 is not changed, the non-conductive portion 1
By providing the 4a, the coupling between the inner conductors 11a of the resonator that is too large can be reduced, so that dielectric filters having various characteristics can be realized without increasing the size of the dielectric block.

For the same reason, even when a small-sized dielectric block is used, the coupling between the inner conductors of the resonator and the coupling between the input and output terminals due to the metallization forming method for forming the input and output terminals are performed. It is possible to realize ideal dielectric filter characteristics because the strength of the coupling can be adjusted.

Next, dielectric filters according to fourth to sixth embodiments of the present invention will be described. These have two through holes formed in the dielectric block. In each of the structures of FIGS. 1, 3 and 5 showing the first to third embodiments, the non-through holes 11 are respectively formed. The only difference is that the through hole is used, and the other points are the same.

FIGS. 7 to 9 show the frequency characteristics of the dielectric filters according to the fourth to sixth embodiments, respectively.
FIGS. 7 to 9 and FIGS. 2, 4 and 6 showing frequency characteristics of the respective dielectric filters according to the first to third embodiments of the present invention.
Is compared, the pass band A in the frequency characteristics of the fourth to sixth embodiments of the present invention is the same as the pass band of the frequency characteristics of the first to third embodiments.

[0054]

As described above, according to the present invention, even when the shape of the dielectric block is kept constant, the non-through-hole-forming portion is provided on a part of the opening surface of the non-through hole. It is possible to change the magnitude of the coupling between the resonators. Therefore, when 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.

Similarly, even when a small-sized dielectric block is used, the strength of the coupling between the inner conductors of the resonator and the coupling between the resonators of the input / output terminals can be adjusted by the metallization forming method. Therefore, it is possible to realize ideal characteristics of the dielectric filter, and it is possible to reduce the size of the dielectric filter.

In addition, when changing the characteristics of the conventional monolithic filter, it was necessary to change the shape of the dielectric block, which made it difficult to change the design. A variety of different types of dielectric filters can be manufactured at low cost, and it is possible to realize a surface mount type dielectric filter that is easy to design and develop and can use a common mold.

[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 frequency characteristic diagram 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 frequency characteristic diagram 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 frequency characteristic diagram of a dielectric filter according to a third embodiment of the present invention.

FIG. 7 is a frequency characteristic diagram of a dielectric filter according to a fourth embodiment of the present invention.

FIG. 8 is a frequency characteristic diagram of a dielectric filter according to a fifth embodiment of the present invention.

FIG. 9 is a frequency characteristic diagram 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 frequency characteristic diagram of a conventional dielectric filter in which two non-through holes are formed in a dielectric block.

FIG. 12 is a frequency characteristic diagram when the electrode area of the input / output terminal of a dielectric filter in which two non-through holes are formed in a conventional dielectric block is increased.

FIG. 13 is a frequency characteristic diagram of a conventional dielectric filter in which two through holes are formed in a dielectric block.

FIG. 14 is a frequency characteristic diagram when the electrode area of input / output terminals of a dielectric filter in which two through holes are formed in a conventional dielectric block is increased.

[Explanation of symbols]

 Reference Signs List 1 dielectric filter 10 dielectric block 11 non-through hole 11a inner conductor (of resonator) 12 electrode 13 input / output terminal (electrode) 14a, 14b, 14c non-conductor-formed portion 15 short-circuit end 16 open end 17 non-through hole opening surface A Passband L Length of non-formed part φ Diameter of inner conductor

Claims (8)

[Claims] 1. The non-through-hole excluding a part of a non-through-hole opening surface in which a plurality of non-through-holes are formed from one surface of a dielectric block toward an opposing surface, and a region around an input / output terminal. A dielectric filter, wherein the entire surface including the inner surface of the filter is covered with a conductor. 2. The dielectric filter according to claim 1, wherein a conductor-free portion that is not covered with a conductor on the opening surface of the non-through hole is arranged between the non-through holes. 3. The dielectric filter according to claim 1, wherein the coupling between the resonators is adjusted by changing the size of the non-conductor-formed portion. 4. The filter according to claim 1, wherein said conductor-free portion is formed after covering the entire surface of said input / output terminal except for the region surrounding said input / output terminal with said conductor.
4. The method for manufacturing a dielectric filter according to any one of items 3 to 3. 5. A part of a through hole opening surface in which a plurality of through holes are formed, a region around input / output terminals, and a part of a region for forming a resonator open end are removed from one surface of a dielectric block. A dielectric filter, wherein the entire surface including the inner surface of the through hole is covered with a conductor. 6. The dielectric filter according to claim 5, wherein a conductor-free portion on the opening surface of the through-hole, which is not covered by the conductor, is arranged between the through-holes. 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 conductor-free portion is formed after covering the entire surface except for a region around the input / output terminal and a partial region for forming a resonator open end with the conductor, and forming a filter characteristic. 8. The method of manufacturing a dielectric filter according to claim 5, wherein