JPH1168406A - Dielectric filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dielectric filter having high degree of freedom in design capable of forming an attenuation pole at a required position without requiring a metallic case and independently of the height of a pass band. SOLUTION: At least one slit 14 is formed on a corresponding part between adjacent non-through holes 11 extending parallel out of plural non-through holes 11 opened on one face out of the periphery of a block 10 consisting of a dielectric material. An inner peripheral electrode is formed in each of plural non-through holes 11. The periphery of the block 10 is provided with an earth electrode 12 and an I/O electrode 13. The earth electrode 12 is formed also on the surface of the slit 14.

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 in radio communication in a high frequency band or the like.

[0002]

2. Description of the Related Art As a dielectric filter of this type, there is a monolithic filter which has a small leakage of an electromagnetic field and does not require a metal case. The coupling between resonators of a monolithic filter includes capacitive coupling and inductive coupling. The relationship between the type of coupling and the attenuation pole is as follows. In the case of capacitive coupling, the attenuation pole is configured in a frequency band lower than the pass band, and in the case of inductive coupling, the attenuation pole is configured in a frequency band higher than the pass band.

FIG. 9 shows a conventional example of a monolithic filter in which two non-through holes are formed, which is hereinafter referred to as a non-through hole type monolithic filter. Two non-through holes 11 are formed in a block made of a dielectric material, that is, a dielectric block 10. The entire surface of the dielectric block 10 is covered with the electrode 12. The electrodes 12 are also formed as inner electrodes on the inner surfaces of the two non-through holes 11. As a result, the inner peripheral electrodes on the inner surfaces of the two non-through holes 11 can be regarded as inner conductors of the two coaxial resonators. Two input / output terminals 13 are further formed on the outer peripheral surface of the dielectric block 10 so as to be separated from the electrodes 12. When this monolithic dielectric filter is mounted on a mounting substrate or the like such that the electrode 12 is at the ground potential, the input / output terminals 13
And functions as a band-pass filter composed of two resonators.

FIG. 10 shows characteristics of the non-through-hole type monolithic filter shown in FIG. A portion indicated by A is a pass band, and the attenuation pole B is formed in a frequency band higher than the pass band.

In general, a dielectric filter is used for radio communication in a high frequency band, and is often used mainly for a portable telephone, a cordless telephone, and the like. However, the frequency band used and required characteristics differ depending on the system. . Therefore, by providing an attenuation pole near the band where the amount of attenuation is required according to the system, desired characteristics are realized for the dielectric filter.

[0006]

In the case of the non-through-hole type monolithic filter shown in FIG. 9, since a capacitance is generated between the tip of the non-through hole, which is the open end of the resonator, and the outer peripheral surface ground electrode, capacitive coupling is performed. As a result, the resonator coupling becomes inductive coupling, and an attenuation pole is formed in a frequency band higher than the pass band. That is, the non-through-hole type monolithic filter of FIG. 9 has the characteristic that the attenuation pole B is formed in a frequency band higher than the pass band A as shown in FIG. Therefore, there is no problem in using the present invention in a system requiring a large amount of attenuation in the band in which the attenuation pole B is formed, but it cannot cope with a system requiring an amount of attenuation other than the frequency band of the attenuation pole B. It is necessary to change the position of the attenuation pole in order to realize a filter having characteristics compatible with the system.

However, the conventional non-through-hole type monolithic filter shown in FIG. 9 has a low degree of freedom in design and cannot form an attenuation pole in a frequency band lower than a pass band. In other words, the conventional non-through-hole type monolithic filter cannot cope with a system requiring a large amount of attenuation in a frequency band lower than the pass band. In general, in most systems, bandpass filters require significant attenuation below the passband, so that conventional non-through-hole monolithic filters cannot be accommodated in most systems.

The present invention provides an attenuation pole at a desired position irrespective of the height of a pass band, while maintaining the advantages of a conventional non-through-hole type monolithic filter that has a small electromagnetic field leakage and does not require a metal case. It is an object to provide a dielectric filter which can be formed and has a high degree of design freedom.

[0009]

Accordingly, the present invention reduces the inductive coupling of the resonator-to-resonator coupling by forming slits between the resonators, and makes the coupling between the resonators capacitive. The attenuation pole is formed in a frequency band lower than the pass band. Also, since the inductive coupling is strongly coupled near the short-circuited end of the resonator, a slit is formed near the short-circuited end to efficiently make the coupling between the resonators capacitive and to reduce the frequency band lower than the pass band. An attenuation pole is configured.

According to the present invention, a block made of a dielectric material having a plurality of non-through holes which are open on one surface and extend side by side, an inner peripheral electrode provided in each of the plurality of non-through holes, A ground electrode provided on an outer peripheral surface, and a dielectric filter including an input / output electrode provided on a part of the block, wherein a dielectric filter is provided between adjacent non-through holes on the outer peripheral surface of the block. A dielectric filter is provided in which at least one slit is provided in a corresponding portion.

Preferably, the ground electrode is also provided on a surface of the at least one slit.

Preferably, the plurality of non-through holes extend in parallel with each other, and the slit extends along the plurality of non-through holes.

Preferably, the at least one slit is formed near a surface of the block where the plurality of non-through holes are opened.

Preferably, the characteristics are adjusted by the length of the at least one slit.

Preferably, the characteristic is adjusted by the depth of the at least one slit.

[0016]

FIG. 1 shows a dielectric filter according to an embodiment of the present invention. This dielectric filter is a non-through-hole type monolithic filter, and a block made of a dielectric material, that is, a dielectric block 10 is provided with two non-through holes 11.
Are formed parallel to each other. The entire surface of the dielectric block 10 is covered with the electrode 12. The electrodes 12 are also formed as inner electrodes on the inner surfaces of the two non-through holes 11. As a result, the inner peripheral electrodes on the inner surfaces of the two non-through holes 11 can be regarded as inner conductors of the two coaxial resonators. On the outer peripheral surface of the dielectric block 10, two input / output terminals 13 (only one is shown) are formed separately from the electrodes 12.

On the outer peripheral surface of the dielectric block 10, two upper and lower slits 14 extending in parallel with the longitudinal direction of the non-through hole 11 are formed at a portion corresponding to between the two non-through holes 11. The electrode 12 is also provided on the surface of each slit 14. Each slit 14 has a V-shaped cross section, and is formed following a surface having an opening of the non-through hole 11.

This dielectric filter has an electrode 12 on the outer peripheral surface.
When the electrodes of the slit 14 are mounted on a wiring board or the like so as to be at the ground potential, it functions as a bandpass filter composed of two resonators between the input / output terminals 13.

FIG. 2 shows the frequency characteristics of the dielectric filter shown in FIG. A portion indicated by A is a pass band, and the attenuation pole B is formed in a frequency band lower than the pass band. In the case of a conventional non-through-hole type dielectric filter, it was impossible to form an attenuation pole in a frequency band lower than the pass band. However, the dielectric filter shown in FIG. 1 can realize the attenuation pole.

3 to 8 show dielectric filters according to other different embodiments of the present invention. In these dielectric filters, the same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

The dielectric filter shown in FIGS.
4 differs from the dielectric filter of FIG. In the dielectric filter of FIGS. 3 to 8 as well, the attenuation pole can be formed in a frequency band lower than the pass band, similarly to the frequency characteristics of the dielectric filter shown in FIG.

The dielectric filter shown in FIGS. 1, 3, 4, 5, 6, 7, and 8 has a slit 14
, The attenuation pole frequency can be changed depending on the depth. When the slit is made deep, the attenuation pole frequency moves to the low frequency side, and when the slit is made shallow, the attenuation pole frequency moves to the high frequency side.

The dielectric filter shown in FIGS. 1, 3, 4, 5, 6, 7, and 8 has a slit 14
, The attenuation pole frequency can be changed. When the slit is lengthened, the attenuation pole frequency moves to the lower frequency side, and when the slit is shortened, the attenuation pole frequency moves to the higher frequency side.

By utilizing the relationship between the shape of the slit 14 and the attenuation pole frequency, an attenuation pole can be formed in an arbitrary frequency band.

The relationship between the slit shape and the attenuation pole frequency can be applied to a filter in which the attenuation pole is formed in a frequency band higher than the pass band. That is, although the frequency characteristic of the conventional non-through-hole type monolithic filter shown in FIG. 9 is such that the attenuation pole is formed in a frequency band higher than the pass band, FIG. When a shallow slit or a short slit similar to that shown in FIGS. 3 to 8 is formed, the attenuation pole moves to the lower frequency side. Therefore, it is possible to configure the attenuation pole in an arbitrary frequency band.

Although the description has been given of the case where two non-through holes are formed in the dielectric block, at least two, that is, a plurality of non-through holes may be used, and a structure in which three or more non-through holes are formed can be similarly performed. At least one slit is formed in the dielectric block, but three or more slits may be formed. Needless to say, the shape of the slit is not limited to the illustrated example, but can be variously modified. The electrode serving as the ground electrode may be formed on the entire surface of the dielectric block, or may be formed only on the surface excluding one or both of the surface having the non-through hole opening and the surface facing the opening. Is also good.

[0027]

As described above, according to the present invention,
Surface mount with a high degree of design freedom, with the ability to freely set the frequency band that constitutes the attenuation pole while maintaining the function of a non-through-hole type dielectric filter that minimizes electromagnetic field leakage and does not require a metal case It is possible to realize a type dielectric filter.

[Brief description of the drawings]

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

FIG. 2 is a graph showing characteristics of the dielectric filter of FIG.

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

FIG. 4 is an external perspective view of a dielectric filter according to still another embodiment of the present invention.

FIG. 5 is an external perspective view of a dielectric filter according to still another embodiment of the present invention.

FIG. 6 is an external perspective view of a dielectric filter according to still another embodiment of the present invention.

FIG. 7 is an external perspective view of a dielectric filter according to still another embodiment of the present invention.

FIG. 8 is an external perspective view of a dielectric filter according to still another embodiment of the present invention.

FIG. 9 is an external perspective view of a conventional dielectric filter.

FIG. 10 is a graph showing characteristics of the dielectric filter of FIG. 9;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Dielectric block 11 Non-through hole 12 Electrode 13 I / O terminal 14 Slit A Pass band B Attenuation pole

Claims (6)

[Claims] 1. A block made of a dielectric material having a plurality of non-through holes that are open on one surface and extend side by side, inner peripheral electrodes provided in each of the plurality of non-through holes, and provided on an outer peripheral surface of the block. A ground electrode and an input / output electrode provided in a part of the block, wherein the dielectric filter includes a portion corresponding to a portion between adjacent ones of the plurality of non-through holes on an outer peripheral surface of the block. A dielectric filter provided with at least one slit. 2. The dielectric filter according to claim 1, wherein said ground electrode is also provided on a surface of said at least one slit. 3. The dielectric filter according to claim 1, wherein the plurality of non-through holes extend in parallel with each other, and the slit extends along the plurality of non-through holes. 4. The dielectric filter according to claim 1, wherein the at least one slit is formed near a surface of the block where the plurality of non-through holes are opened. 5. The dielectric filter according to claim 1, wherein characteristics are adjusted by a length of said at least one slit. 6. The dielectric filter according to claim 1, wherein characteristics are adjusted by a depth of said at least one slit.