JP2810621B2 - Multilayer 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 laminated dielectric filter suitable for a high-frequency circuit, and more particularly, to a method in which a plurality of stripline type resonance electrodes are arranged in parallel in a dielectric substrate and electromagnetically coupled to each other. The present invention relates to a triplate-type integral laminated dielectric filter.

[0002]

2. Description of the Related Art In recent years, high-frequency filters used in high-frequency circuit radio equipment such as portable telephones and automobile telephones, and antenna duplexers and the like, use filters made of various dielectric ceramics in order to reduce loss. One of them is described in, for example, Japanese Patent Application Laid-Open No. 59-516.
As disclosed in Japanese Patent Application Publication No. 06-2006 or the like, a dielectric filter having a triplate-type laminated structure is known.

FIG. 1 shows an example of a dielectric filter having such a structure, in which a dielectric filter 1 includes a plurality of dielectric filters 3 in a pattern shown in FIG. Strip line type resonance electrode 2
(Here, two) and a set of input / output electrodes respectively connected to the first and last stages (at both ends in the left-right direction in the figure) via predetermined input / output capacitors 4 and 4, while ground conductors 5 and 5 'are provided on the outer surface in a ground pattern surrounding the ground conductors.
Are provided, and input / output terminals 6, 6 corresponding to the input / output electrodes 4, 4 are provided. Then, surface earth conductors 5 and 5 provided on the upper and lower surfaces which are the main surfaces of the dielectric substrate 3 are provided.
Is combined with each resonance electrode 2 as an internal line,
While each constitutes a triplate type resonator, the ground conductor 5 'on the side surface short-circuits one end of each resonator and eliminates electromagnetic effects of peripheral metals and devices. .

By the way, in such a laminated dielectric filter, as shown in FIG. 2, the pass frequency band is usually set to the center of the band of the filter, and at this time, the reflection characteristic is also set to the pass frequency band. It is designed to have the least reflection. Further, in that case, the resonators are designed so that the resonance frequency is the same.

[0005] However, the characteristics required for the filter include attenuation characteristics outside the pass frequency band, and the required attenuation characteristics may be severe on the higher side than the pass frequency band and severe on the lower side. In some cases. In such a case, the priority is given to the side with higher demand for the attenuation characteristic, and the required pass frequency band is biased with respect to the filter characteristic band, whereby the attenuation characteristic can be easily improved. In addition, by making the resonance frequency of each resonator different, the reflection characteristics can be adjusted to a biased pass frequency band.

However, in order to make the resonance frequency of the resonator in the above-mentioned laminated dielectric filter different,
This can be achieved by changing the electrode pattern of the resonator, or by providing an electrode pattern that provides the open-end capacitance of the resonance electrode, but changing the electrode pattern requires changing the printing mask. This is not easy, and also increases the manufacturing cost of the dielectric filter.

[0007]

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a triplate-type integrated dielectric filter having an integrated laminated structure. Without changing the electrode pattern of the resonance electrode, the resonance frequency of the resonator can be easily changed to shift the frequency with the least reflection from the center of the filter characteristic band, and the reflection characteristic to the pass frequency. The purpose is to be able to match the band.

[0008]

According to the present invention, in order to solve the above-mentioned problem, a plurality of stripline-type resonance electrodes are parallel to each other in a direction parallel to a plate surface in a dielectric substrate. In a laminated dielectric filter having a structure in which an earth conductor is provided on the outer surface of the dielectric substrate, the side edges of the first and last electrodes located at both ends in the arrangement direction of the plurality of resonance electrodes. And the ground conductors provided on the side surfaces of the dielectric substrate corresponding to the electrodes, so that the difference between the distances is at least one.
A multi-layer dielectric filter characterized by having a thickness of 0 μm or more is the gist of the invention.

[0009]

In summary, according to the present invention, in the arrangement direction of the plurality of resonance electrodes provided in the dielectric substrate of the multilayer dielectric filter, a side edge of the resonance electrode located at one end in the arrangement direction is provided. Make the distance between the corresponding ground conductor on the side of the dielectric substrate and the distance between the side edge of the resonance electrode located on the other end and the corresponding ground conductor on the side of the dielectric substrate different. , The difference between their distances is at least 1
0 μm or more, whereby the capacitance of the two resonance electrodes with respect to the ground conductor is changed, and the characteristic impedance of each of the resonance electrodes is made different. It is possible to make the frequencies of the two resonators effectively different from each other, so that the frequency with the least reflection of the reflection characteristics is advantageous from the center of the band of the filter characteristics without changing the electrode pattern. I was able to bias to.

Moreover, as described above, the change in the resonance frequency of the two resonators does not change the electrode pattern.
Since it can be realized by simply changing the distance between the resonance electrodes at both ends in the electrode arrangement direction and the ground conductor on the side surface, the production of the intended laminated dielectric filter becomes extremely simple. In addition, the increase in the manufacturing cost can be effectively suppressed.
In general, a laminated dielectric filter is generally manufactured by cutting out individual filters from a laminate obtained by laminating unfired dielectric substrates provided with a predetermined electrode pattern, and firing the resultant. Of course, the cutting of individual filters from such laminates
By changing the position, the distance between the two resonance electrodes at both ends of each filter and the ground conductor provided on the side of the dielectric substrate can be easily varied.
This is because the resonance frequency of each resonator can be made different.

[0011]

In the laminated dielectric filter according to the present invention, the side edges of the two electrodes located at both ends in the arrangement direction of the plurality of resonance electrodes provided in the dielectric substrate are provided. The structure of the conventional laminated dielectric filter is adopted as it is, except that the distance between the dielectric layer and the ground conductor provided on the side surface of the dielectric substrate is different.

That is, similar to the multilayer dielectric filter 1 having the conventional structure shown in FIG. 1, the multilayer dielectric filter according to the present invention also has an integrated dielectric formed by laminating a plurality of dielectric layers. A substrate 3 is provided, and a plurality of strip line type single-ended short-circuit type resonance electrodes 2 are formed in parallel with each other with respect to a predetermined one of the dielectric layers. At opposing positions, opposing electrodes connected to the ground conductors 5, 5 'on the outer surface are provided.
The other dielectric layer overlaps the first and last stages of the resonance electrode 2 (resonance electrodes located at both ends in the left-right direction in the drawing) so as to overlap with each other with a predetermined overlapping area in the laminating direction. , A pair of input / output electrodes 4,
4 are provided to form an integrated laminated structure. The top and bottom main surfaces of the dielectric substrate 3 are provided with surface ground conductors 5, and the four side surfaces are also connected to the side ground conductors 5 ′ so as to connect the top and bottom main surface top conductors 5 ′.
Are formed, and input / output terminals 6, 6 for connecting a set of input / output electrodes 4, 4 to the outside are provided as in the conventional case.

According to the present invention, in the laminated dielectric filter having such a structure, two resonance electrodes positioned at both ends in the left-right direction in the drawing direction in which the plurality of resonance electrodes 2 are arranged, that is, Side edges of the first-stage resonance electrode 2 and the last-stage resonance electrode 2, and ground conductors 5 ′, 5 ′ provided on the side surfaces of the dielectric substrate 3 corresponding to the electrodes 2, 2.
5 ′, in other words, the distance between the left side edge of the resonance electrode 2 on the left side in the figure and the side ground conductor 5 ′ formed on the left side of the dielectric substrate 3: a, The distance A between the right edge of the right resonance electrode 2 and the side ground conductor 5 ′ formed on the right side of the dielectric substrate 3 is made different (a ≠ A). The capacitance between the electrodes 2, 2 and the left and right side ground conductors 5 ', 5' is made different.

In such a case, the magnitude of the effect of the capacitance from the side ground conductor 5 'is directly related to the distance between the resonance electrodes 2, 2 and the side ground conductors 5', 5 '. Therefore, the difference (a-A) in the distance from the ground conductor 5 'formed on the side surface of the dielectric substrate 3 is the difference in the magnitude of the effect of the capacitance, and, consequently, the resonance frequency of the resonator. Will affect the degree of change. For this reason, in the present invention, such a difference in the distance (a-A)
Is made to be at least 10 μm or more, thereby effectively changing the resonance frequencies of the two resonators, so that the frequency with the least reflection of the reflection characteristic is advantageously shifted from the center of the filter characteristic band. It was made possible to bias. In addition, the ground conductor 5 'on the side
When the distance (a, A) between the electrode and the resonance electrode 2 is 0.3 mm or less, such a difference in distance: | a−A | is more effectively set to 20 μm or more, and The distance (a, A) between the side surface ground conductor 5 'and the resonance electrode 2 is 0.3 to
In the case of about 1 mm, the difference between the distances: | a−
A | is more preferably at least 20 μm, even more preferably 3 μm.
It will be 0 μm or more. However, if such a difference in distance: | a−A | is too large, the characteristics of the entire filter are destroyed.
Generally, it is desirable that the thickness be 200 μm.

In any case, as described above, the laminated dielectric filter according to the present invention is provided with the side edges of the first and last stage resonance electrodes 2 and 2 and the side ground conductors 5 'and 5 corresponding to those electrodes. ′ Is 10 μm.
m, the structure of the conventional laminated dielectric filter can be adopted as it is, and therefore, a quarter-wave resonator is formed in the dielectric substrate 3, In other words, if a single-ended short-circuit type stripline-type resonance electrode is built in, an input / output electrode is provided for the electrode, and a ground conductor is provided on the outer surface (especially the side surface) of the dielectric substrate, the present invention is applicable. The invention can be applied to known triplate-type dielectric filters having various structures. In addition, it goes without saying that the present invention can be applied to a case where three or more resonance electrodes 2 are provided as well as a case where two or more resonance electrodes 2 are provided as illustrated.

[0016] Such a dielectric filter can be easily manufactured according to a well-known conventional method of manufacturing a laminated substrate, and each electrode (on the surface of such a dielectric filter) can be formed. In general, the ground conductor and the input / output terminals are formed after the respective layers of the dielectric substrate are laminated and integrated.

In the above-described laminated dielectric filter, since the resonance electrodes and the input / output electrodes are completely incorporated in the dielectric substrate, these electrodes are formed. A conductor having a small specific resistance is advantageously used as the conductor. This is because the loss at the electrode increases the loss in the pass band of the filter, and especially when dealing with electromagnetic waves in the microwave band, the resistance of the conductor of the coupling circuit needs to be low. Au with low resistance
, Ag-based or Cu-based conductors are preferably used.

In the case where Ag-based or Cu-based conductors are used, their melting points are low (1100 ° C.) because they have low melting points and are difficult to co-fire with ordinary dielectric materials. It is necessary to use a dielectric material that can be fired at a lower temperature than the following. Also, due to the nature of the device as a microwave filter, the temperature characteristic (temperature coefficient) of the resonance frequency of the formed resonance circuit is ± 50 ppm /
It is preferable to use a dielectric material having a temperature of not more than ° C. As such a dielectric material, for example, a glass-based material such as a mixture of cordierite-based glass powder, TiO ₂ powder, and Nd ₂ Ti ₂ O ₇ powder, or BaO—TiO ₂ —RE ₂ O
₃ -Bi ₂ O ₃ based compositions (RE: rare earth component) is a ceramic dielectric material, such as those obtained by adding a small amount of glass forming component or glass powder is.

[0019]

Hereinafter, typical examples of the present invention will be described to clarify the present invention more specifically. However, the present invention imposes no restrictions on the description of such examples. It goes without saying that you don't receive anything. In addition, various changes, modifications, improvements, etc., based on the knowledge of those skilled in the art, may be made to the present invention based on the knowledge of those skilled in the art, in addition to the above-described specific configurations and the following embodiments. It is to be understood that what is gained.

Embodiment 1 A laminated dielectric filter 1 provided with two resonance electrodes 2 and 2 having the structure shown in FIG. The width is 1 mm, the space between the two resonance electrodes 2, 2 is 1 mm, and the distance between the resonance electrodes 2, 2 and the side ground conductors 5 ', 5':
Various dielectric filters having different values of | a−A | were obtained by fabricating a size of a and A (where a> A) of about 0.8 mm.

Specifically, BaO—TiO ₂ —Nd ₂ O
₃ -Bi with ₂ O ₃ based dielectric material powder, a mixture of the dielectric material powder and glass powder, and further blending in a predetermined organic binder, after preparing the green tape, this green tape, Ag paste By screen printing an electrode pattern that gives an electrode of the above size, then laminating and pressing and firing, and by completely integrating,
The desired dielectric filter was obtained.

The reflection characteristics of the thus obtained dielectric filters having various values of | a-A | were examined, and the results are shown in Table 1 below. The dielectric constant of the dielectric in this dielectric filter is 80, and the required pass frequency band of the filter is 1900 MHz ± 10 MHz.
It is. FIG. 3 shows a filter No. 3 according to the present invention.
The reflection characteristics of the filter No. 4 as a comparative example are shown.

As is clear from the results in Table 1 and FIG. 3, since a> A in the distance between each resonance electrode 2 and the side ground conductor 5 ', the resonance electrode 2 on the A side
Approaching the side surface, the characteristic impedance of the A-side resonance electrode 2 is reduced, and the resonance frequency of the A-side resonance electrode 2 is increased. The peak at which the reflection of the reflection characteristic becomes small occurs on the low frequency side.

[0024]

[Table 1]

Embodiment 2 As in Embodiment 1, the length of the resonance electrode 2 is 3.
3 mm, the width of the resonance electrode 2 is 0.5 mm, the space between the two resonance electrodes 2, 2 is 0.8 mm, and the space between the resonance electrodes 2, 2 and the side ground electrodes 5 ', 5'. distance:
a, A (where a> A) is a laminated dielectric filter having a size of about 0.2 mm, and a difference between the distances: | a−A
Various dielectric filters having different values of | were obtained. Here, the filter has a very small shape, and the electrode pattern also requires high accuracy.
As a binder for the electrode paste, a UV-curable binder was used, and a high-precision pattern was realized by photolithography.

The reflection characteristics of various dielectric filters having different | a-A | differences in the distance between the resonance electrode and the side-surface ground electrode thus obtained are shown in Table 2 below. The following results were obtained. As is apparent from the results, by setting the difference | a−A | of the distance between the resonance electrodes 2 and 2 and the side-surface ground conductors 5 ′ and 5 ′ to 10 μm or more, the resonance of the two resonators is achieved. The frequency can be easily changed, and the reflection characteristics can be matched well to the required pass frequency band.

[0027]

[Table 2]

[Brief description of the drawings]

FIG. 1 is an exploded explanatory view showing an example of a laminated structure of a conventional laminated dielectric filter.

FIG. 2 is a graph illustrating a relationship between a reflection characteristic and a transmission characteristic in a normal dielectric filter.

FIG. 3 is a graph showing reflection characteristics and transmission characteristics of the multilayer dielectric filters of Filter Nos. 3 and 4 obtained in Example 1.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 laminated dielectric filter 2 resonance electrode 3 dielectric substrate 4 input / output electrode 5 surface ground conductor 5 ′ side ground conductor 6 input / output terminal

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-369103 (JP, A) JP-A-4-369102 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01P 1/203 H01P 1/205

Claims (1)

(57) [Claims] 1. A structure in which a plurality of stripline type resonance electrodes are arranged parallel to each other in a direction parallel to a plate surface in a dielectric substrate, and a ground conductor is provided on an outer surface of the dielectric substrate. In the laminated dielectric filter of (1), the side edges of the first-stage and last-stage electrodes located at both ends in the arrangement direction of the plurality of resonance electrodes and a ground conductor provided on the side surface of the dielectric substrate corresponding to the electrodes. A laminated dielectric filter characterized in that the distances between them are different and the difference between the distances is at least 10 μm or more.