JP3161211B2 - 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 dielectric filter used in a microwave band, and more particularly to an improvement in frequency characteristics of a laminated dielectric filter having a structure including a dielectric substrate and various electrodes provided therein. It is.

[0002]

2. Description of the Related Art In recent years, in communication devices using microwaves, such as mobile phones and car phones, filters using various dielectrics have been used to reduce loss. Above all, dielectric ceramics are preferably used because they are highly reliable and have a high dielectric constant, and are therefore suitable for downsizing of filters. In general, a dielectric filter using such dielectric ceramics is configured as a tri-plate type filter having a laminated structure having a strip line type transmission line, and a plurality of unplated electrodes provided with unfired electrodes. The fired dielectric sheets are laminated, and they are simultaneously fired to be integrated to produce a laminated dielectric filter as a target.

Specifically, for example, Japanese Patent Application Laid-Open No.
In Japanese Patent Application Publication No. 6 (1994) -6, etc., a plurality of resonance electrodes arranged in parallel with each other, an input electrode overlapping the resonance electrode on the input end side with a dielectric layer interposed therebetween, and a resonance electrode on the output end side And an output electrode overlapping with a dielectric layer in between,
In each case, a laminated dielectric filter having a structure in which it is provided inside a dielectric substrate has been disclosed.
No. 525, U.S. Pat. No. 4,418,324 and the like disclose a filter in which the resonance electrode, the input electrode, and the output electrode are built in a dielectric substrate.
A dielectric filter having a structure in which a coupling electrode capable of coupling with both predetermined two resonance electrodes via a dielectric material, in other words, with a predetermined coupling capacitance, is disclosed, and Japanese Patent Publication No. Sho 62-19081 is further disclosed. No.
In a band-pass filter composed of two distributed constant type resonators and an input / output electrode coupled to each resonator at the input / output end by a capacitor, the input / output electrodes are arranged in a capacitive coupling relationship. The resulting filter structure is disclosed.

By the way, in this type of laminated dielectric filter, in order to obtain a desired frequency characteristic, as described above, in the dielectric substrate, only the resonance electrodes constituting the resonator are provided. Instead, the input / output electrode and the coupling electrode are provided with a predetermined coupling capacitance with respect to a predetermined one of such resonance electrodes. Each of the input / output electrode and the coupling electrode is an electrode part that forms a predetermined coupling capacitance, and the electrode part, in other words, the capacitance formed thereby is connected to an external terminal or the other electrode part. However, as the frequency increases, the input / output electrodes and the coupling electrodes become simpler in the capacitance forming portion and the electrode for the wiring portion. Instead, it exhibits characteristics as a distributed constant element, and exhibits resonance characteristics at a certain frequency. This appears as a peak on the frequency characteristics of the filter, and degrades the spurious characteristics of the filter.

Here, the spurious characteristic of the filter is
The filter exhibits attenuation characteristics at two to three times or more of the pass band of the filter, and what is required as such spurious characteristics is an attenuation amount at a frequency that is an integral multiple of the center frequency of the filter. For this reason, when the above-mentioned peaks caused by the input / output electrodes and the coupling electrodes occur in the vicinity of such a frequency that requires attenuation, the filter cannot satisfy the required spurious characteristics. is there.

A strip line (line) having a constant characteristic impedance resonates at a frequency at which the electrical length is 波長 wavelength. This also applies to input / output electrodes and coupling electrodes. It is. In particular, the coupling electrode has capacitance electrode portions formed at both ends because of its necessity. Therefore, the capacitance also affects the resonance frequency. The presence of this capacitance causes the resonance frequency to shift lower than the frequency determined by the electrical length. Further, such a capacitance value is determined in order to obtain a desired frequency characteristic, and the capacitance value cannot be changed due to the movement of the peak by the coupling electrode. Also, changing the distance between the resonance electrodes to change the length of the wiring portion forming the coupling electrode cannot be adopted because the influence on the inductive coupling between the resonators is large. . Also, regarding the input / output capacitance, increasing the distance between the resonator (resonance electrode) and the filter side wall by changing the length of the wiring portion of the input / output electrode increases the width of the entire filter. This is contrary to the demand for smaller filters, and by shortening the distance to the side wall, if the wiring part is shortened, resonance will be caused by the filter side wall approaching. This results in deterioration of the Q value of the filter and increases the insertion loss of the filter, so that the filter cannot be used.

[0007]

The present invention has been made in view of the above circumstances, and an object thereof is to change an input / output capacitance of an input / output electrode and a coupling capacitance of a coupling electrode. without, electricity for their input and output
Resonance frequency of pole and coupling electrode (peak on frequency characteristics)
It is an object of the present invention to provide a laminated dielectric filter structure capable of easily realizing the shift of the filter.

[0008]

According to the present invention, in order to solve the above-mentioned problems, a plurality of stripline-type resonance electrodes are provided in a dielectric substrate, and an input of the resonance electrodes is provided. An input / output electrode composed of an electrode portion forming a predetermined input / output capacitance and a wiring portion for connecting the electrode portion to an external terminal is provided for each of the end side and the output end side. Wherein the characteristic impedance of at least one wiring portion of the input / output electrode is changed between a central portion and an end portion of the laminated dielectric filter. The main object is a type dielectric filter.

Further, in the present invention, a plurality of strip line type resonance electrodes are provided in a dielectric substrate, and a predetermined coupling capacitance is provided for each of two predetermined resonance electrodes. A coupling electrode composed of an electrode portion to be formed and a wiring portion for connecting the electrode portion is provided, and a predetermined input is provided for each of the input and output terminals of the resonance electrodes. In a laminated dielectric filter having a structure in which an input / output electrode composed of an electrode portion forming an output capacitor and a wiring portion for connecting the electrode portion to an external terminal is provided, the coupling electrode and A laminated dielectric filter characterized in that the characteristic impedance of at least one of the input / output electrodes is changed between a central portion and an end portion thereof. Also, it is an gist thereof.

According to one advantageous aspect of the present invention, in the above-described laminated dielectric filter, the change in the characteristic impedance of the wiring portion is caused by changing the pattern width of the conductor pattern providing the wiring portion to the wiring width. This can be realized by making the central portion and the end portion of the portion different.

According to another advantageous aspect of the present invention, the change in the characteristic impedance of the wiring portion in the above-mentioned laminated dielectric filter is caused by the internal ground which overlaps only with the central portion of the wiring portion. This is achieved by providing an electrode in the dielectric substrate and electrically connecting the internal ground electrode to an external ground electrode formed on the outer surface of the dielectric substrate.

[0012]

[Action and Effect] In summary, the spurious characteristics required for the filter, so that above, from where it is attenuation at integer multiples of the center frequency of the filter, input and output electrodes
Even if the peak of the resonance frequency of the coupling electrode occurs in the frequency band where the attenuation is specified, the peak may be shifted to either the high frequency side or the low frequency side of the specified frequency. In the present invention, the width of the wiring portion of the input / output electrode or the coupling electrode is changed at a central portion thereof, or an internal ground electrode is provided so as to overlap only the central portion. Te, the characteristic impedance of such wiring portions, be those was allowed varied between its central portion side portion and the both end side portions, thereby output capacitance and coupling capacitance in the input-output electrode and the coupling electrode Thus, the above-mentioned effective shift of the peak was made possible without changing.

FIG. 1 shows an equivalent circuit in which strip lines (lines) having different characteristic impedances at the central portion and the end portions on both sides are connected, where the sum of the three lines is shown. The electrical length is 18 at 1 GHz
0 °. In this equivalent circuit, when the resonance frequency when the electric length of the central part is changed is when the characteristic impedance of the central part is twice and half that of the characteristic impedance of the both ends. Is calculated by a computer circuit simulation, and the result is shown in FIG.

And, as is apparent from FIG. 2,
When the characteristic impedance of the central portion of the strip line is high, the resonance frequency shifts low, and when the characteristic impedance is low, the reverse is true. Therefore, in the input / output electrode and the coupling electrode provided in the laminated dielectric filter, the characteristic impedance of the wiring portion is made different between the both end portion side portion and the central portion side portion, so that the resonance frequency is increased. ,
That is, the peak can be freely shifted on both the high frequency side and the low frequency side. For example, in the wiring portion of the coupling electrode, if the pattern width of the conductor pattern that gives it is increased in the central portion, the characteristic impedance of the central portion decreases, and the peak shifts higher. On the other hand, when the pattern width of the conductor pattern at the central portion is reduced, the characteristic impedance at the central portion increases, and the peak shifts lower. In addition, when an internal ground electrode is added to the input / output electrode and the coupling electrode so as to overlap only the central portion of the wiring portion, the substrate thickness at the central portion of the strip line is substantially reduced. The characteristic impedance decreases and the resonance frequency shifts higher.

[0015] Thus, according to the present invention, by for varying the characteristic impedance of the wiring portions of the input and output electrodes and the coupling electrode between its central portion side portion and the both end side portion, input and output It is possible to freely shift the resonance frequency (peak on the frequency characteristic) of the electrode for connection or the electrode for coupling to the high frequency side or the low frequency side, thereby sufficiently satisfying the spurious characteristics of the filter.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, in order to clarify the present invention more specifically, representative embodiments of the present invention will be described in detail with reference to the drawings.

First, FIGS. 3 and 4 show an example of a laminated dielectric filter having a structure according to the present invention. FIG. 3 is a schematic development view of such a filter, and FIG. 4 is a perspective view thereof. Are respectively shown. In these figures, a laminated dielectric filter 2 is constituted by laminating and integrating a plurality of dielectric layers 4a to 4g that provide a dielectric substrate (4), and these dielectric layers 4a to 4g are formed.
One of them: a single-ended short-circuit type resonance electrode 6 constituting a quarter wavelength strip line resonator on 4d
a and 6b are formed in parallel with each other, and opposing electrodes 8a and 8b are formed at a predetermined distance from the open ends of the resonance electrodes 6a and 6b.

Also, the resonance electrodes 6a, 6b are placed on the dielectric layers 4b, 4f located above and below the dielectric layer 4d.
Earth electrode 1 overlapping the open end side of the
0, 12 are formed, and the internal ground electrodes 10, 12 are formed.
Is connected to an external earth electrode 14 formed over substantially the entire surface of the dielectric substrate (4) as shown in FIG. Further, the resonance electrodes 6a and 6b are connected to the external earth electrode 14, respectively. Note that the external ground electrode 14 is provided on the side surface of the dielectric substrate (4).
Are provided, and input / output terminals 18 are provided in the input / output terminal portions 16, 16, respectively.

On the dielectric layers 4c and 4e located above and below the dielectric layer 4d on which the resonance electrodes 6a and 6b are formed, a coupling electrode 20 and a pair of input / output Electrodes 22, 22 are provided. Specifically, the coupling electrode 20 includes electrode portions 20a, 2 at both ends.
0a and a wiring portion 20b connecting these electrode portions, and the electrode portions 20a, 20a at both ends are overlapped with the corresponding resonance electrodes 6a, 6b via the dielectric layer 4c, so that a predetermined portion is formed. In the meantime, the wiring portion 20b has a structure in which the central portion has a wide portion 20b 'in which the pattern width of the conductor pattern is wider than the end portion. The pair of input / output electrodes 22 and 22 are connected to the corresponding resonance electrodes 6 respectively.
electrode portions 22a, 22a which overlap with a, 6b via a dielectric layer 4d to form a predetermined input / output capacitance;
Wiring portions 22b, 22b connecting these electrode portions 22a, 22a to external input / output terminals 18, 18, respectively.
It is composed of

In the laminated dielectric filter 2 having such a structure, predetermined electrodes are respectively provided on predetermined dielectric layers 4b to 4f, and upper and lower dielectric layers 4a and 4g are further provided on these dielectric layers. Are laminated and press-bonded to form an integrated structure, and then fired to form an integrated laminate. Then, an external ground electrode 14 is formed on the upper and lower surfaces and the side surfaces excluding the input / output terminal portions 16 and 16. Further, the input / output terminals 16, 16 are manufactured by forming input / output terminals 18, 18, which are connected to the ends of the wiring portions 22b, 22b of the input / output electrodes 22, 22, respectively.

The laminated dielectric filter 2 having such a structure
In the above, in the wiring portion 20b, the coupling electrode 20 is formed as a wide portion 20b 'in which the pattern width of the conductor pattern providing the wiring portion 20b is larger at the center portion than at the end portion. As a result, the characteristic impedance of the central portion (20b ') of the wiring portion 20b becomes lower than that of the narrow end portion, whereby the peak shifts higher.

FIGS. 5 and 6 show that the wiring portion 20 b of the coupling electrode 20 having the structure described above has a wide portion 20 b.
The frequency characteristics of the filter according to the present invention provided with b 'and the conventional filter having the coupling electrode 20 in which the wiring portion 20b has the same width without the wide portion 20b' are clarified. Although each graph is shown, even from the comparison of those graphs,
It is very clear that the peaks have shifted.
That is, in FIG. 6 showing the frequency characteristics of the conventional filter, the input / output power is set to twice the center frequency of the filter.
It is observed that the peak due to the resonance of the electrode and the coupling electrode occurs, in the filter according to the present invention, the As is clear from FIG 5 showing a frequency characteristic, input-output electrodes twice the frequency positions And the peak due to the resonance of the coupling electrode has shifted to the higher frequency side.
This is due to the result of changing the thickness of the wiring portion 20b of the coupling electrode 20.

In the above embodiment, as shown in FIG. 7A, a wide portion 20b 'in which the pattern width of the conductor pattern is wide is formed at the central portion of the wiring portion 20b of the coupling electrode 20. The wiring portion 20b
As shown in FIG. 7 (b), the central side portion of the conductive pattern is narrowed so that the pattern width of the conductor pattern is reduced.
In this case, the characteristic impedance of the central portion (20b '') is higher than that of the end portion, and the peak shifts to the lower frequency side. .

According to the present invention, a wide portion 20b 'and a narrow portion 20b "are provided at the center portion of the wiring portion 20b of the coupling electrode 20 as in the above example. The wiring portions 22b of the output electrodes 22, 22,
It is possible to adopt a configuration in which a central portion of at least one of the portions 22b is a wide portion or a narrow portion, and FIG. 8 shows an example thereof. Since the filter structure of the embodiment shown in FIG. 8 is substantially the same as the filter of the previous example, only different parts will be described, and the same parts as those of the previous example will be denoted by the same reference numerals. Detailed description is omitted.

In short, in the laminated dielectric filter shown in FIG. 8, the wiring portion 20 of the coupling electrode 20
b does not have a wide portion, and instead has a pair of input / output electrodes 22, 22 formed on one dielectric layer 4e that provides the dielectric substrate (4). In the wiring portions 22b and 22b, the wide portion 22 in which the pattern width of the conductor pattern providing the wiring portions is widened
b 'and 22b'. Therefore, the input / output electrodes 22,
The wiring portions 22b, 22b have wide portions 22 respectively.
b ', 22b', the characteristic impedance at such wiring portions 22b, 22b is
In the central part of the electrode portions 22a, the central part is changed to be lower than the end part on the side of the electrode part 22a, so that the peak in the frequency characteristic can be effectively shifted to the high frequency side.

In the example shown in FIG. 8, wide portions 22b 'and 22b' are formed on the wiring portions 22b and 22b of the pair of input / output electrodes 22 and 22, respectively.
As in the previous example, it is also possible to provide a narrow portion as shown in FIG. 7B, in which case the characteristic impedance of the central portion becomes high, and the peak shifts to the low frequency side. It will be.

Further, the coupling electrode 20 of the laminated dielectric filter and the wiring portion 20 of the pair of input / output electrodes 22 and 22 are provided.
b; In the above example, the change in the characteristic impedance at 22b, 22b is realized by providing a wide portion or a narrow portion. It is also possible to cause a characteristic impedance difference between the end part and the ground part by bringing the part closer to the ground electrode side than the side part. By providing an overlapping internal ground electrode, such a change in characteristic impedance is realized.

FIG. 9 shows an example of a change in the characteristic impedance due to the provision of the internal ground electrode in the laminated dielectric filter having the structure as in the previous example. That is, the internal ground electrodes 1 provided on the dielectric layers 4b and 4f, respectively.
Extensions 10a, 12a extending from 0 and 12, respectively, are formed so that the extensions 10a, 12a vertically overlap only with the central portion of the wiring portion 20b of the coupling electrode 20 in the stacking direction. It is.

As described above, the wiring portion 2 of the coupling electrode 20
0b, the extension 10 of the internal earth electrodes 10, 12
When the a and 12a overlap, the thickness of the dielectric layer between the portion, that is, the external ground electrode 14 at the central portion of the wiring portion 20b is substantially reduced.
As a result, the characteristic impedance of the central portion of the wiring portion 20b becomes lower than that of the end portion thereof, and the resonance frequency shifts to the higher frequency side.

Further, such an internal ground electrode can be provided for at least one of the pair of input / output electrodes 22, 22, so that the characteristic impedance of the wiring portions 22b, 22b is changed. However, an example is shown in FIG. In this case, four dielectric layers 4a, 4d, 4e, and 4g are used, and electrodes similar to those in the previous example are formed for each of the dielectric layers. A U-shaped internal ground electrode 24 having a predetermined width with respect to the dielectric layer 4g;
26, 26 are provided so as to sandwich the pair of input / output electrodes 22, 22 from above and below, respectively. More specifically, the U-shaped central portions of the internal grounding electrodes 24 and 26 overlap each other only from above and below with respect to the central portion of the wiring portion 22b of the input / output electrode 22. The two ends of the U-shaped internal ground electrodes 24 and 26 are connected to the external ground electrode 14 formed on the side surface of the dielectric substrate (4).

As described above, in the dielectric substrate (4), the wiring portions 22b, 22b of the input / output electrodes 22, 22 are formed.
Of the input / output electrodes 22, 22 by adding internal ground electrodes 24, 26 which overlap with the central portion thereof and are short-circuited to the ground electrode 14 on the outer surface.
The substrate thickness of the strip line at the center of b, 22b becomes substantially equal to that obtained when the substrate becomes thinner, the characteristic impedance decreases, and the resonance frequency shifts higher.

In the example shown in FIGS. 9 and 10, the coupling electrode 20 and the input / output electrodes 22, 22 are overlapped from the top and bottom with the central portion of the wiring portion 20b; 22b, 22b. , Respectively, the internal ground electrode 10
a, 12a; 24, 26 are provided on both sides, but such an internal ground electrode may be provided only on one side in the direction of lamination of the dielectric layers, and a pair of input / output electrodes It may be provided for at least one of the electrodes 22, 22, and it is also possible to provide an internal ground electrode for both the coupling electrode 20 and the input / output electrodes 22, 22.

Although the representative embodiments of the present invention have been described in detail above, it is needless to say that the present invention is not limited by the description of such embodiments. In addition, the present invention, in addition to the above embodiments, unless departing from the spirit of the present invention,
It should be understood that various changes, modifications, improvements, and the like can be made based on the knowledge of those skilled in the art.

Further, according to the present invention, a 1/4
A wavelength-type resonator is formed, in other words, a single-ended short-circuit type stripline-type resonance electrode is built in, and an input / output electrode is provided with a predetermined capacitive coupling thereto, or in addition thereto, a resonance-use electrode is provided. As long as a predetermined electrode is provided with a coupling electrode with a predetermined capacitive coupling, it can be applied to a triplate type dielectric filter having various known structures. The arrangement pattern and number of each electrode formed on the outer surface and each electrode incorporated therein can also be appropriately changed. For example, the number of arranged resonance electrodes is not limited to the case of two as illustrated. It is also possible to configure a dielectric filter in an arrangement of three or more filters.

[Brief description of the drawings]

FIG. 1 is a diagram showing an equivalent circuit in a state where strip lines having different characteristic impedances at a center portion and both end portions are connected.

FIG. 2 is a graph showing a calculation result of a resonance frequency when an electric length of a central portion is changed in the equivalent circuit in FIG.

FIG. 3 is a schematic development view showing an example of a laminated dielectric filter according to the present invention.

FIG. 4 is a perspective view of the laminated dielectric filter shown in FIG.

5 is a graph showing frequency characteristics of the laminated dielectric filter having the structure shown in FIGS. 3 and 4. FIG.

FIG. 6 is a graph showing a frequency characteristic of the laminated dielectric filter having the same width without changing the width of the wiring portion of the coupling electrode in the structure shown in FIGS. 3 and 4;

FIG. 7 is an explanatory view showing various forms of a coupling electrode,
(A) shows an example in which a wide portion is provided in the wiring portion, and (b) shows an example in which a narrow portion is provided in the wiring portion.

FIG. 8 is a schematic developed view showing another example of the laminated dielectric filter according to the present invention.

FIG. 9 is a schematic developed view showing still another example of the laminated dielectric filter according to the present invention.

FIG. 10 is a schematic developed view showing another example of the laminated dielectric filter according to the present invention.

[Explanation of symbols]

2 Laminated dielectric filter 4a, 4b, 4c, 4d, 4e, 4f, 4g Dielectric layer 6a, 6b Resonant electrode 8a, 8b Counter electrode 10, 12 Internal earth electrode 14 External earth electrode 16 Input / output terminal 18 Output terminal 20 Coupling electrode 20a, 22a
Electrode part 20b, 22b Wiring part 20b 'Wide part 20b "Narrow part 22 Input / output electrode

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiko Watanabe 2-3-20 Nakamagome, Ota-ku, Tokyo Maisonazare 301 (56) References JP-A-6-291511 (JP, A)

Claims (2)

(57) [Claims] 1. An electrode part in which a plurality of stripline type resonance electrodes are provided in a dielectric substrate, and a predetermined coupling capacitance is formed for each of predetermined two of the resonance electrodes, and the electrodes. An electrode part for providing a coupling electrode composed of a wiring part for connecting the parts and forming a predetermined input / output capacitance with respect to the input terminal side and the output terminal side of the resonance electrodes; And a wiring portion for connecting the electrode portion to an external terminal. A laminated dielectric filter having a structure provided with an input / output electrode, wherein the coupling electrode and the input / output electrode The pattern width of the conductor pattern giving at least one wiring portion,
The characteristic impedance of the wiring portion is changed between the central portion and the both end portions by differentiating between the central portion and the end portion of the wiring portion, and the frequency is changed. A laminated dielectric filter characterized by shifting the peak position in characteristics. 2. An electrode part in which a plurality of stripline type resonance electrodes are disposed in a dielectric substrate, and a predetermined coupling capacitance is formed between each of the predetermined two of the resonance electrodes and the electrodes. An electrode part for providing a coupling electrode composed of a wiring part for connecting the parts, and forming a predetermined input / output capacitance with respect to the input terminal side and the output terminal side of the resonance electrodes. And a wiring portion for connecting the electrode portion to an external terminal. A laminated dielectric filter having a structure provided with an input / output electrode, wherein the coupling electrode and the input / output electrode An internal ground electrode overlapping the dielectric substrate only at a central portion of at least one wiring portion via a dielectric layer is provided in the dielectric substrate, and the internal ground electrode is formed on an outer surface of the dielectric substrate. By electrically connecting to the external earth electrode
By changing the characteristic impedance of the wiring portion between the central portion and the both end portions , the frequency characteristic is changed.
A multilayer dielectric filter characterized by shifting the upper peak position .