JP4136050B2 - Multilayer filter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multilayer dielectric filter having band-pass filter characteristics used in a high-frequency circuit such as a mobile communication device such as a mobile phone or a cordless phone.
[0002]
[Prior art]
4A is an external view of a conventional multilayer filter, FIG. 4B is a perspective view showing the external appearance, FIG. 5A is a cross-sectional view taken along line EE of FIG. 4B, and FIG. It is the equivalent circuit diagram. As shown in FIG. 4B, this multilayer filter has ground terminals 2 and 3 on both end faces of a substantially rectangular parallelepiped base 1 made of a ceramic dielectric, and an input terminal 4 and an output terminal 5 on both side faces. And have.
[0003]
This multilayer filter is manufactured by a sheet lamination method or a screen printing method. In FIG. 4A, reference numerals 1a to 1i denote dielectric layers. Reference numerals 7, 8, and 9 denote internal ground electrodes formed on the dielectric layers 1a, 1f, and 1h, respectively, and both ends thereof are connected to the ground terminals 2 and 3 shown in FIG. Reference numerals 10a and 10b denote inductor electrodes which are formed on the dielectric layer 1b and function as strip lines.
[0004]
Reference numerals 11a and 11b denote matching capacitance electrodes formed on the dielectric layer 1d, which are connected to the input terminal 4 and the output terminal 5, respectively. Reference numeral 12 denotes an attenuating capacitance electrode formed on the dielectric layer 1c and having both ends opposed to the matching capacitance electrodes 11a and 11b via the dielectric layer 1d and capacitively coupling the matching capacitance electrodes 11a and 11b.
[0005]
Reference numerals 13a and 13b denote first capacitor electrodes sandwiched between the matching capacitor electrodes 11a and 11b and the ground electrode 8 through the dielectric layers 1e and 1f, respectively. Reference numerals 13c and 13d denote dielectric layers 1g and 13g, respectively. This is a second capacitor electrode which is sandwiched and opposed between the ground electrodes 8 and 9 via 1h.
[0006]
The hot electrode side of the inductor electrode 10a is connected to the second capacitor electrode 13c and the first capacitor electrode 13a through via holes 14e, 14c and 14a. The inductor electrode 10b has a hot terminal side connected to the second capacitor electrode 13d and the first capacitor electrode 13b through via holes 14f, 14d, and 14b. The ground sides of the inductor electrodes 10a and 10b are connected to the ground terminal 2 at one end of the base 1 shown in FIG. Such a connection relationship is shown in the cross-sectional view of FIG. In FIG. 5A, reference numeral 14 denotes a series of via holes 14e, 14c, 14a or 14f, 14d, 14b.
[0007]
In the equivalent circuit diagram of FIG. 5B, the inductor electrodes 10a and 10b form inductances La2 and Lb2, respectively, and are mutually coupled (M). Further, the via holes 14c and 14a (14e is ignored because the inductance is small) constitutes an inductance La1, and the via holes 14d and 14b (14f is ignored because the inductance is small) forms an inductance Lb1.
[0008]
Therefore, the inductance La of the circuit electrically coupled to the input terminal 4 side is
La = La1 + La2 and the inductance Lb of the circuit electrically coupled to the output terminal 5 side is
Lb = Lb1 + Lb2.
[0009]
In addition, matching capacitors Ci and Ci are formed by the matching capacitor electrodes 11a and 11b and the first capacitor electrodes 13a and 13b, respectively. The matching capacitance electrodes 11a and 11b and the attenuation capacitance electrode 12 form an attenuation capacitance Cp between the input terminal 4 and the output terminal 5.
[0010]
Capacitances Ca1 and Cb1 are formed between the first capacitor electrodes 13a and 13b and the ground electrode 8, respectively. Capacitances Ca2, Ca3, Cb2, and Cb3 are formed between the second capacitor electrodes 13c and 13d and the ground electrodes 8 and 9, respectively. These capacities Ca1 + Ca2 + Ca3 = Ca,
Each component of Cb1 + Cb2 + Cb3 = Cb is the inductance La,
The equivalent circuit shown in FIG. 5B is configured by being connected in parallel to the component Lb.
[0011]
[Problems to be solved by the invention]
When the multilayer filter is manufactured by, for example, a sheet lamination method, a predetermined electrode is formed on a green sheet to be the dielectric layers 1a to 1h, and the green sheet on which the electrode is formed and the dielectric green sheet 1i that is the uppermost layer. After obtaining a laminated material by laminating, it is divided into individual pieces. The inductor electrodes 10a and 10b connected to the ground terminal 2 change in length due to the stacking shift at the time of stacking and the cutting shift at the time of splitting, so that the lengths of the electrodes 10a and 10b change. There is a problem that inductance (coupling value) due to induction changes, characteristics vary, and yield is low.
[0012]
In view of the above problems, an object of the present invention is to provide a multilayer filter having a high yield by minimizing fluctuations in an inductance value and a coupling value due to misalignment or cutting.
[0013]
[Means for Solving the Problems]
In order to achieve this object, the multilayer filter according to claim 1 of the present invention includes an input terminal and an output terminal provided on both side surfaces of a substrate made of a ceramic dielectric,
A ground terminal provided on both end faces of the substrate;
At least two or more layers of ground electrodes provided inside the base and connected at both ends to ground terminals on both ends of the base;
A plurality of inductor electrodes provided inside the substrate, one end of which is electrically coupled to the input terminal and the output terminal, respectively, and coupled inductively;
In the multilayer filter having capacitor electrodes respectively provided corresponding to the respective inductor electrodes inside the base and constituting LC resonators,
The plurality of inductor electrodes are formed in parallel with each other over a range that does not reach the ground terminals at both ends in a long straight line in the opposing direction of the ground terminals at both ends of the base,
Wherein the hot terminal side and the capacitor electrode of each inductor electrodes are connected by via holes,
The ground side end of each inductor electrode is connected to at least one ground electrode through a via hole,
The inductance from the capacitor electrode to the ground electrode is the inductance of the via hole that connects the capacitor electrode and the inductor electrode, the inductance of the inductor electrode, and the inductance of the via hole that connects the inductor electrode and the ground electrode It is characterized by comprising the sum of
[0014]
According to the first aspect, since both ends of the inductor electrode are connected to the capacitor electrode and the ground electrode, respectively, the length of the inductor electrode and the change in the coupling value between the inductor electrodes due to the stacking shift or cutting shift are small.
[0015]
The multilayer filter according to claim 2 is the method according to claim 1.
A ground side end portion of each inductor electrode is connected to at least one ground electrode through a via hole at a substantially central portion between ground terminals at both ends of the base.
[0016]
According to the second aspect of the present invention, since the ground side of the inductor electrode is connected to the center portion of the ground electrode by a via hole, an inductance stacking deviation between the connection portion between the via hole and the ground electrode and the ground terminal at the end of the substrate is reduced. The change due to the cutting deviation is smaller than when the connection portion between the via hole and the ground electrode is provided at a portion other than the central portion.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a multilayer structure diagram showing an embodiment of a multilayer filter according to the present invention, FIG. 2 (A) is a sectional view corresponding to FIG. 5 (A), and FIG. 5 (B) is an equivalent circuit diagram thereof.
[0018]
1 and the cross-sectional view of FIG. 2 (A) are different from the conventional multilayer structure shown in FIG. 4 (A) in that the ground-side ends of the inductor electrodes 10a and 10b are connected to via holes 15a, This is because it is connected to the ground electrode 7 via 15b. The inductor electrodes 10a and 10b are formed in a line in parallel over a range that does not reach the ground terminals 2 and 3 at both ends while forming a long straight line in the opposing direction of the ground terminals 2 and 3 at both ends of the base 1. In the present embodiment, the via holes 15 a and 15 b are connected to the central portion between the ground terminals 2 and 3 in the ground electrode 7. The hot terminals of the inductor electrodes 10a and 10b are respectively connected to the capacitor electrodes 13a, 13c, 13b, and 13d through the via holes 14a, 14c, and 14e, or the via holes 14b, 14d, and 14f, respectively, as in the prior art. Connected to.
[0019]
With such a configuration, the inductance of the via holes 14c and 14a is La1, the inductance of the via holes 14d and 14b is Lb1, the inductances of the inductor electrodes 10a and 10b are La2 and Lb2, and the inductances of the via holes 15a and 15b are La3 and Lb3. Then, the inductance La of the resonance circuit on the input terminal 4 side and the inductance Lb of the resonance circuit on the output terminal 5 side are as follows.
La = La1 + La2 + La3
Lb = Lb1 + Lb2 + Lb3
Here, the inductor electrodes 10a and 10b do not change in length even when there is a stacking shift in the stacking process or a cut from the stacking material to the individual piece, so that the values of the inductances La2 and Lb2 are affected by the shift. In addition, the inductances La1, La2, Lb1, and Lb2 of the via holes are not affected. Further, since the lengths of the inductor electrodes 10a and 10b are not affected by the deviation, the variation in the coupling degree of the mutual induction (M) is reduced. For these reasons, variations in filter characteristics due to the deviation are reduced.
[0020]
In this multilayer filter, the vertical width is set to 3.2 mm in the opposing direction of the ground terminals 2 and 3, the lateral width in the opposing direction of the input terminal 4 and the output terminal 5 is set to 2.5 mm, and the height is set to 1.5 mm. In addition, when the inductor electrodes 10a and 10b are connected to the ground terminal 2, the ground side end of the ground electrode 7 is connected to the center between the ground terminals 2 and 3 via the via holes 15a and 15b as in the present embodiment. In the case of connection, changes in characteristics due to stacking deviation or cutting deviation were examined.
[0021]
FIG. 3A shows the transmission characteristics of the filter when the amount of stacking deviation and cutting deviation in the 1.9 GHz band bandpass filter changes by ± 0.2 mm. In FIG. 2 (A), FIG. 5 (A), the inductor electrodes 10a, deviation of 10b has a minus direction by polarization direction by polarization to the ground terminal 2 side (left side) plus a ground terminal 3 side (right side) did. As can be seen from FIG. 3A, in the case of the present invention, the change of the pass band with respect to the shift amount is significantly smaller than that of the conventional example.
[0022]
FIGS. 3B and 3C show changes due to a shift in the center frequency fo and the specific bandwidth w of the bandpass filter. The center frequency fo is the center frequency of the frequencies fa and fb (where fb> fa) where the transmission characteristic S21 and the reflection characteristic S11 of the filter intersect, and the specific bandwidth w is the passband fw ( (the difference between fa and fb) and the center frequency fo. These related formulas are described below.
fo = (fa + fb) / 2
fw = fb−fa
w = fw / fo
As shown in FIG. 3B, according to the present invention, the center frequency fo hardly changes in the range where the deviation amount is ± 0.2 mm, but in the conventional example, the center frequency fo is about ± 0.08 GHz. Varies.
[0023]
As shown in FIG. 3C, in the case of the conventional example, the change of the specific bandwidth w is about ± 0.02 in the range where the deviation amount is ± 0.2 mm. The change of the specific bandwidth w is about ± 0.008, which is much smaller than the conventional example.
[0024]
As described above, according to the present invention, changes in the center frequency and the pass bandwidth due to the stacking error and the cutting error are significantly reduced as compared with the conventional case.
[0025]
When practicing the present invention, the connection point between the via holes 15a and 15b and the ground electrode 7 is more preferably approximately at the center between the ground terminals 2 and 3, as shown in the present embodiment. This is because a small change in inductance component existing between the connection point between the via holes 15a and 15b and the ground electrode 7 and the ground terminals 2 and 3 is smaller if the connection point is the center. is there.
[0026]
In addition, it is possible to configure a multilayer filter even when the attenuation capacitor electrode 12 is not provided. However, by providing the attenuation capacitor electrode 12, the amount of attenuation in the bands on both sides of the pass band can be increased and a multilayer with good characteristics can be formed. A filter can be obtained.
[0027]
In addition, providing the matching capacitance electrodes 11a and 11b and facing the capacitor electrodes 13a and 13b through the dielectric layer can be achieved by providing the matching capacitance electrodes with an appropriate area and an interval from the capacitor electrodes 13a and 13b. However, it is also possible to adopt a configuration in which the input terminal 4 and the output terminal 5 are connected to the capacitor electrodes 13a and 13b, respectively.
[0028]
Further, in the embodiment of FIGS. 1 and 2, the capacitor electrode may be only the second capacitor electrodes 13c and 13d, and the capacitor electrode is electrically coupled to the input terminal 4 and the output terminal 5, respectively. As a thing, you may provide the thing of three or more layers.
[0029]
【The invention's effect】
According to claim 1, each inductor electrode is connected to the input terminal and the output terminal via the capacitor electrode, respectively, and the hot terminal side of each inductor electrode and the capacitor electrode are connected by a via hole, the ground-side end of each inductor electrodes, since it is connected to one of the ground electrodes through the via hole, the degree of coupling is reduced between the length and the inductor electrode of the inductor electrode due to laminating misalignment or disconnection deviation Ya center frequency Changes in filter characteristics such as passband width can be reduced.
[0030]
According to claim 2, since the ground side end of each inductor electrode is connected to a substantially central portion between the ground terminals at both ends of at least one ground electrode via a via hole, stacking misalignment or cutting misalignment The change in filter characteristics due to can be further reduced.
[Brief description of the drawings]
FIG. 1 is a multilayer structure diagram showing an embodiment of a multilayer filter according to the present invention.
2A is a cross-sectional view corresponding to FIG. 5A of the multilayer filter of FIG. 1, and FIG. 2B is an equivalent circuit diagram thereof.
FIGS. 3A and 3B are diagrams showing changes in frequency characteristics due to misalignment and cutting misalignment between the conventional example and the present invention, corresponding to each misalignment amount, and FIG. 3B is a misalignment misalignment and misalignment between the conventional example and the present invention. FIG. 6C is a diagram showing a change in the center frequency characteristic corresponding to the amount of deviation of the band, and FIG. 10C is a diagram showing a change in the relative bandwidth corresponding to the amount of deviation of the stacking deviation and the cutting deviation of the conventional example and the present invention.
FIG. 4A is a multilayer structure diagram showing an example of a conventional multilayer filter, and FIG. 4B is a perspective view showing its appearance.
5A is an EE cross-sectional view of FIG. 4B, and FIG. 5B is an equivalent circuit diagram thereof.
[Explanation of symbols]
1: Base, 1a to 1i: Dielectric layer, 2: 3, Ground terminal, 4: Input terminal, 5: Output terminal, 7, 8, 9: Ground electrode, 10a, 10b: Inductor electrode, 11a, 11b: Matching Capacitance electrode, 12: attenuation capacitor electrode, 13a, 13b: first capacitor electrode, 13c, 13d: second capacitor electrode, 14a-14f, 15a, 15b: via hole

Claims (2)

An input terminal and an output terminal provided on both side surfaces of a base made of a ceramic dielectric;
A ground terminal provided on both end faces of the substrate;
At least two or more layers of ground electrodes provided inside the base and connected at both ends to ground terminals on both ends of the base;
A plurality of inductor electrodes provided inside the substrate, one end of which is electrically coupled to the input terminal and the output terminal, respectively, and coupled inductively;
In a multilayer filter having a capacitor electrode provided corresponding to each inductor electrode inside the substrate and constituting an LC resonator, respectively.
The plurality of inductor electrodes are formed in parallel with each other over a range that does not reach the ground terminals at both ends in a long straight line in the opposing direction of the ground terminals at both ends of the base,
Wherein the hot terminal side and the capacitor electrode of each inductor electrodes are connected by via holes,
The ground side end of each inductor electrode is connected to at least one ground electrode through a via hole,
The inductance from the capacitor electrode to the ground electrode is the inductance of the via hole that connects the capacitor electrode and the inductor electrode, the inductance of the inductor electrode, and the inductance of the via hole that connects the inductor electrode and the ground electrode A multilayer filter characterized by comprising the sum of In claim 1,
The multilayer filter, wherein a ground side end portion of each inductor electrode is connected to at least one ground electrode through a via hole at a substantially central portion between ground terminals at both ends of the substrate.

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