JPH08335803A - Filter - Google Patents

Abstract

PURPOSE: To provide a filter of a multilayer structure that has the excellent characteristic in its small size. CONSTITUTION: An inductor composed of the microstrip lines 17a and 17b and the via holes 18a and 18b which are formed inside a dielectric substrate including the 1st and 2nd dielectric layers 11 and 15 of rectangular shapes, a capacitor composed of the input/output electrodes 12a and 12b and the capacitor electrodes 16a and 16b are connected in parallel to the capacitor. One of both ends of each of two resonators to which the via holes 18a and 18b are magnetically connected is connected to the input terminals 20a and 20b respectively. Then the other end of each of both resonators is connected to a ground electrode 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter, and more particularly to a filter having inductors and capacitors connected in parallel, and two resonators to which the inductors are magnetically coupled.

[0002]

18 and 19 are a sectional view and a plan view showing an example of a conventional filter, respectively.

The filter 40 includes a first protective layer 41, and shield electrodes 42a, 42 are provided on the protective layer 41.
b, the dielectric layer 43, the three coils 44a, 44b and 4
4c including coil electrode 44, dielectric layer 45, pole forming capacitor electrode 46, dielectric layer 47, input / output impedance adjusting capacitor electrodes 48a and 48b, dielectric layer 49, parallel resonator capacitor electrodes 50a and 50b, dielectric Body layer 51, shield electrodes 52a and 52b, dielectric layer 5
3, trimming electrodes 54a and 54b, and the second protective layer 55 are laminated in this order.

On the side surface of the filter 40, eight terminals 56a to 56h having a U-shaped cross section are formed. And this filter 40 becomes an equivalent circuit shown in FIG.

[0005]

However, although the filter 40 has a multi-layer structure, since the coil electrode 44 has a planar structure, the shape is determined by the size of the coil, and it cannot be made smaller. It was difficult. Further, when the center frequency of the filter is equal to or higher than 1.5 GHz, the element value of the coil or the capacitor becomes small, so that it is difficult to realize the element value with this structure.

Further, as shown in FIG. 19, since the strip line is formed by a conductive film by screen printing, bleeding occurs, and there is a limit in minimizing the interval. Therefore, the magnetic coupling is stripline 44
In the case of the interval between a and 44b, there is a limit in reducing the magnetic coupling degree M, and there is a problem that the bandwidth is limited from bandwidth = center frequency × magnetic coupling degree M.

The present invention has been made to solve the above problems, and an object thereof is to provide a small-sized filter having a multi-layer structure and excellent characteristics.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, according to the present invention, an inductor and a capacitor formed inside a substrate made of a dielectric material are connected in parallel, and the inductor is magnetically coupled to each other. Including a resonator,
One end of each resonator is connected to the input / output terminal,
In a filter in which the other end of each of the two resonators is connected to a ground electrode, the inductor is formed of at least a via hole.

Further, the inductor is composed of a via hole and a microstrip line, and both the microstrip line formed inside the substrate and the capacitor are connected inside the substrate. .

[0010]

According to the filter of the first aspect, since the inductor is composed of at least a via hole, the element values of the inductor and the capacitor can be increased as compared with the conventional circuit.

Further, since the inductor is composed of at least the via hole, the inductance component becomes large as compared with the conventional linear pattern.

Further, since the inductor magnetically coupled with the magnetic coupling degree M is composed of via holes and the interval can be narrowed as compared with the conventional screen printing, the magnetic coupling degree M can be reduced.

Further, since the filter is composed of at least a via hole and a capacitor, and the via hole is a component of almost only inductance and the capacitor is also a component of almost only capacitance, it is close to the configuration of the lumped constant circuit of LCR.

According to the filter of the second aspect, since the inductor and the capacitor constituted by the microstrip line are connected inside the dielectric substrate, the interval between the capacitor electrode and the ground electrode should be narrowed. Therefore, the inductance component generated between the capacitor electrode and the ground electrode can be reduced.

Further, since the microstrip line is used for the inductor, the line width of the microstrip line is larger than that of the strip line having the same shape, and the line resistance can be reduced.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. In each embodiment, the same or equivalent parts as those in the first embodiment are designated by the same reference numerals, and the description of the overlapping parts will be omitted.

1 and 2 are a sectional view and a plan view, respectively, showing a filter according to a first embodiment of the present invention. The filter 10 includes a rectangular sheet-shaped first layer 11 made of, for example, a dielectric material. Although the first layer 11 is formed by laminating a large number of dielectric layers in this embodiment,
For example, it may be formed of only one dielectric layer.

Input / output electrodes 12a and 12b are formed on one main surface of the first layer 11 in the vicinity of opposite ends thereof.
Then, from the input / output electrodes 12 a and 12 b toward the end portion of the one main surface of the first layer 11, the extraction portion 121 is provided.
a and 121b extend.

A ground electrode 13 is formed on the other main surface of the first layer 11 excluding the edge portion.
Then, the lead-out portions 131a and 131b extend from the substantially central portions of the opposite ends of the ground electrode 13 toward the end of the other main surface of the first layer 11, and the lead-out portions 131 are formed.
The a and 131b are respectively positioned in the vertical direction with respect to the lead-out portions 121a and 121b of the input / output electrodes 12a and 12b when seen in a plan view.

Here, the ground electrode 13 is opposed to the input / output electrodes 12a and 12b when seen in a plan view. Therefore, the ground electrode 13, the first layer 11, and the input / output electrodes 12a and 12b form the capacitor C of the two resonators Q1 and Q2.
2 and C4 (FIG. 3) are configured.

Further, on the other main surface of the first layer 11, a first protective layer 14 made of, for example, a dielectric is formed so as to sandwich the ground electrode 13.

On the other hand, a second layer 15 made of, for example, a dielectric is formed on one main surface of the first layer 11 so as to sandwich the input / output electrodes 12a and 12b. Second layer 15
Is formed by laminating a large number of dielectric layers in this embodiment, but may be formed of only one dielectric layer, for example.

On the upper surface of the second layer 15, the capacitor electrodes 16a and 16b and the microstrip line 1 are provided.
7a and 17b are formed. The capacitor electrodes 16a and 16b are located in the vicinity of the ends of the upper surface of the second layer 15, and when viewed in a plan view, the input / output electrode 12 is formed.
It is located on the same end side as a and 12b. Also, these microstrip lines 17a and 17b are
71a and 171b are capacitor electrodes 16a and 16b
And the other ends 172a and 172b are connected to the second layer 15
Is located approximately in the center of the upper surface of the.

Here, the capacitor electrodes 16a and 16b
Faces the input / output electrodes 12a and 12b in a plan view. Therefore, the capacitor electrodes 16a and 16b, the second layer 15, and the input / output electrodes 12a and 12b form capacitors C1 and C3 (FIG. 3) of the two resonators Q1 and Q2. Then, in the microstrip lines 17a and 17b, the inductor S of the two resonators Q1 and Q2 is
L1 and SL2 (FIG. 3) are constructed.

Further, the ground electrode 13 and the other ends 172a and 172 of the microstrip lines 17a and 17b.
Via holes 18a and 18b are formed so as to penetrate the first layer 11 and the second layer 15 between them and b, and are filled with conductive materials 181a and 181b.

Then, in the via holes 18a and 18b,
Inductors L1 and L2 of the two resonators Q1 and Q2
(FIG. 3) is constructed.

Further, a second protective layer 19 made of, for example, a dielectric is formed on the upper surface of the second layer 15 so as to sandwich the capacitor electrodes 16a and 16b and the microstrip lines 17a and 17b.

Further, the filter 10 has an input terminal 20a on one side surface, an output terminal 20b on the other side surface, and a side surface on which the input / output terminals 20a and 20b are formed. The ground terminals 20c and 20d are respectively formed on the other side surfaces that are vertically positioned.

The filter 10 has an equivalent circuit shown in FIG. That is, this filter 10 has two resonators Q1 and Q2.

In one resonator Q1, inductors L1 and SL1 and a capacitor C1 which are connected in series, and a capacitor C2 are connected in parallel. Similarly, the other resonator Q2 also has inductors L2 and S connected in series.
L2 and the capacitor C3 and the capacitor C4 are connected in parallel.

Here, the inductors L1 and L2 composed of the via holes 18a and 18b of the resonators Q1 and Q2,
They are coupled with a magnetic coupling degree M. Then, a stray capacitance Cs is generated between the inductors L1 and L2.

Further, one ends of the resonators Q1 and Q2 are connected to the input / output terminals 20a and 20b, respectively.

The other ends of the resonators Q1 and Q2 are connected to the ground terminals 20c and 20d, respectively, and the ground electrode 13 is formed between the other ends of the resonators Q1 and Q2 and the ground terminals 20c and 20d. Inductor L
3 and L4 occur.

An inductor L5 formed by the ground electrode 13 is generated between the other ends of the resonators Q1 and Q2.

In the circuit shown in FIG. 3, the inductor L
The inductances of L1, L2, L3, L4 and L5 are 0.77, 0.77, 0.05, 0.05 and 0.
01 (nH) and capacitors C1, C2, C3, C4
And Cs capacitances of 2.7, 10, 2.7, respectively.
10 and 0.2 (pF), and the dimensions of the microstrip lines SL1 and SL2 are 2.2 × 0.15, respectively.
(Mm) (length x width) with a ground gap of 1.0
FIG. 4 shows frequency characteristics of the reflection coefficient and the passage coefficient in the case of (mm), and FIG. 5 shows a Smith chart of the reflection coefficient.

It can be seen from FIGS. 4 and 5 that the insertion characteristic and the attenuation characteristic of the filter are improved.

As described above, according to this embodiment, since the inductor is composed of the via holes 18a and 18b and the microstrip lines 17a and 17b,
The element values of the inductor and the capacitor can be increased as compared with the conventional circuit, and the flexibility of the element configuration increases when used at a frequency of 1.5 GHz or higher.

Since the inductor is composed of the via holes 18a and 18b and the microstrip lines 17a and 17b, the insertion characteristic and the attenuation characteristic of the filter are improved.

Further, inductors are used as via holes 18a and 18b and microstrip lines 17a and 17b.
By configuring with, compared to the conventional linear pattern,
Since the inductance component increases, the filter can be downsized.

Further, by forming the inductor by the microstrip lines 17a and 17b, the line width becomes larger than that of the strip lines having the same shape, and thus the line resistance becomes small. Therefore, the insertion loss of the filter is reduced.

Since the inductor magnetically coupled with the magnetic coupling degree M is composed of the via holes 18a and 18b,
The interval can be narrowed as compared with the conventional screen printing. Therefore, since the magnetic coupling degree M can be made smaller than in the conventional case, bandwidth = center frequency × magnetic coupling degree M
It is possible to reduce the bandwidth.

FIG. 6 is a plan view showing a filter according to the second embodiment of the present invention. The filter 10a differs from the filter 10 (FIGS. 1 and 2) in that the microstrip lines 21a and 21b are formed by meander lines.

In this case, the inductance component can be further increased by the microstrip lines 21a and 21b formed of meander lines. Therefore, the same effect as the filter 10 (FIGS. 1 and 2) can be obtained, and the filter can be further downsized.

7 and 8 are a sectional view and a plan view, respectively, showing a filter according to the third embodiment of the present invention. The filter 10b is different from the filter 10 (FIGS. 1 and 2) in that it does not include the microstrip lines 17a and 17b, and is different from the filter 10 in that the ground electrode 13, the first layer 11, Input / output electrodes 12a and 12
b, the second layer 15, the capacitor electrodes 16a and 16b,
The second protective layer 19 is sequentially laminated. Then, between the end portions of the capacitor electrodes 16a and 16b located substantially in the center of the upper surface of the second layer 15 and the ground electrode 13, so as to penetrate the first layer 11 and the second layer 15,
Via holes 18a and 18b are formed, and conductive material 181 is formed.
a and 181b are filled.

Like the filter 10, the filter 10b has an input terminal 20a formed on one side surface thereof, an output terminal 20b formed on the other side surface thereof, and ground terminals 20c and 20d formed on the other side surface thereof, respectively. It is formed.

According to this embodiment, the ground electrode 13, the first layer 11 and the input / output electrodes 12a and 12b constitute the capacitors C2 and C4 (FIG. 3), and the capacitor electrodes 16a and 16b and the second electrode. The layer 15 and the input / output electrodes 12a and 12b form capacitors C1 and C3 (FIG. 3), and the via holes 18a and 18b form the inductor L1.
And L2 (FIG. 3) are configured. And beer hole 1
Inductors L1 and L2 formed of 8a and 18b are coupled with a magnetic coupling degree M.

In this case, the filter is composed of a via hole and a capacitor, the via hole is almost an inductance component, and the capacitor is also a capacitance component. Therefore, since the structure is close to that of the lumped constant circuit of LCR, the same effect as that of the filter 10 (FIGS. 1 and 2) can be obtained, and a spurious-free filter can be manufactured.

9 and 10 are a sectional view and a plan view, respectively, showing a filter according to the fourth embodiment of the present invention.
This filter 10c is a filter 10 (FIGS. 1 and 2).
In comparison with, the via holes 2 are provided for connecting the inductors SL1 and SL2 (FIG. 3) and the capacitors C1 and C3 (FIG. 3).
2a and 22b are used, but the first protective layer 1
4, a ground electrode 13, a first layer 11, input / output electrodes 12a and 12b, a second layer 15, a capacitor electrode 1
The layers 6a and 16b, the third layer 23, the microstrip lines 17a and 17b, and the second protective layer 19 are sequentially stacked. And the capacitor electrodes 16a and 1
6b and one ends 171a and 171b of the microstrip lines 17a and 17b, via holes 22a and 22b are formed so as to penetrate the third layer 23, and the ground electrode 13 and the microstrip lines 17a and 17b are formed.
Between the other ends 172a and 172b of the first layer 1
Via holes 18a and 18b are formed so as to penetrate the first, second layer 15 and the third layer 23, and are filled with conductive materials 181a and 181b.

Here, the third layer 23 is formed by laminating a large number of dielectric layers in the present embodiment, but may be formed of only one dielectric layer, for example.

Like the filter 10, the filter 10c has an input terminal 20a formed on one side surface thereof and an output terminal 20b formed on the other side surface thereof, and ground terminals 20c and 20d formed on the other side surface thereof. It is formed.

According to this embodiment, the ground electrode 13, the first layer 11 and the input / output electrodes 12a and 12b constitute the capacitors C2 and C4 (FIG. 3), and the capacitor electrodes 16a and 16b and the second electrode. The layer 15 and the input / output electrodes 12a and 12b form capacitors C1 and C3 (FIG. 3), and the via holes 18a and 18b form the inductor L1.
And L2 (FIG. 3) are configured to include inductors SL1 and SL2 in the microstrip lines 17a and 17b.
(FIG. 3) is constructed. Then, the inductors L1 and L2 composed of the via holes 18a and 18b are coupled to each other with the magnetic coupling degree M.

In this case, the inductors SL1 and SL
2 and the capacitors C1 and C3 are connected to via holes 22.
Since a and 22b are used, the distance between the capacitor electrodes 16a and 16b and the ground electrode 13 can be narrowed, so that the inductance component generated between the capacitor electrodes 16a and 16b and the ground electrode 13 can be reduced. it can. Therefore, it is possible to obtain the same effect as the filter 10 (FIGS. 1 and 2) and to manufacture a filter having good spurious characteristics.

11 and 12 show the fifth embodiment of the present invention.
4A and 4B are a cross-sectional view and a plan view showing the filter according to the example of FIG. The filter 10d is different from the filter 10 (FIGS. 1 and 2) in that an inductor formed of a microstrip line is magnetically coupled, and includes a rectangular sheet-shaped first layer 11 formed of, for example, a dielectric. .

Input / output electrodes 12a and 12b are formed near one end of one main surface of the first layer 11. Then, the lead-out portions 12 extending to the ends of the first layer 11 respectively.
It has 1a and 121b.

A ground electrode 13 is formed on the other main surface of the first layer 11 except for the edge portion.
Then, the lead-out portions 131 a and 131 b extend from the substantially central portions of the opposite ends of the ground electrode 13 toward the end portion of the other main surface of the first layer 11, respectively, and the lead-out portion 131.
a and 131b are the input / output electrodes 1 when viewed in plan.
It is positioned perpendicular to the lead-out portions 121a and 121b of 2a and 12b.

Here, the ground electrode 13 opposes the input / output electrodes 12a and 12b when viewed two-dimensionally. Therefore, the ground electrode 13, the first layer 11, and the input / output electrodes 12a and 12b form the capacitor C of the two resonators Q1 and Q2.
2 and C5 (FIG. 11) are configured.

Further, a first protective layer 14 made of, for example, a dielectric is formed on the other main surface of the first layer 11 so as to sandwich the ground electrode 13.

On the other hand, a second layer 15 made of, for example, a dielectric is formed on one main surface of the first layer 11 so as to sandwich the input / output electrodes 12a and 12b.

In the vicinity of one end of the upper surface of the second layer 15,
Capacitor electrodes 16a and 16b are formed. The capacitor electrodes 16a and 16b are located on the same end portion side as the input / output electrodes 12a and 12b when seen in a plan view.

Here, the capacitor electrodes 16a and 16b
Faces the input / output electrodes 12a and 12b in a plan view. Therefore, the capacitor electrodes 16a and 16b, the second layer 15, and the input / output electrodes 12a and 12b form capacitors C2 and C5 (FIG. 13) of the two resonators Q1 and Q2.

A third layer 23 made of, for example, a dielectric is formed on the upper surface of the second layer 15 so as to sandwich the capacitor electrodes 16a and 16b.

A capacitor electrode 24 is formed in a substantially central portion of the upper surface of the third layer 23 near one end thereof. And
The capacitor electrode 24, when viewed in plan,
It is located on the same end side as a and 12b and partially overlaps with the capacitor electrodes 16a and 16b.

Here, the capacitor electrode 24 opposes the ground electrode 13 when viewed two-dimensionally. Therefore, the capacitor electrode 24, the first layer 11, the second layer 15, and the third layer 23
And the ground electrode 13 form a capacitor C3 (FIG. 13) between the resonator Q1 and the resonator Q2.

On the upper surface of the third layer 23, a fourth layer 25 made of, for example, a dielectric is formed so as to sandwich the capacitor electrode 24.

On the upper surface of the fourth layer 24, one ends 171a and 171b are located on the same end side as the input / output electrodes 12a and 12b, and the other ends 172a and 172b are located on the opposite end side. , Microstrip line 17a
And 17b are formed.

In addition, the capacitor electrodes 16a and 16b and one end 17 of the microstrip lines 17a and 17b.
Via holes 22a and 22b are formed between 1a and 171b so as to penetrate the third layer 23 and the fourth layer 25, and the ground electrode 13 and the other ends 172a and 172b of the microstrip lines 17a and 17b are formed. Between the via holes 18a and 18b so as to penetrate the first layer 11, the second layer 15, the third layer 23, and the fourth layer 25.
Are formed, and the via holes 18a, 18b, and 2 are formed.
Conductive materials 181a, 181b, 221 are provided on 2a and 22b.
a and 221b are filled.

Then, the microstrip line 17a
And 17b form inductors SL1 and SL2 (FIG. 13) of the two resonators Q1 and Q2, and the via hole 2
2a and 22b form inductors L1 and L2 (FIG. 13) of the two resonators Q1 and Q2, and the via hole 1
8a and 18b constitute inductors L3 and L4 (FIG. 13) of the two resonators Q1 and Q2.

Further, a second protective layer 19 made of, for example, a dielectric is formed on the upper surface of the fourth layer 25 so as to sandwich the microstrip lines 17a and 17b.

Input / output terminals 20a and 20b are formed on one side surface of the filter 10d, and ground terminals 20c and 20d are formed on the other side surfaces thereof.
Is formed.

Although the fourth layer 25 is formed by laminating a large number of dielectric layers in this embodiment, it may be formed of only one dielectric layer.

The filter 10d has an equivalent circuit shown in FIG. That is, the filter 10d has two resonators Q1 and Q2.

In one resonator Q1, inductors L1, L3 and SL1 connected in series and a capacitor C2 are connected in parallel. Similarly, the other resonator Q2 also has inductors L2, L4 and SL2 connected in series.
And a capacitor C5 are connected in parallel. further,
A capacitor C3 is provided between the inductors SL1 and SL2.
Is connected.

Here, the inductor S composed of the microstrip lines 17a and 17b of the resonators Q1 and Q2.
L1 and SL2 are coupled with a magnetic coupling degree M.

One end of the two resonators Q1 and Q2 is connected to the input / output terminal 2 via the capacitors C1 and C4.
0a and 20b connected to two resonators Q1 and Q2
The other end of is connected to the ground terminals 20c and 20d.

Further, an inductor L5 formed by the ground electrode 13 is generated between the other ends of the two resonators Q1 and Q2 and the ground terminals 20c and 20d.

In the circuit shown in FIG. 13, the inductor L
The inductances of 1, L2, L3, L4 and L5 are 0.8, 0.8, 0.05, 0.05 and 0.08, respectively.
(NH), the capacitors have capacitances of C1, C2, C3, C4 and C5 of 0.55, 1.3, 0.
6, 0.55 and 1.3 (pF), and the dimensions of the microstrip lines SL1 and SL2 are 2.2 ×, respectively.
FIG. 14 shows the frequency characteristics of the reflection coefficient and the passage coefficient when 0.15 (mm) (length × width) and the ground gap is 1.0 (mm), and a Smith chart of the reflection coefficient is shown in FIG.
5 shows.

It can be seen from FIGS. 14 and 15 that the insertion characteristic and the attenuation characteristic of the filter are improved.

Although FIG. 13 shows a circuit having only lower poles, in the case of making poles on both sides, as shown in FIG. 16, between the one ends of the resonators Q1 and Q2, a pole is formed. A circuit in which the capacitor C6 is connected may be used. The pole forming capacitor C6 is composed of a stray capacitance generated between the input / output terminals 20a and 20b. Therefore, an electrode or the like for forming only the pole forming capacitor C6 is unnecessary.

As described above, according to the present embodiment, the via holes 22a and 22b are used to connect the inductors SL1 and SL2 to the capacitors C2 and C5, so that the capacitor electrodes 16a and 16b and the ground electrode 1 are connected.
Since it is possible to narrow the distance from the capacitor 3, the inductance component generated between the capacitor electrodes 16a and 16b and the ground electrode 13 can be reduced. Therefore, it is possible to manufacture a filter having good spurious characteristics.

Further, the inductors are used as the via holes 18a and 18b and the microstrip lines 17a and 17b.
Since it is a circuit composed of and, compared with the conventional circuit, it is possible to increase the element values of the inductor and capacitor.
When used at a frequency of 1.5 GHz or higher, the degree of freedom in element configuration increases.

Further, since the inductor is composed of the via hole and the microstrip line, the inductance component becomes large as compared with the conventional linear pattern, so that the filter can be downsized.

Further, by forming the inductor by the microstrip line, the loss is smaller than that of the strip line having the same shape, so that the element characteristics are improved.

FIG. 17 is a plan view showing a filter according to the seventh embodiment of the present invention. This filter 10e is different from the filter 10d in the microstrip line 21.
The difference is that a and 21b are formed by meander lines.

In this case, it is possible to further increase the inductance component by the microstrip lines 21a and 21b formed of meander lines. Therefore, the filter 10d (FIGS. 11 and 12)
It is possible to obtain the same effect as the above and further downsize the filter.

[0085]

According to the filter of the first aspect, since the inductor is composed of at least a via hole, the element values of the inductor and the capacitor can be increased as compared with the conventional circuit. Therefore, 1.5G
When used at a frequency of Hz or higher, the degree of freedom in the element configuration increases.

Since the inductor is composed of at least the via hole, the insertion characteristic and the attenuation characteristic of the filter are improved.

Further, by forming the inductor with at least a via hole, compared with the conventional linear pattern,
Since the inductance component increases, the filter can be downsized.

Further, since the inductor which is magnetically coupled with the magnetic coupling degree M is composed of the via hole, the interval can be narrowed as compared with the conventional screen printing. Therefore, since the magnetic coupling degree M can be made smaller than in the conventional case, the bandwidth can be made narrower from bandwidth = center frequency × magnetic coupling degree M.

Further, the filter is composed of a via hole and a capacitor, the via hole is almost an inductance component, and the capacitor is also a capacitance component. Therefore, since the configuration is similar to that of the lumped constant circuit of LCR, it is possible to fabricate a spurious-free filter.

According to the filter of the second aspect, since the inductor and the capacitor formed of the microstrip line are connected inside the dielectric substrate, the gap between the capacitor electrode and the ground electrode is narrowed. Therefore, the inductance component generated between the capacitor electrode and the ground electrode can be reduced. Therefore, it is possible to manufacture a filter having good spurious characteristics.

Further, by forming the inductor by the microstrip line, the line width becomes larger than that of the strip line having the same shape, and thus the line resistance becomes small. Therefore, the insertion loss of the filter is reduced.

[Brief description of drawings]

FIG. 1 is a sectional view showing a filter according to a first embodiment of the present invention.

2 is a perspective plan view of the filter shown in FIG. 1. FIG.

FIG. 3 is an equivalent circuit diagram of the filter shown in FIG.

FIG. 4 is a graph showing frequency characteristics of the filter shown in FIG.

FIG. 5 is a Smith chart of the filter shown in FIG.

FIG. 6 is a perspective plan view showing a filter according to a second embodiment of the present invention.

FIG. 7 is a sectional view showing a filter according to a third embodiment of the present invention.

8 is a perspective plan view of the filter shown in FIG. 7. FIG.

FIG. 9 is a sectional view showing a filter according to a fourth embodiment of the present invention.

10 is a perspective plan view of the filter shown in FIG. 9. FIG.

FIG. 11 is a sectional view showing a filter according to a fifth embodiment of the present invention.

12 is a perspective plan view of the filter shown in FIG. 11. FIG.

FIG. 13 is an equivalent circuit diagram of the filter shown in FIG.

14 is a graph showing frequency characteristics of the filter shown in FIG.

FIG. 15 is a Smith chart of the filter shown in FIG.

FIG. 16 is an equivalent circuit diagram showing a filter according to a sixth embodiment of the present invention.

FIG. 17 is a perspective plan view showing a filter according to a seventh embodiment of the present invention.

FIG. 18 is a cross-sectional view showing a conventional filter.

FIG. 19 is a perspective plan view of the filter shown in FIG.

20 is an equivalent circuit diagram of the filter shown in FIG.

[Explanation of symbols]

10, 10a, 10b, 10c, 10d, 10e
Filters 12a, 12b Input / output electrodes 13 Ground electrodes 16a, 16b, 24 Capacitor electrodes 17a, 17b, 21a, 21b Microstrip lines 18a, 18b, 22a, 22b Via holes L1, L2, L3, L4, L5, SL1, SL2
Inductors C1, C2, C3, C4, C5, C6 Capacitors Q1, Q2 Resonators

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenji Asakura Inventor Kenji Ara 226-10 Tenjin, Nagaokakyo City, Kyoto Murata Manufacturing Co., Ltd.

Claims (2)

[Claims] 1. An inductor and a capacitor formed inside a substrate made of a dielectric material are connected in parallel, and the resonator includes two resonators magnetically coupled to each other. One end of each of the two resonators is an input / output terminal. A filter in which the other end of each of the two resonators is connected to a terminal and is connected to a ground electrode, wherein the inductor is formed of at least a via hole. 2. The inductor comprises a via hole and a microstrip line, and both the microstrip line formed inside the substrate and the capacitor are connected inside the substrate. The filter according to claim 1.