JPH1155003A - Laminated dielectric filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To build a filter in a circuit board so as to reduce its area and to thin it while suppressing the increase of a loss. SOLUTION: Three 1/4 wavelength strip line type resonance lines 11a, 11b and 11c are formed on one main surface of a 2nd dielectric layer 4. The middle resonance line 11b is formed on the main face of a 1st dielectric layer and connected to a 1st capacity electrode 12b wider than the middle resonance line 11b. The resonance lines 11a and 11b on both the sides are connected to a 2nd capacity electrode 12a formed on the main surface of the 1st dielectric layer 2, 3rd capacity electrode 12c, 4th capacity electrode 13a formed on the main surface of a 3rd dielectric layer 5, and 5th capacity electrode 13c.

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 which can be built in a circuit board for an RF module or the like and which is used in a filter or a duplexer incorporated in a radio-frequency circuit radio section of a portable communication telephone or the like.

[0002]

2. Description of the Related Art Conventionally, as a laminated dielectric filter,
Using a dielectric material having a relative dielectric constant of 30 to 80, a quarter-wavelength stripline resonance element is provided in two or more dielectric layers, and a conductor is filled in the via hole to fill the quarter-wavelength stripline resonator. A proposal has been made to reduce the occupied area of a dielectric filter by using a resonance line in which stripline resonance elements are connected in the vertical direction, thereby reducing the length of the resonance line in the extending direction (Japanese Patent Laid-Open No. Hei 10 (1994)). 6-97
No. 705).

[0003] In recent years, with the miniaturization of mobile phones, modularization of electronic components has progressed, and band pass filters (Band Pass filters) have been developed.
It is required that filters, such as filters, hereinafter referred to as BPFs, and low-pass filters (hereinafter, referred to as LPFs), etc., and passive circuits, such as impedance matching circuits, be built into the circuit board. I have. The miniaturization of the dielectric filter for the BPF can be performed using the above-described conventional technology. As a material of a dielectric layer used in a conventional dielectric filter, a material having a relative dielectric constant of about 30 to 80 is used,
In order to further reduce the size, it is conceivable to further improve the relative permittivity.

[0004]

SUMMARY OF THE INVENTION However, the LPF
10-20
It is necessary to use a circuit board with a low relative dielectric constant, and when a matching circuit and a dielectric filter as a BPF are simultaneously formed in a circuit base formed of a dielectric material having such a low dielectric constant. However, it is difficult to reduce the size of the dielectric filter.

Further, in the conventional dielectric filter, since the resonance line for the quarter wavelength strip line resonance element extends over two or more dielectric layers, the total thickness of the dielectric filter is 2 mm.
That is all. 0.8-1.2mm
It cannot be built into a circuit board of a certain degree. If such a laminated dielectric filter is made thinner in order to make it thinner, the ground electrode becomes too close to the resonance electrode, and there is a problem that the loss increases.

Accordingly, the present invention has been completed in view of the above circumstances, and it is an object of the present invention to reduce the size and thickness without increasing loss and to incorporate the matching circuit and the like into a circuit board. It is to provide a possible dielectric filter.

[0007]

According to the laminated dielectric filter of the present invention, at least three dielectric layers of first to third dielectric layers are provided between two dielectric layers each having a ground electrode formed thereon. In the laminated dielectric filter provided, three strip line type resonance lines are provided substantially in parallel on a main surface of a second dielectric layer, and a middle resonance line is a main line of the first dielectric layer. The first is formed on the surface and is wider than the middle resonance line.
The resonance lines on both sides are connected to the second and third capacitance electrodes formed on the main surface of the first dielectric layer and the fourth and fourth resonance electrodes formed on the main surface of the third dielectric layer. The first to fifth capacitance electrodes, that is, the capacitance electrodes on the open end side of the resonance line form a resonance capacitance. The resonance frequency 1 / {2π (LC) ^1/2 } (L: inductance, C: capacitance) of the stripline type resonator becomes large,
L can be reduced. As a result, the size of the laminated dielectric filter is reduced. In addition, a strip line type resonance line
Unlike the case where the layers are provided in layers or more, the ground electrode does not exist inside, so that the thickness of the laminated dielectric filter is reduced.

Further, by increasing the width of the first capacitor electrode where the electromagnetic field concentration occurs most in the pass band, an increase in loss can be suppressed and prevented, and the thickness of the laminated dielectric filter can be reduced. At the same time, by providing the second to fifth capacitance electrodes on the upper and lower two layers of the second dielectric layer, it is possible to prevent the occupation area of the multilayer dielectric filter from increasing due to the increase in the width of the first capacitance electrode. be able to.

[0009]

FIG. 1 is a schematic development view of a laminated dielectric filter (hereinafter, referred to as a filter) F of the present invention, and FIG.
FIG. 3 is a perspective view showing the external appearance of the filter F and omitting the internal structure, FIG. 3 is a cross-sectional view of the filter F taken along line AA in FIG. 2, and FIG. 5 is an equivalent circuit diagram of the filter F.

In FIG. 1, reference numerals 1 to 6 denote dielectric layers, of which 2 is a first dielectric layer, 4 is a second dielectric layer, 5 is a third dielectric layer, and 11a, 11b, and 11c are dielectric layers. 3 (three stages) substantially parallel resonant lines 12a, 12b, 1/4 wavelength strip line type formed on one main surface of the two dielectric layers 4;
12c is the second, first and third layers formed on the first dielectric layer 2.
13a and 13c are the fourth and fifth capacitance electrodes formed on the third dielectric layer 5, 14a and 14c are the first and second input / output electrodes, and 21 and 22 are the uppermost and lowermost, respectively. Ground electrode (earth electrode) formed on lower dielectric layers 1 and 6
It is. As shown in the figure, the resonance line 11b is a middle resonance line, and the resonance lines 11a and 11c are on both sides.

A via hole 41a is provided in the dielectric layer 3 for electrically connecting the resonance line 11a to the second capacitor electrode 12a. A via hole 41b is provided in the second dielectric layer 4 and
A via hole 41c for electrically connecting the first capacitor 1a to the second capacitor electrode 12a is provided in the third dielectric layer 5 to provide a resonance line 11a.
Via hole for electrically connecting the fourth capacitor electrode 13a to the
2a is a via hole provided in the dielectric layer 3 for electrically connecting the resonance line 11b to the first capacitance electrode 12b, and 42b is a second hole.
A via hole provided in the dielectric layer 4 for electrically connecting the resonance line 11b to the first capacitor electrode 12b.
The via hole 43b is provided in the second dielectric layer 4 for conducting connection between the resonance line 11c and the third capacitance electrode 12c. The via hole 43b is provided in the second dielectric layer 4 for conduction connection between the resonance line 11c and the third capacitance electrode 12c. This is a via hole provided in the dielectric layer 5 for electrically connecting the resonance line 11c to the fifth capacitor electrode 13c.

The filter according to the present invention comprises the earth electrodes 21 and
At least three dielectric layers of a first dielectric layer 2, a second dielectric layer 4, and a third dielectric layer 5 are disposed between the two dielectric layers 1 and 6 on which the respective layers 2 are formed. Alternatively, a dielectric layer provided with input / output electrodes and the like may be separately provided. In addition, an electrode that can be formed on the back surface of the first dielectric layer 2 such as the ground electrode 21 may share the dielectric layer.

As shown in FIG. 1, the filter F is formed by forming electrodes made of a conductive material on one surface of a plurality of dielectric layers made of unfired green sheets or the like by a printing method or the like. It is manufactured by stacking these dielectric layers and sintering and integrating them so that the electrodes do not short-circuit between the dielectric layers 1 to 6.

On one main surface of the second dielectric layer 4, three substantially parallel resonance lines 11a of a quarter wavelength strip line type are provided.
11b, 11c are formed, and one main surface of the first dielectric layer 2 is connected to the resonance lines 11a, 11b, 11c and arranged in parallel with the resonance lines 11a, 11b, 11c. 12a, a first capacitance electrode 12b, and a third capacitance electrode 12c are formed.

Input / output electrodes 14a and 14c are formed on one main surface of the dielectric layer 3 laminated on the upper surface of the first dielectric layer 2, and the first input / output electrode 14a is An input / output capacitor is constituted by arranging it so as to overlap with the capacitance electrode 12a, and an interstage capacitor is constituted by arranging it so as to overlap with the first capacitance electrode 12b. Similarly,
The second input / output electrode 14c constitutes an input / output capacitor by being arranged so as to overlap with the third capacitance electrode 12c, and constitutes an interstage capacitor by being arranged so as to overlap with the first capacitance electrode 12b. .

On one main surface of the dielectric layer 5 laminated on the upper surface of the second dielectric layer 4, a fourth capacitance electrode 13a and a fifth capacitance electrode 13c are overlapped with the resonance lines 11a and 11c. Be placed.

As shown in FIGS. 1 and 2, ground electrodes 21 and 22 are formed on two opposing sides of the filter and on two sides perpendicular to the longitudinal direction of the resonance lines 11a, 11b and 11c. The resonance lines 11a, 11b, 11c and the second capacitance electrodes 12a,
The first capacitance electrode 12b and the third capacitance electrode 12c are connected to only one of the ground electrodes 31 and 32.

The dielectric material constituting the dielectric layers 1 to 6 has a relative dielectric constant of about 10 to 20,
bCaO · cTiO ₂ (25 ≦ a ≦ 35, 0.3 ≦ b ≦
7,60 ≦ c ≦ 70, a + b + c = 100 weight ratio)
3-20 parts by weight of a boron-containing compound in terms _of B ₂ O _3, lithium-containing compound Li ₂ O ₃ in terms of a well and a material obtained by adding 1 to 10 parts by weight, thereby, in the circuit based on slope of the filter is incorporated A matching circuit can be integrated. Further, the resonance lines 11a, 11b, 1
1c, a second capacitance electrode 12a, a first capacitance electrode 12b,
The third capacitor electrode 12c, the fourth capacitor electrode 13a, the fifth capacitor electrode 13c, the input / output electrodes 14a and 14c are made of copper,
It is desirable to form using a conductor with low electric resistance such as silver or gold. And each of the dielectric layers 1 to 6 is 900 to 100
Simultaneous firing with a circuit board is preferably performed using a low-temperature firing material of about 0 ° C., and efficient manufacturing can be achieved by simultaneous firing at a low temperature.

The filter of the present invention has a shape as shown in FIG. 3 when used alone. The input / output electrodes 14 are provided on two side surfaces different from the two side surfaces on which the ground electrodes 31 and 32 of the filter are provided.
Input / output electrodes 33 and 34 are formed at positions corresponding to a and 14c. 1, the same parts as those in FIG. 1 are denoted by the same reference numerals, and 41a to 41c are grouped together, 41, 42a, 42b are grouped together, and 42, 43a to 43c.
Were collectively represented as 43.

When the filter of the present invention is incorporated in a circuit board, the configuration is as shown in FIG. The dielectric layer 1 does not exist, the ground electrode 21 is formed on the lower surface side of the first dielectric layer 2, and the dielectric layer 7 is newly provided on the dielectric layer 6. And
Input / output electrodes 48 and 49 are newly formed on the dielectric layer 7 to input and output signals to the input / output electrodes 14a and 14c. The input / output electrodes 14a, 14c and the input / output electrode 48,
Via holes 49 (46 a to 46 d) and via holes 47 (47 a to 47 d) are provided between them and are electrically connected.

In this case, it is preferable to use a via hole, a vertical electrode, or the like instead of the ground electrodes 31, 32 and the input / output electrodes 33, 34 because they can be installed at any positions on the circuit board.
In order to protect the ground electrode 21, the first dielectric layer 2
Further, a dielectric layer may be further provided below.

FIG. 5 shows an equivalent circuit of the filter of the present invention, which will be described below. Resonance line 11a, 1
1b and 11c, resonance inductors 51, 52, 53
And the second capacitance electrode 12a and the first capacitance electrode 1
2b, a third capacitance electrode 12c, a fourth capacitance electrode 13a,
The fifth capacitor electrode 13c allows the resonance capacitor 54,
55 and 56 are configured. An input / output capacitor 57 is provided between the input / output electrode 14a and the second capacitor electrode 12a, and an interstage capacitor 59 is provided between the input / output electrode 14a and the first capacitor electrode 12b. Similarly, an input / output capacitor 58 is provided between the input / output electrode 14c and the third capacitor electrode 12c, and an interstage capacitor 60 is provided between the input / output electrode 14c and the first capacitor electrode 12b.

Resonant lines 11a and 11b, 11b and 11c
Are respectively magnetically coupled, which is represented by a mutual inductance M in the equivalent circuit. In this equivalent circuit, the interstage capacitors 59,
A half-wavelength resonance circuit is formed by the resonance line 60 and the resonance lines 11a, 11b, 11c, and one of the attenuation poles is formed.
In addition, phase inversion occurs between the paths of the inter-stage capacitors 59 and 60, the input and output capacitors 57 and 58, and the path of the magnetic coupling (M), thereby forming another attenuation pole on the low frequency side.

In the filter of the present invention, an input / output capacitor is formed between the fourth capacitor electrode 13a and the fifth capacitor electrode 13c on the third dielectric layer 5 in order to increase the capacity of the input / output capacitor. Input / output electrodes may be newly added.
When changing the mutual inductance M, the distance between the resonance lines 11a, 11b, 11c is changed, or the second capacitance electrode 12a, the first capacitance electrode 12b, the third capacitance electrode 12c, and the fourth capacitance electrode 13a are changed. , Fifth capacitance electrode 13
This can be handled by changing the length of c.

[0025]

According to the present invention, the middle resonance line is formed on the main surface of the first dielectric layer and connected to the first capacitor electrode wider than the middle resonance line. The second and third capacitor electrodes formed on the main surface of the first dielectric layer and the third
By being connected to the fourth and fifth capacitance electrodes formed on the main surface of the dielectric layer, each capacitance electrode forms a resonance capacitance. Unlike the case where the two resonance lines are provided in two or more layers and overlapped with each other, since the ground electrode does not exist inside, the laminated dielectric filter becomes thin.

Further, by increasing the width of the first capacitor electrode where the electromagnetic field concentration occurs most in the pass band, an increase in loss can be suppressed and prevented, and the thickness of the laminated dielectric filter can be reduced. At the same time, by providing the second to fifth capacitance electrodes on the upper and lower two layers of the second dielectric layer, it is possible to prevent the occupation area of the multilayer dielectric filter from increasing due to the increase in the width of the first capacitance electrode. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic development view of a laminated dielectric filter F of the present invention.

FIG. 2 is a perspective view showing the appearance of a multilayer dielectric filter F according to the present invention, with the internal configuration omitted.

FIG. 3 is a sectional view of a multilayer dielectric filter F of the present invention.

FIG. 4 is a cross-sectional view when the laminated dielectric filter F of the present invention is built in a circuit board.

FIG. 5 is an equivalent circuit diagram of the laminated dielectric filter F of the present invention.

[Explanation of symbols]

 1: Dielectric layer 2: First dielectric layer 3: Dielectric layer 4: Second dielectric layer 5: Third dielectric layer 6: Dielectric layer 11a, 11b, 11c: Resonant line 12a: Second capacitance Electrode 12b: first capacitor electrode 12c: third capacitor electrode 13a: fourth capacitor electrode 13c: fifth capacitor electrode 14a, 14c: input / output electrode 21, 22: ground electrode 31, 32: ground electrode 33, 34: input / output electrodes 41 to 47: via holes 51 to 53: resonance inductors 54 to 56: resonance capacitors 57, 58: input / output capacitors 59, 60: interstage capacitors

Claims (1)

[Claims] 1. A laminated dielectric filter having at least three dielectric layers of first to third dielectric layers disposed between two dielectric layers each having a ground electrode formed therein, wherein Three strip line type resonance lines are provided substantially parallel to the main surface of the dielectric layer, and the middle resonance line is formed on the main surface of the first dielectric layer and is wider than the center resonance line. The resonance lines on both sides connected to the first capacitance electrode are the second and third capacitance electrodes formed on the main surface of the first dielectric layer and the fourth resonance line formed on the main surface of the third dielectric layer. , A laminated dielectric filter connected to a fifth capacitor electrode and sintered and integrated.