JP3482090B2 - Multilayer 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 multilayer filter, and more particularly to a substrate built-in multilayer filter built in an RF module substrate, for example, a high frequency circuit used in a high frequency circuit radio such as a mobile phone. TECHNICAL FIELD The present invention relates to a laminated filter used for a filter, a duplexer or the like.

[0002]

2. Description of the Related Art Conventionally, as an example of a laminated filter, one described in JP-A-6-97705 is known. In this laminated filter, a resonance line forming a part of a quarter-wavelength stripline resonance element is formed by printing a conductive material on the main surface of two or more dielectric layers, and each resonance line is formed. Are connected by via holes or through holes, and are laminated and integrated with the dielectric layer on which the ground electrode is formed and the dielectric layer on which the input / output electrodes are formed. Thereby, the multilayer filter is downsized.

[0003]

With the miniaturization of mobile phones, modularization of electronic parts is progressing, and it is required to incorporate passive circuits such as filters and matching circuits in a substrate. The filter circuit can be miniaturized by using the conventional technique as described above. As the dielectric material of the dielectric layer used in the conventional multilayer filter, one having a relative dielectric constant of about 30 to 80 is used.
In order to further reduce the size, it is considered to further improve the relative permittivity of the dielectric material. However, in order to incorporate a matching circuit or the like, it is necessary to use a substrate having a low relative dielectric constant of about 10 to 20, and a filter is simultaneously formed in a substrate formed of a dielectric material having such a low relative dielectric constant. When configured, it becomes difficult to reduce the size of the filter circuit.

An object of the present invention is to reduce the size of a laminated filter that can be built in a substrate without increasing the relative permittivity of the dielectric material forming the substrate.

[0005]

A laminated filter according to the present invention is a laminated filter in which a plurality of dielectric layers are laminated and which has a stripline type resonance circuit of two or more stages, which is a stripline type resonance circuit. Exists over at least two or more dielectric layers of the plurality of dielectric layers, and each has a resonance line and a resonance capacitor electrode connected to the resonance line. Resonance lines forming a stripline type resonance circuit are formed on the same dielectric layer, an open end side of the resonance lines forms a resonance capacitance electrode, and at least one resonance capacitance electrode among the resonance capacitance electrodes is It is characterized in that it is on a dielectric layer different from that of the resonance capacitance electrode.

According to the above-mentioned structure, it is possible to increase the area of each resonance capacitance electrode, and it is possible to obtain a larger resonance capacitance necessary for downsizing the filter.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic development view of a substrate built-in laminated filter to which an embodiment of the present invention is applied.
This multilayer filter with a built-in substrate is formed at the same time as a substrate on which a plurality of dielectric layers are laminated, and an electrode layer made of a conductive material is formed on one surface of a dielectric layer made of unfired green sheet by printing or the like. Then, the layers are appropriately laminated and fired.

As shown in FIG. 1, a ground electrode 21 is formed on the main surface of the dielectric layer 1 arranged at the bottom in the thickness direction. On the main surface of the dielectric layer 2 laminated on the upper surface of the dielectric layer 1, a resonance capacitance electrode 12C forming a part of a quarter-wavelength resonance circuit is formed. A resonance capacitor is formed between the resonance capacitance electrode 12C and the ground electrode 21.

Dielectric layer 3 laminated on top of dielectric layer 2
On the main surface of the resonance line 11A, 11B, 11C forming a part of the three-stage quarter-wave type stripline resonance circuit.
Is formed. Input / output electrodes 31 and 32 are formed on the main surface of the dielectric layer 4 laminated on the upper surface of the dielectric layer 3. A part of the first input / output electrode 31 constitutes an input / output capacitor by being arranged so as to face the first-stage resonance line 11A, and another part thereof faces the third-stage resonance electrode 11C. By arranging them in the same manner, a zero point forming capacitor is formed. Similarly, a part of the second input / output electrode 32 is arranged to face the second-stage resonance electrode 11B to form an input / output capacitor, and faces the third-stage resonance electrode 11C. By arranging them in the same manner, a zero point forming capacitor is formed.

Dielectric layer 5 laminated on the main surface of dielectric layer 4
Resonant capacitance electrodes 12A and 12B are formed on the main surface of the. A ground electrode 22 is formed on the main surface of the dielectric layer 6 laminated on the dielectric layer 5. A resonance capacitor is formed between the resonance capacitance electrodes 12A and 12B and the ground electrode 22.

Resonant line 11A formed on the dielectric layer 3,
11B is a resonance capacitor electrode 12 formed on the dielectric layer 5.
A and 12B are connected via via holes 41 and 42, respectively. Further, the resonance line 11C formed on the dielectric layer 3 is the resonance capacitance electrode 12C formed on the dielectric layer 2.
To the via hole 43. Thus, the resonance lines 11A, 11B and 11C, the resonance capacitance electrodes 12A, 12B and 12C and the via holes 41 and 4 are formed.
2 and 43 form a three-stage 1/4 wavelength stripline resonance circuit.

Resonant capacitance electrodes 12A, 12B, 12C
Are formed separately for the dielectric layer 2 and the dielectric layer 5, and can have a larger area than when they are formed on the same dielectric layer. Therefore, the resonance capacitor electrode 12
By making the area of A, 12B, and 12C as large as possible, the length of the resonance lines 11A, 11B, and 11C can be shortened, and it is possible to obtain a laminated filter having a large resonance capacitance with a small occupied area. Become. Especially when built in a substrate, the resonance lines 11A, 11B, 11C
The side to which the via hole is not connected is connected to the ground electrodes 21 and 22 by a via hole or a vertical electrode. The outer circumferences of the ground electrodes 21 and 22 are connected by via holes or vertical electrodes.

Further, by reducing the thickness of the dielectric layer 6, it is possible to reduce the shape of the resonance capacitance electrodes 12A and 12B, and by reducing the thickness of the dielectric layer 2, the resonance capacitance electrode 12C. It is possible to reduce the shape of the device, and it is also possible to reduce the size of this substrate-embedded multilayer filter. Resonance line 11A, 11
The dielectric layers 3 and 4 located above and below B and 11C are preferably as thick as possible in order to reduce the loss of the filter. The via holes 41, 42, 43 may be composed of vertical electrodes or the like.

The dielectric material constituting each of the dielectric layers 1 to 6 has a relative dielectric constant of about 10 to 20,
It is possible to integrally incorporate the matching circuit in the substrate in which the filter circuit is incorporated. Further, the ground electrodes 21 and 22, the resonance lines 11A, 11B and 11C, the resonance capacitance electrodes 12A, 12B and 12C, and the input / output electrode 3
1, 32 and the via holes 41, 42, 43 are made of silver,
It is formed by using a low resistance conductor such as copper or gold. Therefore, each dielectric layer is preferably co-fired with the substrate using a low temperature sintering material having a firing temperature of about 900 ° C to 1000 ° C.

In one embodiment of the present invention as described above,
The equivalent circuit is as shown in FIG. This will be described below. In this laminated filter, the resonance lines 11A and 11 that form a quarter-wave stripline resonator are used.
B and 11C form resonance inductors 51, 52 and 53, and resonance capacitance electrodes 12A, 12B and 12C form resonance capacitors 54, 55 and 56.

An input / output capacitor 57 is formed between the input / output electrode 31 and the first-stage resonant line 11A,
A zero-point forming capacitor 59 is configured with the third-stage resonance line 11C. Similarly, an input / output capacitor 58 is formed between the input / output electrode 32 and the second-stage resonance line 11B, and a zero-point forming capacitor 60 is formed between the third-stage resonance line 11C. There is.

Resonant lines 11A and 11B, 11B and 11C
Are respectively porcelain-coupled, and are represented by M in the equivalent circuit. On the high frequency side of the pass band, the zero point forming capacitors 59 and 60 and the resonance lines 11A and 11
A half-wavelength type resonance circuit is configured by B and 11C, and one of attenuation poles is formed. In addition, phase inversion occurs in the paths of the zero-point forming capacitors 59 and 60, the input / output capacitors 57 and 58, and the path of the porcelain coupling M, and another attenuation pole is formed.

[0018]

In the laminated filter according to the present invention, the area of the resonance capacitor electrode can be made large, whereby the resonance line can be shortened and the filter can be miniaturized. Further, even with a dielectric material having a small relative permittivity, it is possible to form a small filter circuit, so that it is possible to simultaneously incorporate the matching circuit and the like in the same substrate.

[Brief description of drawings]

FIG. 1 is a schematic development view of a laminated dielectric filter in which an embodiment of the present invention is adopted.

FIG. 2 is an equivalent circuit diagram thereof.

[Explanation of symbols]

1-6 Dielectric layer 11A, 11B, 11C resonant line 12A, 12B, 12C Resonant capacitance electrode 21,22 Earth electrode 31, 32 Input / output electrodes 41, 42, 43 beer holes 51, 52, 53 Resonance inductor 54,55,56 Resonant capacitors 57,58 Input / output capacitors 59,60 Zero point forming capacitor

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Claims (2)

(57) [Claims] 1. A multilayer filter having a plurality of dielectric layers laminated and having two or more stages of stripline resonance circuits , wherein each stripline resonance circuit is at least one of the plurality of dielectric layers. with present over two or more dielectric layers, respectively resonant lines and the resonance line
And a capacitance electrode for resonance connected to the path, to form the stripline type resonance circuit having two or more stages.
A resonance line is formed on the same dielectric layer, an open end side of the resonance line forms a resonance capacitance electrode, and at least one resonance capacitance electrode among the resonance capacitance electrodes is different from another resonance capacitance electrode. Is on another dielectric layer. 2. The multilayer filter according to claim 1, wherein the stripline resonance line is a three-stage stripline resonance line.