JPH0846401A - Stacked bandpass filter - Google Patents

Abstract

(57) [Summary] [Structure] A laminated bandpass filter having a plurality of dielectric layers, and having a plurality of electrodes magnetically and capacitively coupled to each other formed on one main surface side of the dielectric layers. There
It has a plurality of poles on the low frequency side of the resonance point, and is characterized in that a resonance circuit is formed between the input terminal and the ground terminal, between the output terminal and the ground terminal, and between the input terminal and the output terminal. [Effect] Since the low-frequency side of the resonance frequency has a plurality of poles, the attenuation of the low-frequency can be increased, which can reduce the influence of the low-frequency noise and improve the reliability of the filter. Can be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated band pass filter used in a portable radio or the like and capable of reducing the influence of noise from the outside. The present invention relates to a filter that can obtain an attenuation amount.

[0002]

2. Description of the Related Art Conventionally, bandpass filters have been used for receiving only a specific frequency in mobile communication devices such as mobile phones, wireless devices, tuners, etc. Accordingly, the bandpass filter itself is required to be downsized. inside that,
Recently, stacking of bandpass filters using a co-firing technique has been advanced.

Therefore, a laminated band pass filter will be described with reference to FIGS. FIG. 8 is an example of an equivalent circuit of a conventional laminated bandpass filter. According to FIG. 8, this bandpass filter has a pair of input / output terminals 51 and 52 and resonance circuits 53 and 54. Input terminal 51 and resonance circuit 53, output terminal 52 and resonance circuit 54
Are coupled by a capacitor 55 and a capacitor 56, respectively, and the other ends of the resonance circuits 53 and 54 are both grounded. Each of the resonance circuit 53 and the resonance circuit 54 is composed of inductors 57 and 58 and capacitors 59 and 60 that are connected in parallel.
Are coupled with a magnetic coupling degree M.

FIG. 9 shows a laminated band pass filter forming such an equivalent circuit. FIG. 9A is a perspective view of the laminated bandpass filter, and FIG. 9B is an exploded perspective view thereof. As is clear from FIG. 9A, the laminated bandpass filter 61 is a substantially rectangular parallelepiped, and is composed of a laminated body of four dielectric layers 62, 63, 64 and 65. Then, in FIG. 9B, a pair of input / output electrodes 6 are formed on the surface of the dielectric layer 63 with a constant interval.
6 and 67 are formed, a pair of electrodes 68 and 69 are formed on the surface of the dielectric layer 44, and a ground electrode 70 is further formed on the surface of the dielectric layer 65.

According to such a structure, as shown in FIG. 8, the input / output electrodes 66 and 67 are coupled via the capacitor 71 formed of the dielectric layer 63, and the input electrode 66 and the electrode 6 are connected.
8. Since the output electrode 67 and the electrode 69 sandwich the dielectric layer 63, the capacitor 5 in the equivalent circuit of FIG.
Bound by 5 and 56. Further, the electrode 68 and the electrode 69 are coupled with a magnetic coupling degree M. Further, the electrodes 68 and 69 form the inductors 57 and 58 of the resonance circuits 53 and 54 in the equivalent circuit of FIG.

The input / output electrodes 66 and 67 are the dielectric layer 4
3 to the end portion, and is electrically connected to the pair of external electrodes 72 and 73 formed on the surface. Further, the electrodes 68, 69 and the ground electrode 70 are also the dielectric layer 6
4 and the end portion of the dielectric layer 65, and are electrically connected to the ground terminal 74 formed on one surface of the substantially rectangular parallelepiped.

FIG. 10 shows the attenuation characteristic of the bandpass filter having such a configuration. As is clear from FIG.
The low frequency side and the high frequency side of the resonance point A have one pole B and C, respectively.

[0008]

However, each of the conventional bandpass filters shown above has only one pole on the low frequency side and one on the high frequency side of the resonance point A. Since the amount of attenuation on the low frequency side is insufficient, it is easily affected by low frequency noise,
This has been a major factor in reducing the reliability of a filter that is generally used as a consumer device.

Therefore, it is an object of the present invention to provide a laminated bandpass filter which is less likely to be affected by noise on the low frequency side.

[0010]

As a result of repeated studies on the above-mentioned problems, the inventor of the present invention formed a plurality of poles on the low frequency side, and thus was not easily affected by noise on the low frequency side. It is found that a plurality of poles are formed by forming a resonance circuit between the input terminal and the ground terminal through a capacitor in the equivalent circuit, and forming a resonance circuit between the input terminal and the output terminal. The present invention has been completed.

That is, the laminated band-pass filter of the present invention has a plurality of dielectric layers and a plurality of electrodes formed on one main surface side of the dielectric layers and magnetically and capacitively coupled to each other. A multilayer bandpass filter having a plurality of poles on the low frequency side of the resonance point, and further, in an equivalent circuit, a resonance circuit is formed via a capacitor between an input terminal and a ground terminal. In addition, a resonance circuit is formed between the input terminal and the output terminal.

[0012]

According to the present invention, the capacitor and the resonance circuit are formed between the input terminal and the ground terminal, and the equivalent circuit is formed by serially forming the resonance circuit between the input terminal and the output terminal. The resonance circuit formed by the capacitor between the input terminal and the battlefield carbon and the inductor in the resonance circuit forms the first pole on the low frequency side of the resonance frequency,
Further, the resonance circuit between the input terminal and the output terminal forms the second pole. Thereby, a plurality of poles can be formed on the low frequency side of the resonance point in the multilayer bandpass filter, and the influence of low frequency noise can be reduced. Further, since the adjustment of the resonance circuit between the input terminal and the output terminal can be easily configured by the electrode pattern shape, a plurality of poles can be formed with a simple configuration, and the filter itself. Since it can be formed with a simple laminated structure, a high-performance filter can be manufactured at low cost.

[0013]

1 to 8 showing an embodiment of the present invention.
It will be specifically described with reference to.

FIG. 1 is an equivalent circuit in the laminated bandpass filter of the present invention. According to FIG. 1, this bandpass filter has a pair of input / output terminals 1 and 2 and resonance circuits 3 and 4. Input terminal 1, resonance circuit 3, output terminal 2
And the resonance circuit 4 are coupled by a capacitor 5 and a capacitor 6, respectively, and the other ends of the resonance circuits 3 and 4 are both grounded. Each of the resonance circuit 3 and the resonance circuit 4 is composed of inductors 7 and 8 and capacitors 9 and 10 that are connected in parallel, and the inductors 7 and 8 are coupled with a magnetic coupling degree M. Further, the resonance circuit 3 and the resonance circuit 4 are coupled by the capacitor 11.

Degree of magnetic coupling M in the resonance circuit of FIG.
2 is separated from the inductor 7 and the inductor 8 and regarded as one inductor, and an equivalent circuit is created, the equivalent circuit of FIG. According to the equivalent circuit of FIG.
The resonance circuit 14 having the inductor 13 and the resonance circuit 17 having the capacitor 15 and the inductor 16 are coupled by the resonance circuit 20 having the capacitor 18 and the inductor 19. The input terminal 21 is the capacitor 2
The resonance circuit 20 is coupled to the resonance circuit 20 via the capacitor 24, and the output terminal 23 is coupled to the resonance circuit 20 via the capacitor 24.

The input terminal 21 and the output terminal 23 are connected by a capacitor 25. Further, the other ends of the resonance circuit 14 and the resonance circuit 17 are grounded.

Next, FIG. 3 shows a basic structure of a laminated band pass filter forming an equivalent circuit as shown in FIGS. 1 and 2. FIG. 3A is a perspective view of the laminated bandpass filter, and FIG. 3B is an exploded perspective view thereof. As is apparent from FIG. 3A, the laminated bandpass filter 26 has a substantially rectangular parallelepiped shape, and is composed of a laminated body of four dielectric layers 27, 28, 29 and 30. Then, in FIG. 3B, a pair of input / output electrodes 31, 32 are formed on the surface of the dielectric layer 28 with a constant interval.
Are formed on the surface of the dielectric layer 29, and a pair of electrodes 33,
34 is formed, and a ground electrode 35 is further formed on the surface of the dielectric layer 30.

Then, the input terminal 31 and the output terminal 32
Are led out to the side surface of the filter, and the external electrodes 36, 37
It is connected to the. The electrodes 33 and 34 and the ground electrode 35 are also led out to the side surface and connected to a ground terminal 38 formed on one surface of the filter.

Next, FIG. 4 shows the attenuation characteristics of the filter in which each electrode pattern is formed as shown in FIG. As is clear from FIG. 4, one pole X is provided on the high frequency side of the resonance frequency F.
However, two poles Y and Z are formed on the low frequency side.

The greatest feature of the electrode pattern shape shown in FIG. 3 is that the distance between the electrodes 33 and 34 on the ground end side is widened and the distance on the open end side is narrowed. That is, widening the space on the ground end side means reducing the size of the inductor 19 in the equivalent circuit of FIG. 2, and narrowing the space on the open end side means increasing the capacitance of the capacitor 18. It is a thing.

As a result, the capacitor 22 and the resonance circuit 1
One pole is formed on the low frequency side of the resonance frequency by the inductor 13 in FIG. 4, but the spacing of the patterns of the electrodes 33 and 34 is adjusted according to the above, and the capacitance of the inductor 19 (L) and the capacitance (C) of the capacitor 18 are By increasing the product of (L × C), one more pole can be formed on the low frequency side.

Further, as the distance between the input / output terminals 31 and 32 becomes smaller, the pole Z shifts to the high frequency side, and the electrode 3
The smaller the distance between the open ends of the electrodes 3 and 34, the wider the distance between the poles X and Y. Therefore, the attenuation characteristics can be adjusted by finely adjusting the pattern shapes of these.

Next, based on the above basic structure, two types of laminated band pass filters were manufactured. The electrode patterns of these laminated bandpass filters are shown in FIG.
In FIG. 5, (a) is the product of the present invention and (b) is the comparative product. Each of the bandpass filters has an electrode pattern of seven layers with a dielectric layer interposed between them, and the first to
Layer 39 is an input / output terminal pattern, second layer 40 is a capacitance adjustment pattern, third layer 41 is an electrode pattern, fourth layer 42 is a ground electrode pattern, and fifth layer 43 and sixth layer 44 are resonance frequency adjustments. The electrode pattern for the seventh layer 45 is a ground electrode pattern. 5A and 5B, the electrode pattern of the third layer is changed.

Then, the end portions of the electrode pattern of the third layer 41 and the electrode patterns for adjusting the resonance frequency of the fifth layer 43 and the sixth layer 44 are both led to the side surface of the filter, and these are connected to the first external portion. The ground electrode pattern of the fourth layer 42, the resonance frequency adjusting electrode pattern of the fifth layer 43, and the end portion of the ground electrode pattern of the seventh layer 45 are connected to each other by electrodes (not shown), And derive these in the second
Were connected by external electrodes (not shown).

The attenuation characteristics of the filters shown in FIGS. 5 (a) and 5 (b) are shown in FIGS. 6 and 7, respectively. In FIG. 6, which shows the attenuation characteristics of the filter of FIG. 5A in which the electrode pattern of the third layer is I-shaped, the resonance frequency is 1.8 GHz,
Although it had a pole only at 0.8 GHz, FIG.
In FIG. 7, which shows the attenuation characteristics of the filter in which the electrode pattern of the third layer in FIG.
Resonant frequency at 4GHz, 1.5GHz, 1.2G
It was possible to form poles at two positions of Hz and 0.6 GHz.

[0026]

As described above in detail, according to the present invention, since the laminated bandpass filter has a plurality of poles on the low frequency side of the resonance frequency, the attenuation of the low frequency can be increased. As a result, the influence of low frequency noise can be reduced, and the reliability of the filter can be improved.

[Brief description of drawings]

FIG. 1 is a basic equivalent circuit diagram of a laminated bandpass filter of the present invention.

2 is an equivalent circuit diagram obtained by converting the equivalent circuit of FIG.

3A and 3B are views for explaining a basic structure of a laminated bandpass filter of the present invention, FIG. 3A is a perspective view of the filter, and FIG. 3B is an exploded perspective view for explaining an electrode pattern.

FIG. 4 is a diagram showing an attenuation characteristic of the bandpass filter based on FIG.

FIG. 5 is a view for explaining an electrode pattern in a specific example of the laminated bandpass filter of the present invention,
(A) is a figure which shows the electrode pattern of this invention product, (b) is a comparative product.

FIG. 6 is a diagram showing attenuation characteristics in the laminated bandpass filter of the present invention in FIG. 5 (a).

FIG. 7 is a diagram showing an attenuation characteristic in the laminated bandpass filter of the comparative product of FIG. 5 (b).

FIG. 8 is a typical equivalent circuit diagram of a conventional laminated bandpass filter.

FIG. 9 is a diagram for explaining a typical electrode pattern of a conventional laminated bandpass filter.

FIG. 10 is a diagram showing typical attenuation characteristics of a conventional laminated bandpass filter.

[Explanation of symbols]

1, 21 Input terminal 2, 23 Output terminal 3, 4, 14, 17, 20 Resonant circuit 5, 6, 9, 10, 12, 15, 18, 22, 24, 2
5 Capacitors 7, 8, 13, 16, 19 Inductors 27, 28, 29, 30 Dielectric layer M Magnetic coupling degree 31 Input terminal 32 Output terminal 33, 34 Electrode 35 Ground electrode

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[Procedure amendment]

[Submission date] August 23, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

FIG. 9 shows a laminated band pass filter forming such an equivalent circuit. FIG. 9A is a perspective view of the laminated bandpass filter, and FIG. 9B is an exploded perspective view thereof. As is clear from FIG. 9A, the laminated bandpass filter 61 is a substantially rectangular parallelepiped, and is composed of a laminated body of four dielectric layers 62, 63, 64 and 65. Then, in FIG. 9B, a pair of input / output electrodes 6 are formed on the surface of the dielectric layer 63 with a constant interval.
6, 67 are formed, a pair of electrodes 68, 69 are formed on the surface of the dielectric layer 64, and a ground electrode 70 is further formed on the surface of the dielectric layer 65.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

The input / output electrodes 66 and 67 are the dielectric layer 6
3 to the end portion, and is electrically connected to the pair of external electrodes 72 and 73 formed on the surface. Further, the electrodes 68, 69 and the ground electrode 70 are also the dielectric layer 6
4 and the end portion of the dielectric layer 65, and are electrically connected to the ground terminal 74 formed on one surface of the substantially rectangular parallelepiped.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

[0012]

According to the present invention, a resonance circuit is formed between the input terminal and the output terminal while a resonance circuit is formed between the input terminal and the ground terminal, and a resonance circuit is formed between the input terminal and the output terminal. A first pole is formed on the low frequency side of the resonance frequency by the resonance circuit formed by the capacitor and the inductor in the resonance circuit, and a second pole is formed by the resonance circuit between the input terminal and the output terminal. Is. Thereby, a plurality of poles can be formed on the low frequency side of the resonance point in the multilayer bandpass filter, and the influence of low frequency noise can be reduced.
Further, since the adjustment of the resonance circuit between the input terminal and the output terminal can be easily configured by the electrode pattern shape, a plurality of poles can be formed with a simple configuration, and the filter itself. Since it can be formed with a simple laminated structure, a high-performance filter can be manufactured at low cost.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.
It will be specifically described with reference to.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

FIG. 1 is an equivalent circuit in the laminated bandpass filter of the present invention. According to FIG. 1, this bandpass filter has a pair of input / output terminals 1 and 2 and resonance circuits 3 and 4. Input terminal 1, resonance circuit 3, output terminal 2
And the resonance circuit 4 are coupled by a capacitor 5 and a capacitor 6, respectively, and the other ends of the resonance circuits 3 and 4 are both grounded. Each of the resonance circuit 3 and the resonance circuit 4 is composed of inductors 7 and 8 and capacitors 9 and 10 that are connected in parallel, and the inductors 7 and 8 are coupled with a magnetic coupling degree M. Further, the resonance circuit 3 and the resonance circuit 4 are coupled by the capacitor 11. Furthermore, the input terminal 1 and the output terminal 2 are connected by a capacitor 11 '.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

Next, FIG. 4 shows the attenuation characteristics of the filter in which each electrode pattern is formed as shown in FIG. As is apparent from FIG. 4, one pole X is formed on the high frequency side of the resonance point F, and two poles Y and Z are formed on the low frequency side.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Name of item to be corrected] 0025

[Correction method] Change

[Correction content]

The attenuation characteristics of the filters shown in FIGS. 5 (a) and 5 (b) are shown in FIGS. 6 and 7, respectively. In FIG. 7, which shows the attenuation characteristic of the filter of FIG. 5B in which the electrode pattern of the third layer is I-shaped, the resonance point is at 1.8 GHz, and the resonance characteristic is 0.
Although it had a pole only at 8 GHz, FIG.
6, which shows the attenuation characteristic of the filter in which the electrode pattern of the third layer is changed to the L shape, has a resonance point at 1.4 GHz, and has 1.5 GHz, 1.2 GHz and 0.6 GHz.
It was possible to form poles at three points.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] Explanation of code

[Correction method] Change

[Correction content]

[Explanation of reference numerals] 1,21 input terminal 2,23 output terminal 3,4,14,17,20 resonant circuit 5,6,9,10,11,11 ', 12,15,18,
22, 24, 25 Capacitors 7, 8, 13, 16, 19 Inductors 27, 28, 29, 30 Dielectric layer M Magnetic coupling degree 31 Input terminal 32 Output terminal 33, 34 Electrode 35 Ground electrode

[Procedure Amendment 9]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

FIG.

[Procedure Amendment 10]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

[Procedure Amendment 11]

[Document name to be corrected] Drawing

[Correction target item name] Figure 8

[Correction method] Change

[Correction content]

[Figure 8]

Claims (2)

[Claims] 1. A multilayer bandpass filter having a plurality of dielectric layers, the plurality of electrodes being formed on one main surface side of the dielectric layers and magnetically and capacitively coupled to each other, wherein A multilayer bandpass filter having a plurality of poles on the low frequency side of the point. 2. A laminated bandpass filter having a plurality of dielectric layers, and having a plurality of electrodes magnetically and capacitively coupled to each other, which are formed on one main surface side of the dielectric layers, and are equivalent to each other. In the circuit, a resonance circuit is formed between an input terminal and a ground terminal via a capacitor, and a resonance circuit is formed between an input terminal and an output terminal.