JPH08237060A - Noise filter - Google Patents

Abstract

PURPOSE: To provide a noise filter with an excellent attenuation characteristic even when an insertion circuit is designed for a high frequency circuit by selecting a conductor resistance of a coil for a signal side to be higher than a coil conductor resistance of a ground side. CONSTITUTION: The filter is made up of a laminated body 1 comprising 5-layered ceramic layers 1a-1e, for example, input terminal electrodes 6, 7 at signal line side formed on an outer surface of the body 1 and a ground side terminal electrode. In this case, the conductor resistance of the signal side coil is selected larger than that of the ground side coil. Thus, the impedance of the signal side coil is selected higher. As the method to increase the conductor resistance of the signal side coil comprising signal line conductor coil patterns 2b-2d, a material having a comparatively higher sheet resistance is used for a metallic material for the signal line conductor coil patterns 2b-2d or a conductor width of the signal line conductor coil patterns 2b-2d is made narrower to increase the resistance physically.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise filter,
In particular, the present invention relates to a noise filter suitable for a high frequency circuit.

[0002]

2. Description of the Related Art In a conventional noise filter, a signal line conductor coil pattern and a ground line conductor coil pattern are arranged between ceramic layers in a laminated body formed by laminating a plurality of ceramic layers.

Specifically, a first signal line conductor coil pattern and a second ground line conductor coil pattern are arranged between predetermined ceramic layers, and a first signal line conductor coil is provided between adjacent ceramic layers between the predetermined ceramic layers. A second ground line conductor coil pattern for facing the pattern and generating a capacitance component between them and a second signal line conductor for facing the pattern and generating a capacitance component between the first ground line conductor coil patterns The coil pattern was arranged. The first and second signal line conductor coil patterns are spirally connected to each other to form a signal-side coil, and the first and second ground line conductor coil patterns are spirally connected to each other. To form a coil on the ground side.

As a manufacturing method, a conductor film serving as a substantially C-shaped signal line conductor coil pattern and a conductor film serving as a substantially C-shaped ground line conductor coil pattern are formed on a green sheet serving as a ceramic layer. The conductive films are formed by a conductive paste so that their openings are opposed to each other, and these green sheets are laminated and integrated and integrally fired.

As the green sheet, two types of green sheets are used in which the signal line conductor coil pattern and the ground line conductor coil pattern are the target positions. One end of the first signal line conductor coil pattern formed on the first green sheet is connected to the other end of the second signal line conductor coil pattern turn formed on the second green sheet via a via hole conductor, and Further, one ground line conductor coil pattern is formed on the first lean sheet so that one end is connected to the other end of the second ground line conductor coil pattern formed on the second green sheet via a via hole conductor. The first ground line conductor coil pattern and the second green formed on the first green sheet are opposed to the first signal line conductor coil pattern and the second ground line conductor coil pattern formed on the second green sheet. The sheet and the second signal line conductor coil pattern are laminated so as to face each other.

Each of the signal line conductor coil pattern and the ground line conductor coil pattern thus formed on one green sheet is, for example, a low resistance material such as an Ag-based (Ag simple substance or Ag alloy) conductor or a Cu-based conductor. Since the conductive paste containing the as a main component was formed in substantially the same shape, the signal-side coil and the ground-side coil had a relatively low impedance.

The above-described noise filter has an inductance component generated by the coil on the signal side and a coil on the ground side, and a mutual inductance component between the two coils.
Further, it is constituted by a high capacitance component generated between both coils, and a predetermined damping characteristic is obtained.

Generally, the noise filter is set so that the difference between the absolute value of the impedance (input impedance) of the external circuit (insertion circuit) and the impedance of the noise filter is large in the frequency band to be removed.

The impedance of the distributed constant type noise filter which is widely used at present is about 10Ω. On the other hand, the input impedance on the insertion circuit side is approximately 500Ω.
Has become. Therefore, there is a large difference between both impedances, and a sufficient attenuation characteristic could be derived.

[0010]

However, even if the operating frequency of the insertion circuit is, for example, 50 MHz, harmonic components are generated on the higher frequency side than the predetermined band. Then, as shown by the solid line A in FIG. 6, the input impedance of the insertion circuit drops significantly over a frequency range of 50 to 200 MHz, and is, for example, 250Ω at 100 MHz and 10 at 200 MHz.
It drops to 50Ω at 0Ω and 400MHz. Also,
In the band from about 200 MHz to about 600 MHz, the input impedance is 100Ω or less.

Therefore, the frequency of the insertion circuit is, for example, 50M.
In Hz, the input impedance is about 500Ω, and even if the difference with the impedance of the noise filter is sufficiently large and there is an attenuation effect, for example, in the high frequency region, the absolute value of the input impedance of the insertion circuit and the impedance of the noise filter is The difference relatively decreases, and as a result, the attenuation effect in the high frequency band deteriorates. In addition, in FIG. 6, the dotted line indicates the impedance of the above noise filter.

The present invention has been devised in view of the above problems, and an object thereof is to provide a noise filter capable of sufficiently deriving a noise attenuation effect even when the input impedance of an insertion circuit is lowered. To provide.

[0013]

According to the present invention, a first signal line conductor coil pattern and a first ground line conductor coil pattern are provided between adjacent layers of a laminate formed by laminating a plurality of ceramic layers. A second signal line conductor coil pattern that opposes the first ground line conductor coil pattern and a second ground line conductor coil pattern that opposes the first signal line conductor coil pattern are respectively arranged, and A noise filter in which first and second signal line conductor coil patterns are connected to each other to form a signal side coil, and the first and second ground line conductor coil patterns are connected to each other to form a ground side coil, respectively. , The conductor resistance of the coil on the signal side is larger than the conductor resistance of the coil on the ground side. It is a filter.

[0014]

According to the present invention, by increasing the conductor resistance of the signal side coil, the inductance component and the resistance component are connected in series on the signal side coil side in terms of an equivalent circuit. As a result, the impedance of the conventional coil on the signal side is about 50 to 200Ω,
High impedance can be achieved.

Here, when the frequency of the insertion circuit is relatively low (for example, 50 MHz), the input impedance is, for example, 5.
Since it is very large, such as 00Ω, a sufficient impedance difference is generated even in the present invention having a high impedance, and a sufficient attenuation characteristic can be maintained as in the conventional case.

Moreover, in a high frequency region (for example, 200 to 60)
At 0 MHz), even when the input impedance of the insertion circuit is significantly reduced, the difference between the input impedance of the insertion circuit and the impedance of the noise filter can be made larger than in the conventional case, so that sufficient attenuation characteristics can be achieved.

Moreover, since the conductor resistance of the signal line conductor coil pattern forming the coil on the signal side is large, this causes the conductor loss to act more effectively.

Further, due to the difference between the impedance of the coil on the signal side and the impedance of the coil on the ground side, the effect of circulating the noise component to the coil on the ground side becomes remarkable, and higher attenuation characteristics can be obtained.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The noise filter of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is an external perspective view of a noise filter according to the present invention, FIG. 2 is a cross-sectional view thereof, FIG. 3 is a view showing a connection state of each coil pattern, and FIGS. [Fig. 3] is a plan view of a conductor film which becomes a signal line conductor coil pattern and a conductor film which becomes a ground line conductor coil pattern, respectively, which are formed on a sheet which becomes a ceramic layer.

The noise filter of the present invention is a laminated body 1 formed by laminating, for example, five ceramic layers 1a to 1e.
And the signal line side input terminal electrodes 6 and 7 and the ground side terminal electrode 8 formed on the outer surface of the laminate 1.

The laminate 1 is made of alumina, BaTiO ₃ , T
The ceramic layers 1a to 1e are made of a ceramic such as iO ₂ , Mn-Zn, or Ni-Zn, or a mixture of such a ceramic and a crystallized glass component.

Each ceramic layer 1a and 1b of this laminated body 1
, 1b and 1c, and 1c and 1d, signal line conductor coil patterns 2b to 2d and ground line conductor coil patterns 3b to 3d are arranged in parallel.

Here, the ceramic layer 1 shown in FIG.
The signal line conductor coil patterns arranged between a and 1b and 1c and 1d are referred to as first signal line conductor coil patterns 2b and 2d, and the ground line conductor coil patterns are referred to as first ground line conductor coils. Pattern 3
b, 3d. Incidentally, FIG. 4A shows the ceramic layer 1c.
1d and 1d (on the ceramic layer 1d), the first signal line conductor coil pattern 2d and the first ground line conductor coil pattern 3d are shown.

Further, the ceramic layer 1b shown in FIG.
And the signal line conductor coil pattern arranged between 1c and 1c is referred to as a second signal line conductor coil pattern 2c,
The ground line conductor coil pattern is referred to as a second ground line conductor coil pattern 3c. Incidentally, FIG. 4 (b) shows between the ceramic layers 1b and 1c, that is, the ceramic layer 1c.
The upper conductor coil patterns 2c and 3c are shown.

Incidentally, between the ceramic layers 1d and 1e,
The lead-out conductor pattern 2e for connecting the other end of the first signal line conductor coil pattern 2d to the input terminal electrode 6 on the signal line side is the other end of the first ground line conductor coil pattern 3d and the ground side terminal. A lead conductor pattern 3e for connecting to the electrode 8 is formed.

The thickness of the ceramic layer 1b includes the other end of the first signal line conductor coil pattern 2b between the ceramic layers 1a and 1b and the second signal between the ceramic layers 1a and 1b. Via-hole conductors 4b are formed to connect the line conductor coil patterns 2c, and via-hole conductors 5b are formed to connect the other end of the first ground line conductor coil patterns 3b and the second ground line conductor coil patterns 3c. ing. Similarly, FIG.
As shown in (b), the thickness of the ceramic layer 1c also includes the other end portion of the second signal line conductor coil pattern 2c between the ceramic layers 1b and 1c and the first portion between the ceramic layers 1c and 1d. Via-hole conductor 4c for connecting to the signal line conductor coil pattern 2d, and via-hole conductor 5c for connecting the other end of the second ground line conductor coil pattern 3c and the first ground line conductor coil pattern 3d. Has been formed. In addition, as shown in FIG. 4A, the thickness of the ceramic layer 1d also depends on the other end of the first signal line conductor coil pattern 2d between the ceramic layers 1c and 1d and the ceramic layers 1d and 1e. A via-hole conductor 4d for connecting one end of the lead-out conductor pattern 2e is formed, and a via-hole conductor 5d for connecting the other end of the second ground line conductor coil pattern 3d and one end of the lead-out conductor pattern 3e, respectively. ing.

As a result, the laminated body 1 has a signal of about 1.5 turns including the first signal line conductor coil pattern 2b, the second signal line conductor coil pattern 2c, and the first signal line conductor coil pattern 2d. Side coil is formed, and the first ground line conductor coil pattern 3b and the second ground line conductor coil pattern 3 are formed.
c, a coil on the ground side of about 1.5 turns composed of the first ground line conductor coil pattern 3d is formed, and a capacitance component is generated between both coils.

The terminal electrodes 6, 7, 8 are made of an Ag-based conductor film, and if necessary, a plating layer such as Ni plating or solder plating is deposited on the conductor film.

The signal-side output terminal electrode 7 is formed on the end face portion of the laminate 1 where one end of the first signal line conductor coil pattern 2b extends, and the signal-side input terminal electrode 6 is the first signal line conductor. The other end of the lead conductor pattern 2e connected to the coil pattern 2d is formed on the end face portion of the laminated body 1 that extends. That is, the signal-side terminal electrodes 6 and 7 are formed on a pair of end faces of the laminated body 1 which face each other.

The ground side terminal electrodes 8 are respectively formed on the other pair of end faces different from the pair of end faces of the laminated body 1 on which the signal side terminal electrodes 6 and 7 are formed, and the first ground line conductor coil pattern 3d and The other end of the lead-out conductor pattern 3e to be connected is formed on the end face portion of the laminated body 1 which extends. Each of the terminal electrodes 6, 7 and 8 is a laminated body 1
Although it is formed on the end face portion of the above, the front surface and / or the back surface of the laminate 1 may be used to connect to each other by a conductor film.

With the above configuration, the signal side input / output side terminal electrodes 6 and 7 are connected to an external circuit (insertion circuit), and the ground side terminal electrode 8 is connected to the ground potential.
An attenuation pole at a predetermined frequency is generated by each inductance component of the signal side coil and the ground side coil, a mutual inductance component, and a high capacitance component generated between both coils, so that the attenuation characteristic of a predetermined amount of attenuation can be obtained.

Here, the characteristic feature of the present invention is that the conductor resistance of the signal side coil is larger than the conductor resistance of the ground side coil. The coil impedance is high.

As described above, as a method for increasing the conductor resistance of the signal-side conductor coil patterns 2b, 2c, and 2d on the signal side, the metal material forming the signal line conductor coil patterns 2b, 2c, and 2d is used. A material having a relatively high sheet resistance may be used, or the conductor width of the signal line conductor coil patterns 2b, 2c, 2d may be narrowed to physically increase the resistance.

For example, the signal line conductor coil pattern 2
When controlling with b, 2c, 2d conductor materials,
A high resistance metal material having a sheet resistance of 50 mΩ / □ or more, for example, RuO ₂ or Ag-pd alloy is used for a part or all of the signal line conductor coil patterns 2b, 2c, 2d.
The ground line conductor coil patterns 2b, 3c, 3
For d, a conductor whose main component is a low resistance metal material such as an Ag-based or Cu-based material is used as in the related art.

As a result, the signal side input / output terminal electrodes 6,
Conductor resistance between 7 and 2 to 200Ω, for example, 50
The impedance of the coil on the signal side can be further increased by about 50 to 100Ω as compared with the impedance of the coil on the signal side of the related art.

The ground side coil is basically the same as the conventional one, and the conductor resistance 2 at both ends of the ground side coil is
It can be less than Ω, for example, 0.5Ω, and the impedance is about 10Ω.

If this state is shown by an equivalent circuit, as shown in FIG. 5, the signal line conductor coil patterns 2b, 2c,
Since the resistance component is added to 2d itself, the resistance component R _{1 is present} between L _{1 to} L ₃ indicating the signal line conductor coil patterns 2b, 2c, and 2d that form the signal side coil.
~ R ₃ will be connected in series. In FIG. 5, LG _{1 to} LG ₃ represent the inductance components of the ground line conductor coil patterns 3b to 3d, and C
_{1 to} C ₂ represent combined capacitance components generated when the signal line conductor coil patterns 2b to 2d and the ground line conductor coil patterns 3b to 3d face each other.

The signal line conductor coil pattern 2b,
When the conductor widths of the signal line conductor coil patterns 2b, 2c, and 2d are controlled by the conductor widths of 2c and 2d, the conductor resistance between the input / output terminal electrodes 6 and 7 of the signal side coil is 20 to 20.
It may be reduced to 200Ω. Similarly, the ground line conductor coil patterns 3b, 3c, 3
If the conductor width of d is equal to the conductor resistance of both ends of the ground side coil,
It may be adjusted so that it becomes Ω or less. However, changing the conductor width is accompanied by a change in the capacitance component, so that the adjustment must be careful.

By doing so, for example, when the operating frequency of the insertion circuit is about 50 MHz, the difference between the input / output impedance of the insertion circuit and the impedance of the signal side coil of the noise filter is large, as in the conventional case, so that it is sufficient. Attenuation characteristics can be obtained.

On the higher frequency side than the attenuation band, for example, 2
Even if the input impedance of the insertion circuit at 00 to 600 MHz becomes, for example, 100Ω or less, the impedance of the coil on the signal side is higher than in the conventional case, and therefore the difference from the input impedance of the insertion circuit is Since it can be made larger than the conventional one, the damping effect can be sufficiently exerted.

Further, since the conductor resistance of the signal line conductor coil patterns 2b, 2c and 2d forming the coil on the signal side is high, the passage tends to be blocked.

Moreover, even when the noise filter alone is viewed, the impedance of the coil on the ground side does not substantially change, and only the coil on the signal side has a high impedance. Therefore, the coil on the signal side is grounded via the capacitance component. The effect of returning the noise component to the coil on the side is increased, which also promotes the damping effect.

The inventor has found that the input / output terminals of the coil on the signal side (total pattern length: about 10 mm, width: 0.2 to 0.3 m)
m) and the conductor resistance between the input / output terminals of the coil and the noise filter of the present invention, which is 50Ω (impedance of the coil on the signal side is 60Ω), is 0.5Ω (impedance is 10.0Ω). A conventional noise filter was prepared and the amount of attenuation was measured at a frequency of 1 MHz to 1 GHz.

In the product of the present invention, the conductor resistance of the coil on the ground side is 0.5Ω (impedance is 1
0.0 Ω).

As a result, in the noise filter of the present invention,
The attenuation was 50 dBμV at 50 MHz, 45 dBμV at 300 MHz, and 35 dBμV at 700 MHz.
Attenuation of 70 dBμV at MHz, Attenuation of 6 at 300 MHz
The attenuation amount is 2 dBμV and 40 dBμV at 700 MHz, and the product of the present invention can obtain good attenuation characteristics as a whole.
High attenuation characteristics were obtained in the band of 50 to 600 MHz.

Next, considering the difference between the input impedance of the insertion circuit and the impedance of the noise filter depending on the frequency also with reference to FIG. 6, the input impedance of the insertion circuit is greatly reduced on the high frequency side, and the conventional noise filter is used. The difference from the impedance of
In the above-described noise filter of the present invention,
Between 600 MHz, the difference between the absolute values of both impedances can be made very large as compared with the conventional noise filter (dotted line in the figure), and excellent attenuation characteristics can be obtained.

The solid line C indicates a frequency of 200 MH when the conductor resistance between the input and output terminals of the coil on the signal side is further increased to 200Ω (impedance of about 250Ω).
In a high frequency range of z or higher, the difference between the absolute values of both impedances can be made very large as compared with the conventional noise filter (dotted line in the figure).

That is, according to the present invention, it is easy to control the conductor resistance of the signal side coil so that the impedance of the signal side coil is set to a predetermined value in response to a desired high frequency region where excellent attenuation characteristics are obtained. Therefore, a noise filter compatible with high frequency operation can be obtained.

In the above-mentioned embodiment, the laminated structure, the number of laminated layers, etc. can be arbitrarily changed, and the above-mentioned only a part of the coil on the signal side, that is, only one signal line conductor coil pattern. The resistance may be increased by performing an operation.
In addition, a part of each ground line conductor coil pattern may be directly extended to the end face of the laminated body, and two ground side terminal electrodes may be provided in the extended portion.

[0051]

According to the present invention, of the signal side coil and the ground side coil arranged between the layers of the ceramic layers, the conductor resistance of the signal side coil is set to be high to make the impedance high. Even if the input impedance becomes lower due to the higher frequency of the circuit, it is possible to sufficiently secure the impedance difference of the noise filter,
It becomes a noise filter that can obtain excellent attenuation characteristics.

Further, the impedance difference between the coil on the signal side and the coil on the ground side promotes the effect of circulating the noise due to the capacitance component, which also provides a noise filter having a further excellent attenuation characteristic.

[Brief description of drawings]

FIG. 1 is an external perspective view of a noise filter of the present invention.

FIG. 2 is a sectional structural view taken along the line AA of FIG.

FIG. 3 is a schematic diagram showing a connection state of substantial conductor coil patterns of the noise filter of the present invention.

4A and 4B are schematic plan views showing respective conductor coil patterns of a sheet.

FIG. 5 is an equivalent circuit diagram of the noise filter of the present invention.

FIG. 6 is a characteristic diagram showing the relationship between the frequency of the insertion circuit for IC operation and the input impedance and the impedance of the noise filter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Laminated body 1a-1e ... Ceramic layer 2b-2d ... Signal line conductor coil pattern 3b-3d ... Ground line conductor coil pattern 4b-4d, 5b-5d ... Via hole Conductors 6, 7 ... I / O terminal electrodes on the signal side 8 ... Terminal electrodes on the ground side

Claims (1)

[Claims] 1. A first signal line conductor coil pattern and a first signal line conductor coil pattern are provided between layers of a laminated body formed by laminating a plurality of ceramic layers.
A second signal line conductor coil pattern facing the first ground line conductor coil pattern and a second ground line facing the first signal line conductor coil pattern between adjacent layers. Conductor coil patterns are respectively arranged, and the first and second signal line conductor coil patterns are connected to each other to connect the signal side coil to each other, and the first and second ground line conductor coil patterns are connected to each other. A noise filter comprising ground-side coils respectively, wherein the conductor resistance of the signal-side coil is larger than the conductor resistance of the ground-side coil.