JP3134841B2 - Multilayer noise filter for differential transmission line - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a differential transmission line product.
The present invention relates to a layered noise filter .

[0002]

2. Description of the Related Art Generally, as shown in FIG. 10, in a measuring instrument or the like, a weak detection signal detected by a sensor 1 or the like is amplified by a differential amplifier 2. By the way, when the signal lines 3a and 3b connecting the sensor 1 and the differential amplifier 2 are exposed to a radiation electromagnetic field (radio wave), noise accompanying the radiation electromagnetic field enters the differential amplifier 2. The noise is amplified and output by the differential amplifier 2 and causes a problem that a control system or the like using a signal output from the sensor 1 as a control signal malfunctions.

In order to solve such a problem, capacitors C1 and C2 are connected between the non-inverting input terminal and the inverting input terminal of the differential amplifier 2 and between the inverting input terminal and the ground, respectively. 2 was removed. The capacitor C1 removes normal mode noise (see arrow A1) flowing through the two signal lines 3a and 3b. The common mode noise flowing through the two signal lines 3a and 3b is transmitted through the capacitors C1 and C2 to the arrows A2 and A2.
It flows to the ground as indicated by A3. As a result, noise accompanying electromagnetic field radiation is removed before input to the differential amplifier 2. Conventionally, a two-terminal capacitor has been used as each of the capacitors C1 and C2.

[0004]

By the way, in a two-terminal capacitor, generally, in a high frequency region, as shown in FIG. 11, a residual inductance La and a residual resistance Ra are generated in the external electrodes 11a and 11b, respectively. These residual inductance La and residual resistance Ra are inserted in series with the capacitor. The two-terminal capacitor 13 having such an equivalent circuit is connected to the capacitors C1 and C1 in the circuit of FIG.
When used as C2, the residual inductance La and the residual resistance Ra are electrically connected between the signal lines 3a and 3b and between the signal line 3b and the ground, so that the insertion loss of the two-terminal capacitor 13 decreases in a high frequency region, There is a problem that noise due to electromagnetic field radiation cannot be sufficiently removed.

Accordingly, an object of the present invention is to provide a laminated noise filter for a differential transmission line having excellent noise removal characteristics.

[0006]

In order to achieve the above object, a laminated noise filter for a differential transmission line according to the present invention is provided.
Filter is the inside of the laminate constituted by stacking a pair of through transmission lines and a plurality of insulating layers, said pair of through transmission lines
The central part of the capacitor faces through the insulating layer to form a capacitor.
And arranged so that both ends of the pair of through transmission lines do not face each other via the insulating layer.
Is characterized by being electrically connected to the four signal external electrodes provided on a surface of the laminate.

With the above configuration, a capacitance is formed between the through transmission lines facing each other with the insulating layer interposed therebetween. Therefore,
Normal mode noise flowing through the through transmission line is removed by this capacitance. Since the inductance and the resistance generated in the signal external electrode are inserted in series with the signal line, the inductance and the resistance do not become the residual inductance and the residual resistance but are used as a choke.

[0008] Further, a laminate for a differential transmission line according to the present invention.
The type noise filter includes a ground electrode opposed to the pair of through transmission lines with an insulating layer therebetween, and both ends of the ground electrode are electrically connected to ground external electrodes provided on the surface of the multilayer body, respectively. It is characterized by doing. According to the above configuration, a capacitance is formed between the through-transmission line and the ground electrode facing each other with the insulating layer interposed therebetween.
Therefore, the common mode noise flowing through the through transmission line is
It flows to ground via this capacitance.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a differential transmission line according to the present invention will be described.
An embodiment of a laminated noise filter for use in the present invention will be described in detail with reference to the accompanying drawings.

First Embodiment, FIGS. 1 to 4 FIG. 1 is an exploded perspective view of a first embodiment of a multilayer noise filter for a differential transmission line according to the present invention. The differential transmission line
The laminated noise filter 20 for use includes through transmission lines 21 and
Insulating sheets 31 and 32 provided with the respective sheets 2 and a cover sheet 33 disposed on the upper side where the insulating sheets 31 and 32 are stacked. The through transmission lines 21 and 22 are formed on the surfaces of the insulating sheets 31 and 32 by a method such as printing, sputtering, or vapor deposition. The material of the through transmission lines 21 and 22 is Ag, A
g-Pd, Cu, Ni, etc. are used. Sheets 31 to 3
As the material of No. _3, a ceramic dielectric material such as SrTiO ₃ or an insulator material is used.

The through transmission line 21 has one end 21a exposed at the left corner on the back side of the sheet 31, and the other end 21b.
Are exposed at the right corner on the back side of the seat 31. One end 22 a of the through transmission line 22 is exposed at the left corner on the front side of the seat 32, and the other end 22 b is exposed at the right corner on the front side of the seat 32. Through transmission line 21
And 22 oppose each other with the insulating sheet 31 interposed therebetween. An electrostatic capacitance C11 determined by the facing area, spacing, and dielectric constant of the insulating sheet 31 is formed in the facing portion.

After the above-mentioned insulating sheets 31 to 33 are stacked, they are integrally fired to form a laminate 34 as shown in FIG. Signal external electrodes 41a, 41b and 42a, 42b are provided at four corners of the laminate 34, respectively. Both ends 21a, 21b of the through transmission line 21 are connected to the signal external electrodes 41a, 41b, respectively, and the through transmission line 2 is connected to the signal external electrodes 42a, 42b.
The two ends 22a and 22b are connected to each other.
These signal external electrodes 41a-42b are made of Ag, Ag-
It is formed by applying and baking a conductive paste such as Pd, Cu or the like, or by performing dry plating. FIG. 3 is an electrical equivalent circuit diagram of the multilayer noise filter 20 for a differential transmission line.

As shown in FIG. 4, the differential noise filter 20 for a differential transmission line is connected between signal lines 3a and 3b connecting the sensor 1 and the differential amplifier 2 as an example. The operation and effect of the transmission line laminated noise filter 20 will be described. For example, when normal mode noise (see arrow A1) flowing through the signal line 3a enters the through transmission line 21, the normal mode noise is removed by the capacitance C11. Thereby, it is possible to prevent normal mode noise from entering the differential amplifier 2. Since the inductances and resistances generated in the signal external electrodes 41a to 42b are inserted in series with the signal lines 3a and 3b, these inductances and resistances do not become residual inductances and residual resistances, and are used as chokes. Thus, the effect of removing noise in a high frequency region can be improved as compared with the related art.

[Second Embodiment, FIGS. 5 to 9] FIG. 5 is an exploded perspective view of a second embodiment of the multilayer noise filter for a differential transmission line according to the present invention. The differential transmission line
Laminated noise filter 50 includes through transmission lines 21 and
2, the insulating sheets 31 and 32 provided with the ground electrodes 23 and 24, respectively.
36, and these insulating sheets 31, 32, 35, 36
And a cover sheet 33 and the like disposed on the upper side of the stack.

The through transmission line 21 has one end 21a exposed at the left corner on the back side of the sheet 31, and the other end 21b.
Are exposed at the right corner on the back side of the seat 31. One end 22 a of the through transmission line 22 is exposed at the left corner on the front side of the seat 32, and the other end 22 b is exposed at the right corner on the front side of the seat 32. Through transmission line 21
And 22 are opposed to each other at the center with the insulating sheet 31 interposed therebetween to form a capacitance C11.

One end 23a, 24a of the ground electrode 23, 24 is exposed at the center of the back side of the sheet 35, 36, and the other end 23b, 24b is the sheet 35, 24b.
36 is exposed at the center of the front side. The ground electrode 23 is connected to the penetrating transmission line 2 with the insulating sheet 35 interposed therebetween.
1, and a capacitance C12 is formed. The ground electrode 24 is connected to the transmission line 22 with the insulating sheet 32 interposed therebetween.
And a capacitance C13 is formed.

The above insulating sheets 31 to 33, 35, 3
After being stacked, they are integrally fired to form a laminate 37 as shown in FIG. The signal external electrodes 41a, 41b, 42a, 4
2b are provided respectively. Furthermore, the ground external electrodes G1 and G
2 are provided. Signal external electrodes 41a, 4
Both ends 21a and 21b of the through transmission line 21 are connected to 1b, respectively, and both ends 22a and 22b of the transmission line 22 are connected to the signal external electrodes 42a and 42b, respectively. The ground external electrode G1 has a ground electrode 23,
The ends 23a, 24a of the ground electrodes 23, 24 are connected to the ends 23a, 24a of the ground electrodes 23, 24.
b is connected. FIG. 7 shows a laminated noise for a differential transmission line.
FIG. 3 is an electrical equivalent circuit diagram of a noise filter 50.

As shown in FIG. 8, the laminated noise filter 50 for a differential transmission line is inserted into the signal lines 3a and 3b connecting the sensor 1 and the differential amplifier 2 as an example.
The operation and effect of the differential transmission line laminated noise filter 50 will be described. For example, when normal mode noise (see arrow A1) flowing through the signal line 3a enters the through transmission line 21, the normal mode noise is removed by the capacitance C11. When common mode noise (see arrow A2) flowing through the signal line 3a enters the through transmission line 21,
It flows to the ground via the capacitance C12 formed between the through transmission line 21 and the ground electrode 23. Similarly,
When common mode noise (see arrow A3) flowing through the signal line 3b enters the through transmission line 22, the through transmission line 2
2 formed between the ground electrode 24 and the ground electrode 24
3 to ground. Thereby, noise accompanying the electromagnetic field radiation is removed before entering the differential amplifier 2, and input to the differential amplifier 2 can be prevented. Moreover, three capacitances C11 and C
Since the C12 and C13 are formed, the mounting area on the printed circuit board can be smaller than when a plurality of conventional two-terminal capacitors are combined.

In recent years, when a digital signal is transmitted by a signal line, a differential transmission system has been often used. At this time, when noise enters the signal line together with the digital signal transmitted from the transmission side, the noise is radiated from the signal line into space as electromagnetic interference noise (EMI noise). As a countermeasure for this, as shown in FIG. 9, if the differential transmission line laminated noise filter 50 of the second embodiment is connected to the output of the digital signal transmission amplifier 51, the signal is transmitted together with the digital signal through the signal lines 3a and 3b. Side 52
Can be removed before being sent to the signal lines 3a and 3b, and the problem associated with electromagnetic interference noise can be eliminated.

[Other Embodiments] The present invention is not limited to the above-described embodiments, and can be variously modified within the scope of the gist.
For example, in the second embodiment, the ground electrode 23 shown in FIG.
Either the insulating sheet 35 on which the ground electrode 24 is formed or the insulating sheet 36 on which the ground electrode 24 is formed can be omitted.

Also, a laminated noise filter for a differential transmission line
In the case of manufacturing the data line, the method is not necessarily limited to a method of stacking insulating sheets or the like having a signal line provided on the surface thereof and then firing them integrally. As the insulating sheet, a pre-fired one may be used. Further, a laminated noise filter for a differential transmission line may be manufactured by a method described below. That is, after forming an insulating layer with a paste-like insulating sheet material by means such as printing, a paste-like conductive material is applied to the surface of the insulating layer to form a signal line. Next, a paste-like insulating material is applied from above the signal line to form an insulating layer in which the signal line is embedded. Similarly, by performing electrical connection of necessary portions of the signal line while successively coating the differential transmission line having a multilayer structure,
, A laminated noise filter is obtained.

[0022]

As is apparent from the above description, according to the present invention, the normal mode noise flowing through the through transmission line is removed by the capacitance formed between the transmission lines facing each other with the insulating layer interposed therebetween. can do. Furthermore, since the inductance and resistance generated in the signal external electrode are inserted in series with the signal line, it can be used as a choke, and the laminated type for differential transmission lines with excellent insertion loss characteristics
A noise filter can be obtained.

Further, by providing a ground electrode facing the through transmission line with an insulating layer interposed, a capacitance is formed between the through transmission line and the ground electrode, and common mode noise flowing through the through transmission line is reduced. The current can flow to the ground via the capacitance, and a laminated noise filter for a differential transmission line having more excellent insertion loss characteristics can be obtained. Moreover, since a plurality of capacitances can be formed in one component, the mounting area on the printed circuit board can be smaller than when a plurality of conventional two-terminal capacitors are combined.

[Brief description of the drawings]

FIG. 1 shows a laminated noise filter for a differential transmission line according to the present invention.
FIG. 2 is an exploded perspective view showing the configuration of the first embodiment of the filter .

FIG. 2 is a diagram showing a laminated noise filter for a differential transmission line shown in FIG. 1 ;
Perspective view showing an appearance of the filter.

FIG. 3 is a diagram showing a laminated noise filter for a differential transmission line shown in FIG. 1 ;
FIG. 2 is an electrical equivalent circuit diagram of Luta .

FIG. 4 is a diagram showing a laminated noise filter for a differential transmission line shown in FIG. 1 ;
FIG. 4 is an explanatory diagram of a noise removing operation of a filter .

FIG. 5 is a diagram illustrating a laminated noise filter for a differential transmission line according to the present invention.
FIG. 6 is an exploded perspective view illustrating a configuration of a second embodiment of a filter .

6 is a diagram showing a laminated noise filter for a differential transmission line shown in FIG. 5 ;
Perspective view showing an appearance of the filter.

7 is a diagram showing a laminated noise filter for a differential transmission line shown in FIG. 5 ;
FIG. 2 is an electrical equivalent circuit diagram of Luta .

8 is a diagram showing a laminated noise filter for a differential transmission line shown in FIG. 5 ;
FIG. 4 is an explanatory diagram of a noise removing operation of a filter .

FIG. 9 is a diagram showing a laminated noise filter for a differential transmission line shown in FIG. 5 ;
FIG. 5 is an explanatory diagram in which a filter is applied to noise removal of a digital signal.

FIG. 10 is an explanatory diagram of noise removal by a conventional two-terminal capacitor.

FIG. 11 is an electric equivalent circuit diagram of a two-terminal capacitor in a high frequency region.

[Explanation of symbols]

Reference Signs List 20: laminated noise filter for differential transmission line 21, 22, transmission line 23, 24: ground electrode 31, 32: insulating sheet 33: cover sheet 34, 37 ... laminate 35, 36: insulating sheet 41a, 41b , 42a, 42b: Signal external electrode 50: Multilayer noise filter G1, G2 for differential transmission line: Ground external electrode

Claims (3)

(57) [Claims] Inside of 1. A laminate constituted by stacking a pair of through transmission lines and a plurality of insulating layers, a central portion of the pair of through-transmission lines are opposed via the insulating layer, a capacitor
And arranged so that both ends of the pair of through transmission lines do not face each other via the insulating layer.
Is, four multilayer noise filter for differential transmission line, characterized in that each electrically connected to a signal external electrode provided on a surface of the laminate. 2. A ground electrode facing the pair of through transmission lines with the insulating layer interposed therebetween,
2. The multilayer noise filter for a differential transmission line according to claim 1, wherein both ends of the multilayer noise filter are electrically connected to ground external electrodes provided on the surface of the multilayer body. 3. A central portion of the pair of through transmission lines is a straight line.
And facing each other via the insulating layer,
The transmission lines are axisymmetric with each other and have equal lengths
The difference according to claim 1 or 2, wherein
Multilayer noise filter for dynamic transmission lines.