JP2000261271A - Lamination type low pass filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a lamination type low pass filter which has a sharp attenuation characteristic and a satisfactory spurious characteristic and where impedance design is easy and the earth state on the ground side is stable. SOLUTION: Capacitor electrodes 23 and 24 constitute a first capacitor C1, and capacitor electrodes 25 and 26 constitute a second capacitor C2. Capacitor electrodes 27 and 28 constitute a capacitor Co for resonance point adjustment. Coil conductors 29a to 29e constitute a spiral coil L1. The coil L1 is arranged like the letter U in the lamination direction of a sheet 32. The coil L1 has one end electrically connected to capacitor electrodes 23 and 28 in a laminate and has the other end electrically connected to capacitor electrodes 25 and 27.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated low-pass filter, and more particularly to a laminated low-pass filter used as a noise filter for electronic equipment such as video equipment and personal computer equipment.

[0002]

2. Description of the Related Art As a low-pass filter for removing noise from a video signal line or a clock signal line of a video device or a personal computer, a low-pass filter having a pass band of 100 to 150 MHz is currently mainstream. This low-pass filter is usually composed of a T-type LC circuit or a π-type LC circuit.

For example, FIG. 9 is an exploded perspective view showing a conventional laminated low-pass filter 1 composed of a π-type LC circuit. The low-pass filter 1 includes coil conductors 2a to 2
It is composed of an insulating sheet 10 provided with d, an insulating sheet 10 provided with no electrodes in advance, and the like. The coil conductors 2a to 2d are electrically connected in series via via holes 3a to 3c provided in the insulating sheet 10 to form a spiral coil L having an axis parallel to the direction in which the insulating sheets 10 are stacked. You.

[0004] After each insulating sheet 10 is stacked,
It is integrally fired to form a laminate 4 as shown in FIG. The resonance point adjusting capacitor electrodes 7a and 7b are disposed on the upper surface of the multilayer body 4 with the insulating film 5 interposed therebetween, thereby forming the resonance point adjusting capacitor Co. On the lower surface of the multilayer body 4, capacitor electrodes 8a and 8b and a ground internal electrode 9 are arranged with the insulating film 6 interposed therebetween, and capacitors C1 and C2 are formed, respectively.

Further, an input external electrode 13 and a ground external electrode 15 are formed on the front side surface of the multilayer body 4, and an output external electrode 14 and a ground external electrode 16 are formed on the rear side surface of the multilayer body 4. ing. One end of the coil L (specifically, the end of the coil conductor 2d), the resonance point adjusting capacitor electrode 7a, and the capacitor electrode 8a are electrically connected to the input external electrode 13. The other end of the coil L (specifically, the end of the coil conductor 2a), the resonance point adjusting capacitor electrode 7b, and the capacitor electrode 8b are electrically connected to the output external electrode 14. The ground internal electrode 9 is electrically connected to the ground external electrodes 15 and 16.

[0006]

The characteristics required of the low-pass filter 1 differ depending on the application, and require a steep damping characteristic, or place emphasis on spurious characteristics, and further necessitate an impedance design. And so on. However, it is difficult to satisfy these requirements only with the conventional low-pass filter 1. Therefore, if a steep attenuation characteristic is to be obtained by using the conventional low-pass filter 1, a trap circuit composed of external components such as an inductor and a capacitor must be additionally provided to increase the attenuation at a target frequency. I had to.

In order to obtain good spurious characteristics using the conventional low-pass filter 1, the entire printed wiring board on which the low-pass filter is mounted is shielded so that signal noise does not leak to the outside. I needed to. Further, if a desired impedance design is to be performed, an impedance matching circuit formed by external components such as inductors and capacitors must be added to achieve impedance matching.

In the conventional low-pass filter 1, since the coil L and the capacitors C1 and C2 are electrically connected via the external electrodes 13 and 14, the external electrodes 13 and 14
Due to the influence of the residual inductance component included in the above, the variation in the characteristics was large. Further, the conventional low-pass filter 1 has a problem that the ground-side inductance component is large and the grounding state is unstable. Further, in the case of connecting the resonance point adjusting capacitor Co in parallel with the coil L in the conventional low-pass filter 1, it is necessary to pass through the external electrodes 13 and 14, and this residual inductance also increases the characteristic variation.

An object of the present invention is to provide a laminated low-pass filter having steep attenuation characteristics and good spurious characteristics, easy impedance design, and stable grounding on the ground side. .

[0010]

In order to achieve the above object, a laminated low-pass filter according to the present invention comprises:
(A) a laminate formed by stacking an insulating layer, a coil conductor, and a capacitor electrode; (b) an input external electrode, an output external electrode, and a ground external electrode provided on the surface of the laminate; A first coil configured to be electrically connected to coil conductors and arranged in a U-shape in the stacking direction of the laminate, and (d) first and second capacitors configured by the capacitor electrodes; (E) a hot-side capacitor electrode of the first capacitor is electrically connected to the input external electrode, a hot-side capacitor electrode of the second capacitor is electrically connected to the output external electrode, and a ground external electrode is connected to the ground external electrode. The ground-side capacitor electrodes of the first and second capacitors are electrically connected, and the first capacitor is connected to the hot-side capacitor electrode of the first capacitor in the laminate. Electrically connected to one end of the le,
And electrically connecting the other end of the first coil to the hot-side capacitor electrode of the second capacitor;
It is characterized by.

With the above configuration, it is not necessary to electrically connect the first coil and the first and second capacitors arranged in a U-shape via the external electrodes, and an unnecessary residual inductance component is inserted on the ground side. Not done. Therefore, the ground state of the low-pass filter is stabilized.

Further, the laminated low-pass filter according to the present invention further includes second and third coils configured by electrically connecting coil conductors, wherein the hot-side capacitor electrode of the first capacitor is connected to the second coil. And the hot external capacitor electrode of the second capacitor is electrically connected to the output external electrode via the third coil. Thereby, a steep attenuation characteristic is obtained in the laminated low-pass filter. Then, the winding direction of the second coil and the winding direction of the first coil are set to be opposite to each other, and the winding direction of the third coil and the winding direction of the first coil are set to be opposite to each other. Electromagnetic coupling between the first coil and the second and third coils is suppressed.

Further, by arranging the first coil in a U-shape, a resonance point adjusting capacitor can be electrically connected in parallel to the first coil without interposing an external electrode, and the attenuation characteristic can be adjusted. By adjusting the capacitance value of the resonance point adjusting capacitor, the adjustment can be performed accurately, easily and reliably.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a laminated low-pass filter according to an embodiment of the present invention.

[First Embodiment, FIGS. 1 to 3] As shown in FIG. 1, a laminated low-pass filter 21 includes hot-side capacitor electrodes 23 and 25 and a resonance-point adjusting capacitor electrode 2.
, A ground-side capacitor electrode 24, 26 and a resonance-point adjusting capacitor electrode 2.
An insulating sheet 32 provided on the surface with a coil conductor 29;
Insulating sheet 32 provided with a to 29e on its surface
And an insulating sheet 32 whose surface is not provided with a conductor in advance. The capacitor electrodes 23 to 28 and the coil conductors 29a to 29e are formed on the insulating sheet 3 by a method such as printing.
2 is formed on the surface. Coil conductors 29a to 29e
Ag, Ag-Pd, Cu, Ni, and the like are used as the material for these. As a material of the sheet 32, a magnetic material such as ferrite, a dielectric material such as ceramic, or an insulator material is used.

The coil conductors 29a to 29e are provided with openings 34c, 34d, 35c,
Bare (via) connection is electrically connected in series through 35d,
The spiral first coil L1 wound in the counterclockwise direction is configured. The first coil L1 is arranged in a U-shape in the stacking direction of the sheets 32. That is, the first coil L1 is
On the left side of the low-pass filter 21, the coil conductors 29a, 29
b, and has a coil conductor 2 on the right side.
It has a helical portion composed of 9d and 29e, both of which are electrically connected via a coil conductor 29c. Thus, by arranging the first coil L1 in a U-shape, the height of the low-pass filter 21 can be reduced. In addition, since both ends of the first coil L1 are close to each other, the resonance point adjusting capacitor electrode 27 can be formed with short wiring.
And 28 can be opposed to each other, so that the resonance point adjusting capacitor Co and the first coil L1 can be electrically connected without an external electrode.

One end (specifically, the coil conductor 29a) of the first coil L1 is electrically connected to a lead portion of the resonance point adjusting capacitor electrode 28 through an opening 34b provided in the sheet 32. The other end of the first coil L1 (specifically, the coil conductor 29e) is connected to the opening 3 provided in the sheet 32.
It is electrically connected to the lead portion 25a of the hot-side capacitor electrode 25 through 5a and 35b.

The hot side capacitor electrode 23 is a sheet 32
The drawer 23 a is exposed on the left side of the sheet 32. Hot side capacitor electrode 25
Is disposed on the front side of the sheet 32, and the drawer portion 25a
Are exposed on the right side of the sheet 32. The resonance point adjusting capacitor electrode 27 is disposed at the center of the sheet 32,
The hot side capacitor electrode 25 is electrically connected to the lead portion 25a.

On the other hand, the ground-side capacitor electrode 24 is disposed on the back side of the sheet 32, and its end is exposed on the back side of the sheet 32. The ground-side capacitor electrode 24 and the hot-side capacitor electrode 23 constitute a first capacitor C1. The ground-side capacitor electrode 26 is disposed on the front side of the sheet 32, and its end is connected to the sheet 32.
It is exposed on the near side. The ground-side capacitor electrode 26 and the hot-side capacitor electrode 25
The capacitor C2 is formed. The resonance point adjusting capacitor electrode 28 is provided at the center of the sheet 32 and is electrically connected to the lead portion 23 a of the hot-side capacitor electrode 23 through an opening 34 a provided in the sheet 32.
The resonance point adjusting capacitor electrode 28 and the resonance point adjusting capacitor electrode 27 constitute a resonance point adjusting capacitor Co.

After the above-mentioned insulating sheets 32 are stacked, they are integrally fired to form a laminate 38 as shown in FIG. An input external electrode 41 and an output external electrode 42 are provided on left and right end surfaces of the laminate 38, respectively. Laminate 3
Ground external electrodes 4 are provided on the entire rear and front side surfaces of
3, 44 are provided.

The input external electrode 41 is electrically connected to the lead portion 23a of the hot capacitor electrode 23 of the first capacitor C1, and the output external electrode 42 is electrically connected to the lead portion 25a of the hot capacitor electrode 25 of the second capacitor C2. Connected. The ground external electrodes 43 and 44 are electrically connected to the ground-side capacitor electrodes 24 and 26 of the first and second capacitors C1 and C2, respectively.
These external electrodes 41 to 44 are made of Ag, Ag-Pd, N
It is formed by applying a conductive paste such as i, Cu or the like, followed by baking or dry plating.

FIG. 3 is an electric equivalent circuit diagram of the low-pass filter 21. This low-pass filter 21 is a π-type LC
And a resonance point adjusting capacitor Co in parallel with the first coil L1 arranged in a U-shape.
Is connected.

The low-pass filter 21 having the above configuration
Means that the first coil L1 and the first and second capacitors C1 and C2 arranged in a U-shape form a bare
Connected, eliminating the need for conventional electrical connection via external electrodes. Therefore, since unnecessary residual inductance components are not inserted into the ground side of the low-pass filter 21, the grounding state of the low-pass filter 21 is stabilized, and good spurious characteristics can be obtained. Further, by disposing the first coil L1 in a U-shape, the resonance point adjusting capacitor Co can be electrically connected to the first coil L1 in parallel without passing through an external electrode. The adjustment of the capacitance value is easy, and the adjustment of the attenuation characteristic can be performed accurately, easily and reliably.

Further, the inductance of the first coil L1 and the capacitance of the capacitors C1, C2, and Co can be arbitrarily changed by adjusting the number of stacked sheets 32. As a result, a desired impedance design can be easily performed without requiring an impedance matching circuit separately formed by external components such as inductors and capacitors.

[Second Embodiment, FIGS. 4 to 7] As shown in FIG. 4, the laminated low-pass filter 51 of the second embodiment
Is obtained by further adding a second coil L2 and a third coil L3 to the low-pass filter 21 of the first embodiment. The insulating sheet 32 having the coil conductors 52a to 52c and 53a to 53c provided on the surface thereof, and the insulating sheet 32 having the shield electrode 59 provided on the surface, respectively, are the first sheet.
It is laminated on the upper side of the insulating sheet 32 constituting the low-pass filter 21 described in the embodiment. However, the lead portion 2 of the hot-side capacitor electrodes 23 and 25 of the second embodiment
3a and 25a partially change the pattern of the first embodiment.

The coil conductors 52a to 52c are electrically connected in series in a bare (via) manner through openings 55a and 55b provided in the insulating sheet 32, respectively, and form a spiral second coil L2 wound clockwise. Constitute. Coil 53
a to 53c are electrically connected in series in a bare (via) manner through openings 56a and 56b provided in the insulating sheet 32, respectively, and are spirally wound third coils L wound clockwise.
Constituting No. 3.

One end (specifically, the coil conductor 52a) of the second coil L2 is exposed on the left side of the sheet 32, and the other end (specifically, the coil conductor 52c) is provided on the opening 5 formed in the sheet 32.
A bare (via) connection is made to the hot-side capacitor electrode 23 of the first capacitor C1 through 5c. One end of the third coil L3 (specifically, the coil conductor 53a) is
2 and the other end (specifically, the coil conductor 53
c) is barely connected to the hot-side capacitor electrode 25 of the second capacitor C2 through the opening 56c provided in the sheet 32.

After the above-mentioned insulating sheets 32 are stacked, they are integrally fired to form a laminate 60 as shown in FIG. An input external electrode 61 and an output external electrode 62 are provided on the left and right end surfaces of the laminate 60, respectively. Laminate 6
Ground external electrodes 6 on the entire side surface on the back side and near side
3, 64 are provided. The input external electrode 61 is electrically connected to one end (coil conductor 52a) of the second coil L2, and the output external electrode 62 is electrically connected to one end (coil conductor 53a) of the third coil L3. Ground external electrodes 63 and 64 are connected to the first and second capacitors C, respectively.
1 and C2, and are electrically connected to the lead-out portions of the shield electrodes 59.

FIG. 6 is an electrical equivalent circuit diagram of the low-pass filter 51. This low-pass filter 51 is composed of three coils L1, L2, L3 and two capacitors C1, C2. Further, the resonance point is adjusted in parallel with the first coil L1 arranged in a U-shape. Capacitor Co is connected.

The low-pass filter 51 having the above configuration
Has a built-in fifth-order circuit composed of three coils L1, L2, L3 and two capacitors C1, C2, while exhibiting the operational effects of the low-pass filter 21 of the first embodiment. Can be further increased at the above frequency, and a steep attenuation characteristic can be obtained. And
By setting the winding direction of the second coil L2 and the winding direction of the first coil L1 in opposite directions, and setting the winding direction of the third coil L3 and the winding direction of the first coil L1 in opposite directions. , The coils L1 and L2 and the coils L1 and L3 are hardly electromagnetically coupled to each other, so that it is not necessary to set a large interval between the coils L1 and L2 and between the coils L1 and L3. And height reduction can be achieved.

Furthermore, the low-pass filter 51 can be electromagnetically shielded by the shield electrode 59 disposed on the low-pass filter 51 and the ground external electrodes 63 and 64 disposed on both sides of the low-pass filter 51. Therefore, the structure is less susceptible to external electromagnetic noise. Therefore, the spurious characteristics of the low-pass filter 51 can be further improved. FIG. 7 is a graph showing the attenuation characteristic of the low-pass filter 51.

[Other Embodiments] The laminated low-pass filter according to the present invention is not limited to the above-described embodiment, but can be variously modified within the scope of the gist.

For example, in FIG. 4, the resonance point adjusting capacitor Co and the first and second capacitors C1 and C2 may be configured as shown in FIG. Here, 71, 7
2 is a ground-side capacitor electrode of the first and second capacitors C1 and C2, 73 and 74 are hot-side capacitor electrodes of the first and second capacitors C1 and C2, respectively.
75 is a capacitor electrode for adjusting the resonance point. The hot side capacitor electrodes 73 and 74 also function as resonance point adjustment capacitor electrodes, and together with the resonance point adjustment capacitor electrode 75, constitute a resonance point adjustment capacitor Co. The capacitor electrode 73 is connected to the second coil L2 through the opening 76a, and is connected to the first coil L2 through the openings 76b and 76c.
Connect to 1. Similarly, the capacitor electrode 74 has an opening 77
a to the third coil L3 and through the opening 77
b, 77c to the first coil L1.

The number of turns of the first, second and third coils is arbitrary, and the number of layers of the first and second capacitors and the resonance point adjusting capacitor is also arbitrary. Further, the laminated low-pass filter may be a ladder-type LC circuit or the like in addition to the π-type LC circuit.

In the case of manufacturing a laminated low-pass filter, the method is not necessarily limited to a method in which insulating sheets or the like provided with internal conductors such as coil conductors on the surface are stacked and then integrally fired. As the insulating sheet, a pre-fired one may be used. Further, a laminated low-pass filter may be manufactured by a method described below. That is, after an insulating layer is formed from a paste-like insulating material by printing or the like, a paste-like conductive material is applied to the surface of the insulating layer to form an internal conductor. Next, a paste-like insulating material is applied over the inner conductor to form an insulating layer in which the inner conductor is embedded. Similarly, a necessary portion of the internal conductor is electrically connected to the low-pass filter having a laminated structure by successively applying layers.

[0036]

As is apparent from the above description, according to the present invention, the first coil and the first and second capacitors arranged in a U-shape are electrically connected in the laminated body. No electrical connection via external electrodes is required. Therefore, since no unnecessary residual inductance component is inserted into the ground side of the low-pass filter, the ground state of the low-pass filter is stabilized, and good spurious characteristics can be obtained.

Further, by arranging the first coil in a U-shape, a resonance point adjusting capacitor can be electrically connected in parallel to the first coil without using an external electrode. By adjusting the value, adjustment of the attenuation characteristic can be performed accurately, easily, and reliably.

Further, the inductance of the coil and the capacitance of the capacitor can be arbitrarily changed by adjusting the number of turns and the number of layers. As a result, a desired impedance design can be easily performed without requiring an impedance matching circuit separately formed by external components such as inductors and capacitors.

Further, the first, second and third coils and the first coil
By configuring the fifth-order circuit with the second capacitor and the second capacitor, the attenuation at the target frequency can be further increased, and a steep attenuation characteristic can be obtained. Then, the winding direction of the second coil and the winding direction of the first coil are set to be opposite to each other, and the winding direction of the third coil and the winding direction of the first coil are set to be opposite to each other. Since the first coil and the second and third coils are less likely to be electromagnetically coupled, it is not necessary to set a large interval between the first coil and the second and third coils, and the low-pass filter is reduced in size and height. Becomes possible.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a first embodiment of a multilayer low-pass filter according to the present invention.

FIG. 2 is an external perspective view of the laminated low-pass filter shown in FIG.

FIG. 3 is an electric equivalent circuit diagram of the multilayer low-pass filter shown in FIG.

FIG. 4 is an exploded perspective view showing a second embodiment of the multilayer low-pass filter according to the present invention.

5 is an external perspective view of the multilayer low-pass filter shown in FIG.

FIG. 6 is an electric equivalent circuit diagram of the laminated low-pass filter shown in FIG.

FIG. 7 is a graph showing attenuation characteristics of the multilayer low-pass filter shown in FIG.

FIG. 8 is a partially exploded perspective view showing another embodiment.

FIG. 9 is an exploded perspective view showing a conventional laminated low-pass filter.

10 is an external perspective view of the multilayer low-pass filter shown in FIG.

[Explanation of symbols]

 21, 51: Laminated low-pass filter 23: Hot-side capacitor electrode of first capacitor 24: Ground-side capacitor electrode of first capacitor 25: Hot-side capacitor electrode of second capacitor 26: Ground-side capacitor electrode of second capacitor 27, 28: capacitor electrode for resonance point adjustment 29a-29e: coil conductor 32: insulating sheet 38, 60: laminate 41, 61: input external electrode 42, 62 ... output external electrode 43, 44, 63, 64: ground external electrode 52a to 52c, 53a to 53c: coil conductor C1: first capacitor C2: second capacitor Co: resonance point adjusting capacitor L1: first coil L2 arranged in a U shape L2: second coil L3: third coil

Continued on the front page F-term (reference)

Claims (4)

[Claims] 1. A laminate comprising an insulating layer, a coil conductor, and a capacitor electrode stacked on each other, an input external electrode, an output external electrode, and a ground external electrode provided on a surface of the laminate, A first coil arranged in a U-shape in the stacking direction of the laminated body, and first and second capacitors constituted by the capacitor electrodes; A hot-side capacitor electrode of one capacitor is electrically connected, a hot-side capacitor electrode of the second capacitor is electrically connected to the output external electrode, and a ground side of the first and second capacitors is connected to the ground external electrode. A capacitor electrode is electrically connected, and one end of the first coil is connected to a hot-side capacitor electrode of the first capacitor in the laminate. The electrically connected, and layered low-pass filter, characterized in that, for electrically connecting the other end of the first coil the hot-side capacitor electrode of the second capacitor. 2. The apparatus further comprises a second coil and a third coil electrically connected to a coil conductor, wherein a hot-side capacitor electrode of the first capacitor is electrically connected to the input external electrode via the second coil. And the second
The multilayer low-pass filter according to claim 1, wherein a hot-side capacitor electrode of the capacitor is electrically connected to the output external electrode via the third coil. 3. The winding direction of the second coil and the winding direction of the first coil are opposite to each other, and
3. The laminated low-pass filter according to claim 2, wherein a winding direction of the coil and a winding direction of the first coil are opposite to each other. 4. The multilayer low-pass filter according to claim 1, wherein a resonance point adjusting capacitor is electrically connected in parallel with the first coil.