JP2018078471A - Low pass filter - Google Patents

Abstract

A low-pass filter having a small number of parts and a low manufacturing cost is provided. A low-pass filter including a plurality of capacitors and a plurality of coils, the plurality of capacitors facing a first surface on which a plurality of island-shaped pattern electrodes are formed and the plurality of pattern electrodes. In this way, a plurality of coils are formed of a linear conductor bent in a meander shape, and the linear conductor is a plurality of conductors between both ends. The portions are bent so as to be connectable to the plurality of pattern electrodes, the conductor portions are respectively connected to the plurality of pattern electrodes, and both ends of the linear conductor extend to the same surface as the second surface of the dielectric substrate. ing. [Selection] Figure 1

Description

  The present invention relates to a low-pass filter including a plurality of capacitors and a plurality of coils.

In a mobile communication device such as a cellular phone, a low pass filter is often used to attenuate a harmonic region with respect to a transmission signal.
Patent Document 1 discloses a method of configuring a low-pass filter by disposing a plurality of discrete capacitors on a case and connecting a plurality of coils.
Patent Document 2 discloses a method in which a plurality of capacitors are formed in one dielectric block, and adjacent capacitors are connected by a coil formed of a single linear conductor bent in a meander shape.

JP-A-4-287401 JP2015-139191A

In recent years, mobile communication devices are required to be smaller and have higher performance, and at the same time, cost reduction is also required. The parts used are also required to have high performance through downsizing and optimal design, and further cost reduction is required by reducing the number of parts.
However, in the case of Patent Document 1, since a plurality of discrete capacitors are arranged on the case and a plurality of coils are connected, the number of parts is large and there is a problem in cost reduction.

In the case of Patent Document 2, a plurality of capacitors are formed by a single dielectric substrate, and the coil is also formed by one linear conductor bent in a meander shape, so that the number of parts is reduced. The connector is used to connect to an external circuit, and the number of parts is still not reduced.
In Patent Document 2, as a method not using a connector, a method of forming an electrode 110a on the end face of the dielectric substrate 110 as shown in FIG. However, in the case of such a method, it is necessary to provide a connection electrode for connecting to an external circuit on the second surface (not shown) which is the end surface and the back surface of the dielectric substrate, which increases the number of electrode forming steps. There is a problem that the manufacturing cost increases. In FIG. 14, one linear conductor 120 bent in a meander shape is connected to the pattern electrodes 110a, 110b, and 110c on the dielectric substrate 110.

  The present invention has been made in view of the above situation, and an object of the present invention is to provide a low-pass filter with a small number of parts and low manufacturing costs.

According to the present invention, the object as described above is achieved.
A low pass filter comprising a plurality of capacitors and a plurality of coils,
The plurality of capacitors are formed of a dielectric substrate having a first surface on which a plurality of island-shaped pattern electrodes are formed and a second surface on which electrodes are formed so as to face the plurality of pattern electrodes. ,
The plurality of coils are formed of linear conductors bent in a meander shape,
In the linear conductor, a plurality of conductor portions between both end portions are bent so as to be connectable to the plurality of pattern electrodes, respectively, and the conductor portions are respectively connected to the plurality of pattern electrodes. The portion is provided with a low-pass filter extending to the same surface as the second surface of the dielectric substrate.

  According to the present invention, it is possible to provide a low-pass filter with a small number of parts and low manufacturing costs.

It is a typical perspective view which shows 1st Embodiment of the low-pass filter by this invention. It is a disassembled perspective view of the low pass filter shown in FIG. It is a longitudinal cross-sectional view which shows the state by which the low-pass filter shown in FIG. FIG. 4 is an equivalent circuit of the low-pass filter shown in FIG. It is a typical perspective view which shows 2nd Embodiment of the low-pass filter by this invention. It is a partial longitudinal cross-section which shows 3rd Embodiment of the low-pass filter by this invention. It is a typical perspective view which shows 4th Embodiment of the low-pass filter by this invention. It is a top view which shows 5th Embodiment of the low-pass filter by this invention. It is a top view which shows 1st Embodiment of the low-pass filter by this invention. It is a top view which shows 6th Embodiment of the low-pass filter by this invention. It is a top view which shows the modification of the low-pass filter of 6th Embodiment. It is a typical perspective view which shows the modification of 1st-4th and 6th embodiment. It is a typical perspective view which shows the other modification of 1st-4th and 6th embodiment. It is a typical perspective view which shows the low-pass filter described in patent document 2.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
FIG. 1 is a schematic perspective view showing a first embodiment of a low-pass filter according to the present invention. FIG. 2 is an exploded perspective view of the low-pass filter shown in FIG. FIG. 3 is a longitudinal sectional view showing a state where the low-pass filter shown in FIG. 1 is mounted on a mounting board. FIG. 4 is an equivalent circuit of the low-pass filter shown in FIG.

In this embodiment, as shown in FIG. 4, a five-stage low-pass filter having three capacitors C1 to C3 and two coils L1 and L2 is configured.
As shown in FIGS. 1 to 3, the three capacitors C <b> 1 to C <b> 3 include three island-like pattern electrodes 11 a, 11 b, 11c is formed, and the electrode 11d is formed on the second surface S2 (lower surface side) of the dielectric substrate 11 so as to face the three pattern electrodes 11a, 11b, and 11c. That is, the capacitors C1 to C3 are formed by the pattern electrodes 11a, 11b, 11c and the electrode 11d facing each other across the dielectric. In addition, although the electrode 11d is grounded here, it does not necessarily need to be grounded and it is sufficient if it is set to a fixed potential.

The dielectric substrate 11 has a basic shape having a length L, a width W, and a thickness T. The length L of the dielectric substrate 11 is, for example, about 22 mm, the width W is, for example, about 5 mm, and the thickness T is, for example, about 1 mm. As a material of the dielectric substrate 11, for example, a forsterite ceramic mainly composed of Mg ₂ SiO ₄ and having a relative dielectric constant ε _r of about 10 can be used.

As the pattern electrodes 11a, 11b, 11c and the electrode 11d, for example, silver electrodes are used. The capacitance values of the capacitors C1 to C3 are determined by the characteristics of the low-pass filter, and the capacitance values can be changed by changing the areas of the pattern electrodes 11a, 11b, and 11c. The capacitance values of the capacitors C1 to C3 can all be the same, but can also be set differently. The intervals between the pattern electrodes 11a, 11b, and 11c need not be equal, and can be set as appropriate in order to change the length of the linear conductor 12 between the pattern electrodes.
The linear conductor 12 is bent in a meander shape and connected to the three pattern electrodes 11a, 11b, and 11c. The connection method is, for example, soldering, but a conductive adhesive or the like may be used.

The two coils L <b> 1 and L <b> 2 are formed by a single linear conductor 12. As the linear conductor 12, a conductive wire can be used. For example, a round bar wire having a diameter of 0.5 mm is used. The linear conductor 12 is bent in a meander shape on the same surface.
Here, in this embodiment, a rectangular wave shape is taken as an example of a meander shape, but a sine wave shape, a trapezoidal wave shape, an inverted trapezoidal wave shape, or the like may be used. In addition, the shape of the linear conductor between the pattern electrodes is “U” in the case of rectangular wave, trapezoid in the case of trapezoidal wave, and inverted trapezoid in the case of inverted trapezoidal wave, but the shape is particularly limited The shape may be a semicircular shape or a semi-elliptical shape.

As described above, by connecting the pattern electrodes 11a, 11b, and 11c and the linear conductor 12 at three points, a five-stage low-pass filter is configured.
A single linear conductor 12 is connected to the pattern electrodes 11a, 11b, and 11c to form two coils L1 and L2.
Both end portions of the linear conductor 12 extend in the length L direction of the dielectric substrate 11 and are bent at both end surfaces S4 and S5 of the dielectric substrate 11 so as to be flush with the second surface. ing.

  As shown in FIG. 3, the low-pass filter shown in FIG. 1 can be mounted on the mounting substrate 13. A signal line 13a and an electrode 13b are formed on the mounting substrate 13, both ends of the linear conductor 12 and the signal line 13a are connected, and the electrode 11d and the electrode 13b are connected. The electrode 13b is connected to the electrode 11d and is grounded. However, the electrode 13b does not necessarily have to be grounded, and may have a fixed potential. With this structure, when the surface mounting is performed on the mounting substrate 13, an external signal can be taken in from the signal line 13 a without providing connection electrodes on the end surface and the second surface of the dielectric substrate 11. Therefore, it is possible to provide an inexpensive low-pass filter with a simplified manufacturing process in which the process of forming electrodes on the dielectric substrate 11 is simplified.

[Second Embodiment]
FIG. 5 is a schematic perspective view showing a second embodiment of the low-pass filter according to the present invention. The present embodiment shows a low-pass filter in which a metal case is put on the low-pass filter of the first embodiment shown in FIGS.
In the present embodiment, as shown in FIG. 5, a metal case 14 having a length L and a width W substantially the same as those of the dielectric substrate 11 and a height H including the thickness of the dielectric substrate 11 is provided. ing. The height H of the low-pass filter obtained by adding the thickness of the dielectric substrate 11 to the height of the metal case 14 is about 10 mm, for example. In the present embodiment, the side electrode 11e is formed on the side surface S3 (see FIG. 2) of the dielectric substrate 11, and the side electrode 11e is connected to the electrode 11d. The metal case 14 is connected to the side electrode 11e. With such a structure, an electromagnetic shield is improved and a low-pass filter having a good attenuation characteristic is provided. In addition, the structure which covers the metal case demonstrated by this embodiment is applicable also in the 3rd-6th embodiment mentioned later.

[Third Embodiment]
FIG. 6 is a partial cross-sectional view showing a third embodiment of the low-pass filter according to the present invention. The configuration of the low-pass filter of this embodiment is the same as that of the low-pass filter of FIGS. 1 to 4 except for the shape of the end of the linear conductor 12. The same constituent members as those of the low-pass filter of FIGS.
According to this embodiment, both ends of the linear conductor 12 are bent so as to be parallel to the end surface of the dielectric substrate 11 and flush with the second surface of the dielectric substrate 11. The end of the linear conductor 12 is connected to the signal line 13a substantially perpendicular to the surface of the signal line 13a. With such a structure, the number of portions where the linear conductor is bent is reduced, and the manufacturing cost is further reduced. The configuration of this embodiment can also be applied to the fourth to sixth embodiments described later.

[Fourth Embodiment]
FIG. 7 is a schematic perspective view showing a fourth embodiment of the low-pass filter according to the present invention. The same constituent members as those of the low-pass filter of FIGS.
In FIG. 7, a notch 11f having a width W1 and a length L1 is formed in the L direction (length direction) from the respective end surfaces S4 and S5 of the dielectric substrate 11. The width W1 is about 0.6 mm, for example, and the length L1 is about 3 mm, for example. The linear conductor 12 has substantially the same shape as that of the first embodiment, and a connection portion with the signal line 13 a is inserted into the notch portion 11 f of the dielectric substrate 11. Both end portions of the linear conductor 12 are isolated from and electrically separated from the electrode 11d formed on the second surface S2 of the dielectric substrate 11. When the linear conductor 12 and the electrode 11d are electrically separated, it is preferable to remove the electrode 11d in the region of the width W1 + width α and the length L1 + width β around the notch 11f. The width α and the width β may be the same length (α = β) or may be different (α> β or α <β). With such a structure, when the linear conductor 12 is connected to the pattern electrodes 11a and 11c, positioning can be performed accurately, manufacturing variation can be suppressed, and a low-pass filter with good yield can be manufactured.
The substrate thickness of the dielectric substrate 11 is preferably 1/2 or more of the thickness (dimension in the H direction) of the linear conductor 12. With such a thickness, the linear conductor 12 can be accurately positioned, and can be prevented from falling down, resulting in a better yield. Note that the configuration of this embodiment can also be applied to fifth and sixth embodiments described later.

[Fifth Embodiment]
FIG. 8 is a top view showing a fifth embodiment of the low-pass filter according to the present invention. FIG. 9 is a top view showing a first embodiment of a low-pass filter according to the present invention.
As shown in FIG. 9, in the first embodiment, when viewed from above the dielectric substrate surface, the pattern electrodes 11a, 11b, 11c are arranged in a straight line, and the linear conductors 12 are also arranged in a straight line. Has been.
As shown in FIG. 8, the configuration of the low-pass filter according to the present embodiment is such that the arrangement of the pattern electrodes of the low-pass filter is two rows, and the linear conductors 12 are alternately connected to the two rows of pattern electrodes.

As shown in FIG. 8, the pattern electrode is composed of the pattern electrodes 11a and 11c in the first row and the pattern electrode 11b in the second row, and when the linear conductor 12 is viewed from above the dielectric substrate surface, The pattern electrodes in the first row and the pattern electrodes in the second row are alternately connected so as to have a rectangular wave shape.
The linear conductor 12 may be formed to have a trapezoidal wave shape or an inverted trapezoidal wave shape when viewed from above the dielectric substrate surface.
The low-pass filter according to the present embodiment has a larger width W than the first embodiment, but can reduce the length L.

[Sixth Embodiment]
FIG. 10 is a top view showing a sixth embodiment of the low-pass filter according to the present invention. FIG. 11 is a top view showing a modified example of the low-pass filter of the present embodiment.
In the low-pass filter shown in FIGS. 1 to 9, both end portions of the linear conductor 12 are extended to the end faces S4 and S5 (direction parallel to the arrangement direction of the plurality of pattern electrodes). In the present embodiment, both end portions of the linear conductor 12 are on the side surface S3 side (a direction perpendicular to the arrangement direction of the plurality of pattern electrodes) or on the side surfaces S3 and S6 side (a direction perpendicular to the arrangement direction of the plurality of pattern electrodes). It was extended.
Depending on the layout of the signal lines 13 a of the mounting substrate 13, it may be better to extend both ends of the linear conductor 12 to the side surface instead of the end surface side of the dielectric substrate 11. Both end portions of the linear conductor 12 may be extended to one side S3 or S6 side as shown in FIG. 10, or may be extended to the side S3 or S6 side as shown in FIG. Good.
Further, both end portions of the linear conductor 12 may be extended to the end surface S4 side and the side surface S3 side or S6 side, and extended to the end surface S5 side and the side surface S3 side or S6 side. Also good.
In the present embodiment, when the same configuration as that of the fourth embodiment is applied, the end surfaces S4 and S5, the side surfaces S3 and S6, the side surfaces S3 and S6, and the end surface S4 and the side surfaces S3 and S6 of the dielectric substrate 11 A notch portion is formed, and the linear conductor 12 is inserted into the notch portion of the dielectric substrate 11 at the connection portion with the signal line of the mounting substrate.

As mentioned above, although each embodiment of the low-pass filter of the present invention was described, in each embodiment, various forms are possible as shown below.
The number of stages of the low-pass filter is not limited to this embodiment, and the present invention can be applied to a low-pass filter having six or more stages.
The dielectric substrate is not limited to ceramics but may be a resin substrate.
-The pattern electrode may be a copper electrode limited to a silver electrode.
-The material of the coil is not limited to copper but may be a conductor.
The cross-sectional shape of the linear conductor is not limited to a circle and may be a rectangle.

  In the first to fourth and sixth embodiments, as shown in FIGS. 1 and 7, the linear conductor 12 is bent in a meander (meander) shape on the same plane perpendicular to the dielectric substrate surface. However, as shown in FIG. 12, the “U” -shaped portions 12a and 12b of the linear conductor 12 are bent, and the meander (in the same plane inclined by a certain angle from the plane perpendicular to the dielectric substrate surface). It may be bent in a meandering manner. By doing in this way, when the linear conductor 12 is arrange | positioned in the space of the metal case 14 like 2nd Embodiment, the linear conductor 12 is arrange | positioned diagonally with respect to a dielectric substrate surface. Therefore, the length of the linear conductor 12 can be increased.

  Further, as shown in FIG. 13, when the linear conductor 12 is bent at a surface inclined by a certain angle from a plane perpendicular to the dielectric substrate surface, a “U” -shaped portion 12a of the linear conductor 12, It is also possible to bend 12b alternately left and right with respect to the arrangement direction of the pattern electrodes 11a to 11c. Even in such a configuration, when the linear conductor 12 is disposed in the space of the metal case 14 as in the second embodiment, the linear conductor 12 is disposed obliquely with respect to the dielectric substrate surface. Therefore, the length of the linear conductor 12 can be increased. Furthermore, this configuration has an advantage that the upper side can be made long so that the inverted trapezoidal portions do not overlap when the linear conductor is bent into an inverted trapezoidal wave shape.

  In each embodiment, capacitors are formed at both ends of a plurality of island-shaped pattern electrodes to form a five-stage low-pass filter. However, instead of forming a capacitor on one of the ends of the plurality of island-shaped pattern electrodes, a four-stage low-pass filter with two capacitors and two coils, or an even-numbered low-pass filter with even more stages is formed. Also good.

  The low-pass filter of the present invention can be used in various measuring devices, audio devices, mobile communication, satellite communication devices, and the like.

DESCRIPTION OF SYMBOLS 11 Dielectric substrate 11a, 11b, 11c Pattern electrode 11d Electrode 12 Linear conductor 13 Mounting board 14 Metal case

Claims (7)

A low pass filter comprising a plurality of capacitors and a plurality of coils,
The plurality of capacitors are formed of a dielectric substrate having a first surface on which a plurality of island-shaped pattern electrodes are formed and a second surface on which electrodes are formed so as to face the plurality of pattern electrodes. ,
The plurality of coils are formed of linear conductors bent in a meander shape,
In the linear conductor, a plurality of conductor portions between both end portions are bent so as to be connectable to the plurality of pattern electrodes, respectively, and the conductor portions are respectively connected to the plurality of pattern electrodes. The portion extends to the same surface as the second surface of the dielectric substrate. The dielectric substrate has notches at portions located at both ends of the linear conductor, and both ends of the linear conductor are inserted into the notch, and the dielectric substrate The low-pass filter according to claim 1, wherein the low-pass filter extends to the same surface as the second surface.
  3. The low pass filter according to claim 1, wherein both ends of the linear conductor are isolated from the electrode formed on the second surface.   The low-pass filter according to claim 2, wherein the dielectric substrate has a thickness equal to or greater than ½ of the thickness of the linear conductor.   5. The low-pass filter according to claim 1, wherein both end portions of the linear conductor extend in a direction perpendicular to an arrangement direction of the plurality of pattern electrodes.   One of both ends of the linear conductor extends in a direction perpendicular to the arrangement direction of the plurality of pattern electrodes, and the other of the both ends extends in a direction parallel to the arrangement direction of the plurality of pattern electrodes. The low-pass filter according to any one of claims 1 to 4. On the surface, there is a mounting substrate on which a fixed potential electrode and two signal lines are formed,
The electrode of the second surface and the electrode at the fixed potential are connected, and both end portions of the linear conductor are connected to the two signal lines, respectively. The low pass filter described in 1.

Images