JPH10150337A - Reflection characteristic adjustment method for lc low pass filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection characteristic adjustment method by which the reflection characteristic is easily adjusted. SOLUTION: In an LC low pass filter 1 composed of a dielectric thin film 4 which is laminated to an insulation base board 2 provided with spiral inductors L1 , L2 and capacitors which are formed with conductor layers formed on the respective surfaces via the dielectric thin film 4, the reflection characteristic is adjusted by forming an eliminating part (x) for eliminating partially an earth electrode 18 in the middle of left and right capacitor electrodes 16a, 16b formed on the prescribed conductor layer. Thus, the method realized on excellent effect that the attenuation is simply adjusted by the post-processing and the LC low pass filer with an optimum attenuation characteristic is manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LC filter used for various wireless communication devices such as a portable telephone and a car telephone, and to a method for adjusting the reflection characteristic thereof.

[0002]

2. Description of the Related Art A low-pass filter provides a filtering function of passing a low-frequency signal of a specific frequency or lower and removing a harmonic signal of a predetermined frequency or more. An LC low-pass filter comprising a combination of an inductor and a capacitor is used. Are known. In this LC low-pass filter, a plurality of capacitors C ₁ , C ₂ , C ₃ are formed in parallel, one end is connected to ground, and inductors L ₁ , L _{2 are} respectively connected between the other ends of the capacitors C ₁ , C ₂ , C _{3. 2} and each inductor L ₁ ,
The L ₂ configured so as to serially connect (see FIG. 9).

[0003] The conventional LC low-pass filter includes one in which a conductive layer is metallized on a dielectric sheet by a printing method and fired integrally, or one in which components of a chip inductor and a chip capacitor are individually mounted. General.

On the other hand, in recent years, there has been an increasing demand for downsizing, higher density, and lower price of electronic devices. And in order to respond to these demands, miniaturization of individual components such as the inductor L and the capacitor C is required. The capacitance value of the resonance capacitor is determined by the dielectric constant of the dielectric material used, the thickness of the dielectric layer, and the area of the upper and lower electrodes, and the inductance value of the inductor is determined by the conductor length and the conductor width.

[0005]

The above-mentioned conventional LC low-pass filter, which is printed by metallizing and integrally firing on a dielectric sheet, has a limited capacity density, so that further miniaturization is difficult. Met.

Further, in the conventional copper metallization firing method, there has been a problem of the influence of frit during copper metallization and an increase in loss in a high frequency region due to surface roughness. That is, in the copper metallization sintering method, a frit is added to increase the adhesion to the ceramic, but the purity of the material is reduced due to the frit, and the conductivity is reduced to that of pure copper. It will be about half. Also, at higher frequencies,
Electrons flow on the surface of the copper body. However, since the surface is roughened by copper metallization, it is greatly affected by the surface roughness. As described above, in the high frequency region, when the conductive layer is formed by the copper metallization firing method, a large conductive loss occurs.

Therefore, the present inventors have developed a small surface area,
In addition, an LC low-pass filter that is easy to manufacture and has small conduction loss has been proposed. The LC low-pass filter having such a configuration has the following configuration. That is,
A first conductive layer is formed on an insulating substrate, a dielectric thin film is further laminated on the insulating substrate, and a second conductive layer is formed on an upper surface thereof. Region, the other half surface portion is an inductor formation region, and in the inductor formation region, two spiral inductors wound toward the center are arranged side by side on one conductive layer, and in the capacitor formation region, In one conductive layer, an electrode of an intermediate capacitor is formed in an intermediate portion thereof, connected to outer winding portions of both spiral inductors, and ground electrodes are formed on both sides of the capacitor electrode. On both sides of the conductive layer, the electrodes of the input side and the output side are formed, and the connection path extends from the electrodes to a position immediately above the center of the two spiral inductors. A ground electrode is formed in a middle portion of both capacitor electrodes of the conductive layer, and an extended end of the connection path and a center of the spiral inductor are electrically connected to each other through a conductive hole formed in the dielectric thin film. The capacitor electrode and the ground electrode are opposed to each other via the dielectric thin film, and an input capacitor, an intermediate capacitor, and an output capacitor are formed in parallel, and one end is connected to ground. The spiral inductors are located between the other ends of the spiral inductors, and the two spiral inductors are connected in series.

In this configuration, a thin film forming technique is used on a substrate, as compared with a conventional configuration in which an inductor is externally mounted or various inductors and capacitors are formed on a single substrate. Since it is formed by forming a conductive layer or a dielectric thin film, the formation is easy and suitable for mass production.

It has been found that in such an LC low-pass filter, by improving its reflection characteristics, the characteristics can be improved, for example, the pass band width can be clearly defined and the transmission loss can be reduced. An object of the present invention is to provide a reflection characteristic adjusting method having such a configuration and capable of easily adjusting the reflection characteristic.

[0010]

According to the present invention, there is provided the above-mentioned LC low-pass filter, wherein an earth electrode formed in the other conductive layer at an intermediate portion between the two capacitor electrodes is partially removed from an edge of the electrode. L, characterized in that
This is a method for adjusting the reflection characteristics of the C low-pass filter.

In this configuration, when the area of the ground electrode is reduced by 10 to 30%, a pole having a large reflection waveform is formed, and the reflection characteristics are improved. In addition, the deletion area is 3
If it is 0% or more, the pass band width is widened, and a frequency at which the reflection characteristics are insufficient in the band appears.

[0012]

1 to 4 show an LC low-pass filter 1 according to the present invention. This LC low pass filter 1
The input capacitor C ₁ , the intermediate capacitor C ₂ and the output capacitor C ₃ are formed in parallel, one end of each is connected to ground, and a spiral inductor L ₁ is connected between the other ends of the capacitors C ₁ and C _2. , Capacitors C ₂ , C ₃
Located spiral inductor L ₂ is between the other end of both spiral inductor L _1, L ₂ are connected in series, in which so as to constitute an equivalent circuit of FIG.

Here, an insulating substrate 2 made of an alumina substrate
Has a thickness of 0.635 mm. A first conductive layer 3 is formed on the insulating substrate 2 by a copper plating method. A dielectric thin film 4 made of an organic insulating film such as a polyimide resin is laminated on the insulating substrate 2 by a spin coating method or the like.
Further, a second conductive layer 10 is formed on the dielectric thin film 4 by a copper plating method. The thickness of the copper film of the first conductive layer 3 is 5 μm. The dielectric thin film 4 has a thickness of 3 μm, and the copper coating of the second conductive layer 10 has a thickness of 5 μm.

Each of the insulating substrate 2 and the dielectric thin film 4 can be made sufficiently small, for example, a square of 3 mm square, and the total thickness is an extremely thin shape of 0.7 mm or less. .

[0015] Then, a half portion of the laminated structure and the capacitor formation region F _1, the other half portion inductor forming region F
_{And 2} .

In the inductor forming region F ₂ ,
The first conductive layer 3 has two spiral inductors L ₁ and L ₂ wound in parallel from the outside toward the center.

Meanwhile, the In the capacitor formation region F _1, the first conductive layer 3, the intermediate portion thereof, to form the electrode 6 of the intermediate capacitor C _2, at its inner central position, both the spiral inductor L _1, L ₂ of the outer winding portion 7a, 7b
I try to connect with. The capacitor electrode 6
Are formed on both sides of the ground electrode 8a, 8b. The ground electrodes 8a and 8b are connected to the surroundings of the L ₁ and L ₂ and the L
It is extended to between _1, L _2. That is, the two spiral inductors L ₁ and L ₂ and the intermediate capacitor C
_A ground electrode layer 8 is formed on the entire surface excluding the _second electrode 6. As a result, the ground electrode layer 8c is interposed between the two spiral inductors L ₁ and L ₂ , and as described later, the magnetic field coupling between the spiral inductors L ₁ and L ₂ is interrupted, and mutual electromagnetic interference is prevented. I am trying to do it.

[0018] and further, the second conductive layer 10, on its both sides, an input side capacitor C _1, the output side capacitor C ₃ of the electrode 16a formed on the dielectric thin film 4, 16b
Respectively, and from the electrode to a position directly above the center of the two spiral inductors L ₁ and L ₂ , the connection path 17 is formed.
a, 17b. Thus, the second conductive layer 10
The connection passage 17a, except 17b, the formed only in the capacitor formation region F _1, the capacitor formation region F
₁ , a ground electrode 18 is formed at an intermediate portion between the capacitor electrodes 16a and 16b.

Furthermore, wherein the dielectric thin film 4, at a position directly above the center of the spiral inductors L _1, L _2, through hole 2
0,20 is formed, via a conductor hole 20, 20, the connecting passage 17a, and the extending end of 17b, and so as to electrically connect the center of the spiral inductors L _1, L _2. Further, the ground electrode 18 has a conductive hole 2
1, 21 are formed to ensure connection with the ground electrodes 8a, 8b. Further, a ground electrode 25 is formed on the lower surface of the insulating substrate 2 as shown in FIG.

Thus, the capacitor electrode 16a and the ground electrode 8a, the capacitor electrode 6 and the ground electrode 18 face each other, and the capacitor electrode 16b and the ground electrode 8b face each other via the dielectric thin film 4. input capacitor C _1, intermediate capacitor C ₂ and the output side capacitor C ₃ are arranged in parallel. One end of each capacitor is grounded. And the input side capacitor C
₁ and located spiral inductor L ₁ is between the other end of the intermediate capacitor C _2, together with the spiral inductor L ₂ is located between the other end of the intermediate capacitor C ₂ and the output side capacitor C _3, both spiral inductor L _1, L ₂ are connected in series, and an equivalent circuit shown in FIG. 9 is formed.

In such a configuration, on the insulating substrate 2,
A first conductive layer 3 is formed by a copper plating method, then a dielectric thin film 4 is formed by a spin coating method, and a second conductive layer 10 is further formed by a copper plating method. By forming, a small LC low-pass filter can be easily manufactured.

Further, in the above configuration, the ground electrode layer 8c is interposed between the two spiral inductors L ₁ and L ₂ . Therefore, the spiral inductor L
_1, L ₂ can be adjacent, by the ground electrode layer 8c, electromagnetic mutual interference is prevented, the magnetic field coupling is interrupted. Therefore, the spiral inductors L ₁ and L ₂ ,
Each of the capacitors C ₁ , C ₂ , and C ₃ can be densely arranged on the insulating substrate 2 and the dielectric thin film 4.

In the above-described structure, the first conductive layer 3 and the second conductive layer 10 may be formed by a sputtering method or a thin film forming technique combining these with photolithography in addition to the plating method described above. Formed by However, as described above, the copper plating method is optimal.

By the way, in such a configuration, the present inventors made the two conductive electrodes 10a, 16a,
It has been found that a new attenuation pole is generated in the reflection characteristic by partially removing the earth electrode 18 formed in the middle part of the electrode 16b from the edge of the electrode. That is, as shown in the chain line in FIG. 1 and FIG.
7 and 8 show a rectangular removal part x formed at the left corner of
As shown by, two attenuation poles α and β appeared in the reflected waveform. Comparing this with the configuration shown in FIG. 2 in the original state without the removal portion x, it can be seen that a single relatively shallow attenuation pole appears in the reflected waveform of this configuration as shown in FIG.

Here, the graph of FIG. 6 has the configuration shown in FIG. 2 and the ground electrode 18 has a horizontal dimension; X = 1 mm, a vertical dimension; Y = 1 mm, and the area of the ground electrode 18 is 1 mm ² . In this example, the reflection waveform was measured without forming the removed portion x. On the other hand, FIG. 7 shows a configuration similar to the above, in which the area of the ground electrode 18 is reduced by 10% and the reflection waveform is measured. In this configuration, two attenuation poles α and β are generated as described above,
The amount of attenuation is larger than in the case where there is no removal part x in FIG. At this time, the frequency interval between the poles g = 50 MHz
It is.

FIG. 8 shows the same configuration as that described above, except that the area of the ground electrode 18 is reduced by 20%. In this configuration, the frequency interval between the poles g = 4
00 MHz. Thus, it can be seen that the distance between the attenuation poles further increases the amount of attenuation.

That is, the larger the area of the removed portion x, the wider the frequency interval g.

As described above, by forming the removed portion x on the ground electrode 18, two attenuation poles can be generated, and by changing the area of the removed portion x, the amount of attenuation can be adjusted. It can be seen that the attenuation characteristics can be changed.

[0029] Thus, by trimming current daytime capacitor C _2, it is possible to choose the reflection characteristics optimally.

[0030]

The present invention relates to an LC low-pass filter having a structure in which a dielectric thin film is laminated on an insulating substrate having a spiral inductor, and a capacitor is formed by a conductive layer formed on each surface through the dielectric thin film. Since the reflection characteristics are adjusted by partially removing the ground electrode in the middle of the left and right capacitor electrodes formed on the predetermined conductive layer, the attenuation can be easily adjusted by post-processing. There is an excellent effect that an LC low-pass filter having optimum attenuation characteristics can be manufactured.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an insulating substrate 2 and a dielectric thin film 4 of an LC low-pass filter 1 separately.

FIG. 2 is a plan view of the LC low-pass filter 1. FIG.

FIG. 3 is a plan view of a dielectric thin film 4;

FIG. 4 is a vertical sectional side view of the LC low-pass filter 1.

FIG. 5 is a plan view of the LC low-pass filter 1 with the ground electrode 18 removed.

FIG. 6 is a frequency characteristic diagram of the LC low-pass filter when the ground electrode 18 is not removed.

FIG. 7 shows the L when the ground electrode 18 is removed by 10% in area.
It is a frequency characteristic figure of a C low pass filter.

FIG. 8 shows a case where the earth electrode 18 is removed by 20% in area.
It is a frequency characteristic figure of a C low pass filter.

FIG. 9 is an equivalent circuit diagram.

[Explanation of symbols]

1 LC low-pass filter 2 insulating substrate 3 first conductive layer 4 dielectric film 8a, 8b, 8c ground electrode 10 the second conductive layer 16a, 16b capacitor electrodes 18 grounded electrodes L _1, L ₂ inductor C _1, C _2, C ₃ capacitor x removal part

Claims (2)

[Claims] A first conductive layer is formed on an insulating substrate, a dielectric thin film is further laminated on the insulating substrate, and a second conductive layer is formed on an upper surface thereof. The half surface portion is a capacitor formation region, the other half surface portion is an inductor formation region, and in the inductor formation region, two spiral inductors wound toward the center are arranged in parallel on one conductive layer, and the capacitor is formed. In the formation region, an electrode of an intermediate capacitor is formed in an intermediate portion of one of the conductive layers, connected to outer winding portions of both spiral inductors, and ground electrodes are formed on both sides of the capacitor electrode. Further, input and output capacitor electrodes are formed on both sides of the other conductive layer, respectively, and the connection path extends from the electrodes to a position immediately above the centers of the two spiral inductors. put out At the same time, an earth electrode is formed on the other conductive layer at an intermediate portion between the two capacitor electrodes, and further, through a conduction hole formed in the dielectric thin film, an extending end of the connection path and a center of the spiral inductor. Are electrically connected to each other, whereby the capacitor electrode and the ground electrode are opposed to each other via the dielectric thin film, and an input capacitor, an intermediate capacitor, and an output capacitor are formed in parallel, and one end is grounded. An LC in which the spiral inductors are respectively positioned between the other ends of the capacitors and both spiral inductors are connected in series.
In the low-pass filter, a reflection characteristic of the LC low-pass filter is characterized in that an earth electrode formed at an intermediate portion between both capacitor electrodes of the other conductive layer is partially removed from an edge of the electrode. Adjustment method. 2. The method for adjusting the reflection characteristic of an LC low-pass filter according to claim 1, wherein the removal area of the ground electrode is removed within a range of 30% or less.