JPH0878218A - Signal transmission element - Google Patents

Abstract

PURPOSE: To provide a signal transmission element having high frequency band blocking characteristics and low frequency band passing characteristics with which the high frequency component of a high frequency region can be absorbed without fail. CONSTITUTION: The signal transmission element contains an earth electrode 1, a signal wire electrode 2 and an insulated substrate 3. The above-mentioned electrodes 1 and 2 are provided on the insulated substrate 3. The insulated substrate 3 is made of a composite member which is formed by mixing ferromagnetic metal powder and insulating resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal transmission device,
More specifically, the present invention relates to a low-pass (high-frequency blocking) signal transmission element that attenuates high-frequency components by absorption.

[0002]

2. Description of the Related Art A low-pass (high-pass blocking) signal transmission element is typically a low-pass filter. Conventional general low-pass filters utilize the difference in frequency characteristics between impedance matching and mismatching, and reflect the signals that belong to the frequency band on the high frequency side to obtain the required filter characteristics. It has gained. However, in the reflection type low pass filter, the reflected unnecessary frequency component may be returned to the preceding stage of the filter, and may cause an unexpected oscillation in the circuit, for example. The absorption type low-pass filter is a type of filter that absorbs unnecessary frequency components, and improves the above-mentioned drawbacks of the reflection type low-pass filter.

Absorption low pass filters have already been proposed. For example, one using ferrite is one example, and specifically, ferrite beads and the like are already widely used. However, the frequency band that ferrite can absorb is in the frequency range lower than 2 GHz, and is about 2 GHz.
In the frequency band of z or higher, the absorption effect is low, and passage is permitted.

As another prior art, USP 4,297,661 discloses a high-pass filter in which microstrip is made of ferrite. This high-pass filter utilizes a phenomenon in which the absorbing action occurs on the low frequency side and the absorbing action does not occur on the high frequency side.

In both of the above two types, G
Unwanted signal components in the high frequency region above Hz cannot be suppressed by absorption.

Schiffres is an IEEE Trans Electron
Magn Compt. EMC-6 55-61 1964 proposes a coaxial transmission line using ferrite, but this coaxial transmission line is mainly for the purpose of acquiring characteristics in the MHz band, and GHz or higher. Does not disclose the transmission characteristics and the reflection characteristics in the high frequency region. In the high frequency region of GHz or higher, it seems that transmission still occurs.

It has been reported that an attempt is made to combine a non-magnetic material having an absorbing effect on the high frequency side and a ferrite to remove a signal by absorption even on the high frequency side. Schlicke is IEE
Examples are the EMI filter proposed by E Spectrum 59-68 1967 and the low-pass EMI filter proposed by Bogar in Proc. Of IEEE 67 159-163 1979.
In these prior arts, a part of the insulator of the coaxial filter is formed by laminating a ferrite and a dielectric. Fiallo also proposed a microstrip filter combining ferrite and dielectric in his PhD thesis 1993 in Pennsylvania State University. However, in these prior arts, a multilayer structure is inevitably adopted, and the structure becomes complicated.

Next, USP 4,146,854 discloses an attenuating element using a ferrite bead and a radio wave absorber made of a metal or resin composite member, and in Japanese Patent Laid-Open No. 4-127701. A technique of using a radio wave absorbing material for a part of a non-magnetic microstrip line is disclosed. However, in any case, the electromagnetic wave absorber or the electromagnetic wave absorbing substance is
It is only used supplementarily for the purpose of suppressing high frequency components that cannot be absorbed.

Further, US Pat. No. 4,301,428 discloses an electric wire or cable containing a conductive element having an appropriate electric resistance and a magnetic absorption mixture. The conductive element is
It has a composite structure in which a non-conductive core made of fiber, resin, glass or the like is coated with a thin conductive metal layer. The magnetic absorption mixture is non-conductive and coats the conductive element. However, providing the signal line with an electrical resistance value not only removes noise components but also attenuates the signal components, which is problematic in applications that handle minute signals, for example. In addition, the preceding example discloses electric wires, and does not describe a case as a circuit element.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a signal transmission device having high-frequency blocking and low-pass characteristics which can surely absorb high frequency components in the high frequency region.

Another object of the present invention is to provide a signal transmission device having high-frequency blocking and low-pass characteristics capable of reliably absorbing high frequency components of 1 GHz or higher.

Still another object of the present invention is to provide a signal transmission device having a simple structure.

[0013]

In order to solve the above problems, a signal transmission device according to the present invention comprises an insulating substrate, at least one ground electrode, at least one signal line electrode, and an insulating substrate. including. Each of the electrodes is provided on the insulating base. The insulating substrate is a composite member in which ferromagnetic metal powder and insulating resin are mixed.

Preferably, the ferromagnetic metal powder is iron. The particle size of the ferromagnetic metal powder is preferably 0.01
It is in the range of μm to 100 μm. The content of the ferromagnetic metal powder contained in the insulating substrate is preferably 30 vo
It is in the range of l% to 70 vol%. The insulating resin forming the insulating substrate is preferably epoxy, phenol or rubber.

[0015]

In the signal transmission device according to the present invention, since at least one ground electrode and at least one signal line electrode are provided on the insulating base, the ground electrode can be applied to a signal transmission path. Is grounded, and the signal line electrode is inserted into the signal transmission path to obtain a signal transmission element that performs signal transmission.

Since the insulating base is made of a composite material in which ferromagnetic metal powder and insulating resin are mixed, unnecessary high frequency components in the high frequency region contained in the frequency signal passing through the signal electrode are reliably absorbed by the insulating base. Can be absorbed by Specifically, it serves as a signal transmission element that causes an absorption action (high-frequency rejection) in a high frequency band of 1 GHz or higher, and passes a signal belonging to a frequency band lower than that (low-pass). Also,
The impedance can be made substantially constant up to a frequency of about 20 GHz, and the reflection can be set to about -10 dB. Therefore, the signal transmission element according to the present invention is suitable for use as a low-pass filter.

Moreover, the insulating substrate for absorbing the high frequency component is a composite member in which ferromagnetic metal powder and insulating resin are mixed,
Since the grounding electrode and the signal line electrode are provided on the insulating base, the structure is extremely simplified.

The low-pass and high-pass blocking mechanism of the signal transmission device according to the present invention is as follows.

In the transmission line, the reflection gain S11 (ω) and the transmission gain S21 (ω) are expressed by the following equations, where Γ is the reflectance of the element and T is the transmittance.

S11 (ω) = (1−T² ) Γ / (1 ー T² Γ²) S21 (ω) = (1 ー Γ²) T / (1-T² Γ²) Γ = {(μ_eff/ ε_eff  )^1/2 ー Zo} / {(μ_eff/ ε_eff )^1/2 + Zo
 } T = exp {-iω (ε_effμ_eff)^1/2Expressed as x}. Where ε_effIs the complex effective permittivity of the material,
μ_effIs the complex effective permeability of the material. Complex effective permittivity
ε_effAnd complex effective permeability μ_effIs actually a complex of materials
It is a combination of permittivity and complex permeability with shape factors.
It Zo is the characteristic impedance of the circuit.

First, in order to cause absorption in the high frequency region, the transmittance T must be close to zero. The condition is that (ε _eff μ _eff ) becomes negative in an imaginary number or a real number. That is, the imaginary number component of either or both of ε _eff and μ _eff exists, and the greater the value, the greater the absorption in the transmission line. In other words, the material loss angle (tan δ) increases at high frequencies.

Further, the reflectance Γ must be close to zero in order to reduce the reflection over all frequencies (to reduce S11). Therefore, (μ _eff / ε _eff ) ^1/2 needs to be close to the characteristic impedance Zo over all frequencies.

In the case of the absorption phenomenon due to ferrite or the like, generally, the imaginary number component becomes zero at about 2 GHz, and the transmittance T
Becomes close to 1 in the high range, and as a result, the low-pass effect cannot be obtained.

On the other hand, the composite member used in the present invention has a remarkable absorption from about 1 GHz, and has an absorption even at 20 GHz or more, and also has a dielectric absorption. Therefore, unlike ferrite materials, the transmittance T is close to zero up to high frequencies.

In general, the real number components of the dielectric constant ε and the magnetic permeability μ decrease with frequency in the absorption region. Therefore, when there is absorption, the characteristic impedance Zo of the signal transmission element changes with frequency, and as a result, the reflectance Γ increases and the reflection becomes significant.

However, in the case of the composite member used in the present invention, although the magnetic permeability is remarkably decreased with an increase in frequency, at the same time, the dielectric constant is also decreased, and the change in impedance is reduced accordingly. As a result, less reflection occurs. Therefore, it is possible to realize a low-pass filter that exhibits a high-frequency blocking effect by absorption in a high-frequency region, and it is possible to obtain a signal transmission element with less reflection.

In the present invention, a preferred example of the ferromagnetic metal powder is iron powder. Other than iron, other ferromagnetic metal powder such as nickel or cobalt can also be used. These ferromagnetic metal powders may be used alone or in combination. The insulating resin to be mixed with the ferromagnetic metal powder may be of any type, but it has been confirmed that good characteristics can be obtained with a phenol type, an epoxy type or a rubber type. These insulating resins can be used alone or in combination.

When iron is used as the ferromagnetic metal powder, the particle size is preferably in the range of 0.01 μm to 100 μm, and the content thereof is preferably in the range of 30 vol% to 70 vol%. If the particle size of the ferromagnetic metal powder is smaller than 0.01 μm, not only a sufficient absorption effect cannot be obtained, but also the insulating resin cannot be sufficiently kneaded, and a uniform signal transmission element with uniform characteristics can be obtained. Hard to get. On the other hand, when the particle size of the ferromagnetic metal powder is larger than 100 μm, the surface of the insulating substrate is roughened and it becomes impossible to form a good electrode. Also,
The particle size becomes large, making it difficult to handle in practice. The more preferable range of the particle size of the ferromagnetic metal powder is 0.1 μm to 10 μm.
Is.

If the content of the ferromagnetic metal powder is less than 30 vol%, sufficient attenuation cannot be obtained. When the content of the ferromagnetic metal powder is more than 70 vol%, it becomes difficult to uniformly mix it with the resin, and the insulation resistance between the electrodes is significantly deteriorated. A more preferable composition range of the content of the ferromagnetic metal powder is 40 vol% to 63 vol%.

[0030]

1 is a perspective view of a signal transmission device according to the present invention. The signal transmission element according to the present invention includes at least one ground electrode 1, at least one signal line electrode 2, and
The insulating base 3 is included. The ground electrode 1 and the signal line electrode 2 are provided on the insulating base 3 with a space therebetween.
In the embodiment, the ground electrode 1 is provided on one surface of the insulating substrate 3, and the signal line electrode 2 is provided on the other surface of the insulating substrate 3.

The insulating substrate 3 is a composite member in which ferromagnetic metal powder and insulating resin are mixed. The ferromagnetic metal powder is iron. When the starting material is a powder having a relatively large particle size, several commercially available iron powders are sieved through a mesh, and when the particle size is small, spherical iron synthesized from an intermetallic compound can be used. This iron is known as carbonyl iron, and in the present invention, it is used in an amount of 0.01 μm to 10 μm.
Various particle sizes can be selected over 0 μm. On the other hand, the insulating resin used at the same time is one kind selected from phenol-based, epoxy-based or rubber-based.

Next, a method for manufacturing the signal transmission element will be briefly described. First, the ferromagnetic metal powder and the insulating resin are mixed respectively, and by pressing, the length is 10 mm, the width is 5 mm, and the height is 30 mm.
A rectangular parallelepiped sample was formed. Next, this sample was subjected to an appropriate heat treatment to cure the insulating resin to obtain a composite member. Furthermore, after adjusting this sample to a thickness of 0.4 mm, an insulating substrate 3 was obtained by cutting out. The insulating base 3 is
Length L1 is 10 mm, width W1 is 5 mm, thickness H1 is 0.4 mm
Met. The ground electrode 1 is formed on the entire surface of one side of the insulating base 3.
And the signal line electrode 2 was formed on the other opposite surface. The ground electrode 1 and the signal line electrode 2 can be formed by vacuum vapor deposition, for example. The electrode composition material of the signal line electrode 2 was adjusted so that the characteristic impedance of the element was 50Ω. Thereby, the line width W of the signal line electrode 2
No. 2 was 0.3 mm to 0.8 mm, and a signal transmission element having a microstrip line structure with a line length of 10 mm was obtained.

In order to evaluate the characteristics of the signal transmission element, the transmission characteristics S11, S21 of the composite member forming the insulating base 3 are described.
Was measured and evaluated by comparison with the transmission characteristics S11 and S21 of the conventional insulating substrate material. As a sample for the comparative example, a high frequency ferrite material and a rubber-ferrite composite member were used.

A network analyzer HP8720C (manufactured by Hewlett and Packard) and a measurement jig HP83040 (manufactured by Hewlett and Packard) were used to evaluate the signal transmission element. In addition, the complex permittivity of the material,
The complex magnetic permeability is measured by using an impedance analyzer HP4291A (manufactured by Hewlett Packard) by forming a parallel plate capacitor and a toroidal core up to 1 GHz, and by inserting the toroidal core into the air rising above 1 GHz. It was measured with a network analyzer HP8720C (manufactured by Hewlett and Packard) using HP85071A (manufactured by Hewlett and Packard).

FIG. 2 is a diagram showing the complex magnetic permeability characteristics of an iron-phenol resin composite member (iron 60 vol%, particle size 2 μm),
Fig. 3 shows the same iron-phenol resin composite member (iron 60vol)
%, Particle diameter 2 μm). FIG. 4 and 5 are diagrams showing the complex magnetic permeability characteristic and the complex dielectric constant characteristic of the conventional NiZn ferrite, respectively.
In the figure, the horizontal axis represents frequency, and the vertical axis represents relative permeability μ or relative permittivity ε and loss angle δ.

In the case of iron-phenol resin composite member, GH
In the z region, the permeability loss angle δ (FIG. 2) and the permittivity loss angle δ (FIG. 3) increase, and they continue up to the high frequency region. The relative permeability μ decreases as the loss angle δ increases (FIG. 2). Also, it can be seen that the relative permittivity ε also gradually decreases (FIG. 3).

On the other hand, in the case of NiZn ferrite, as shown in FIG. 4, the loss angle δ associated with the magnetic permeability has a large value at about 1 GHz, and becomes almost zero in a frequency range higher than that. Along with this, the relative magnetic permeability μ also significantly decreases in the GHz region, and approaches to 1. Further, as shown in FIG. 5, the relative permittivity ε tends to be slightly decreased, and the change in the loss angle δ is very small. Therefore, when the insulating substrate is made of NiZn ferrite, there is a GHz region where the filter characteristic is lost.

FIG. 6 shows an iron-phenol resin composite member (iron 6
It is a figure which shows the transmission characteristic at the time of using 0 vol%, a particle size of 2 micrometers, and the sample of FIG. 2 and FIG. As shown in the figure, in the transmission characteristic S21, the attenuation becomes remarkable from about 1 GHz, and this attenuation continues up to the measurement upper limit of 20 GHz, and a low pass filter is obtained. It can be seen that the reflection characteristic S11 has an attenuation of about −10 dB up to about 10 GHz, and the reflection is sufficiently suppressed.

FIG. 7 is a diagram showing transmission characteristics when a conventional NiZn type ferrite is used. In the transmission characteristic S21, attenuation is observed at about 1 GHz, but attenuation is reduced again at frequencies higher than that, and low-pass characteristics cannot be obtained.

FIG. 8 is a diagram showing transmission characteristics when a conventional NiZn-based ferrite rubber-based resin composite member is used.
In this case as well, similar to FIG. 7, the low-pass characteristic cannot be obtained.

FIG. 9 is a diagram collectively showing the evaluation results of the transmission characteristics of the respective elements of sample Nos. 1 to 38 obtained by using iron as the ferromagnetic metal powder and varying its particle size and content. is there. The transmission characteristics S11 and S12 were evaluated by the gain of the transmission characteristics S11 and S21 in each case, with the passband frequency being 100 MHz and the stopband frequency being 5 GHz. As the insulating resin, phenol, epoxy, or rubber type was used as appropriate.

Sample Nos. 2 to 13, 17 to 23, 29 to 35 containing iron powder having a particle size of 0.01 to 100 μm in a content range of 30 to 70 vol%.
Has a transmission gain S21 of −100 at a pass band frequency of 100 MHz.
0.2 dB or -0.3 dB, stop band frequency 5 GHz
-15 dB to 45 dB, pass band frequency 100M
The attenuation at Hz is small, and the attenuation at the stop band frequency of 5 GHz is large. Further, the reflection gain S11 is in the range of −22 dB to −26 dB at the pass band frequency of 100 MHz,
The stop band frequency is 5 GHz and is in the range of -9 dB to -12 dB.

On the other hand, sample number 1 using iron powder with a particle size of 0.005 μm, sample number 14 using iron powder with a particle size of 200 μm, and the content of iron powder from 30 vol% to 70 vol
Sample numbers 15, 16, 24-28, 3 not in the 1% range
6 to 38 are transmission gain S21 or reflection gain S1 at a pass band frequency of 100 MHz and a stop band frequency of 5 GHz.
In any one of 1), deterioration is recognized. Therefore, 30 vo of iron powder with a particle size in the range of 0.01 μm to 100 μm is used.
It is preferably contained in the range of 1% to 70 vol%. In addition, there is almost no difference in characteristics depending on the type of insulating resin.

10 and 11 are perspective views of another embodiment of the signal transmission device according to the present invention. In the figure, the same reference numerals as those in FIG. 1 denote the same components. FIG.
In the embodiment of No. 0, the ground electrode 1 is provided from one surface to the other surface of the insulating substrate 3, and is provided at a distance d from the signal line electrode 2. In the embodiment of FIG. 11, the signal line electrode 2
1, 22 are provided on the side surface of the insulating base 3.

FIG. 12 is a perspective view of another embodiment of the signal transmission device according to the present invention. In the figure, a ground electrode 1
1 and 12 are provided on opposite sides of the insulating substrate 3, and the signal line electrode 2 is a triplate-type signal transmission element that is embedded in the insulating substrate 3 so as to face the ground electrodes 11 and 12. There is. The signal line electrode 2 has a line width W4 of 1 m.
m, and the line thickness t is 30 μm. The insulating substrate 3 is an iron-phenol resin composite member (iron 50 vol%, particle size 2 μm).
m), width W3 is 4 mm, thickness H3 is 3.5 mm,
The length L3 is 3.2 mm. Although not shown, another grounding electrode may be provided on the side surface and the grounding electrodes may be provided on four surfaces.

FIG. 13 is a diagram showing the transmission characteristics of the signal transmission element shown in FIG. As shown, the transmission characteristic S21
In Fig. 2, the attenuation becomes remarkable from about 1 GHz, and sufficient attenuation characteristics can be obtained even at 20 GHz which is the upper limit of measurement, and the filter becomes a low-pass filter. In the reflection characteristic S11, there is attenuation of about −10 dB up to about 10 GHz, and reflection is sufficiently suppressed.

FIG. 14 is a perspective view of another embodiment of the signal transmission device according to the present invention. In the figure, the signal line electrode 2
Is made of a copper wire having a diameter d1 of 0.2 mm. The insulating substrate 3 is an iron-phenol resin composite member (iron 50 vol.
%, Particle size 2 μm), width W5 is 4 mm, thickness H5
Is 3.5 mm and the length L5 is 10 mm.

FIG. 15 is a diagram showing the transmission characteristics of the signal transmission element shown in FIG. As shown, the transmission characteristic S21
In Fig. 2, it is found that the attenuation becomes remarkable from about 1 GHz, and this attenuation characteristic continues until the upper limit of measurement of 20 GHz, and the filter becomes a low-pass filter. In the reflection characteristic S11, there is attenuation of about −10 dB up to about 10 GHz, and reflection is sufficiently suppressed.

[0049]

As described above, according to the present invention, the following effects can be obtained. (A) It is possible to provide a signal transmission element having high-frequency blocking and low-pass characteristics that can reliably absorb high-frequency components in the high-frequency region. (B) It is possible to provide a signal transmission element having high-frequency blocking and low-pass characteristics that can reliably absorb high-frequency components of 1 GHz or higher. (C) It is possible to provide a signal transmission element having a simple structure.

[Brief description of drawings]

FIG. 1 is a perspective view of a signal transmission device according to the present invention.

FIG. 2 is a diagram showing frequency-complex magnetic permeability characteristics of an iron-phenol resin composite member.

FIG. 3 is a diagram showing frequency-complex dielectric constant characteristics of an iron-phenol resin composite member.

FIG. 4 is a diagram showing frequency-complex magnetic permeability characteristics of a conventional NiZn ferrite.

FIG. 5 is a diagram showing frequency-complex dielectric constant characteristics of a conventional NiZn ferrite.

FIG. 6 is a diagram showing transmission characteristics when an iron-phenol resin composite member is used.

FIG. 7 is a diagram showing transmission characteristics when a conventional NiZn-based ferrite is used.

FIG. 8 is a diagram showing transmission characteristics when a conventional NiZn-based ferrite rubber-based resin composite member is used.

FIG. 9 is a diagram collectively showing evaluation results of transmission characteristics of each element.

FIG. 10 is a perspective view of another embodiment of the signal transmission device according to the present invention.

FIG. 11 is a perspective view of another embodiment of the signal transmission device according to the present invention.

FIG. 12 is a perspective view of another embodiment of the signal transmission device according to the present invention.

13 is a diagram showing transmission characteristics of the signal transmission element shown in FIG.

FIG. 14 is a perspective view of another embodiment of the signal transmission device according to the present invention.

15 is a diagram showing transmission characteristics of the signal transmission device shown in FIG.

[Explanation of symbols]

 1 ground electrode 2 signal line electrode 3 insulating substrate

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Makoto Kobayashi 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDC Corporation (72) Inventor Taro Miura 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDC Co., Ltd. (72) Inventor Yasushi Iijima 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDC Corporation (72) Inventor Takahide Kurahashi 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDC Corporation

Claims (5)

[Claims] 1. A signal transmission element including at least one ground electrode, at least one signal line electrode, and an insulating base, wherein each of the electrodes is provided on the insulating base, The insulating base is a signal transmission element made of a composite material in which ferromagnetic metal powder and insulating resin are mixed. 2. The signal transmission element according to claim 1, wherein the signal transmission element is used as a low-pass filter. 3. The signal transmission device according to claim 1, wherein the ferromagnetic metal powder has a particle size of 0.01 μm to 10 μm.
Signal transmission element in the range of 0 μm. 4. The signal transmission device according to claim 1, wherein the insulating base has a content of the ferromagnetic metal powder of 30 vol.
% To 70vol% signal transmission element. 5. The signal transmission element according to claim 1, wherein the insulating resin is at least one of epoxy, phenol, and rubber.