JP2000009773A - High frequency current detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high frequency current detecting device which easily takes matching of a characteristic impedance in a bonding wire and capable of detecting at vector a high frequency current with an accurate and strong directivity. SOLUTION: In this current detecting device, a rectangular parallelopiped structure 6 comprising a metal block is provided. An insulating plate 7 is adhered closely and fixed to an upper surface of the structure 6 and an insulating film 2, comprising a PET film is adhered to a bottom surface thereof. Then, a bonding wire 3 comprising a flat metal conductor is disposed on an upper portion of the insulating plate 7 in parallel with the upper surface of the structure 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency current detector for detecting a high-frequency current flowing on the surface of a metal case housing an electric device in a vector manner, and more particularly to detecting a high-frequency current with high accuracy and directivity. The present invention relates to a high-frequency current detection device.

[0002]

2. Description of the Related Art In recent years, in the field of electric equipment, comprehensive utilization technology of electromagnetic energy has been remarkably developed, and effective utilization of electromagnetic energy has become a serious concern.
However, when electromagnetic energy is used for electrical equipment, it is known that electromagnetic energy is emitted from the electrical equipment to a greater or lesser extent. Therefore, the mechanism of generation of the unnecessary energy radiation is being elucidated. For example, in order to detect a source of energy radiation, a high-frequency current detection device that detects a high-frequency current flowing on the surface of a metal case housing an electric device in a vector manner is used. In addition, when the place where the high-frequency electromagnetic energy leaks is clear, and when it is desired to detect only the leaking high-frequency current, having strong directivity can eliminate external noise entering from a random direction and obtain a high SN ratio. It is extremely advantageous in that it can be made. Therefore, a high-frequency current detection device is required to have accurate and strong directivity.

Here, the structure of a conventional high-frequency current detecting device will be specifically described with reference to FIG. A hollow rectangular parallelepiped case 1 is provided in the high-frequency current detection device. In the rectangular parallelepiped case 1, four front, rear, left and right side surfaces and an upper surface are formed of metal walls, and a bottom surface is formed of an insulating plate 12 instead of a metal wall. Further, inside the rectangular parallelepiped case 1, a coupling wire 3 made of a flat metal conductor is arranged near the insulating plate 12. The coupling wire 3 is disposed substantially parallel to the insulating plate 12, and the core wires of the coaxial cables 5a and 5b are electrically and mechanically connected to both ends. The outer conductors of the coaxial cables 5a and 5b are electrically and mechanically connected and fixed to the front and rear surfaces of the rectangular parallelepiped case 1. Further, coaxial connectors 4a and 4b are connected to the other ends of the coaxial cables 5a and 5b, respectively. These coaxial connectors 4a, 4b are
It is arranged on the upper surface of.

When the above-described high-frequency current detector is used, a matching resistor (terminal resistor, not shown) is connected to the connector 4b, and a measuring cable for signal transmission (not shown) is connected to the connector 4a. Then, the end of the signal transmission measurement cable is connected to the waveform observation device. In this state, the insulating plate 12 is brought into close contact with the metal plate to be measured m, which is the surface of a metal case (in which the electrical equipment is housed) through which the high-frequency current flows, and the high-frequency current on the surface of the metal plate m can be detected and measured.

The basic principle of the above high-frequency current detecting device is as follows.
IEICE Transactions on 83/3 Vol.J66-BN
o. 3 ”is introduced in detail. This basic principle will be described with reference to the model shown in FIG. In FIG. 10, the connection line 3 is arranged above the metal plate m to be measured (one plane of the metal case housing the electrical equipment) so that the two are parallel to each other. It is connected to the metal plate m to be measured at Z1 and Z2 (Z1 = Z2 = Z). At this time, the characteristic impedance of the distributed constant line formed by the coupling line 3 and the metal plate m is W. In such a system, when a plane wave arrives in a mode parallel to the metal plate m to be measured, the current induced in the loads Z1 and Z2 can be analytically given.

Now, a: the length of the distributed constant line is sufficiently short with respect to the wavelength of the plane wave. b: The characteristic impedance W of the distributed constant line is equal to the value Z of the load. When the analytical expression is approximated under the conditions of a and b, the following conclusions can be obtained. That is, for a plane wave traveling in parallel to the distributed constant line formed by the coupling line 3 and the metal plate m to be measured, an induced current flows through the load Z1 in the arrival direction of the plane wave, but flows through the load Z2 on the opposite side. Has no induced current. The above is the basic principle of the high-frequency current detection device. Based on such a basic principle, the high-frequency current detection device has strong directivity and can detect the traveling direction and magnitude of a plane wave arriving in a mode parallel to the metal plate m to be measured in a vector manner. .

[0007]

By the way, in order to detect the waveform of the high-frequency current flowing on the surface of the metal plate m to be measured in a vector with an accurate and strong directivity, the characteristic impedance of the coupling line 3 must always be appropriately adjusted. It is important to keep it at a reasonable value. For this purpose, it is necessary to minimize the coupling of the coupling line 3 with only the high-frequency electromagnetic field flowing on the metal plate m to be measured, and with other external electromagnetic fields. Therefore, in the above document, as shown in FIG. 9, a rectangular parallelepiped case 1 having side walls and an upper surface made of metal walls is provided.
It proposes a method for housing the coupling line 3 inside.

However, in such a high-frequency current detecting device, for the following reasons (1) and (2), the characteristic impedance that the coupling line 3 has with the metal plate m to be measured can be maintained at an appropriate value. It was difficult. (1) In the high-frequency current detecting device shown in FIG.
Are located in the case 1, such as in the immediate vicinity of the insulating plate 12 constituting the bottom surface of the rectangular parallelepiped case 1. For this reason, even if the position of the coupling line 3 changes even a little, the characteristic impedance between it and the metal plate m to be measured greatly changes. In addition, the characteristic impedance with the rectangular parallelepiped case 1 also changes greatly. This causes not only the problem of dimensional errors in manufacturing the rectangular parallelepiped case 1 as a cause of changing the characteristic impedance, but also the size of the gap between the two when the device itself is arranged on the metal plate to be measured (for example, This means that irregularities on the surface of the metal plate m to be measured and errors in the thickness of the coating are serious problems, and the coupling line 3 must always maintain an appropriate value of the characteristic impedance with the metal plate m to be measured. Became difficult.

(2) In the high-frequency current detecting device shown in FIG. 9, the coupling line 3 is connected to the metal plate m to be measured with a predetermined characteristic impedance, and is also connected to the metal walls on the side and top surfaces of the rectangular parallelepiped case 1. Become. In addition, a matching resistor (termination resistor) and a measurement cable are connected to the upper surface of the rectangular parallelepiped case 1 via coaxial connectors 4a and 4b. Therefore, in the high-frequency current detection device, the three members, the coupling line 3, the rectangular parallelepiped case 1, and the metal plate m to be measured, interfere with each other. As a result, there is a problem of a three-conductor system that cannot be expressed by a simple two-conductor system such as the coupling line 3 and the metal plate m to be measured as shown in the basic principle of FIG. It is well known that there is a difference between the two-dimensional problem and the three-dimensional problem in the difficulty of solving the problem, but it is extremely difficult to analyze the conventional example, which can be expressed only by a three-conductor system, and the coupling line 3 is desired. The design method for obtaining the characteristic impedance of the EMI could not be established.

The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to eliminate the connection between a connecting wire and a metal plate to be measured and to make them completely electrically independent. It is another object of the present invention to provide a high-frequency current detecting device which can easily match characteristic impedances in a coupling line and can detect a high-frequency current in a vector with an accurate and strong directivity.

[0011]

In order to achieve the above-mentioned object, a first aspect of the present invention is to provide a rectangular parallelepiped structure made of metal, in which the metal plate to be measured faces a surface to which the metal plate to be measured is in close contact. It is characterized in that a coupling line (consisting of a flat metal conductor) electrically insulated from the structure is arranged on the mating plane in parallel with one plane of the structure. According to the first aspect of the present invention, since the connection line is located on a plane opposite to the surface on which the metal plate to be measured is in close contact, the connection line is less likely to be bonded to the metal plate to be measured, and is not connected to the structure. Will only be combined. That is, the coupling between the coupling line and the metal plate to be measured is eliminated, and both are completely electrically independent, so that the characteristic impedance of the coupling line can be easily matched. Also, since the characteristic impedance of the coupling line is not affected by the surface condition of the metal plate to be measured, once it is adjusted, the constant value can always be maintained, and the high-frequency current can be accurately and strongly directed. Vector detection is possible.

According to a second aspect of the present invention, in the high-frequency current detecting device according to the first aspect, an insulating layer is formed on a surface of the structure to which the metal plate to be measured adheres. According to the second aspect of the present invention having this configuration, since the structure and the metal plate to be measured are in close contact with each other via the insulating layer, a very large floating capacitance is not affected by the surface condition of the metal plate to be measured. May exist between the structure and the metal plate to be measured. Therefore, it is possible to form a state in which the structure is closely coupled to the high-frequency current, and it is possible to make the state of coupling between the structure itself and the metal plate to be measured constant.

According to a third aspect of the present invention, in the high frequency current detecting device according to the second aspect, the insulating layer is formed of a polymer plastic film. According to the third aspect having such a configuration, the connection state between the structure and the metal plate to be measured is kept constant, and the measurement is performed even in an abnormal case where a leakage occurs in the metal case including the metal plate to be measured. It is possible to ensure safety for the user and to prevent the device itself from being damaged.

According to a fourth aspect of the present invention, in the high-frequency current detecting device according to the first, second or third aspect, a coaxial connector to which a matching resistor and a coaxial cable can be connected is provided on a side surface of the structure. And According to the fourth aspect of the invention, by using the coaxial connector, commercially available electronic parts can be used, and the manufacturing cost can be reduced.

According to a fifth aspect of the present invention, in the high-frequency current detector according to the first, second, third or fourth aspect, the length of the coupling line is set to be 80% or less of the length of the plane of the structure. It is characterized by the following. According to the fifth aspect of the invention, it is possible to reliably prevent the connection between the connection line and the metal plate to be measured.

[0016] Claim 6 of the present invention relates to Claims 1, 2, 3,
The high-frequency current detection device according to 4 or 5, wherein a magnet for fixing a structure is provided. Claim 6
According to the invention, the use of the magnet makes it possible to easily attach the detection device to the metal case that houses the electric device.

A seventh aspect of the present invention is characterized in that the structure is covered with a floating metal shield. According to the seventh aspect of the present invention, since the metal shield prevents the coupling line from coupling with the external electromagnetic field, the coupling line 3 can be coupled only with the high-frequency electromagnetic field flowing on the metal plate to be measured.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to the drawings. Note that FIG.
The same reference numerals are given to the same members as those of the conventional example shown in FIG.

(1) First Embodiment [Configuration] The first embodiment corresponds to the first to third aspects of the present invention, and FIG. 1 shows the configuration of the first embodiment. FIG. As shown in FIG. 1, a rectangular parallelepiped structure 6 made of a metal block is provided. This structure 6 is set to a size that occupies most of the volume of the detection device according to the first embodiment. The upper surface of the structure 6 is adhered and fixed to the insulating plate 7, and the lower surface thereof is made of PET.
An insulating film 2 made of a film is attached. Further, on the upper part of the insulating plate 7, the coupling line 3 made of a flat metal conductor is disposed substantially parallel to the upper surface of the structure 6. That is, the coupling wire 3 and the structure 6 are electrically insulated by the insulating plate 7.

Further, on one side of the structure 6, a matching resistor 8 is connected between the coupling line 3 and the structure 6, and on the opposite side, a coaxial cable 9 for signal propagation is provided between the coupling line 3 and the structure 6. Is connected. At this time, the core wire of the coaxial cable 9 is connected to the coupling wire 3, and the outer conductor is connected to the structure 6. Here, the characteristic impedance of the coupling wire 3 with respect to the structure 6, the resistance value of the matching resistor 8, and the characteristic impedance of the coaxial cable 9 are matched. Specifically, the width of the connection line 3 (the length in the direction perpendicular to the paper surface in FIG. 1) and the thickness of the insulating plate 7 (the distance between the connection line 3 and the structure 6) are maintained in an appropriate relationship. By installing, the connecting line 3 is
To a desired value.
In such an embodiment, the insulating film 2 is used for the metal plate m to be measured, which constitutes the metal case housing the electric equipment.
The surface to which is adhered is placed in close contact, and a high-frequency current is measured by measuring a signal transmitted through the coaxial cable 9.

[Operation and Effect] Next, the operation of the first embodiment will be described. In the first embodiment, since the bonding line 3 is firmly fixed on the surface of the structure 6 opposite to the surface to which the metal plate m to be measured is in close contact, the bonding line 3 is bonded to the metal plate to be measured. In short, it only couples with the structure 6, which occupies most of the volume of the detection device. Moreover, the characteristic impedance is not affected by the surface state of the metal plate m to be measured. Therefore, once adjusted, the constant value can always be maintained, and the high-frequency current can be detected vector-wise with accurate and strong directivity.

Further, since the structure 6 and the metal plate m to be measured are adhered to each other via the thin insulating film 2, a very large floating capacitance which is hardly influenced by the surface condition of the metal plate m to be measured. It will be between them. Therefore, a state of being tightly coupled to high-frequency current can be formed,
A fixed coupling state can be maintained.

By such an action, the coupling line 3 and the structure 6 are coupled with an appropriate characteristic impedance, the structure 6 is stably coupled to the metal plate m to be measured, and The plate m and the coupling line 3 are electrically independent. Therefore, the relationship among these three members (the coupling line 3, the structure 6, and the metal plate to be measured m) is not a problem of the three-conductor system but an analysis of the two-conductor system. Furthermore, the connection between the structure 6 and the metal plate m to be measured which are in close contact with each other via the insulating film 2 is considerably denser than the degree of the connection between the structure 6 and the connection line 3. Apparently, it can be regarded as a part of the metal plate m to be measured. Therefore, a configuration faithful to the basic principle of the high-frequency current detection device derived from the relationship between the coupling line 3 and the metal plate m to be measured can be obtained.

Further, in the first embodiment, the insulating film 2 is made of a film of a high insulating material such as a PET film so that it can be applied to a relatively low frequency voltage such as a commercial frequency. The insulation between the metal plate to be measured and the high-frequency current detection device can be ensured. Therefore, even when the high-frequency current detection device is used at the time of an abnormality such as an electric leakage in the metal case, excellent safety for the measurer can be ensured. Also, a great effect can be exerted on the detection device itself in terms of damage prevention.

(2) Second Embodiment [Structure] The second embodiment corresponds to the invention of claim 4, and FIG. 2 is a side sectional view showing the structure of the second embodiment. It is. As shown in FIG. 2, the second embodiment differs from the first embodiment of FIG. 1 in that the rectangular parallelepiped structure is not a metal block as in FIG. 1 but a metal plate. That is, the coaxial connectors 4a and 4b capable of connecting a matching resistor and a coaxial cable are disposed on the left and right side surfaces of the box-shaped structure 6a. The coaxial connectors 4a, 4b have lead wires 10a,
10b are connected, and the ends of these lead wires 10a, 10b penetrate through the upper surface of the structure 6a and the insulating plate 7 to form the coupling wire 3b.
It is connected to the. Since other configurations are the same, the same portions will be described with the same reference numerals.

[Effects] In the second embodiment having the above configuration, in the connection between the coupling line 3 and the structure 6a,
2, all the lead wires 10a and 10b for connecting a matching resistor and a coaxial cable (not shown) can be installed inside the structure 6a, and all the core wires other than the coupling wire 3 can be covered with metal. . Therefore, the influence of external noise can be minimized. Also, the coaxial connector 4
By using a and 4b, commercially available electronic parts can be used, and an inexpensive detection device can be provided.

[Modification of Second Embodiment] As a modification of the second embodiment corresponding to claim 4, as shown in a plan view of FIG. 3, coaxial connectors 4a and 4b are structured. Some are provided only on one side of the object 6a. When it is desired to simultaneously measure signals appearing at both ends of the coupling line 3, ie,
There are cases where it is desired to simultaneously measure an electromagnetic wave propagating from the right direction and an electromagnetic wave propagating from the left direction of the high-frequency current detection device.
At this time, in the embodiment shown in FIG. 3, since the coaxial connectors 4a and 4b are oriented in the same direction, the two coaxial cables connected to the connectors 4a and 4b are oriented in one direction. Not only is easier to handle, but also the coaxial cable is less likely to disturb the electromagnetic field distribution around the high-frequency current detector, and more accurate measurement is possible.

(3) Third Embodiment [Structure] As shown in FIG. 4, the third embodiment (corresponding to claim 5) is different from the second embodiment shown in FIG. The only difference is that the length of the coupling line 3 is limited, and the other configuration is the same. That is, in the fourth embodiment, the connection line 3
Is not more than 80% of the length L6 of the structure 6a.

[Effects] In the third embodiment described above, since the length L3 of the connection line 3 is set to be 80% or less of the length L6 of the structure 6a, the connection line 3 is formed of the structure 6a. When installed at the center of the upper surface, the ends of the structure 6a have a margin la, lb of at least 10% of the length L6 of the structure 6a. The margins la and lb are defined by the coupling line 3 and the metal plate m to be measured.
Has the effect of further reducing the coupling between In addition,
Experience has shown that the margins la and lb are sufficient if the length L6 of the structure 6a is about 10%.

(4) Fourth Embodiment [Configuration] A fourth embodiment shown in FIG. 5 (corresponding to claim 6).
Is characterized in that magnets 11a, 11b, 11c and 11d are attached to both ends of two opposite side surfaces (upper and lower surfaces in FIG. 5) of the structure 6a.

[Function and Effect] The fourth embodiment having the above-described configuration is described.
In the embodiment, the magnets 11a, 11b, 11c, 11
The function of d makes it extremely easy to attach the high-frequency current detector to the metal case that houses the electrical equipment.

[Modification of Fourth Embodiment] As a modification of the fourth embodiment corresponding to claim 6, a magnet 11
In some cases, e and 11f are provided inside the structure 6a (see FIG. 6). According to such an embodiment, the magnet 1
Structure 6a in which 1e and 11f are completely covered metal boxes
Because it is installed inside, the magnet does not disturb the electromagnetic field distribution around the high-frequency current detection device,
Accurate measurement becomes possible.

(5) Fifth Embodiment [Configuration] As shown in the side view of FIG. 7, in a fifth embodiment corresponding to claim 7, a metal shield 21 covering a structure 6a is provided. It is characterized by that. The metal shield 21 is attached to the structure 6a by the insulator supports 22a and 22b.
Is fixed in a floating state.

[Function and Effect] In the fifth embodiment, since the metal shield 21 has the function of blocking the plane wave directly entering the coupling line 3, it has the effect of removing external noise. In addition, the metal shield 21 is floated by being supported by insulating support members 22a and 22b, and is set apart from the coupling line 3 and the structure 6a. Therefore, the coupling line 3, the rectangular parallelepiped structure 6, and the covering It does not disturb the coupling state as a two-conductor system between the three measurement metal plates m.

[Modification of Fifth Embodiment] As a modification of the fourth embodiment corresponding to claim 7, as shown in FIG. 8, only the distal ends of the coaxial connectors 4a and 4b are metal shields. The metal shield 21 may be arranged so as to go outside the metal shield 21. According to such an embodiment, the connection work to the connectors 4a and 4b is easy.

[0036]

As described above, according to the high-frequency current detecting device of the present invention, the connection between the coupling line and the metal plate to be measured is eliminated and both are completely electrically independent, so that the Characteristic impedance matching can be easily achieved, and ideal and close to theoretical values can be obtained without being affected by slight dimensional errors in manufacturing or the state of equipment installation. High-frequency current was able to be detected.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a first embodiment of the present invention.

FIG. 2 is a side sectional view of a second embodiment of the present invention.

FIG. 3 is a plan view of a modified example of the second embodiment of the present invention.

FIG. 4 is a plan view of a third embodiment of the present invention.

FIG. 5 is a plan view of a fourth embodiment of the present invention.

FIG. 6 is a side sectional view of a modification of the fourth embodiment of the present invention.

FIG. 7 is a side view of a fifth embodiment of the present invention.

FIG. 8 is a side view of a modification of the fifth embodiment of the present invention.

FIG. 9 is a side view of a conventional high-frequency current detection device.

FIG. 10 is a basic principle diagram of a general high-frequency current detection device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Rectangular case 2 ... Insulating film 3 ... Coupling wire 4a, 4b ... Coaxial connector 5a, 5b ... Coaxial cable 6, 6a ... Structure 7 ... Insulating plate 8 ... Matching resistance 9 ... Coaxial cable 10a, 10b ... Lead wire 11a, 11b, 11c, 11d, 11e, 11f: magnet 21: metal shield 22a, 22b: insulating support

Claims (7)

[Claims] 1. A high-frequency current detector for detecting a vector of a high-frequency current flowing on the surface of a metal plate to be measured while being in close contact with the metal plate to be measured. In the apparatus, a rectangular parallelepiped structure made of metal is provided, and in this structure, a coupling line made of a flat metal conductor is formed on a plane facing a surface where the metal plate to be measured is in close contact with the structure. Is a high-frequency current detection device, which is electrically insulated and disposed in parallel with the plane. 2. The high-frequency current detection device according to claim 1, wherein an insulating layer is formed on a surface of the structure where the metal plate to be measured adheres. 3. The high-frequency current detecting device according to claim 2, wherein said insulating layer is made of a polymer plastic film. 4. The high-frequency current detection device according to claim 1, wherein a coaxial connector to which a matching resistor and a coaxial cable can be connected is provided on a side surface of the structure. 5. The connection line according to claim 1, wherein a length of the connection line is set to 80% or less of a length of a plane of the structure on which the connection line is provided. 3 or 4
The high-frequency current detection device according to claim 1. 6. The apparatus according to claim 1, wherein a magnet for fixing the structure is provided on the metal plate to be measured.
The high-frequency current detection device according to 2, 3, 4, or 5. 7. A metal shield for covering the structure in a floating state is provided.
7. The high-frequency current detection device according to 4, 5, or 6.