JPH1114679A - High-frequency current detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure a high-frequency current in terms of vector with a strong directivity by using a connector for connecting one edge part of a conductor to a coaxial cable and a connector for connecting the other edge part of the conductor to a junction resistor to as a common axis. SOLUTION: No metal wall exists on the bottom surface of a box-shaped metal case 1 in a rectangular parallelepiped shape and an insulation plate 2 is installed on it. Coaxial connectors 4a and 4b are installed on the front and rear surfaces of the box-shaped metal case 1 and both connectors 4a and 4b have the same central axis. A connection wire 3 is in linear shape and its center axis is the same as that of the coaxial connectors 4a and 4b. The connection line 3 and the coaxial connectors 4a and 4b are installed nearly at the center part of the internal space of the box-shaped metal case 1. Also, the sectional shape of the connection line 3 is circular, and a taper is provided on both end faces as nearly conical shapes 7a and 7b and is connected to the coaxial connectors 4a and 4b. The sectional shape of the inner surface of the box-shaped metal case 1 is in nearly square shape.

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 detecting device for detecting a high-frequency current flowing on a metal surface of a housing or the like housing electric equipment, and more particularly to a high-frequency current detecting device having an accurate current waveform and strong directivity. The present invention relates to a high-frequency current detection device for detecting a high-frequency current in a vector manner.

[0002]

2. Description of the Related Art Effective use of electromagnetic energy is an important issue at present as the technology for comprehensively utilizing electromagnetic energy has been highly developed. However, at present, the use of electromagnetic energy is accompanied by unnecessary radiation of electromagnetic energy to some extent. It is an important issue to elucidate the mechanism of generation of this unnecessary radiated electromagnetic energy. For example, when unnecessary electromagnetic waves are radiated from an electrical device, to find the source of the unwanted electromagnetic wave on the housing that houses the device, the high-frequency current flowing on the housing is detected as a vector with strong directivity. By doing so, the source can be detected.

A conventional high-frequency current detecting device for detecting a high-frequency current flowing in a metal surface of a housing or the like in a vector manner is disclosed in, for example, the Transactions of the Institute of Electronics and Communication Engineers, 83/3 Vol.
66-B No. 3 ”is introduced in detail.

The structure of this conventional high-frequency current detecting device will be described with reference to FIG. On the bottom surface of the rectangular parallelepiped metal case 1, there is no metal wall, and the insulating plate 2 is provided. In the metal case 1, a coupling wire 3 composed of a flat metal conductor is installed in parallel with the bottom surface of the insulating plate 2, and both ends thereof are electrically and electrically connected to the core wires of the coaxial cables 5a and 5b, respectively. Mechanically connected. 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 metal case 1, respectively, and the other ends of the coaxial cables 5a and 5b are connected to the coaxial connectors 4a and 4b, respectively.

When such a high-frequency current detector is used, a matching resistor (termination resistor) not shown is connected to the connector 4b, a coaxial cable for signal transmission not shown is connected to the connector 4a, and the other end is used for waveform observation. Connect to the device. In this state, if the detecting device is installed so that the insulating plate 2 is in close contact with the metal surface on which the high-frequency current to be measured flows,
The high-frequency current can be measured as introduced in the literature.

At this time, in order to detect the high-frequency current waveform accurately and with strong directivity and to detect it in a vector, the characteristic impedance of the flat coupling line 3 between the plate-shaped coupling line 3 and the metal surface to be measured (not shown) is considered. Is exactly coaxial cable 5
a, 5b, the coaxial connectors 4a, 4b, the matching resistance (not shown), and the characteristic impedance of the coaxial cable for signal transmission. The description of this point is described in detail in the above-mentioned paper, and is omitted here.

[0007]

However, the above-mentioned conventional high-frequency current detecting device has various problems.
That is, for various reasons (1) to (3) described below, it has been found that it is difficult to match (match) the characteristic impedance between the coupling line 3 and the metal surface to be measured. (1) The connection between the coupling wire 3 and the coaxial cables 5a, 5b is 90 °
It is bent and the characteristic impedance is disturbed at the end of the coupling line 3.

(2) Since the coupling line 3 is located at a considerably offset position of the metal case 1 and is in the immediate vicinity of the insulating plate 2 constituting the bottom surface, if the position changes even a little, the characteristic impedance greatly changes. Not only is a dimensional error in the production of the measuring device a problem, but also a gap between the two when the measuring device is installed on a metal plate through which a high-frequency current flows. Therefore, when the metal plate is not perfectly flat, alignment cannot be achieved.

(3) Since the coupling wire 3 is flat, it is difficult to theoretically calculate the characteristic impedance, and it is not only difficult to design the device, but also the characteristic impedance greatly changes even with a small dimensional error. I do.

The present invention (corresponding to claims 1 to 8) provides
It was made to solve the above-mentioned problems of the prior art,
An object of the present invention is to provide a high-frequency current detection device capable of measuring a high-frequency current in a vector with strong directivity by adopting a structure in which characteristic impedance of a coupling line can be easily matched.

[0011]

In order to achieve the above object, a first aspect of the present invention is to install a metal conductor as a coupling line substantially parallel to a portion of a box-shaped metal case lacking one plane. In a high-frequency current detection device, a connector for connecting a coaxial cable to one end of the conductor and a connector for connecting a matching resistor to the other end of the conductor are configured to have a common central axis. It is characterized by having done.

According to a second aspect of the present invention, in the high-frequency current detecting device according to the first aspect, the coupling line is provided at a central portion of the box-shaped metal case. According to a third aspect of the present invention, in the high-frequency current detecting device according to the first aspect, a cross section of the coupling line is circular.

According to a fourth aspect of the present invention, in the high-frequency current detecting device according to the first aspect, an end of the coupling line has a conical shape whose radius is gradually reduced. According to a fifth aspect of the present invention, in the high-frequency current detecting device according to the first aspect, a cross section of the box-shaped metal case is substantially square.

According to a sixth aspect of the present invention, in the high-frequency current detecting device according to the first aspect, when a plane lacking the plane of the box-shaped metal case is used as a bottom surface of the case, the positional relationship is perpendicular to the coupling line. The two side surfaces are in contact with the bottom surface, and a gap is provided between the two side surfaces and the bottom surface in a positional relationship parallel to the coupling line.

According to a seventh aspect of the present invention, in the high-frequency current detecting device according to the first aspect, a gap provided between the two side surfaces and the bottom surface in a positional relationship parallel to the coupling line has a taper at an end thereof. It is characterized by attaching.

According to an eighth aspect of the present invention, in the high-frequency current detecting device according to the first aspect, the metal plate forming two side surfaces which are perpendicular to the upper surface of the box-shaped metal case and the coupling line is the same as the above. 2 in a positional relationship parallel to the bond line
It is characterized by protruding from the installation position on the side.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a high-frequency current detecting device according to a first embodiment (corresponding to claims 1 to 5) of the present invention. FIG. 1 (a) is a side view, and FIG. 2) is a longitudinal sectional view as seen from AA.

As shown in FIG. 1, a rectangular parallelepiped box-shaped metal case 1 has no metal wall on the bottom surface, and an insulating plate 2 is provided. Coaxial connectors 4a and 4b are installed on the front and rear metal walls of the metal case 1, and both connectors 4a and 4b are provided.
b have the same central axis. The coupling line 3 is linear and its central axis is the same as the central axis of the coaxial connectors 4a and 4b. The coupling wire 3 and the coaxial connectors 4a and 4b are installed at substantially the center of the internal space of the box-shaped metal case 1.
The cross-sectional shape of the coupling wire 3 is circular, and both ends are tapered to be connected to the coaxial connectors 4a and 4b as substantially conical shapes 7a and 7b, respectively. The inner surface of the box-shaped metal case 1 has a substantially square cross-sectional shape. Note that the method of using the high-frequency current detection device of the present embodiment is as follows.
The description is omitted because it is the same as the conventional high-frequency current detection device.

Next, the operation of the present embodiment will be described.
Since the coupling wire 3 and the coaxial connectors 4a and 4b have a common central axis, the connection between the three members is in the most ideal state, and the end of the coupling wire 3, that is, the coaxial connector 4a
Disturbance of the characteristic impedance at the connection portion with a and 4b can be reduced.

The central portion of the internal space of the box-shaped metal case 1 is a place where the characteristic impedance of the coupling line 3 with respect to the surrounding metal is minimized, which is caused by a change in the position of the coupling line 3. This means that the change in the characteristic impedance is the smallest. Therefore, even if the position of the coupling line slightly changes due to a dimensional error in manufacturing or the state of the metal surface to be measured, a change in characteristic impedance can be minimized.

Further, the circular shape is the shape in which the theoretical value of the characteristic impedance is most easily calculated, and the design becomes easy, and at the same time, the condition is the same in all directions. The characteristic impedance does not greatly change due to the displacement, and the change in the characteristic impedance can be minimized even with a slight dimensional error in manufacturing.

Further, since the end of the coupling wire 3 is close to the front and rear metal walls of the box-shaped metal case 1, the characteristic impedance of this portion tends to be small. Therefore,
By forming both ends of the connection line into substantially conical shapes 7a and 7b, disturbance of the characteristic impedance at the end of the connection line 3 affected by the metal walls on the front and rear surfaces of the box-shaped metal case 1 can be minimized. .

Furthermore, although it is easiest to theoretically calculate the cross-sectional shape of the internal space of the box-shaped metal case 1 in a circular shape, there are difficulties in manufacturing and inconvenience in use. By making the cross-sectional shape square, an action close to a circle can be obtained.

FIG. 2 is a side view of a high-frequency current detecting device according to a second embodiment (corresponding to claim 6) of the present invention. This embodiment differs from the first embodiment of FIG. 1 is a configuration in which notches are provided in metal walls constituting both side surfaces at locations where the side surfaces are in contact with the insulating plate 2, and a gap 6 is provided between both side surfaces and the insulating plate 2, and other configurations are the same. Therefore, the same parts will be described with the same reference numerals.

Next, the operation of this embodiment will be described.
The magnetic field component of the electromagnetic wave propagating in the maximum direction of the directivity of the high-frequency current detection device of the present embodiment is increased more in the detection device by providing a vertical gap on the side surface of the box-shaped metal case 1. invade. As described above, by providing a difference between the structures of the both sides and the front and rear surfaces of the box-shaped metal case 1, strong directivity can be provided.

FIG. 3 is a side view of a high-frequency current detecting device according to a third embodiment (corresponding to claim 7) of the present invention. This embodiment differs from the first embodiment of FIG. A notch is provided in a metal wall constituting both side surfaces at a place where the side surface of one is in contact with the insulating plate 2, a gap 6 is provided on both side surfaces between the insulating plates 2, and tapers 8 a and 8 b are formed at ends of the gap. Only the provided configuration is the same, and the other configurations are the same. Therefore, the same portions will be described with the same reference numerals.

Next, the operation of the present embodiment will be described.
Even if a gap is provided, more accurate waveform observation is possible by minimizing the disturbance of the electromagnetic field at the connection between the side surfaces and the front and rear surfaces of the box-shaped metal case 1 of the high-frequency current detection device of this embodiment. Becomes

FIG. 4 is a block diagram of a high-frequency current detecting device according to a fourth embodiment of the present invention (corresponding to claim 8).
Is a side view, and FIG. 2B is a front view. FIG. 1 shows this embodiment.
The first embodiment differs from the first embodiment in that the front surface of the box-shaped metal case 1
Only the configuration in which the rear and upper metal walls are protruded in the direction of both sides is the same, and other configurations are the same.

Next, the operation of this embodiment will be described.
The protruding metal wall of the box-shaped metal case 1 of the high-frequency current detection device of the present embodiment gives the detection device the effect of a shielding plate for electromagnetic waves traveling in an oblique direction, so that it has stronger directivity. be able to.

As described above, according to the high-frequency current detecting device of the present embodiment, by adopting a structure in which the characteristic impedance of the coupling line 3 can be easily matched, strong directivity, which is the original purpose of the high-frequency current detecting device, is achieved. It is possible to provide a high-frequency current detection device capable of measuring a high-frequency current in a vector with a characteristic.

[0031]

As described above, the present invention (Claim 1)
According to claim 8), it is possible to obtain an ideal and close to theoretical operation which is not affected by a slight dimensional error in the production or a mounting state of the device. The high-frequency current can be detected extremely easily. Further, it is possible to accurately measure the waveform of the high-frequency current. Furthermore, when the leaking place of high-frequency electromagnetic energy is clear and only this leaking high-frequency wave is detected, having strong directivity means that external noise entering from a random direction can be removed and a high SN ratio can be obtained. It is extremely advantageous in that it can be made.

[Brief description of the drawings]

FIGS. 1A and 1B are configuration diagrams of a first embodiment of the present invention, in which FIG. 1A is a side view, and FIG. 1B is a cross-sectional view taken along line AA of FIG.

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

FIG. 3 is a side view of a third embodiment of the present invention.

FIGS. 4A and 4B are configuration diagrams of a fourth embodiment of the present invention, wherein FIG. 4A is a side view and FIG. 4B is a front view.

FIG. 5 is a side view of a conventional high-frequency current detection device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Metal case, 2 ... Insulating plate, 3 ... Bonding wire, 4a, 4b
... coaxial connectors, 5a, 5b ... coaxial cables, 6 ... slits, 7a, 7b ... conical structures, 8a, 8b ... taper.

Claims (8)

[Claims] 1. A high-frequency current detection device comprising a metal conductor provided as a coupling wire substantially parallel to a portion of a box-shaped metal case lacking one plane, wherein one end of said conductor is connected to a coaxial cable. And a connector for connecting the other end of the conductor to the matching resistor as a common central axis. 2. The high-frequency current detection device according to claim 1, wherein the connection line is provided at a central portion of the box-shaped metal case. 3. The high-frequency current detection device according to claim 1, wherein a cross section of the coupling line is circular. 4. The high-frequency current detection device according to claim 1, wherein an end of the coupling line has a conical shape whose radius is gradually reduced. 5. The high-frequency current detection device according to claim 1, wherein the cross section of the box-shaped metal case is substantially square. 6. The high-frequency current detecting device according to claim 1, wherein when a plane lacking the plane of the box-shaped metal case is used as a bottom surface of the case, two side surfaces having a positional relationship perpendicular to the coupling line are the same. A high-frequency current detection device, characterized in that a gap is provided between two bottom surfaces, which are in contact with the bottom surface and have a positional relationship parallel to the coupling line, and the bottom surface. 7. The high-frequency current detecting device according to claim 1, wherein a gap provided between two side surfaces and a bottom surface in a positional relationship parallel to the coupling line is tapered at an end thereof. High-frequency current detector. 8. The high-frequency current detection device according to claim 1, wherein the metal plate forming the upper surface of the box-shaped metal case and two side surfaces having a positional relationship perpendicular to the coupling line is positioned parallel to the coupling line. A high-frequency current detection device protruding from installation positions of two side surfaces having a relationship.