JP2702254B2 - Disturbance electromagnetic wave distribution measuring method and apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring the distribution of an interfering electromagnetic wave generated from an electronic device.

[Conventional technology]

Various types of radio interference caused by electromagnetic interference generated by electronic devices and the like causing electromagnetic interference to peripheral devices have become a problem. For this reason, it has become a social responsibility to manufacture and sell devices that suppress electromagnetic interference generated from devices and do not cause radio interference. In order to suppress this electromagnetic interference wave, it is most effective to specify the position where the electromagnetic interference wave generated from the device is generated and take measures.

Conventionally, the location of an interfering wave source in equipment is determined by using an electromagnetic field near the equipment (equipment) as a small dipole antenna or
This was performed by measuring using a small loop antenna. Although this method has an advantage that it can be easily used, it has a drawback that the reproducibility of the measurement is poor because the sensor is moved while being held by a person's hand, and that the detection of an interference wave source must rely on a person's skill. For this reason, a method of mechanically moving a sensor to obtain reproducibility of measurement has been attempted.

As one of the methods, a method has been attempted in which an electromagnetic field sensor is moved around an electronic device (equipment) using a robot, and the information is visually processed by computer processing. However, since this method moves the sensor three-dimensionally, in order to determine the movement position of the sensor,
It has the disadvantage of requiring a high degree of image processing.

As another method, a method of visually recognizing a large number of sensors arranged in a plane, electronically scanning the sensors, and processing the obtained information using a computer has been attempted. Have been.

This method has a structure in which a large number of electromagnetic field sensors are two-dimensionally arranged at intervals of 1 cm to 0.5 cm and are electronically scanned, so that electromagnetic coupling between adjacent sensors occurs. Variations in the reception characteristics of many sensors occur.
In order to connect a large number of sensors, it is necessary to wire a large number of cables in the apparatus, and there is a problem that the cables are coupled to each other.

[Problems to be solved by the invention]

It is an object of the present invention to solve the above disadvantages in the prior art.

That is, an object of the present invention is to provide a method and an apparatus for measuring the distribution of disturbed electromagnetic waves, which have reproducibility of measurement without depending on human skill, have small measurement errors, and have high measurement accuracy.

[Means for Solving the Problems] To achieve the above object, in the present invention, an electronic device is an object to be measured, and in a disturbance electromagnetic wave distribution measuring device for measuring a distribution of disturbance electromagnetic waves generated therefrom, Several holes with smaller dimensions compared to the size on the conductor surface,
The conductor plate (metal plate) pierced and an electromagnetic field component leaking from the object to be measured disposed near one surface of the conductor plate through a hole pierced in the conductor plate are connected to the conductor plate. An electromagnetic field sensor arranged near the other surface of the conductor plate and measuring the electromagnetic field component as an interfering electromagnetic wave, and measuring the electromagnetic field component by moving the electromagnetic field sensor to another position along the other surface of the conductor plate. An electromagnetic field sensor moving means to be repeated and a processing device for obtaining a disturbing electromagnetic wave distribution from an electromagnetic field component measured at each position are provided.

[Action]

First, a plurality of holes each having a size smaller than the size of an electronic device as an object to be measured are arranged on the conductor surface, and a perforated conductor plate (metal plate) is spatially arranged.

Next, an object to be measured is arranged near one surface of the conductor plate, and an electromagnetic field sensor is arranged near the other surface of the conductor plate. The electromagnetic field sensor measures an electromagnetic field component leaking from an object to be measured through a hole formed in the conductor plate as a disturbing electromagnetic wave. Further, the electromagnetic field sensor is moved to another position along the other surface of the conductor plate, and the measurement of the electromagnetic field component is repeated. The disturbing electromagnetic wave distribution is obtained from the electromagnetic field components measured at each position in this manner.

As a result, (a) Since the electromagnetic field near the hole opened in the metal plate is larger than the electromagnetic field strength of only the direct wave, it can be measured even for a low-level interference wave.

(B) Since only one sensor is used, there is no need to consider electromagnetic coupling with an adjacent sensor.

(C) Since there is only one sensor, there is no need to consider measurement errors due to variations between sensors.

(D) Since there is only one electromagnetic field sensor, there is no need to accommodate a large number of cables in the device. Therefore, there is no coupling between the cables.

There are advantages such as.

Hereinafter, the principle of the method for measuring the distribution of disturbing electromagnetic waves according to the present invention will be specifically described with reference to the drawings.

FIG. 7 is a perspective view for explaining the principle of the method for measuring the distribution of disturbing electromagnetic waves according to the present invention. In the figure, reference numeral 1 denotes a conductor plate, and 2 denotes a hole formed in the conductor plate. When the electronic device 3 to be measured is disposed above the conductor plate 1, the electromagnetic fields radiated from the device 3 are E and H. In addition, although the hole 2 is drawn relatively large in the figure for easy understanding,
Actually, it is considerably smaller than the electronic device 3.

FIG. 7A is a sectional view of the vicinity of the hole 2 of the conductive plate 1 in FIG.

In FIG. 7A, a certain edge of the hole 2 is defined as a point K, a distance in an arbitrary direction from the point K is represented by r, and the direction is represented by an angle θ (an angle between the surface of the conductive plate 1 and the direction). Represent.

At this time, the behavior of the electromagnetic field in the vicinity of the hole 2 will be described. When the thickness of the conductor plate (metal plate) 1 is negligible compared to the wavelength, the electric field strength E near the hole 2 is given by the following equation.

E = | α * sin θ * r ^−1/2 | (r≪1 cm) (1) where α represents a comparison constant. The mark * indicates multiplication. From equation (1), the tangent component of the electromagnetic field is zero on the conductor surface, but becomes infinite once away from the metal surface,
There is a feature that decreases rapidly.

FIG. 8 shows a measurement example of the electromagnetic field distribution at this time. 8th
FIG. 8A is a graph showing a measurement example of the electric field intensity when θ = 270 degrees and the distance r is varied, as seen in FIG. 8A. The above features will be appreciated.

Further, even when the conductor plate 1 is separated from the device 3 by about several cm, an electromagnetic field distribution sufficiently larger than the direct wave from the interference wave source is given. For this reason, when the coupling between the conductor plate and the device is too large, the conductor plate and the device are separated from each other so as to form a coarse coupling, and the interference wave measurement can be performed.

The above is the description of the principle showing that the measurement of the interference electromagnetic wave is possible.

〔Example〕

FIG. 1 is a side sectional view showing a basic structure of a disturbance electromagnetic wave distribution measuring apparatus as one embodiment of the present invention.

In the figure, 1 is a conductor plate, 2 is a hole on the conductor plate, 3 is a device to be measured (electronic device), 4 is a dielectric plate, 5 is an electromagnetic field sensor (in the storage case 6, not shown). ), 6 is a storage case, 7 is a sensor driving system, 8 is an interference electromagnetic wave measurement signal receiving device (measuring device), 9 is a control device, 10 is a data display section, 11 is a coaxial cable, and 12 is a control cable.

Currents are induced in the conductive plate 1 by the disturbing electromagnetic waves from the device under test 3, and these currents become equivalent current radiation sources and emit electromagnetic waves. At this time, the electromagnetic field appearing in the vicinity of the conductor plate 1 is proportional to the intensity of the incoming electromagnetic field. Therefore, the electromagnetic field sensor 5 measures the electromagnetic field, and the sensor driving system 7 moves the electromagnetic field sensor two-dimensionally. By repeating the above, the electromagnetic field distribution can be measured two-dimensionally,
As a result, the disturbing electromagnetic wave distribution can be obtained.

FIG. 2 is a perspective view showing one embodiment of the present invention. In the figure, the same components as those in FIG. 1 are denoted by the same reference numerals.

As already evident, 1 is a conductor plate (30 * 30cm, thickness
2) Hole on conductor (diameter of hole 8mm), 3 is device to be measured, 4 is dielectric plate (30 * 30cm, thickness 3mm), 5 is electromagnetic field sensor (diameter 3cm: same as this application) A patent is pending on the date), 6 is a storage case, 7 is a sensor drive system, 8 is a disturbance electromagnetic wave measurement signal receiving device, 9 is a control device, 10 is a data display unit, 11 is a coaxial cable, and 12 is a control cable.

In FIG. 2, circular holes 2 are provided in a conductor plate 1 at regular intervals for the purpose of detecting electromagnetic waves from the device under test 3. The dielectric plate 4 is composed of the device under test 3 and the conductor plate 1.
Is used to electrically separate the material, and a material transparent to electromagnetic waves, for example, a Teflon plate or the like can be used.

The electromagnetic field sensor 5 as a surface current sensor is used for measuring a current flowing through the conductor plate 1. The sensor drive system 7 is
A device for moving the electromagnetic field sensor 5 two-dimensionally,
It is possible to use a fine moving table of a pulse motor controlled by a command. As the disturbing electromagnetic wave measurement signal receiving device 8, a level meter for measuring disturbing waves such as a test receiver can be used. In addition, a normal computer workstation can be used as the control device 9 and the data display unit 10.

The following is a summary of the procedure for measuring the distribution of the disturbing electromagnetic waves.

(1) The device under test 3 is placed on the dielectric plate 4 and turned on to operate.

(2) The electromagnetic field sensor 5 is moved by a certain amount by the drive system 7.

(3) The output (current) of the electromagnetic field sensor 5 is measured by the receiving device 8.

(4) The measured value of the current at each measurement point is stored, numerically processed, and output to the data display unit 10.

The above processes (2) to (4) are performed by
By repeatedly performing the movement while moving it two-dimensionally, it is possible to two-dimensionally measure the disturbing electromagnetic wave distribution.

In the embodiment shown in FIGS. 1 and 2, the shape of the hole 2 formed in the conductor plate 1 is circular, but it can be made rectangular.

The current distribution in the conductive plate 1 differs between the case where the shape of the hole 2 is circular and the case where it is rectangular. This is shown in FIG.

3 (a) and 3 (b) show the case where the shape of the hole 2 is circular, the current distribution does not particularly differ depending on the direction of the electric field (the current distribution itself does not change even if the flowing direction differs). ).

In contrast, FIGS. 3 (c) and 3 (d) show the case where the shape of the hole 2 is rectangular, but it will be recognized that the current distribution greatly differs depending on the direction of the electric field.

That is, in FIG. 3 (c), since the direction of the rectangle of the hole 2 is parallel to the direction of the electric field E, the displacement current Id is small and the transmission of radio waves is small, whereas in FIG. 3 (d), Since the direction of the rectangle of the hole 2 is orthogonal to the direction of the electric field E, the displacement current Id is large and the transmission of radio waves is also large.

Therefore, by changing the shape of the hole 2, it is possible to give a directional characteristic to the measurement of the interfering electromagnetic wave. When the shape of the hole 2 is rectangular as described above, directivity can be provided to the reception characteristics of the conductor plate 1 with respect to the interfering electromagnetic waves. Therefore, when measuring the disturbing electromagnetic wave distribution in the case where the circuit pattern is linear, such as the substrate of an electronic circuit as the device under test 3, the hole of the conductive plate 1 should be made rectangular rather than circular. There is an advantage that measurement can be performed with increased measurement sensitivity. In addition, there is an advantage that the measurement can be performed by rotating the device under test 3 by 90 degrees, so that the distribution of interfering electromagnetic waves related to the circuit pattern can be measured.

FIG. 4 is a side sectional view showing an example of the electromagnetic field sensor 5 for which a patent application has been filed on the same date as the present application, and FIG. 4A is a top view showing a main part thereof.

In these figures, 21 is a coupling line for obtaining an induced voltage by coupling with an electric field, 22 is a substrate for forming the coupling line, 23 is a ground plane of the substrate, and 24a and 24b are non-reflective terminations of the coupling line 21. Then, a terminating resistor equivalent to a characteristic impedance for extracting an induced voltage, 25 is a signal transmission cable (for example, a coaxial cable), 26 is a housing as a whole storage case, and 27 is a coupling line 21 which is electrically separated. Derivative plate for

In short, on the front side of the circuit board, both the front and back sides of which are grounded, the other part is removed by etching except for the coupling line portion, and both ends of the coupling line are subjected to the characteristic impedance of the circuit board of 50Ω (termination). Terminating to the ground plane with a resistor), take out the voltage at both ends from one of the terminating resistors (24b side in the figure) with a coaxial cable, and cover with a dielectric plate on the coupling line part on the circuit board surface and bond By bonding with the agent, a sensor having the configuration shown in FIG. 4 is obtained.

FIG. 4A is a top view of the coupling line 21 viewed from above, and the x-axis and y-axis are defined as shown.

Here, when an electromagnetic field is incident from the plus direction of the x-axis along the coupling line 21, the voltage guided to the terminal point 24b of the coupling line 21 and taken out through the cable 25 has the following directional characteristics. .

V (θ) = cos ² (θ / 2) (2) At this time, θ indicates an angle between the plane including the coupling line 21 and the incident electromagnetic field. According to equation (2), the electric field has a maximum sensitivity with respect to an electromagnetic field (θ = 0) coming from the plus direction of the x-axis, and has a minimum sensitivity when an electromagnetic field (θ = π) comes from the minus direction of the x-axis. It can be seen that the directivity is high. If the output is taken out from the terminating resistor 24a, the sensitivity is reversed.

Thus, the near electromagnetic field sensor can detect the arrival direction of the electromagnetic field, and can grasp the characteristics of the electromagnetic field distribution in a vector manner.

In practice, an omnidirectional one can be used by combining four such sensors.

 Next, a measurement example will be described.

The distribution of the disturbing electromagnetic wave was measured using the disturbing electromagnetic wave distribution measuring device according to the present invention. FIG. 5 shows the measurement system at that time.

In FIG. 5, reference numeral 13 uses a spherical dipole antenna (diameter: 10 cm) as a disturbance source. Reference numeral 14 denotes a transmitter that supplies a signal to the spherical dipole antenna, and 15 denotes an optical fiber.

In FIG. 5, the spherical dipole antenna 13 is arranged at a position offset from the center of the conductor plate 1, and is installed so that the radiated electric field is parallel to the conductor plate 1. The frequency of the transmitter 14 was set to 100 MHz, and the signal was passed through the optical fiber 15 and given to the spherical dipole antenna 13. Spherical dipole antenna 13
FIG. 6 shows the result of measuring the current induced by the electromagnetic wave radiated by the electromagnetic field sensor 5.

From FIG. 6, it can be seen that the closer to the disturbance source, the greater the detected current. From the above results, it is possible to measure the distribution of interference sources using the apparatus for measuring the distribution of interference electromagnetic waves according to the present invention.

〔The invention's effect〕

As described above, the disturbing electromagnetic wave distribution device according to the present invention measures the disturbing electromagnetic wave distribution by moving one sensor two-dimensionally in the present invention. There is no problem such as variations in the characteristics of each sensor associated with the two-dimensionally arranged electromagnetic interference distribution measurement device, coupling between adjacent sensors, mutual induction between multiple cables, etc. Move the surface current sensor with the sensor driver to keep the reproducibility of measurement for a device that detects an electromagnetic field by exposing one sensor because it is separated from external unnecessary noise by a metal storage case. Since the position of the sensor can be determined with high accuracy for measurement, the reproducibility of measurement is high.The storage case separates the sensor driver and coaxial cable from interfering electromagnetic waves. It is characterized in that it does not receive interference waves from sources other than sensors. As described above, there is an advantage that an inexpensive and high-performance interference electromagnetic wave distribution measuring method and apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a basic structure of one embodiment of the present invention,
FIG. 2 is a perspective view of the same, FIG. 3 is an explanatory view showing the relationship between the shape of the hole and current distribution, FIG. 4 is a side sectional view showing an example of the electromagnetic field sensor, and FIG. FIG. 5, FIG. 5 is a schematic diagram showing an example of a measurement system of an electromagnetic interference wave, FIG. 6 is a characteristic diagram showing a measurement result, FIG. 7 is a perspective view showing a measurement principle according to the present invention, and FIG. FIG. 8 is a characteristic diagram showing an example of measurement of an electromagnetic field distribution, and FIG. 8A is an explanatory diagram showing measurement conditions. DESCRIPTION OF SYMBOLS 1 ... conductor plate, 2 ... hole, 3 ... device to be measured, 4 ... dielectric plate, 5 ... electromagnetic field sensor, 6 ... storage case, 7 ...
... Sensor drive system, 8 ... Receiving device, 9 ... Control device, 10
... Data display section, 11 ... Coaxial cable, 12 ... Control cable, 13 ... Spherical dipole antenna, 14 ... Transmitter, 15 ... Optical fiber

Claims (2)

(57) [Claims] 1. A method for measuring the distribution of electromagnetic interference generated from an electronic device as an object to be measured, wherein a hole having a size smaller than the size of the object is formed in a conductive surface thereof. A first step of spatially disposing a plurality of perforated conductor plates, and disposing the device under test in the vicinity of one surface of the conductor plate, and in the vicinity of the other surface of the conductor plate. A second step of disposing an electromagnetic field sensor; and a third step of measuring, as the disturbing electromagnetic wave, an electromagnetic field component leaking from the DUT through a hole formed in the conductor plate by the electromagnetic field sensor. A fourth step of moving the electromagnetic field sensor to another position along the other surface of the conductor plate and repeating the measurement of the electromagnetic field component; and distributing the disturbing electromagnetic wave distribution from the electromagnetic field component measured at each position. The fifth step of seeking Electromagnetic interference distribution measurement method characterized. 2. A disturbing electromagnetic wave distribution measuring device for measuring a distribution of disturbing electromagnetic waves generated from an electronic device as an object to be measured, wherein a hole having a size smaller than the size of the object to be measured is formed in a conductor surface thereof. A plurality of conductor plates pierced; and an electromagnetic field component leaking through holes pierced in the conductor plate from the DUT arranged near one surface of the conductor plate. An electromagnetic field sensor that is disposed near the other surface of the conductor plate and measures as an interfering electromagnetic wave, and measures the electromagnetic field component by moving the electromagnetic field sensor to another position along the other surface of the conductor plate. A disturbing electromagnetic wave distribution measuring device comprising: an electromagnetic field sensor moving means to be repeated; and a measuring device for obtaining a disturbing electromagnetic wave distribution from an electromagnetic field component measured at each position.