JP3294931B2 - Near magnetic field measurement method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a near-magnetic field measuring apparatus and method suitable for measuring unnecessary electromagnetic radiation and the like generated by electronic equipment and the like.

[0002]

2. Description of the Related Art In the measurement of unnecessary electromagnetic waves radiated from an electronic device or the like, there is an increasing demand for a near magnetic field measurement inside a device in addition to a far electromagnetic field measurement in an anechoic chamber or the like. In particular, with the recent increase in the degree of integration of devices, it has become increasingly necessary to improve the accuracy of near-field measurement.

[0003] As a near magnetic field measuring apparatus that can meet such a demand, for example, “THE HPCLOSE FIELD PROBE: Char”
acteristics and Application to EMI Troubleshooting
(Terrien, M., Hewlett Packard, RF & Microwave Measur
ement Symposium and Exhibition, July 1986)
Are known.

Hereinafter, this prior art will be described with reference to FIG. FIG. 5 shows an example of the configuration of a near-field measuring device according to the related art.

[0005] The conventional near-field measuring device includes a loop antenna 10 for detecting a magnetic field, a balun 40, and a spectrum analyzer 41.

When detecting the magnetic field generated by the magnetic field generating source 1 to be measured, the loop antenna 10 links with the magnetic field to be measured and generates an induced voltage. The balun 40 performs impedance matching (Zi) between the loop antenna 10 and the input of the spectrum analyzer 41, and corrects the frequency characteristics of the loop antenna 10. The spectrum analyzer 41 is connected to the balun 40 and the loop antenna 1
The intensity of the magnetic field generated by the magnetic field generating source 1 is measured based on the induced voltage induced at 0.

[0007]

However, in the conventional near-magnetic field measurement, the output of the loop antenna 10 is, for example, a balun 40 having a low input impedance of 50Ω.
, An induced current ir flows through the loop antenna 10, and power is consumed by the balun 40. As a result, the current is flowing in the magnetic field source 1 to be measured changes. That is, the proximity of the loop antenna 10 disturbs the state of the system to be measured (the magnetic field generating source 1), causing an error in the near magnetic field measurement.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a near-field measuring apparatus and method capable of realizing high-precision near-field measurement without disturbing the state of the system to be measured.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a near-field measuring device for measuring a near magnetic field generated from a device to be measured, which is placed in the magnetic field to generate an induced signal corresponding to the magnetic field. A magnetic field sensor generated inside, and a sensor driving unit for electrically driving the magnetic field sensor by adding a signal for canceling the induced signal; and a sensor driving unit disposed at a measurement position in the magnetic field and driven by the sensor driving unit. A signal detection unit that detects an electric signal flowing through the magnetic field sensor and outputs a signal indicating at least the intensity of the signal, and sets the intensity of the signal to substantially zero based on the signal output from the signal detection unit. Control means for obtaining and outputting a magnetic field at the measurement position by controlling the sensor driving means. .

The above object is also achieved by a near magnetic field measuring method for measuring a near magnetic field generated from a device to be measured,
While electrically driving the magnetic field sensor placed in the magnetic field, detecting an electric signal flowing through the magnetic field sensor, based on the electric signal, so that the electric signal becomes 0,
This is achieved by a near-magnetic field measuring method characterized by controlling the driving state of the magnetic field sensor and obtaining the magnetic field from the driving state when the electric signal becomes substantially zero.

[0011]

In the near-field measuring device to which the present invention is applied, the magnetic field sensor generates an induced signal corresponding to the magnetic field when placed in the magnetic field. In the present invention, the magnetic field sensor is arranged at a measurement position in the magnetic field to be measured, and is electrically driven by the sensor driving means. Further, an electric signal flowing through the magnetic field sensor is detected by the signal detecting means. Finally, the control means controls the sensor driving means based on the signal output from the signal detection means to obtain the magnetic field, and makes the intensity of the electric signal detected by the signal detection means substantially zero.

Here, the case where the intensity of the electric signal becomes 0 means that the induced signal generated in the magnetic field sensor is canceled by the drive signal having the same frequency, intensity and phase as the signal. Therefore, at the time of the cancellation, the drive signal and the induced signal can be said to be the same signals that are going to flow in opposite directions to each other.

On the other hand, the relationship between the magnetic field to be measured and the induced signal generated can be known in advance from the characteristics of the magnetic field sensor.

Therefore, the control means can determine the near magnetic field at the measurement position from the driving state of the sensor driving means at the time when the electric signal output from the signal detecting means becomes zero.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a near magnetic field measuring apparatus to which the present invention is applied will be described with reference to FIGS. Here, for example, an example suitable for measuring a near magnetic field up to a frequency of about 1 GHz generated from an information processing device such as a personal computer or a workstation will be described.

As shown in FIG. 1, the near-field measuring device of the present embodiment has a loop antenna 10 operating as a magnetic field sensor.
A common mode choke 19 for reducing the influence of the stray capacitance, a current detector 11 for detecting a current flowing through the loop antenna 10, and a controller 1 for controlling the measurement operation.
7, a display 18 for displaying a measurement result, and an input device 20 for receiving an external input.

This embodiment further includes a loop antenna 10
The oscillator 16 in which the frequency of the generated AC signal is variable and the generated AC signal 11
6a, and a phase shifter 14 including a phase control circuit 14a that receives the amplified AC signal and adjusts the phase of a signal for driving the loop antenna 10.
And a gain control circuit 1 for adjusting the signal strength of the drive signal.
Variable gain amplifier 13 having buffer amplifier 3a and buffer amplifier 16a
And a switch 15 for controlling the connection between the phase shifter 14 and the phase shifter 14.

This embodiment further includes a buffer amplifier 16b for amplifying an AC signal output from the transmitter 16, a signal 116b output from the buffer amplifier 16a, and a current detector 1b.
And a phase detector 12 for receiving the signal flowing through the loop antenna 10 detected in step 1 and outputting two signals relating to the phase difference between the two signals and the strength of the combined signal formed by multiplying the two signals.

As the loop antenna 10, a circular antenna having a diameter of about 2 to 3 cm is used. Here, the constituent members of the antenna 10 are conductors, and any material can be used as long as it can be processed into the loop antenna 10, but for example, a metal such as copper can be used.

Basically, the phase detector 12 may have any function as a filter and a multiplier. In the present embodiment, the phase detector 12
A signal 112 indicating the state of the phase shift between the two signals is output to the controller 17. Further, the phase detector 12
A signal indicating the strength of the signal obtained by combining the two signals is output to the phase shift control circuit 14a (signal 114) and the gain control circuit 13a (signal 113).

The variable gain amplifier 13 includes a gain control circuit 13
a based on the signal 113 received at
The feedback control is performed so that the intensity indicated by the above becomes substantially zero.

The phase shifter 14 performs feedback control based on the signal 114 received by the phase control circuit 14a such that the phase difference indicated by the signal 114 becomes substantially zero.

The controller 17 is a microcomputer or the like including a CPU and a memory, and receives an output (signal 112) from the phase detector 12 and
Control of the transmission frequency of the transmitter 16 (signal 117), reception of a signal indicating the amplification gain of the variable gain amplifier 13 (signal 113a), reception of a signal indicating the phase of the phase shifter 14 (signal 114a), and switch 15 Of the switching timing (signal 115).

The common mode choke 19 reduces the influence of the stray capacity that occurs when the loop antenna 10 is brought close to the measurement target. That is, when the stray capacitance electrically connects the present embodiment to the object to be measured, a signal flows into the choke 19 from the outside via the loop antenna 10. However, for this signal, the inductance of the choke 19 is very large, so that the flowing current is negligible. Further, a connection line between the loop antenna 10 and the measurement device passes through the inside of the choke 19, but since this connection line includes both input and output lines from the loop antenna 10, the influence of the inductance of the choke 19 is not affected. Absent.

The basic principle of the operation of this embodiment will be described with reference to FIG. Here, FIG. 3A shows an equivalent circuit of the magnetic field generation source 1 and shows a state of the magnetic field generation source 1 alone. FIG. 3B shows an equivalent circuit of the magnetic field generating source 1 and the measuring device when the near-field measuring device (conventional example) of the related art is brought close to the generating source 1, and FIG. ,
2 shows an equivalent circuit of the magnetic field generation source 1 and the near-field measurement device when the near-field measurement device according to the present invention is brought close to the magnetic field generation source.

An equivalent circuit of the magnetic field source 1 to be measured includes an equivalent voltage source 3 for generating a voltage vs [V], a resistor rs
It can be represented by an equivalent internal resistance 4 having [Ω] and an inductance 2 (Ls [H]) of a radiation source that radiates a magnetic field to the outside. When the magnetic field source 1 exists alone as shown in FIG. 3A, the current is flowing through this equivalent circuit is
[A]

[0027]

(Equation 1)

Is as follows.

Next, when the conventional near-field measuring device which receives the loop antenna 10 with the impedance 5 of Zi is brought close thereto, the induced current ir is applied to the loop antenna 10 by the coupling represented by the induced inductance M [H]. As [A] flows, the current flowing in the magnetic field generation source 1 changes to is'.

Here, the equivalent circuit of FIG. 3B can be rewritten as shown in FIG. 7, and the following equation is established.

[0031]

(Equation 2)

Therefore, from the above equations (1) and (2), the current i
s ′ is represented by the following equation.

[0033]

(Equation 3)

Here, the second term of the above equation (3) occurs in the current flowing through the magnetic field generating source 1 which is the object of measurement when the induced current ir flows through the conventional measuring device approached for measurement. The error is shown.

In the present invention, as shown in FIG. 3 (c), the frequency, phase and intensity of the power signal are adjusted and supplied to the loop antenna 10 using the voltage source vr so as to just cancel the induced voltage. The present invention cancels out the induced current ir flowing inside the measuring instrument of the invention (ir = 0).

According to the near-field measuring apparatus of the present invention, the state of the magnetic field source 1 to be measured is not disturbed.
Of the near magnetic field can be measured. Here, the impedance seen from the source 1 is the same as when the near-field measuring device of the present invention is not brought close, and does not consume the energy of the measured magnetic field.

Specifically, in the present embodiment, the controller 17 controls the loop antenna 1 so as to cancel the induced power induced in the loop antenna 10 by the magnetic field to be measured.
The frequency, voltage, and phase of the power signal supplied to 0 are adjusted, and the magnetic field to be measured is obtained based on the adjusted power signal.

Next, the operation of this embodiment will be described with reference to the flowchart of FIG.

First, the controller 17 operates the switch 15
To disconnect the phase shifter 14 from the buffer amplifier 16a (step 302). That is, the loop antenna 1
0 is not driven, and the magnetic field source 1 which is the system to be measured is
The loop antenna 10 is approached and fixed at a predetermined measurement position.

Next, in step 303, the controller 17 operates the oscillator 16 and sets the
Outputs a frequency control signal 117 to 6, firstly, to output an AC signal of an initial set frequency f _0. The generated AC signal is amplified by the buffer amplifier 16b.

On the other hand, the current detector 11 detects an induced signal induced in the loop antenna 10 by the magnetic field to be measured, and outputs the signal to the phase detector 12.

The phase detector 12 multiplies the amplified AC signal output 116b (frequency f ₀ ) by the induced signal (frequency fm) detected by the current detector 11, and obtains the resultant signal. A digital signal 112 indicating a phase difference, for example, three states of phase lag, lead, and coincidence is output.

The controller 17 receives the signal 112 and detects the state of the phase difference between the two signals received by the phase detector 12.

Next, the controller 17 determines whether or not the frequencies of both signals received by the phase detector 12 match based on the signal 112 (step 30).
4). In the present embodiment, when they match, the phase is completely matched for a certain period of time, or the signal 112 indicating the delay and advance of the phase is output alternately.

If it is determined that they do not match, the frequency is changed within a predetermined frequency width (step 30).
5) Return to step 303.

If they match, the frequency f _{0 of the} oscillator 16 transmitted at that time is fixed as the frequency fm of the magnetic field to be measured (step 306).

Here, the phase detector 12 outputs the input signal 11
The Q is higher than the frequency of 6b, and the influence of other frequency components included in the induced signal can be ignored.

In the above steps, energy is taken from the system to be measured as in the conventional technique (FIG. 3).
(B)).

Next, under the control of the controller 17, the switch 15 is turned on, and the signal of the transmitter 16 transmitting at the above fixed frequency is used.
a, the loop antenna 10 is driven via the phase shifter 14 and the variable gain amplifier 13 (step 30).
7).

In the following steps, negative feedback is applied to the phase shifter 14 and the variable gain amplifier 13 so that the output of the current detector 11 becomes 0. Here, what is detected by the current detector 11 is an induced signal induced in the loop antenna 10 and a signal supplied to the loop antenna 10 via the variable gain amplifier 13 or the like in order to cancel the induced signal. It is the sum with the drive signal that is being applied.

The output of the current detector 11 is supplied to the phase detector 12
Is output to the gain control circuit 13a. At this stage, the phase detector 12 receives the AC signal 116b having the same frequency as the frequency of the induced signal obtained in the above step, and operates as a synchronous detector (bandpass filter) for the frequency.

Therefore, the signal 113 output from the detector 12 indicates the intensity of the combined signal of the induced signal and the drive signal at the frequency. In addition,
It is assumed that the phase by the phase shifter 14 is fixed to a predetermined initial phase value.

In such a state, the current detector 11
Is output from a gain control circuit 13 via a phase detector 12.
is detected by a (step 308), the voltage Vm of the induced signal due to the measured magnetic field, the voltage V ₀ which applied drive signal to the loop antenna 10 so as to cancel out it, if it matches, it is determined (Step 309).
Specifically, the matching state is determined by detecting whether or not the intensity of the output signal 113 is minimal. Here, if the signal voltages of the induced signal and the drive signal are exactly the same and have opposite directions, the signal 113 becomes minimum. However, since the phase shift has not been adjusted at this stage, the signal 113 does not become substantially zero when the phase shift remains somewhat.

If they do not match, the gain control circuit 13a
Changes the gain of the variable gain amplifier 13 (step 3
10) Return to step 308 to re-determine the matching state.

If they match, the gain of the variable gain amplifier 13 at that time is fixed, and the loop antenna 10
The signal voltage V ₀ being applied to the voltage Vm of the induced power
Is determined (step 311). Further, the controller 17 outputs a signal 113 indicating the gain of the variable gain amplifier 13 output from the gain control circuit 13a at this time.
Accept a. Here, the voltage value indicates an absolute value, and the directions of both voltages are opposite.

In this embodiment, the gain of the variable gain amplifier 13 is feedback-controlled by the gain control circuit 13a. However, the controller 17 receives the output from the current detector 11 and controls the variable gain amplifier 13. It is good also as composition.

Next, the same adjustment is made for the phase. That is, the phase control circuit 14 a
Is received as a signal 114 via the phase detector 12. Here, the signal 114 indicates the intensity of the composite signal obtained by multiplying the two signals input to the phase detector 12, similarly to the signal 113, and is detected by the phase control circuit 114 (step 312). ). The phase pm of the induced power signal due to the magnetic field to be measured and the phase p _{0 of the} power signal applied from the oscillator 16 and applied to the loop antenna 10 whose phase is adjusted by the phase shifter 14.
Is determined whether they match (step 31)
3).

More specifically, by detecting whether the intensity of the output signal 114 is minimum or substantially zero,
A match is determined. That is, since the frequency and the voltage are obtained in the above steps, if the phases are matched at this stage, the signal detected by the current detector 11 becomes almost 0, and the intensity indicated by the signal 114 is the minimum, or
It becomes 0.

If they do not match, the phase control circuit 14a
Then, the phase change amount of the phase shifter 14 is changed (step 314), and the process returns to step 312 to judge the coincidence state again.

If they match, the phase shift amount of the phase shifter 14 at that time is fixed, and the signal phase p ₀ applied to the loop antenna 10 is changed to the phase p of the induced power signal.
m (step 315). Furthermore, the controller 1
7 receives a signal 113a indicating a phase change of the phase shifter 14 output from the phase control circuit 14a at this time.

In this embodiment, the phase control circuit 14a performs feedback control of the phase shifter 14, but the controller 17 receives the signal from the phase detector 12 and controls the phase change of the phase shifter 14. It is good also as a structure which performs.

By the above steps 308 to 315, in a stable state obtained by feedback control without the intervention of the controller 17 and in which the drive signal applied to the loop antenna 10 cancels the induced signal, the amplitude signal 113a and the phase signal 114a are respectively , The amount corresponding to the magnitude and phase of the magnetic field to be measured. Steps 302 to 306
Then, the frequency of the induced power signal has already been measured. Further, in the present embodiment, the relationship between the magnetic field and the induced signal induced in the loop antenna 10 is input to the controller 17 in advance.

Therefore, the controller 17 controls the frequency control signal 117, the amplitude signal 113a, and the phase signal 11
4a, a measured magnetic field can be obtained, and the result is output to the display 18. Display 1
8 displays the measured magnetic field generated by the magnetic field source 1 to be measured based on the obtained result (step 316).

Here, the magnetic field to be measured may have a plurality of frequency peaks. In such a case, in step 302, the switch is turned on and a coarse spectrum analysis is performed. Steps 303 to 315 are performed on frequency peaks having an intensity equal to or greater than a predetermined threshold value in the measured magnetic field. Is repeated. Thus, for each peak, the frequency is specified with high accuracy, and the intensity and phase of the signal are measured. Further, these results are obtained in step 316 by, for example, plotting the frequency and the intensity as a graph (the diagram shown on the display 18 in FIG. 1)
indicate.

According to the present embodiment, the loop antenna 10 as a magnetic field sensor can be driven to suppress an induced signal flowing through the magnetic field sensor, so that a high-precision near-field measuring device can be provided. . Therefore, the impedance seen from the measured magnetic field generating source is the same as when the near magnetic field measuring device according to the present embodiment is not approached, and the near magnetic field can be measured without consuming the energy of the measured magnetic field.

Further, according to the present embodiment, since the phase and the intensity of the drive signal are feedback-controlled without the intervention of the controller 17, the above-mentioned measurement can be executed at a high speed.

In this embodiment, the frequency is fixed, and then the voltage and the phase are fixed. However, the algorithm for adjusting the drive signal applied to the loop antenna 10 (magnetic field sensor) is not necessarily limited to this. In the present invention, any configuration may be used as long as it can finally generate electric power that matches the induced power induced in the magnetic field sensor.

In this embodiment, the loop antenna 10 is used as the magnetic field sensor, but the present invention is not limited to this. The shape and type of the magnetic field sensor according to the present invention are not limited as long as the magnetic field sensor generates an induced current when placed in a magnetic field to be measured.

In this embodiment, the controller 17 and the oscillator 16 are used to determine the frequency. However, as long as the frequency of the induced signal of the loop antenna 10 can be determined, the method and the configuration of the apparatus are not limited. For example,
The approximate value of the frequency of the signal may be obtained using a spectrum analyzer.

Further, in the present embodiment, the frequency of the magnetic field to be measured is determined without driving the loop antenna 10, but the present invention is not limited to this. For example, after the frequency is determined by the method of the present embodiment, the phase and intensity may be detected in the subsequent steps while driving the loop antenna 10 and finely adjusting the frequency. According to this method, the near magnetic field can be determined with higher accuracy.

Next, another embodiment of the near magnetic field measuring apparatus to which the present invention is applied will be described. In the present embodiment, the vector quantity of the near magnetic field generated from the magnetic field source to be measured is measured using the near magnetic field measuring apparatus shown in the above embodiment.

In this embodiment, the loop antenna 10 which operates as a magnetic field sensor for detecting a magnetic field vector of a magnetic field to be measured is described.
, A loop antenna 20 and a loop antenna 21. The loop antennas 10, 20, and 21 are arranged orthogonally to each other to form orthogonal coordinates used for measurement. Each loop antenna detects a magnetic field component orthogonal to the loop plane. That is, in the present embodiment, the loop antenna 1
0 is the X-axis component of the magnetic field, the loop antenna 20 is the Y-axis component,
The loop antenna 21 detects each of the Z-axis components.

The present embodiment further includes detection / driving units 200, 201, and 202 connected to the loop antennas 10, 20, and 21, respectively, for detecting the power induced in the antenna and driving the antenna. , Detecting / driving units 200 and 20 to drive each loop antenna
1, and an oscillator 16 for outputting an AC signal to the signal generator 202.

In this embodiment, the detecting / driving unit 20
0, 201, 202 and the transmitter 16 are controlled so that the transmitter 16 transmits an AC signal having the same frequency as the induced signal induced in each loop antenna by the magnetic field to be measured. By driving each detection / drive unit to cancel the induced signal of
A controller 17 for obtaining a vector quantity of the magnetic field to be measured;
A display 18 for displaying the determined magnetic field to be measured,
An input device (not shown) for receiving an external input for various settings such as the controller 17;

Detecting / driving units 200, 201 and 202
Have the same configuration, and the specific configuration of each detection / drive unit is the same as that of the above-described embodiment (FIG. 1).
Ref.) Can be used. Therefore, here
The description of the configuration is omitted.

The controller 17 includes a detecting / driving unit 20
0, 201, and 202 receive the output (signal 112) from the phase detector 12 via bus signal lines 210, 211, and 212, respectively, and connect the transmitter 16
Of the transmission frequency of the signal (signal 117), the variable gain amplifier 1
Reception of a signal indicating an amplification gain of 3 (signal 113
a), a signal indicating a signal phase is received by the phase shifter 14 (signal 114a), and switching timing of the switch 15 is controlled (signal 115).

The operation of this embodiment will be described. In the present embodiment, the spatial component of the magnetic field is measured using the above-described embodiment, and the operation of the individual components is the same as that of the above-described embodiment. ,
This will be described below.

In this embodiment, the controller 17
First, the frequency of the magnetic field to be measured is detected from the induced signal induced in any one of the loop antennas, and an oscillation output 116a synchronized with the frequency is generated (steps 301 to 306 in FIG. 2). . Here, in the present invention, which loop antenna is used for frequency detection is not limited. For example, a loop antenna in which a signal having the maximum strength is induced can be used.

The controller 17 outputs the oscillation output 116
a, the detection / drive units 200, 201, 202
Are sequentially driven to detect the magnitude and phase of a magnetic field in a coordinate axis direction orthogonal to each loop antenna direction. In this embodiment, the loop antennas are driven so as to cancel the induced power in each loop antenna. here,
The operation of each component accompanying the detection of the magnitude and phase of the magnetic field component of the magnetic field to be measured orthogonal to each loop antenna direction is the same as in the above embodiment (steps 307 to 315 in FIG. 2).

In the present embodiment, finally (step 316 in FIG. 2), the controller 17 calculates image data based on the magnetic field vector amount obtained above so that the magnetic field to be measured can be visualized, and displays the image data. 18 is displayed. As an image to be displayed, for example, as shown in a display example 300 shown in FIG. 4, the coordinates used for measurement and the magnetic field vector to be measured are superimposed and displayed three-dimensionally on the screen of the display 18. .

According to the present embodiment, the magnetic field of the magnetic field source to be measured can be measured three-dimensionally, and the frequency, intensity and phase of each spatial component of the magnetic field can be measured. , They can be visualized and displayed.

In the present embodiment, three loop antennas and three detection / drive units are provided to determine the magnetic field vector of the magnetic field to be measured. However, the present invention is not limited to this shape. For example, in the near-field measurement apparatus of the above embodiment, a two-dimensional or three-dimensional magnetic field is provided by providing a moving mechanism that can change the installation position of the loop antenna like the arrangement of the loop antenna of this embodiment. A configuration for measuring a vector may be used.

Next, another embodiment of the near magnetic field measuring apparatus to which the present invention is applied will be described with reference to FIG. This embodiment is different from the second embodiment in that a scanning mechanism for moving the entire magnetic field sensor is provided to scan each part of the magnetic field source to be measured.

In this embodiment, as shown in FIG. 6A, a magnetic field detecting mechanism 22 for detecting a vector amount of a magnetic field generated by the magnetic field generating source 1 to be measured, and a part of the magnetic field generating source 1 In order to measure the generated magnetic field, the measurement position displacement mechanism 61 that changes the relative position of the magnetic field detection mechanism 22 with respect to the magnetic field generation source 1 and the magnetic field detection mechanism 22 and the measurement position displacement mechanism 61 are controlled to 1, a controller 17 for obtaining a three-dimensional vector component of a near magnetic field generated from each unit and its distribution, a display 18 for displaying the measurement results, and an input device for receiving external inputs for various settings of the controller 17 and the like ( (Not shown).

This embodiment further includes an electronic circuit board 50 having the magnetic field source 1 to be measured, and a support section 60 for supporting a measurement position displacement mechanism 61.

As shown in FIG. 6B, the magnetic field detecting mechanism 22 operates as a magnetic field sensor, and is connected to the loop antenna 10, the loop antenna 20, and the loop antenna 21 which are orthogonal to each other. ,
By detecting the induced power induced by them and generating a signal for driving the antenna so as to cancel the induced power, the magnetic field detection circuit unit 23 for detecting the frequency, intensity and phase of the magnetic field to be measured is connected. Have.

The magnetic field detection circuit unit 23 includes the detection / drive units 200, 201, and 202 (see FIG. 4) in the second embodiment and the transmitter 1 that outputs an AC signal to each detection / drive unit.
6.

As shown in FIG. 6 (a), the measurement position displacement mechanism 61 includes a magnetic field detection mechanism support member 61b for fixing the magnetic field detection mechanism 22 at one end, and the support member 61b in the y direction (see the arrow in the figure). And a position control unit 61a that receives a control command from the controller 17 and controls a displacement operation in the x, y, and z directions described below.

The measurement position displacement mechanism 61 further holds a position control controller 61a, and holds an x direction drive mechanism 61c for displacing the holding position in the x direction and an x direction drive mechanism 61c. And a z-direction drive mechanism 61d for displacing the position in the z-direction.

The controller 17 controls the magnetic field detection mechanism 22 and the measurement position control mechanism 61 via a bus signal line 230. That is, the controller 17
In the same manner as in the second embodiment, the output (signal 112) from the phase detector 12 is received, the transmission frequency of the oscillator 16 is controlled (signal 117), and the signal indicating the amplification gain of the variable gain amplifier 13 is received. (Signal 113), reception of a signal indicating the phase displacement of the phase shifter 14 (signal 11
4) and control of the switching timing of the switch 15 (signal 115).

The operation of this embodiment will be described. In this embodiment,
The near-field measuring apparatus according to the second embodiment scans the magnetic field generation source 1 to be measured to determine the magnetic field distribution.

That is, in this embodiment, first, the controller 17 controls the measurement position displacement mechanism 61 to
The magnetic field detection mechanism 22 is moved to a preset measurement position. Next, at the measurement position, the vibration frequency, intensity, and phase of the three-dimensional vector of the near magnetic field generated from the magnetic field generation source 1 are measured as in the second embodiment. The detailed operation of the constituent elements of the present embodiment accompanying the magnetic field measurement is the same as that of the above-described second embodiment, and will not be described here.

In this embodiment, the magnetic field vector measurement is performed every time the measurement position is changed, and the magnetic field source 1
The spatial distribution of the three-dimensional vector of the magnetic field generated by is calculated.
Further, image data showing a pseudo three-dimensional image is created so that the measurer can easily see the spatial distribution of the measured magnetic field represented by the obtained three-dimensional vector, and this data is output to the display 18. . The display 18 accepts this data and displays the measurement result.

As an image to be displayed, for example, a magnetic field vector at one frequency among the measured magnetic fields (see display example 300 in FIG. 4) is three-dimensionally arranged corresponding to the measurement position where the vector is measured. And a contour map created using only one component of the intensity of the magnetic field vector. Here, the display of the measurement result is not limited to these examples, and the intensity and phase may be represented by colors.

According to the present embodiment, the frequency component of the magnetic field generated by the magnetic field source 1 to be measured and the spatial distribution of the magnetic field are automatically measured without disturbing the state of the measurement object. Can be.

In the above three embodiments, only the measurement of the spatial magnetic field is described. However, the same measurement position or area is measured at predetermined time intervals, and the change is measured using a moving image or the like. The magnetic field to be measured and its time change may be displayed.

[0097]

According to the present invention, the induction signal flowing through the magnetic field sensor can be canceled, so that the influence of the magnetic field measuring device itself on the system to be measured, which causes an error in the near magnetic field measurement, can be reduced. Therefore, a highly accurate near-field measuring device can be provided.

[0098]

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration in an embodiment of a near-field measurement device to which the present invention is applied.

FIG. 2 is a flowchart showing the operation of the embodiment of FIG. 1;

FIG. 3 is an explanatory diagram illustrating a measurement principle of a near-field measurement device to which the present invention is applied.

FIG. 4 is an explanatory diagram showing a configuration in another embodiment of a near-field measuring device to which the present invention is applied.

FIG. 5 is an explanatory diagram showing a configuration of a conventional near-field measuring device.

FIG. 6A is an explanatory diagram showing a configuration of another embodiment of a near-field measuring device to which the present invention is applied. FIG.
(B): Explanatory drawing which shows the structure of the magnetic field detection mechanism 22 of FIG.6 (a).

FIG. 7 is an equivalent circuit diagram used to explain the effect of a conventional near-field measurement device on a measurement target.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magnetic field generation source to be measured, 2 ... Inductance of magnetic field generation part to be measured, 3 ... Equivalent voltage source of magnetic field generation part to be measured, 4 ... Internal impedance of magnetic field generation part to be measured, 5 ... Receiver impedance of loop antenna, Reference numeral 6: voltage source, 10: loop antenna, 11: current detector, 12: phase detector, 13
... variable gain amplifier, 14 ... phase shifter, 15 ... switch, 1
Reference Signs List 6 oscillator, 16a, 16b buffer amplifier, 17 controller, 20, 21 loop antenna, 22 magnetic field detection mechanism, 40 balun, 41 spectrum analyzer, 50 electronic circuit board, 60 support part, 61 Measurement position displacement mechanism, 200, 201, 202... Detection / drive unit.

Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01R 29/08 G01R 19/00-19/32 G01R 15/00-15/12 G01R 33/02-33/10 JICST file (JOIS)

Claims (15)

(57) [Claims] A near-field measuring device for measuring a near-field generated from a device to be measured, wherein the near-field measuring device is arranged in the magnetic field to generate an induced signal therein in response to the magnetic field; A sensor driving means for electrically driving the magnetic field sensor by adding a signal for canceling the induced signal; and an electric signal flowing at the measurement position in the magnetic field and flowing to the magnetic field sensor driven by the sensor driving means. A signal detection unit that detects and outputs a signal indicating at least the intensity of the signal; and controls the sensor driving unit based on the signal output from the signal detection unit so that the intensity of the signal is substantially zero. A near-field measuring apparatus comprising: a control unit that obtains and outputs a magnetic field at a measurement position. 2. The sensor driving means according to claim 1, wherein said sensor driving means adds a signal for canceling a specific frequency component of said induced signal. The near-field measurement device detects only the signal of the specific frequency component, and wherein the control unit obtains the specific frequency component of the magnetic field at the measurement position. 3. The near-field measuring apparatus according to claim 2, further comprising a display unit for displaying a magnetic field output by the control unit. 4. The sensor according to claim 3, wherein the sensor driving means includes: a transmitter having a variable generation frequency for generating an AC signal for driving the magnetic field sensor; and a signal adjustment unit for adjusting a phase and an intensity of the AC signal. And a means for measuring a near magnetic field. 5. The apparatus according to claim 4, wherein the control means obtains a frequency of a nearby magnetic field to be measured by controlling a frequency of an AC signal generated by the transmitter based on a signal from the signal detection means. A near-field measuring device characterized by the above-mentioned. 6. The signal adjusting device according to claim 5, wherein the signal adjusting means includes a variable gain amplifier for changing the intensity of the AC signal generated by the oscillator, and a phase shifter for changing the phase of the AC signal. The control unit controls the variable gain amplifier and the phase shifter based on the signal from the signal detection unit, and controls the intensity and phase of the AC signal having the same frequency as the frequency of the near magnetic field to be measured. Is changed so that the signal from the signal detecting means becomes substantially zero. 7. The magnetic field sensor according to claim 6, wherein the magnetic field sensor has one or more loop antennas, and the control means is orthogonal to a plane on which the loop portion of each loop antenna is formed, of the near magnetic field to be measured. A near-magnetic field measuring device for determining a magnetic field component to be generated. 8. The magnetic field sensor according to claim 7, wherein, when the magnetic field sensor has two or more loop antennas arranged orthogonally to each other, an image indicating a vector amount of the magnetic field is displayed using the obtained magnetic field component. Image data generating means for generating and outputting image data for performing the operation, wherein the display means receives the image data and displays an image indicating the obtained magnetic field vector amount. Magnetic field measurement device. 9. The image data generating means according to claim 8, wherein said image data generating means outputs image data for three-dimensionally indicating the magnetic field vector based on a specific frequency component among the obtained magnetic field components. A near-magnetic field measuring apparatus, wherein the display means receives the image data and displays the magnetic field vector in a three-dimensional manner. 10. The apparatus according to claim 9, further comprising a scanning unit for changing a measurement position by changing a relative positional relationship between the device to be measured and the magnetic field sensor, wherein the control unit controls the scanning unit. A near-field measurement device that measures a near-field at a plurality of predetermined measurement positions. 11. The magnetic field sensor according to claim 10, wherein the magnetic field sensor has two or more loop antennas arranged orthogonal to each other, and the scanning unit moves the loop antenna relative to the device under test. A moving mechanism for moving, wherein the control means calculates a magnetic field component in two or more spatial coordinate axes orthogonal to each other at a plurality of measurement positions, and the image data generating means calculates a magnetic field component based on the calculated magnetic field component. A near-magnetic field measurement apparatus that generates and outputs image data for displaying an image indicating a spatial distribution of the magnetic field vector in a predetermined measurement range including the plurality of measurement positions based on the measurement data. 12. A near magnetic field measuring method for measuring a near magnetic field generated from a device to be measured, wherein the near magnetic field sensor electrically drives a magnetic field sensor placed in the magnetic field and detects an electric signal flowing through the magnetic field sensor. The driving state of the magnetic field sensor is controlled based on the electric signal so that the electric signal becomes 0, and the magnetic field is changed from the driving state when the electric signal becomes substantially 0. A near-magnetic field measurement method characterized by being determined. 13. The method according to claim 12, wherein a driving frequency of the magnetic field sensor is changed.
The frequency of the near magnetic field to be measured is determined, the magnetic field sensor is driven by using a signal having the same driving frequency as the determined frequency, and the phase and intensity of the signal are adjusted to obtain the electric signal. A near-magnetic field measurement method, wherein a signal is set to substantially zero. 14. A magnetic sensor and a signal for canceling an induced signal generated in the magnetic sensor.
A sensor driving means for detecting an electric signal flowing through the magnetic sensor and outputting the signal
And the signal output from the signal detecting means is set to substantially zero.
As described above, by controlling the sensor driving means,
A near-field measuring device , comprising: a control unit that obtains and outputs a magnetic field at a fixed position . 15. A magnetic sensor and a phase and an intensity of a signal applied to the magnetic sensor, respectively.
Adjusting means for adjusting and detecting an electric signal flowing through the magnetic sensor and outputting the signal
And the intensity of the signal output from the signal detecting means becomes substantially zero.
And a control means for controlling using the adjusting means as described above .