JP5939887B2 - Electromagnetic noise detector - Google Patents

Description

  The present invention relates to an electromagnetic noise detection device that detects an electromagnetic noise distribution of an electronic device in an immunity test or the like.

  In a general immunity test, a test signal that becomes electromagnetic noise is injected into an electronic device to be tested, and malfunction and performance degradation are evaluated. For example, in the case of an immunity test compliant with the ISO 11452-4 standard bulk current injection (BCI) method, a test signal that becomes electromagnetic noise is injected from a current probe into a connection cable (power supply line, signal line, etc.) of the EUT. Evaluate malfunction and performance degradation of the EUT.

  Conventionally, when it is evaluated as non-conforming in such an immunity test, a faulty part of the EUT is searched for and noise countermeasures are taken. However, in the immunity test, since the propagation path of the test signal injected into the EUT cannot be specified, it is a problem that the defective part cannot be easily specified. For this reason, an appropriate noise countermeasure cannot be taken, and the time required for the countermeasure is prolonged.

  For the above problem, conventionally, there has been a method of injecting a test signal into the connection cable of the EUT, detecting noise generated from the EUT by the antenna means, and visualizing the detected noise (for example, Patent Document 1).

JP 2001-124808 A

  Generally, in any electronic device, some signal is switched inside the device, and this signal leaks or conducts to the outside of the device due to impedance mismatching or spatial coupling of the signal transmission path (hereinafter referred to as test equipment noise). Will be called). In the method of Patent Document 1 described above, when the frequency of the EUT noise generated during normal operation of the EUT in a situation where external noise does not affect is the same as the frequency of the test signal injected into this EUT, And EUT noise could not be distinguished. Therefore, there is a problem that it is impossible to distinguish whether the noise detected by the antenna means is a test signal or a test equipment noise, and the propagation path of the injected test signal cannot be specified.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to correctly detect the electromagnetic field intensity of a test signal injected into a test apparatus and obtain an accurate electromagnetic noise distribution.

The electromagnetic noise detection apparatus according to the present invention includes a signal generator that generates a test signal by combining a signal having a first frequency and a signal having a second frequency different from the first frequency, and the signal generator generates the signal. a signal injection unit to inject a test signal to the EUT, generated from equipment under test in the signal injected by the signal injection unit, and a noise detector for detecting an electromagnetic field intensity of the second frequency, the second frequency The frequency is different from the frequency of the electromagnetic field generated from the EUT in a state where the signal injection by the signal injection unit is not performed .
Alternatively, the electromagnetic noise detection apparatus can detect a signal generated by the signal injection unit from the electromagnetic field intensity of the second frequency generated from the EUT during signal injection by the signal injection unit in addition to the signal generation unit, the signal injection unit, and the noise detection unit. Provided with a data processing unit that estimates the true value of the second-frequency electromagnetic field strength corresponding to the test signal by reducing the second-frequency electromagnetic field strength generated from the EUT that has not been injected. It is.

According to the present invention, the test signal including a first frequency and the second frequency is injected into the equipment under test, than was to detect the field strength of the second frequency that occur EUT, the first frequency As an alternative to the electromagnetic noise distribution at, an electromagnetic noise distribution at the second frequency can be obtained approximately.

It is a block diagram which shows the structure of the electromagnetic noise detection apparatus which concerns on Embodiment 1 of this invention. 6 is a graph illustrating the frequency of a test signal injected by the electromagnetic noise detection device according to the first embodiment. The electromagnetic noise distribution of the 1st frequency which a test equipment emits is shown, Fig.3 (a) is an example when electromagnetic field intensity is not stable, and FIG.3 (b) is stable. It is a figure explaining the isolation | separation method in case test equipment noise exists in the 2nd frequency of a test signal. It is a figure explaining the isolation | separation method in case test equipment noise exists in the 2nd frequency of a test signal. It is a block diagram which shows the structure of the electromagnetic noise detection apparatus which concerns on Embodiment 2 of this invention. It is a graph explaining the test signal (amplitude modulation signal) which the electromagnetic noise detection apparatus which concerns on Embodiment 2 inject | pours. It is a graph explaining the relationship between an amplitude modulation signal and a test signal.

Embodiment 1 FIG.
1 includes a first signal generator 1, a second signal generator 2, a coupler 3, an amplifier 4, an injection probe 5, a detection probe 6, an amplifier 7, a field strength meter 8, and a movable part 9. , A scanning unit 10, a data processing unit 11, a display unit 12, and a control unit 13. The signal generator is composed of a first signal generator 1, a second signal generator 2, a coupler 3 and an amplifier 4. The signal injection unit is composed of an injection probe 5. The noise detection unit includes a detection probe 6, an amplifier 7, and a field strength meter 8.

  The first signal generator 1 and the second signal generator 2 are circuits that generate a signal having a first frequency f0 and a signal having a second frequency f1. The coupler 3 is a circuit that combines the signal of the first frequency f0 and the signal of the second frequency f1 generated by the first signal generator 1 and the second signal generator 2 and outputs the result as a test signal. The amplifier 4 is a circuit that amplifies the test signal output from the coupler 3. This test signal is a signal injected into the EUT 100 as interference noise (or referred to as injection noise). Details of the test signal will be described later.

  The injection probe 5 is a probe that injects the test signal amplified by the amplifier 4 into the EUT 100 via the connection cable 101 (power cable or the like) that is a noise application unit. Note that the EUT 100 is an electronic device such as a printed circuit board on which electronic components are mounted. The test signal injected into the connection cable 101 enters the EUT 100 via a wiring pattern, electronic parts, etc., and is radiated to the outside.

  In the illustrated example, a non-contact type current injection probe is used as the injection probe 5. This type of probe clamps to the connecting cable 101 and generates a test signal by electromagnetic induction. The injection probe 5 only needs to be able to inject a test signal into the connection cable 101. A non-contact type probe other than the current injection probe may be used, or a contact type probe that electrically contacts the connection cable 101 and applies a test signal ( (Capacitor probe, CDN; Coupling Decoupling Network) may be used, or an irradiation antenna may be used.

  The detection probe 6 is a probe that detects an electromagnetic field generated in the test equipment 100 and outputs it as a detection signal when a test signal is injected from the injection probe 5 into the test equipment 100. As the detection probe 6, for example, a current probe incorporating a minute loop coil is used. The amplifier 7 is a circuit for amplifying the detection signal detected by the detection probe 6. The electric field strength meter 8 is an electromagnetic field measuring instrument that measures the level of an arbitrary frequency component of the detection signal amplified by the amplifier 7, that is, the electromagnetic field strength of an arbitrary frequency.

  If the level of the test signal injected by the injection probe 5 is high enough to be detected by the detection probe 6, the amplifier 4 may be omitted. If the level of the detection signal detected by the detection probe 6 is high enough to be measured by the electric field intensity meter 8, the amplifier 7 may be omitted.

  The movable part 9 moves the detection probe 6 on the EUT 100 in the X-axis direction (lateral direction), the Y-axis direction (vertical direction), the Z-axis direction (height direction), and the θ direction (rotation direction). It is a device for. The scanning unit 10 is a circuit that controls the movement of the movable unit 9 in the X, Y, Z, and θ directions to scan the detection probe 6 with respect to the EUT 100. The movable unit 9 and the scanning unit 10 cooperate to move the detection probe 6 to the noise detection position on the EUT 100 instructed by the control unit 13.

In general, the level of the detection signal increases when the distance from the substrate of the EUT 100 approaches, and decreases when the EUT 100 leaves, so that the movable unit 9 can move in the Z-axis direction according to the shape of the EUT 100. The scanning unit 10 is configured. In addition, since a loop coil is used for the detection probe 6, the magnetic flux passing through the loop changes according to the angle of the coil, and the level of the detection signal also changes. Yes.
In the illustrated example, the movable portion 9 moves the detection probe 6 in the X, Y, Z, and θ directions and scans the stationary EUT 100. On the contrary, the detection probe 6 is made stationary. The movable unit 9 may move the EUT 100. That is, the scanning method may be arbitrary as long as the detection probe 6 and the EUT 100 can be relatively changed in positional relationship and the electromagnetic noise distribution of the EUT 100 can be measured.

  The data processing unit 11 maps the detection signal level (electromagnetic field strength) for each noise detection position measured by the electric field intensity meter 8 on the two-dimensional plane of the X and Y axes, and generates electromagnetic noise distribution data. The display unit 12 is a display device that displays information such as electromagnetic noise distribution data generated by the data processing unit 11 on a screen. The control unit 13 controls each part of the electromagnetic noise detection apparatus, and sets or scans the first frequency f0 of the first signal generator 1 and the second frequency f1 of the second signal generator 2. The control unit 10 is instructed to control the noise detection position of the detection probe 6, the data processing unit 11 is controlled to numerically process the measurement result of the electric field intensity meter 8, and the display data of the display unit 12 is controlled. .

  The control unit 13 and the data processing unit 11 are realized using, for example, a computer, and a program describing the processing contents of the control unit 13 and the data processing unit 11 is stored in the memory of the computer. The program stored in is executed.

Next, the test signal will be described.
FIG. 2 is a graph for explaining the frequencies of the signals output from the first signal generator 1 and the second signal generator 2, in which the horizontal axis represents the frequency and the vertical axis represents the signal level frequency spectrum. For example, the first frequency f0 is a frequency at which the EUT 100 malfunctioned in advance by performing an electromagnetic noise resistance test (for example, IEC61000-4-3, -4, -6, etc.), and a signal of the first frequency f0 ( The first signal generator 1 generates the injection noise f0) of FIG.

  When a test signal with the first frequency f0 is injected and the EUT 100 malfunctions, the electromagnetic field strength at the first frequency f0 generated in the EUT 100 may be disturbed depending on the degree of malfunction and may not be stable. There is. FIG. 3 is a diagram showing an electromagnetic noise distribution of the first frequency f0 detected by the injection probe 5 injecting a test signal of the first frequency f0 and the detection probe 6 changing the positional relationship with the EUT 100. FIG. 3A shows an example when a disturbance occurs and the electromagnetic field strength is not stable. FIG. 3B shows an example when there is no disturbance and the electromagnetic field strength is stable. In these electromagnetic noise distributions, the darker the color, the greater the electromagnetic field strength. As is clear from a comparison between FIG. 3A and FIG. 3B, an accurate electromagnetic noise distribution cannot be measured unless the electromagnetic field strength is stable.

  Therefore, in the first embodiment, the second signal generator 2 has a signal of the second frequency f1 (f1 = f0 + Δf) that is different from the first frequency f0 and slightly deviated from the first frequency f0 (FIG. 2). Injection noise f1). The injection probe 5 injects a test signal including a signal component of the first frequency f0 and a signal component of the second frequency f1 from the connection cable 101 to the EUT 100. The detection probe 6 receives an electromagnetic field while changing the positional relationship with the EUT 100. The electric field strength meter 8 measures the electromagnetic field strength at the second frequency f1. The electromagnetic field intensity at the first frequency f0 is not measured. Since the first frequency f0 and the second frequency f1 are only slightly shifted from each other, the electromagnetic noise distribution of the second frequency f1 is equal to the first frequency f0 when the EUT 100 malfunctions with the signal component of the first frequency f0. It can be regarded as an electromagnetic noise distribution. Further, since the electromagnetic field intensity at the second frequency f1 is not disturbed, an original electromagnetic noise distribution as shown in FIG. 3B can be obtained. Therefore, the accurate propagation path of the signal component of the first frequency f0 when the EUT 100 malfunctions with the signal component of the first frequency f0 can be approximated by the propagation path of the signal component of the second frequency f1.

The correlation between the EUT noise and the malfunction depends on the configuration of the EUT 100. If there is the EUT 100 that malfunctions when the same frequency as the EUT noise is injected, the malfunction may occur at a completely different frequency. There is also a test device 100.
The above example is effective when the test equipment noise does not exist at the second frequency f1, but as shown in FIG. 4A, the test equipment noise exists at the second frequency f1, and the detection probe. 6 is lower than the detection level of the test equipment noise, the test signal and the test equipment noise cannot be separated.

  In this case, as shown in FIG. 4B, the frequency f2 (f2 = f1 + Δf ′) slightly shifted from the EUT noise of the frequency f1 is set as the second frequency f2. The second signal generator 2 generates a signal (injection noise f2) of the second frequency f2 according to the instruction of the control unit 13, and the combiner 3 combines the signal of the first frequency f0 and the signal of the second frequency f2. Output the test signal. The detection probe 6 receives the electromagnetic field while changing the positional relationship with the EUT 100, and the electric field strength meter 8 measures the electromagnetic field strength at the second frequency f2. Thereby, the injection noise at the frequency f2 can be detected separately from the EUT noise at the frequency f1. Further, since the second frequencies f1 and f2 are slightly shifted, the electromagnetic noise distribution at the second frequency f2 can be regarded as the electromagnetic noise distribution at the second frequency f1, and thus the electromagnetic noise distribution at the first frequency f0. Therefore, the accurate propagation path of the signal component of the first frequency f0 when the EUT 100 malfunctions with the signal component of the first frequency f0 can be approximated by the propagation path of the signal component of the second frequency f2.

  However, the electric field strength meter 8 is designed so that the two slightly shifted frequencies f0 and f1 can be measured separately, and the two slightly shifted frequencies f1 and f2 can be measured separately. It is necessary to set the frequency resolution bandwidth of the total 8 to be narrower than the interval (Δf, Δf ′) between these two frequencies. Thereby, the electromagnetic noise of the frequencies f0, f1, and f2 shows the same tendency.

  4 shows the separation method when the detection level of the test signal by the detection probe 6 is lower than the detection level of the EUT noise, on the contrary, the separation method when it is high is shown in FIG. As shown in FIG. 5A, first, while changing the positional relationship between the detection probe 6 and the EUT 100, the level V1 of the EUT noise at the frequency f1 when the test signal is not injected is measured. Next, as shown in FIG. 5B, test signals of the first frequency f0 and the second frequency f1 are injected from the injection probe 5 and the positional relationship between the detection probe 6 and the EUT 100 is changed. The level V2 of the signal component of the second frequency f1 including the test equipment noise is measured. Next, it is possible to estimate the true value of the electromagnetic field strength of the second frequency f1 corresponding to the test signal by calculating V2-V1 in the data processing unit 11.

  As described above, according to the first embodiment, the electromagnetic noise detection apparatus has the first signal generator 1 that generates the signal of the first frequency f0 and the second frequency f1 (or f2) different from the first frequency f0. A second signal generator 2 for generating a signal, a coupler 3 for synthesizing a signal of the first frequency f0 and a signal of the second frequency f1 to generate a test signal, and injection for injecting the test signal into the EUT 100 The probe 5, the detection probe 6 that receives the electromagnetic field generated from the EUT 100 during signal injection, the electric field strength meter 8 that measures the electromagnetic field strength at the second frequency f1, and the electromagnetic field strength at the second frequency f1 The data processing unit 11 that generates electromagnetic noise distribution data of the EUT 100 based on the above, the display unit 12 that displays the electromagnetic noise distribution data, and the control unit 13 that controls each unit are configured. For this reason, even when the EUT 100 malfunctions due to the injected signal component of the first frequency f0 and the electromagnetic field intensity of the first frequency f0 is disturbed, the electromagnetic field intensity of the second frequency f1 having a different frequency is accurately determined. Can be measured. Therefore, the electromagnetic noise distribution at the second frequency can be approximately obtained as an alternative to the electromagnetic noise distribution at the first frequency f0 where the malfunction has occurred.

  Further, according to the first embodiment, the second frequency f2 is set to a frequency different from the EUT noise generated from the EUT 100 when no signal injection is performed. For this reason, even when the test equipment noise exists at the second frequency f1 and the detection level of the test signal at the second frequency f1 is lower than the test equipment noise level, the test signal is separated by the separation method shown in FIG. The true value of the electromagnetic field intensity at the second frequency f2 corresponding to can be measured, and the electromagnetic field distribution at the second frequency f1 can be approximately obtained.

  Further, according to the first embodiment, the data processing unit 11 is provided in a state in which signal injection is not performed from the electromagnetic field strength (V2) of the second frequency f1 generated from the EUT 100 during signal injection. The electromagnetic field strength (V1) of the second frequency f1 generated from the test equipment 100 is reduced, and the true value of the electromagnetic field strength of the second frequency f1 corresponding to the test signal is estimated. For this reason, when the test equipment noise exists at the second frequency f1 and the detection level of the test signal of the second frequency f1 is higher than the detection level of the test equipment noise, the separation method shown in FIG. Only the electromagnetic field strength of the second frequency f1 of the signal can be estimated.

Embodiment 2. FIG.
FIG. 6 is a block diagram showing a configuration of the electromagnetic noise detection apparatus according to the second embodiment. In FIG. 6, the same or corresponding parts as in FIG. In the electromagnetic noise detection apparatus according to the second embodiment, one signal generator 20 outputs an amplitude modulation signal, and this amplitude modulation signal is used as a test signal.

  FIG. 7 shows an amplitude modulation signal output from the signal generator 20. FIG. 8 shows a frequency spectrum for explaining the relationship between the amplitude modulation signal and the test signal. The signal generator 20 superimposes the carrier wave having the frequency fc shown in FIG. 7A and the modulated signal wave having the frequency fs shown in FIG. 7B to generate an amplitude-modulated wave shown in FIG. 7C. To do. The first frequency f0 corresponds to the frequency fc of the carrier wave, and the second frequency f1 corresponds to the frequency fc + fs of the upper sideband. When the second frequency f1 and the frequency of the EUT noise are the same, the lower sideband frequency fc-fs can be used as the second frequency f2. Of course, the frequency fc−fs of the lower sideband may be used as the second frequency f1, and the frequency fc + fs of the upper sideband may be used as the second frequency f2.

  The control unit 13 sets frequencies fc and fs that can generate a test signal including a desired first frequency f0 and second frequency f1 to the signal generator 20. The frequency fs of the modulation signal is set to a frequency as low as possible so that the difference between the first frequency f0 and the second frequency f1 is small. By setting in this way, a test signal including the signal component of the first frequency f0 and the signal component of the second frequency f1 can be generated and injected into the EUT 100. The detection probe 6 receives an electromagnetic field while changing the positional relationship with the EUT 100 by the movable portion 9, and the electric field strength meter 8 measures the electromagnetic field strength of the second frequency f1 (= fc + fs).

  As described above, according to the second embodiment, the signal generator 20 is configured to amplitude-modulate the carrier wave of the first frequency f0 and generate the test signal including the sideband of the second frequency f1 (or f2). did. For this reason, the signal generation unit can be configured by only the signal generator 20 that generates the amplitude modulation signal. Also in this configuration, as in the first embodiment, the visualization of the propagation path of the signal component of the first frequency f0 when the EUT 100 malfunctions with the signal component of the first frequency f0 is approximate. Will be possible.

  In the present invention, within the scope of the invention, any combination of the embodiments, or any modification of any component in each embodiment, or omission of any component in each embodiment is possible. .

  DESCRIPTION OF SYMBOLS 1 1st signal generator, 2nd 2nd signal generator, 3 coupler, 4,7 amplifier, 5 injection probe, 6 detection probe, 8 electric field strength meter, 9 movable part, 10 scanning part, 11 data processing part, 12 Display unit, 13 control unit, 20 signal generator, 100 EUT, 101 connection cable.

Claims (4)

A signal generator that synthesizes a signal of a first frequency and a signal of a second frequency different from the first frequency to generate a test signal;
A signal injection unit for injecting the test signal generated by the signal generation unit into a test device;
A noise detection unit that detects an electromagnetic field strength of the second frequency generated from the EUT during signal injection by the signal injection unit ;
The electromagnetic noise detection apparatus , wherein the second frequency is a frequency different from a frequency of an electromagnetic field generated from the EUT in a state where the signal injection by the signal injection unit is not performed . A signal generator that synthesizes a signal of a first frequency and a signal of a second frequency different from the first frequency to generate a test signal;
A signal injection unit for injecting the test signal generated by the signal generation unit into a test device;
A noise detection unit for detecting an electromagnetic field intensity of the second frequency generated from the EUT during signal injection by the signal injection unit ;
The second generated from the EUT in a state where the signal injection by the signal injection unit is not performed from the electromagnetic field intensity of the second frequency generated from the EUT during signal injection by the signal injection unit. An electromagnetic noise detection apparatus comprising: a data processing unit that estimates a true value of an electromagnetic field intensity at the second frequency corresponding to the test signal by reducing an electromagnetic field intensity at a frequency . 3. The electromagnetic noise detection apparatus according to claim 1, wherein the signal generation unit amplitude-modulates the carrier wave of the first frequency to generate a test signal including a sideband of the second frequency. 4. . 4. The electromagnetic noise detection apparatus according to claim 1 , wherein the first frequency is a frequency at which the EUT malfunctions. 5.

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