JP2020169915A - Noise injection device and noise injection method for evaluation object, and method for improving specification of noise malfunction point in evaluation object - Google Patents

Abstract

To provide a noise injection device and noise injection method for an evaluation object with which, by injecting common-mode noise into an evaluation object, it is made possible to evaluate the influence of noise due to the mode conversion of common-mode noise, and a method for improving the specification of a noise malfunction point in the evaluation object.SOLUTION: A noise injection device 1 is constituted by comprising a signal generator 2 for generating noise, and a probe 4 for injecting the noise generated by the signal generator 2 into an evaluation object 3. One end 4a of the probe 4 is connected to the terminal of a cable 8 connected to the signal generator 2, and other ends 4b, 4b are bifurcated. Capacitors 9, 9 of the same capacitance for DC cut are provided between the one end 4a and each of the other ends 4b, 4b, respectively. A capacitor 10 for normal mode noise rejection is provided between points A, A. The tip of each of the other ends 4b, 4b which are contacted to the evaluation object 3 is sharpened in shape of a needle.SELECTED DRAWING: Figure 2

Description

The present invention specifies a noise injection device and a noise injection method for an evaluation target that injects noise generated by a signal generator into the evaluation target by a probe, and a noise countermeasure by specifying a location where noise is injected and causes a malfunction. This is related to a method for identifying and improving noise malfunction points of the evaluation target.

Conventionally, as a noise injection device for this kind of evaluation object, for example, there is a noise injection device for a printed circuit board disclosed in Patent Document 1.

In this printed circuit board noise injection device, the noise generated by the signal generator is injected into the power supply and ground pin of the device on the printed circuit board by a probe. The probe is connected to the signal generator with a coaxial cable. The probe signal, the ground pin, is soldered to the power supply of the device, the land or pad to which the ground pin is connected, on a printed circuit board on which the device that injects noise is not mounted. In this state, noise is injected from the probe to the location where the power pin of the device is connected, and the probe for measuring the near magnetic field is placed on the noise-injected printed circuit board and scanned. By this scanning, the near magnetic field on the printed circuit board is measured, and the measured electromagnetic field strength is compared with the reference.

Japanese Unexamined Patent Publication No. 2006-234803

In the immunity (electromagnetic interference sensitivity) test, which is a type of EMC test that measures noise countermeasures for electronic devices, mode conversion occurs when common mode noise enters the evaluation target object, resulting in normal mode noise and malfunction of the evaluation target object. It may cause it to wake up. However, in the conventional noise injection device disclosed in Patent Document 1, the influence of noise due to mode conversion of common mode noise cannot be evaluated without considering the mode of noise to be injected into the evaluation target.

The present invention provides a noise injection device and a noise injection method for an evaluation target, which enables evaluation of the influence of noise due to mode conversion of common mode noise by injecting common mode noise into the evaluation target. It is an object of the present invention to provide a method for identifying and improving a noise malfunction part of an evaluation target object, which makes it possible to identify a part causing a malfunction due to mode-converted noise and take noise countermeasures.

To this end, the present invention
In a noise injection device for an evaluation object, which includes a signal generator that generates noise and a probe that injects the noise generated by the signal generator into the evaluation object.
One end of the probe is connected to the end of the cable connected to the signal generator, the other end is bifurcated, and a DC cut capacitor with the same capacitance value is provided between one end and each branched end. The tip of each other end that comes into contact with the evaluation object is sharp.

Further, the present invention relates to a method for injecting noise generated in a signal generator into an evaluation target by a probe.
One end is connected to the end of the cable connected to the signal generator, the other end is bifurcated, and a DC cut capacitor with the same capacitance value is provided between one end and each branched end, and the evaluation target is It is characterized in that noise is injected into the evaluation object by a probe having a sharp tip at each other end that is brought into contact with the object.

According to this configuration, the noise generated by the signal generator is input to the probe whose one end is connected to the end of the cable, and the noise signal of the same phase, that is, the common mode noise, is generated at the bifurcated other end in the probe. become. This common mode noise is injected into the evaluation target by bringing the tips of the other ends into contact with the two evaluation targets. Therefore, it is possible to evaluate the influence of the injected common mode noise on the evaluation target object from the normal mode noise generated by mode conversion on the evaluation target object. At this time, at the tip of each other end of the probe that is brought into contact with the object to be evaluated, the DC component is cut from the common mode noise by the DC cutting capacitor provided between one end and each branched other end. .. Therefore, when the tip of each other end is brought into contact with the object to be evaluated, there is no risk of electric shock even if the fingertip of the operator touches each tip. Further, since the tip of each other end of the probe is sharp, it is not necessary even if the contact portion with the evaluation object is small such as a terminal pin of an electronic component or a thin one such as a wiring pattern of a circuit board. The tip of each other end of the probe can be reliably and easily brought into contact with the target portion of the evaluation object without touching the portion.

Further, the present invention includes a step of injecting noise into an arbitrary part of the evaluation object by the above noise injection method, a step of confirming a malfunction state of the evaluation object when noise is injected into each part, and an evaluation object. A method for identifying and improving the noise malfunctioning part of the evaluation target object was constructed by including a step of identifying a part where the object causes a malfunction and a step of taking noise countermeasures at the identified malfunctioning part.

According to this configuration, by injecting noise into the evaluation object by the above noise injection method, it is possible to identify the part of the evaluation object that malfunctions due to the noise converted from the common mode to the normal mode, and to evaluate the evaluation object. It becomes possible to easily take measures against noise.

According to the present invention, a noise injection device and a noise injection method for an evaluation object, which makes it possible to evaluate the influence of noise due to mode conversion of common mode noise by injecting common mode noise into the evaluation object. In addition, it is possible to provide a noise malfunction location identification improvement method for an evaluation target object, which makes it possible to identify a location where a malfunction occurs due to mode-converted noise and easily take noise countermeasures.

It is a block diagram which shows the schematic structure of the noise injection apparatus into the evaluation object by one Embodiment of this invention. (A) is an internal configuration of a probe constituting the noise injection device shown in FIG. 1, (b) is an equivalent circuit diagram, and (c) is an appearance. It is a flowchart which shows the noise malfunction part identification improvement method of the evaluation object by one Embodiment of this invention.

Next, a mode for carrying out the noise injection device and the noise injection method to the evaluation object according to the present invention will be described.

FIG. 1 is a block diagram showing a schematic configuration of a noise injection device 1 into an evaluation object according to an embodiment of the present invention.

The noise injection device 1 includes a signal generator 2 that generates noise and a probe 4 that injects the noise generated by the signal generator 2 into the evaluation object 3. In the present embodiment, in the noise injection device 1, a signal amplifier (amplifier) 5, a signal attenuator (attenuator) 6, and a directional coupler (power meter) 7 are connected between the signal generator 2 and the probe 4. Will be done.

The signal generator 2 is composed of a signal generator that outputs a clock waveform signal, a sine wave signal, or the like having an arbitrary frequency. The internal configuration of the probe 4 is shown in FIG. 2A, the equivalent circuit diagram is shown in FIG. 2B, and the appearance is shown in FIG. 2C.

As shown in FIG. 4A, the probe 4 has one end 4a connected to the end of a cable 8 connected to the signal generator 2, and the other ends 4b and 4b bifurcated. DC cutting capacitors 9 and 9 having the same capacitance value are provided between the one end 4a and the other ends 4a and 4a that are branched. The end of the cable 8 and one end 4a of the probe 4 are connected by soldering the end of the cable 8 and each end of the DC cutting capacitors 9 and 9. Further, the tips of the other ends 4b and 4b that come into contact with the evaluation object 3 are pointed like needles. In the present embodiment, the probe 4 is a normal mode noise that connects A between the tip of the DC cut capacitor 9 and the other end 4b and A between the tip of the DC cut capacitor 9 and the other end 4b. The removal capacitor 10 is provided as an X capacitor. Both ends of the normal mode noise removing capacitor 10 are soldered at points A and A. The normal mode noise removing capacitor 10 is preferably provided, but it is not always necessary and may not be provided.

Therefore, as shown in FIG. 3B, the probe 4 is used for removing normal mode noise on the branch side of the DC cut capacitors 9 and 9 connected in parallel and connected in parallel. The capacitor 10 has a circuit configuration that bridges between the DC cutting capacitors 9 and 9. As shown in FIG. 6C, the periphery of the pair of DC cutting capacitors 9 and 9 and the normal mode noise removing capacitor 10 is covered with an insulator 11. The capacitance values of the DC cut capacitors 9 and 9 and the normal mode noise removing capacitor 10 are set to the same value. Considering the DC cut, it is desirable that this capacitance value is about 6.8 [pF] up to a noise frequency of 200 [MHz] and about 4 [pF] up to 200 [MHz] or more.

The noise injection method for the evaluation target according to the embodiment of the present invention is performed using such a noise injection device 1. That is, one end 4a is connected to the end of the cable 8 connected to the signal generator 2, the other ends 4b and 4b are bifurcated, and a direct current having the same capacitance value is connected between the one end 4a and the other ends 4a and 4a. Noise generated by the signal generator 2 is injected into the evaluation object 3 by the probe 4 in which the cutting capacitors 9 and 9 are provided and the tips of the other ends 4b and 4b that are brought into contact with the evaluation object 3 are sharpened. Will be done.

According to the noise injection device 1 and the noise injection method according to the present embodiment, the noise generated by the signal generator 2 is input to the probe 4 to which one end 4a is connected to the end of the cable 8 and is inside the probe 4. At the other ends 4b and 4b branched into two branches, noise signals having the same phase, that is, common mode noise. This common mode noise is injected into the evaluation object 3 when the tips of the other ends 4b and 4b are brought into contact with the two places of the evaluation object 3. Therefore, it is possible to evaluate the influence of the injected common mode noise on the evaluation target 3 from the normal mode noise generated by the mode conversion on the evaluation target 3.

At this time, the tips of the other ends 4b and 4b of the probe 4 that are brought into contact with the evaluation object 3 are the DC cutting capacitors 9 and 9 provided between the one end 4a and the branched other ends 4a and 4a, respectively. As a result, the DC component is cut from the common mode noise. Therefore, when the tips of the other ends 4b and 4b are brought into contact with the evaluation object 3, even if the fingertips of the operator touch the tips, there is no risk of electric shock. Further, since the tips of the other ends 4b and 4b of the probe 4 are pointed like needles, even if the contact portion with the evaluation target 3 is small or thin, the evaluation target does not touch an unnecessary part. The tips of the other ends 4b and 4b of the probe 4 can be reliably and easily brought into contact with the target location of 3.

For example, in injecting noise into the evaluation object 3, each pointed tip of the probe 4 is brought into contact with the terminal pin of the electronic component mounted on the circuit board or the wiring pattern of the circuit board, and the electronic component mounted on the circuit board. When injecting noise generated by the signal generator 2, since the tips of the other ends 4b and 4b of the probe 4 are pointed like needles, there is no need other than the terminal pins of electronic components and the wiring pattern of the circuit board. The tips of the other ends 4b and 4b of the probe 4 can be reliably and easily brought into contact with the small terminal pins and thin wiring patterns of the target electronic component without touching the portion.

Further, in the noise injection device 1 and the noise injection method according to the present embodiment, the normal mode noise appearing at the other ends 4b and 4b branched into two branches in the probe 4 is removed by the normal mode noise removing capacitor 10. Therefore, pure common mode noise is injected into the evaluation target object 3, and the common mode noise is mode-converted so that the influence of the noise on the evaluation target object 3 can be evaluated with high accuracy. Further, the capacitance value in the frequency band of the normal mode noise to be removed by the normal mode noise removing capacitor 10 is inevitably the same as the capacitance value in the frequency band to be cut by the DC cutting capacitors 9 and 9. Therefore, the capacitance value of the normal mode noise removing capacitor 10 can be determined by selecting the same capacitance value of the DC cut capacitors 9 and 9 without calculating the capacitance value. Therefore, the capacitance value of the normal mode noise removing capacitor 10 can be easily selected.

Further, in the noise injection device 1 and the noise injection method according to the present embodiment, when the level of noise generated by the signal generator 2 is small, it is amplified to an appropriate level by the signal amplifier 5, and the probe 4 to the evaluation object 3 Is injected into. Therefore, it is possible to inject a large level of noise into the evaluation object 3. When the level of noise generated by the signal generator 2 is large, it is attenuated to an appropriate level by the signal attenuator 6 and injected from the probe 4 into the evaluation object 3. Therefore, it is possible to prevent the waveform quality of the noise injected from the signal generator 2 into the evaluation object 3 from being deteriorated. Further, when the level of noise reflected from the evaluation object 3 and returned to the signal generator 2 side is large, the level is attenuated to an appropriate level by the signal attenuator 6. Therefore, it is possible to prevent the signal generator 2 from failing due to the large noise returned.

Further, in the noise injection device 1 and the noise injection method according to the present embodiment, the directional coupler 7 is connected between the signal generator 2 and the probe 4. Therefore, it is possible to measure the traveling wave power of noise propagating in the forward direction and the reflected wave power of noise propagating in the reverse direction of the directional coupler 7. Therefore, it is possible to grasp the noise level injected from the probe 4 into the evaluation object 3 and the noise level reflected by the evaluation object 3 and returned to the signal generator 2. Therefore, the noise level injected into the evaluation object 3 and the noise level reflected by the evaluation object 3 are grasped by the directional coupler 7, and the noise level generated by the signal generator 2 is appropriately adjusted. Noise evaluation A constant level of noise can be injected into each injection location without changing depending on the injection location into the object 3. Therefore, it is possible to accurately compare the noise sensitivity resistance at each location of the evaluation target object 3, and it is possible to accurately evaluate the influence of noise on the evaluation target object 3 by the mode conversion of the common mode noise.

Next, a method for identifying and improving noise malfunction locations of the evaluation target according to the embodiment of the present invention will be described. FIG. 3 is a flowchart showing a method for identifying and improving a noise malfunction portion of the evaluation object 3 according to the present embodiment.

In this method, in the first step 101, noise is injected into an arbitrary portion of the evaluation object 3 by the noise injection method of the above embodiment. At this time, when the evaluation object 3 is an in-vehicle device mounted on a vehicle, unmodulated noise is most affected by the in-vehicle device. Therefore, it is preferable that the noise generated by the signal generator 2 is unmodulated. .. Further, when the evaluation object 3 is an IC (integrated circuit), the noise generated by the signal generator 2 is AM-modulated because the IC is more susceptible to noise and malfunctions if it has noise modulation. And FM modulation are preferable. The modulation interval is set according to the interval specified in the ISO11452-9 standard. In addition, the level of noise to be injected is set to a low level such as 1 [dBμV] at the beginning of the test. This is because if a high level of noise is injected from the beginning, the evaluation object 3 may be damaged.

Further, it is desirable that the probe 4 is brought into contact with the probe 4 manually. By manually contacting the circuit board, it is possible to contact not only the power supply and ground of the circuit board but also any part of the circuit board, for example, the terminal pin of each IC, the wiring pattern of the circuit board, and the harness. Further, the contact time of the probe 4 with the evaluation object 3 is set to be longer than the time during which the presence or absence of malfunction can be confirmed by contact, specifically, 3 seconds or longer in accordance with the ISO11452-9 standard.

Next, in step 102, the malfunction status of the evaluation object 3 when noise is injected into each portion is confirmed. If the malfunction of the evaluation object 3 cannot be confirmed, the noise level is increased by, for example, 10 [dBμV], and the malfunction status of the evaluation object 3 is confirmed. The method of confirming the malfunction status differs depending on the type of the evaluation object 3. When the evaluation object 3 is, for example, a camera, the malfunction can be confirmed by the image displayed on the monitor connected to the camera into which noise is injected.

Next, in step 103, a portion where the evaluation object 3 malfunctions is specified. When the evaluation object 3 is, for example, a camera, common mode noise is introduced into the camera to cause mode conversion, so that the image on the monitor is disturbed and nothing can be seen. Therefore, when noise is injected into a portion vulnerable to noise, it is possible to identify the location where the evaluation object 3 malfunctions from the image on the monitor. In this step 103, the mode conversion location is not specified. It is presumed that there are many places where the common mode noise injected by the probe 4 causes mode conversion to normal mode noise, but if the level of normal mode noise after mode conversion is small, this does not matter. In this step 103, the level of the normal mode noise after the mode conversion is considerably high, and the location where the evaluation target 3 causes a malfunction is specified.

Next, in step 104, noise countermeasures are applied to the specific portion of the evaluation object 3 that causes the malfunction specified in step 103. As a noise countermeasure, inserting a filter is mentioned, and it is effective to insert a common mode choke coil or a Y capacitor at a specific place. When the specific location is two lines such as a differential signal line, it is effective to insert a ferrite bead inductor having the same constant. The noise suppression effect before and after the filter is inserted can be confirmed in the state of the image displayed on the monitor, as in the case of confirming the occurrence of a malfunction situation.

According to the noise malfunction location identification improvement method of the evaluation object of the present embodiment, by injecting noise into the evaluation object 3 by the noise injection method of the above embodiment, the evaluation object 3 is changed from the common mode to the normal mode. It is possible to identify a location where a malfunction occurs due to noise converted into a mode, and easily take noise countermeasures for the evaluation object 3.

An experiment for confirming the effect of the noise malfunction location identification improvement method for the evaluation target according to the above embodiment was performed using the evaluation target 3 as a camera. The experiment was carried out according to the above flowchart, and as a result of injecting common mode noise into the camera by the noise injection method according to the above embodiment in the above step 101, it was confirmed that a malfunction occurs in the above step 102, and the above. In step 103, the location where the malfunction occurred was identified. When the common mode noise countermeasure for inserting the common mode choke coil into a specific place was taken in the above step 104, the image displayed on the monitor was distorted, but now it is displayed normally, and the malfunction is improved. Was confirmed. That is, the effect of the noise malfunction location identification improvement method of the evaluation target according to the above embodiment was confirmed.

1 ... Noise injection device 2 ... Signal generator 3 ... Evaluation object 4 ... Probe 4a ... One end of probe 4 4b ... The other end of probe 4 5 ... Signal amplifier 6 ... Signal attenuator 7 ... Directional coupler 8 ... Cable 9 ... DC cut capacitor 10 ... Normal mode noise removal capacitor 11 ... Insulator

Claims (9)

In a noise injection device for an evaluation object, which includes a signal generator that generates noise and a probe that injects the noise generated by the signal generator into the evaluation object.
One end of the probe is connected to the end of a cable connected to the signal generator, the other end is bifurcated, and a DC cutting capacitor having the same capacitance value is inserted between the one end and each of the branched ends. A noise injection device for an evaluation object, each of which is provided and has a sharp tip at the other end of each contact with the evaluation object. The probe includes a normal mode noise removing capacitor that connects between the DC cut capacitor and the tip of one of the other ends, and between the DC cut capacitor and the tip of the other end. The noise injection device for the evaluation object according to claim 1. The noise injection device for an evaluation object according to claim 2, wherein the capacitor for cutting DC and the capacitor for removing normal mode noise have the same capacitance value. The noise injection device for an evaluation object according to any one of claims 1 to 3, wherein a directional coupler is connected between the signal generator and the probe. The noise injection device for an evaluation object according to any one of claims 1 to 4, wherein a signal amplifier is connected between the signal generator and the probe. The noise injection device for an evaluation object according to any one of claims 1 to 5, wherein a signal attenuator is connected between the signal generator and the probe. In the noise injection method for the evaluation target, the noise generated by the signal generator is injected into the evaluation target by the probe.
One end is connected to the end of the cable connected to the signal generator, the other end is bifurcated, and a DC cut capacitor having the same capacitance value is provided between the one end and each of the branched ends. A method for injecting noise into an evaluation object, which comprises injecting noise into the evaluation object by a probe having a sharp tip at the other end of the probe that is brought into contact with the evaluation object. Each pointed tip of the probe is brought into contact with a terminal pin of an electronic component mounted on a circuit board, and noise generated by the signal generator is injected into the electronic component mounted on the circuit board. The method for injecting noise into an evaluation object according to claim 7. A step of injecting noise into an arbitrary portion of the evaluation object by the noise injection method according to claim 7 or 8, and a step of confirming a malfunction state of the evaluation object when noise is injected into each portion. A method for identifying and improving a noise malfunctioning part of an evaluation object, comprising a step of identifying a part where the evaluation object causes a malfunction and a step of taking a noise countermeasure at the specified malfunctioning part.

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