JP7172370B2 - Radiated Emission Measurement Equipment - Google Patents

Description

The present invention relates to a radiated emission measuring device.

In general, electronic equipment may radiate radiated interference waves that affect surrounding electronic equipment and communication equipment. For this reason, it is now necessary to conduct radiated EMI tests to confirm that the field strength of radiated EMI is below the permissible value of international standards before electronic devices are shipped to the market. . For example, Patent Literature 1 discloses an electromagnetic field measuring device that measures the electric field strength of radiated interference waves.

Japanese Patent No. 4915050

However, this electromagnetic field measuring device compares the height of the receiving antenna when the maximum value of the electromagnetic wave is obtained with the radio wave propagation characteristics that are stored in a database for each frequency and polarization, and based on the result of the comparison, the maximum value is Verify the reliability of whether or not it was properly acquired. Therefore, if the database is not complete, this electromagnetic field measurement device may not be able to determine whether the electric field strength distribution measured in the radiated emission test can be used for estimating the maximum radiation position.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a radiated emission measuring apparatus capable of determining whether or not the electric field strength distribution measured in a radiated emission test can be used for estimating the maximum radiation position.

One aspect of the present invention is to measure the electric field intensity in a predetermined frequency band at a plurality of measurement points set on a surface surrounding a radiation source of radiated interfering waves at a first sampling time, whereby the electric field intensity on the surface A first measurement unit that measures the distribution, and at the measurement points where predetermined electric field strengths are measured among the plurality of measurement points, the electric field strength is measured every second sampling time, thereby measuring the electric field strength time waveform. a second measuring unit that applies a median filter to the electric field strength distribution; a calculation unit that applies a median filter to the electric field strength distribution; calculates an allowable rate of spike noise for the electric field strength distribution to which the median filter is applied; A radiated interference measurement device comprising: a calculation unit that calculates a probability that long-period noise is measured; .

According to the invention, it can be determined whether the electric field strength distribution measured in the radiated emission test can be used for estimating the position of maximum radiation.

It is a figure which shows an example of a structure of the radiated emission measuring apparatus which concerns on embodiment. It is a figure which shows an example of the electric field strength distribution which the radiated interference measuring device based on embodiment measured. It is a figure which shows an example of the electric field strength time waveform which the radiated interference measuring device based on embodiment measured. It is a figure which shows an example of the hardware constitutions of the control part which concerns on embodiment. 6 is a flow chart showing an example of processing executed by the radiated emission measuring device according to the embodiment; 6 is a flow chart showing an example of processing executed by the radiated emission measuring device according to the embodiment;

[Embodiment]
An example of the configuration of a radiated emission measurement apparatus according to an embodiment will be described with reference to FIGS. 1 to 4. FIG. FIG. 1 is a diagram showing an example of the configuration of a radiated emission measuring device according to an embodiment.

A radiated interference measuring apparatus 1 shown in FIG. 1 is, for example, an apparatus used in a radiated interference test for measuring radiated interference emitted from a radiation source 100, which is a specimen, according to EMC standards. The radiated emission measurement device 1 is placed in an anechoic chamber with a metal floor forming a ground plane. A radio wave absorber is attached to the inner walls of the anechoic chamber except for the metal floor. Also, the radiation source 100 referred to here is, for example, an electronic device that emits radiation interfering waves.

As shown in FIG. 1, the radiated interference measuring apparatus 1 includes an antenna 11, an antenna mast 12, a turntable 13, a drive control section 14, a first measurement section 21, a second measurement section 22, a control and a section 30 .

The antenna 11 receives radiated interfering waves emitted by the radiation source 100 . Further, the antenna 11 is supported by the antenna mast 12 so as to be able to move up and down, and is arranged at a predetermined distance from the radiation source 100 . The turntable 13 is a disk-shaped turntable provided on the ground plane, and can rotate about an axis perpendicular to the ground plane. A radiation source 100 is placed on a table 200 placed on the turntable 13 . The drive control unit 14 drives the antenna mast 12 to raise and lower the antenna 11 , and drives the turntable 13 to rotate the radiation source 100 and the table 200 .

The first measurement unit 21 is, for example, a superheterodyne spectrum analyzer or an FFT-based spectrum analyzer. The first measurement unit 21 measures the electric field intensity in a predetermined frequency band at a plurality of measurement points set on the surface surrounding the radiation source 100 of the radiated interfering waves at a first sampling time, thereby measuring the electric field intensity on the surface. Measure the distribution.

Specifically, the first measurement unit 21 measures the frequency spectrum of the electric field strength at each measurement point while sweeping the frequency band for measuring the electric field strength every first sampling time. Here, the first sampling time is the electric field intensity measurement time in each frequency band, which is obtained by dividing the time required for sweeping all frequency bands by the number of frequency bands for which the electric field intensity is measured. Then, the first measurement unit 21 maps the electric field intensity on a plane in which the horizontal axis is the azimuth angle of the turntable 13 and the vertical axis is the height of the antenna 11 for each frequency band. Thereby, the first measurement unit 21 measures, for example, the electric field strength distribution shown in FIG.

FIG. 2 is a diagram showing an example of electric field intensity distribution measured by the radiated emission measuring device according to the embodiment. The electric field strength distribution shown in FIG. 2 represents the electric field strength in a predetermined frequency band at a plurality of measurement points set on the plane surrounding the radiation source 100 by a line connecting points of equal electric field strength. These measurement points correspond to the grid points shown in FIG. Also, the first measurement unit 21 measures the electric field strength distribution of the same kind as the electric field strength distribution shown in FIG. 2 for each frequency band.

A plurality of squares S displayed in the electric field intensity distribution shown in FIG. 2 indicate that spike noise was measured at the measurement point. The spike noise referred to here is noise that rarely can be measured by the first measurement unit 21 or the second measurement unit 22 described later, and is emitted by the first measurement unit 21 or the second measurement unit 22 described later. Measured when the interference measurement fails.

Spike noise can be removed by a median filter. The median filter is a filter that extracts the median value of the value of the point of interest to which the filter is applied and the values of points adjacent to the point of interest, and replaces the value of the point of interest with the median value.

The second measuring unit 22 is a measuring device capable of continuously measuring the electric field strength every second sampling time, such as a real-time spectrum analyzer, a spectrum analyzer set to zero span mode, or an EMI receiver. The second measurement unit 22 measures the electric field strength at each second sampling time at the measurement point where the predetermined electric field strength is measured among the plurality of measurement points for a predetermined time, thereby measuring the electric field strength time. Measure the waveform. This predetermined time is also called monitoring time.

The predetermined electric field strength referred to here is, for example, the maximum electric field strength among the electric field strengths measured at these plurality of measurement points, and may be an electric field strength exceeding a predetermined threshold value. Further, the measurement point where the predetermined electric field strength is measured here is the measurement point where the electric field strength measured by the first measuring unit 21 exceeds the predetermined electric field strength threshold. A measurement point at which the electric field strength measured by the first measurement unit 21 is equal to or less than a predetermined electric field strength threshold is also called a null point. Furthermore, the second sampling time is preferably the same length as the first sampling time.

FIG. 3 is a diagram showing an example of an electric field strength time waveform measured by the radiated emission measuring device according to the embodiment. For example, as shown in FIG. 3, the electric field strength time waveform includes points where the electric field strength is approximately 60 dBμV/m and points where the electric field strength is between 20 and 25 dBμV/m. The fact that the electric field strength is about 60 dBμV/m means that the second measuring section 22 was used to successfully measure the noise. On the other hand, the fact that the electric field strength is 20 to 25 dBμV/m means that the second measuring section 22 fails to measure the noise, that is, the second measuring section 22 cannot measure the spike noise. The point is that

Note that the frequency resolution bandwidth of the second measuring section 22 is preferably the same as the frequency resolution bandwidth of the first measuring section 21 . Moreover, the detection method by which the second measurement unit 22 measures the electric field intensity is preferably the same as the detection method by which the first measurement unit 21 measures the electric field intensity distribution.

The control unit 30 includes a calculation unit 301 , a calculation unit 302 and a determination unit 303 .

The calculation unit 301 applies a median filter to the electric field strength distribution measured by the first measurement unit 21 . For example, the calculation unit 301 applies a median filter to each measurement point of this electric field intensity distribution. Moreover, the calculation unit 301 applies a smoothing filter to the electric field intensity distribution measured by the first measurement unit 21 . A smoothing filter is, for example, a low-pass filter or a moving average filter, and is applied to obtain a linear and accurate electric field strength distribution comparable to the case of increasing the capture rate.

The calculation unit 302 calculates the allowable rate of spike noise for the electric field strength distribution to which the median filter is applied. Specifically, the calculator 302 calculates the permissible rate based on the principle described below.

Assuming that the probability of measuring long-term noise is X, and the number of measurement points set on the plane surrounding radiation source 100 is _Nm , the probability of measuring N long-term noise is given by the following equation (1 ). The long-period noise referred to here is noise that can rarely be measured by the first measurement unit 21 or the second measurement unit 22, and the period of occurrence is longer than the first sampling time of the first measurement unit 21. . Equation (1) can also be interpreted as the probability that N spike noises are measured in the electric field intensity distribution before the median filter is applied.

When a one-dimensional median filter is used, the calculation unit 301 extracts the median of the values of the point of interest and the points adjacent to the point of interest, and replaces the value of the point of interest with the median value. Therefore, the calculation unit 301 can remove the spike noise when the spike noises are not adjacent to each other. Here, the probability of adjacent spike noises is represented by the following equation (2).

The probability that N spike noises occur in the electric field intensity distribution measured by the first measurement unit 21 and that the spike noises are adjacent to each other is represented by the following equation (3). Equation (3) is the product of Equations (1) and (2).

In the electric field strength distribution to which the median filter is applied by the calculation unit 301, the probability P(X) that N _S or less spike noises are measured is expressed by the following equation (4).

When the probability P(X) that N _S or less spike noises are measured is given, the calculation unit 302 calculates the probability X that the long-period noise is measured using the equation (4) using a median filter. is calculated as the allowable rate X of spike noise for the electric field intensity distribution to which is applied.

Further, the calculation unit 302 calculates the probability X _m that the long-period noise is measured based on the electric field strength temporal waveform measured by the second measurement unit 22 . For example, when the electric field strength is measured _NP times every second sampling time during the monitoring time, the calculation unit 302 calculates a statistical value of the measured values of the electric field strength for _NP times, such as an average value or a median value. do. Also, here, the object is to determine that spike noise is occurring when the electric field strength measured at every second sampling time deviates from the statistical value by more than a predetermined threshold. Therefore, the calculation unit 302 sets the predetermined threshold to, for example, half the statistical value. Then, the calculation unit 302 counts the number of times _NSP that the electric field strength becomes equal to or less than the predetermined threshold when the electric field strength is measured N _P times for each second sampling time during the monitoring time, and the long-period noise is Calculate the measured probability X _m =N _SP /N _P .

In this case, the determination unit 303 determines whether or not the probability _Xm that long-period noise is measured is equal to or less than the allowable rate X. If it is determined that the long-period noise measured probability X _m is less than or equal to the allowable rate X, the electric field strength distribution measured by the first measuring unit 21 can be used to estimate the maximum radiation position. On the other hand, if it is determined that the long-period noise measured probability X _m exceeds the allowable rate X, the electric field strength distribution measured by the first measurement unit 21 cannot be used to estimate the maximum radiation position. .

Furthermore, the calculation unit 302 calculates the statistical value of the electric field strength for each second sampling time, the difference between the electric field strength for each second sampling time and the statistical value, the allowable rate X, and the second measurement unit 22 for each second sampling time. A threshold number of times, which is the product of the number of times _NP of measuring the electric field intensity, may be calculated. The statistical values referred to here are, for example, average values and median values. Also, here, the object is to determine that spike noise is occurring when the electric field strength measured at every second sampling time deviates from the statistical value by more than a predetermined threshold. Therefore, the calculation unit 302 sets the difference threshold for the difference between the electric field intensity for each second sampling time and the statistical value to be half the statistical value.

In this case, the determining unit 303 determines that the number of times the difference between the electric field intensity measured by the second measuring unit 22 for each second sampling time and the statistical value of the electric field intensity for each second sampling time exceeds a predetermined difference threshold is , is equal to or less than the number of times threshold. If it is determined that the number of times the difference exceeds the predetermined difference threshold is equal to or less than the number threshold, the electric field intensity distribution measured by the first measurement unit 21 can be used to estimate the maximum radiation position. On the other hand, if it is determined that the number of times the difference exceeds the predetermined difference threshold exceeds the number of times threshold, the electric field intensity distribution measured by the first measurement unit 21 cannot be used to estimate the maximum radiation position. .

4 is a diagram illustrating an example of a hardware configuration of a control unit according to the embodiment; FIG. As shown in FIG. 4 , the controller 30 includes a main controller 310 , an input device 320 , an output device 330 , a storage device 340 and a bus 350 .

The main control unit 310 includes a CPU (Central Processing Unit) and a RAM (Random Access Memory), controls transmission and reception of data between the input device 320, the output device 330 and the storage device 340, and controls the output device 330 and It controls the operation of storage device 340 .

The input device 320 is a device used for inputting data necessary for operating the radiated interference measurement device 1, such as a keyboard, mouse, and touch panel.

The output device 330 is a device, such as a display, used to output information related to the operation of the radiated emission measuring device 1 .

The storage device 340 is a device used to store data, such as a hard disk device or an optical disk device. The storage device 340 also includes a storage medium 345 , stores data in the storage medium 345 , and reads data from the storage medium 345 . Storage medium 345 is a storage medium used to store data, such as a hard disk or an optical disk. Further, the storage medium 345 may store programs that implement the calculation unit 301, the calculation unit 302, and the determination unit 303, respectively. In this case, the main control unit 310 implements the functions of the calculation unit 301, the calculation unit 302, and the determination unit 303 by reading and executing these programs.

The bus 360 connects the main controller 310, the input device 320, the output device 330 and the storage device 340 so that they can communicate with each other.

Next, an example of the operation of the radiated interference measurement device according to the embodiment will be described with reference to FIGS. 5 and 6. FIG. 5 and 6 are flowcharts showing an example of processing executed by the radiated emission measurement device according to the embodiment.

In step S<b>10 , the control unit 30 receives an input of measurement conditions when the first measurement unit 21 measures the electric field intensity distribution. The measurement conditions referred to here include, for example, the frequency band for measuring the electric field intensity distribution, the measurement range in the height direction based on the ground plane, the interval between measurement points in the height direction, the measurement range in the azimuth direction, and the azimuth direction. In the field strength distribution to which the first sampling time, the second sampling time, the detection method of each of the first measurement unit 21 and the second measurement unit 22, the frequency resolution bandwidth and the monitoring time, and the median filter are applied The allowable number of noise spikes N _S , the probability P(X) that less than or equal to N _S noise spikes are measured, and the difference threshold.

In step S20, the calculation unit 302 calculates the allowable rate X of spike noise for the electric field strength distribution to which the median filter is applied. In this case, the calculation unit 302 calculates the number N _S of spike noises allowed in the electric field strength distribution to which the median filter is applied and the probability P(X) that N _S or less spike noises are measured. is used for the calculation.

In step S30, the control unit 30 sets the first measurement unit 21 to measure the electric field strength distribution with the first sampling time, detection method, and frequency resolution bandwidth that have been received in step S10.

In step S40, the control unit 30 controls the drive control unit 14 to drive the antenna mast 12, and measures the electric field intensity at the lower limit measurement point of the measurement range in the height direction for which the input was accepted in step S10. Antenna 11 is moved to a position where Further, in step S40, the control unit 30 controls the drive control unit 14 to the azimuth angle at which the electric field strength at the lower limit measurement point of the measurement range in the azimuth angle direction whose input was accepted in step S10 can be measured. Rotate the turntable 13 .

In step S50, the control unit 30 acquires data indicating the current height of the antenna 11 and data indicating the azimuth angle of the turntable 13 from the drive control unit 14, and calculates the electric field intensity measured by the first measurement unit 21. get. The data indicating the height of the antenna 11, the data indicating the azimuth angle of the turntable 13, and the electric field strength acquired in step S50 are stored in the storage device 340 in association with each other.

In step S60, the control unit 30 controls the drive control unit 14 to rotate the turntable 13 by the distance between the measurement points in the azimuth direction for which the input was received in step S10.

In step S70, the control unit 30 acquires data indicating the current azimuth angle of the turntable 13 from the drive control unit 14, and determines that the current azimuth angle of the turntable 13 is in the direction of the azimuth angle whose input was accepted in step S10. Determine whether or not the upper limit of the measurement range is reached. When the control unit 30 determines that the current azimuth angle of the turntable 13 is the upper limit of the measurement range in the azimuth angle direction (step S70: Yes), the process proceeds to step S80, and the current azimuth angle of the turntable 13 is not the upper limit of the measurement range in the azimuth direction (step S70: No), the process returns to step S50.

In step S80, the control unit 30 controls the drive control unit 14 to drive the antenna mast 12, and raises the antenna 11 by the distance between the measurement points in the height direction for which the input was received in step S10.

In step S90, the control unit 30 acquires data indicating the current height of the antenna 11 from the drive control unit 14, and determines that the current height of the antenna 11 is the measurement range in the height direction for which the input was received in step S10. is the upper limit of . When the control unit 30 determines that the current height of the antenna 11 is the upper limit of the measurement range in the height direction (step S90: Yes), the process proceeds to step S100, and the current height of the antenna 11 is increased. If it is determined that it is not the upper limit of the measurement range in the vertical direction (step S90: No), the process returns to step S50.

The radiated interference measuring apparatus 1 measures the electric field intensity distribution in a predetermined frequency band at a plurality of measurement points set on the plane surrounding the radiated emission source 100 of the radiated interference through the above-described steps S10 to S90. do. That is, the radiated interference measuring apparatus 1 changes the height of the antenna 11 and the azimuth angle of the turntable 13 in order to search for the position where the maximum electric field strength can be measured, and measures Measure the electric field intensity distribution at

In step S100, the calculation unit 301 applies a median filter and a smoothing filter to the electric field intensity distribution of each frequency band.

In step S110, control unit 30 receives an input of the determination frequency band. The determination frequency band referred to here is a frequency band for determining whether or not the electric field strength distribution to which the median filter is applied can be used for estimating the maximum radiation position.

In step S120, the control unit 30 specifies the height of the antenna 11 and the azimuth angle of the turntable 13 at which the maximum electric field intensity is measured in the electric field intensity distribution in the judgment frequency band, and data indicating the height and the Data indicating the azimuth angle is stored in the storage device 340 .

In step S130, the control unit 30 controls the drive control unit 14 to drive the antenna mast 12 and move the antenna 11 to the height specified in step S120. Also, in step S130, the control unit 30 controls the drive control unit 14 to rotate the turntable 13 to the azimuth angle specified in step S120.

In step S140, the control unit 30 sets the second measurement unit 22 so as to measure the electric field strength distribution with the second sampling time, detection method, and frequency resolution bandwidth that have been input in step S10.

In step S150, the control unit 30 uses the second measurement unit 22 to measure the electric field strength every second sampling time during the monitoring time, and measures the electric field strength time waveform. The electric field strength temporal waveform measured in step S150 is stored in the storage device 340. FIG.

In step S160, the calculation unit 302 calculates the statistical value of the electric field strength for each second sampling time, the difference between the electric field strength for each second sampling time and the statistical value, the tolerance calculated in step S20, and the second measurement unit 22 is the product of the number of times the field strength is measured every second sampling time. The statistical value, the difference, and the frequency threshold calculated by the calculator 302 are stored in the storage device 340 .

In step S170, the determining unit 303 determines the number of times that the difference between the electric field intensity measured by the second measuring unit 22 for each second sampling time and the statistical value of the electric field intensity for each second sampling time exceeds a predetermined difference threshold. is equal to or less than the number of times threshold. If the determination unit 303 determines that the number of times the difference exceeds the predetermined difference threshold is equal to or less than the number of times threshold (step S170: Yes), the process proceeds to step S180, and the number of times the difference exceeds the predetermined difference threshold is If it is determined that the number of times exceeds the threshold (step S170: No), the process proceeds to step S190.

In step S180, the control unit 30 causes the output device 330 to display information indicating that the electric field intensity distribution to which the median filter is applied can be used for estimating the maximum radiation position, and terminates the process.

In step S190, the control unit 30 causes the output device 330 to display information indicating that the electric field strength distribution to which the median filter is applied cannot be used for estimating the maximum radiation position, and terminates the process.

In addition, when performing the determination described above with a plurality of determination frequencies, the EMI measuring apparatus 1 may repeat steps S110 to S190.

The radiated emission measuring device 1 according to the embodiment has been described above. The radiated interference measurement device 1 calculates, for example, the allowable rate X of spike noise for the field strength distribution to which the median filter is applied using the above equation (4), and determines the long-period noise based on the field strength time waveform. is measured, and it is determined whether the probability that long-period noise is measured is equal to or less than the allowable rate X. That is, the radiated interference measuring apparatus 1 performs the determination based on the allowable rate X of spike noise, which has a clear relationship with the electric field intensity distribution to which the median filter is applied. Therefore, the radiated emission measuring apparatus 1 can accurately determine whether or not the electric field strength distribution to which the median filter is applied can be used for estimating the maximum radiation position.

In addition, the radiated interference measurement device 1 calculates the threshold for the number of times, which is the product of the allowable rate X and the number of times the second measurement unit 22 measures the electric field strength every second sampling time, and the second measurement unit 22 measures It is determined whether or not the number of times the difference between the obtained field strength for each second sampling time and the statistical value of the field strength for each second sampling time exceeds a predetermined difference threshold is equal to or less than the number of times threshold. That is, the EMI measurement apparatus 1 performs the determination based on the frequency threshold directly derived from the spike noise tolerance X, which has a clear relationship with the field strength distribution to which the median filter is applied. Therefore, the radiated emission measuring apparatus 1 can accurately determine whether or not the electric field intensity distribution to which the median filter is applied can be used for estimating the maximum radiation position.

In addition, the radiated interference measurement apparatus 1 uses the second measurement unit 22 to measure the electric field strength time waveform at the measurement point where the maximum electric field strength among the plurality of measurement points set on the plane surrounding the radiation source 100 is Adopt the measured points. In this case, the radiated emission measurement device 1 determines whether the field strength distribution to which the median filter is applied using the field strength time waveform with a good S/N ratio can be used for estimating the maximum radiation position. do. Therefore, the radiated emission measurement apparatus 1 can perform the determination more accurately.

In addition, the radiated interference measuring apparatus 1 uses the first measurement unit 21 among a plurality of measurement points set on the surface surrounding the radiation source 100 as measurement points for measuring the electric field intensity time waveform by the second measurement unit 22. Employ a measurement point where the electric field strength measured by exceeds a predetermined electric field strength threshold. That is, the radiated interference measuring apparatus 1 employs measurement points other than the null points described above as the measurement points for measuring the electric field intensity time waveform by the second measurement unit 22 . In this case, the radiated interference measuring apparatus 1 uses the electric field strength time waveform measured at the measurement point other than the measurement point where the S/N ratio deteriorates, and the electric field strength distribution to which the median filter is applied is the maximum radiation position. Determine if it can be used for estimation. Therefore, the radiated interference measuring apparatus 1 can prevent the accuracy of the determination from deteriorating.

In addition, the radiated interference measuring apparatus 1 sets the first sampling time of the first measuring section 21 and the second sampling time of the second measuring section 22 to the same length. Alternatively, the radiated interference measurement apparatus 1 makes the frequency resolution bandwidth of the first measurement section 21 and the frequency resolution bandwidth of the second measurement section 22 the same. Therefore, the radiated interference measuring apparatus 1 sets the same setting of the first measuring unit 21 and the setting of the second measuring unit 22, so that the electric field intensity distribution to be determined and the allowable rate X or By increasing the correlation with the frequency threshold, the determination of whether the median filtered electric field strength distribution can be used to estimate the maximum radiation position can be performed more accurately.

In addition, the radiated interference measuring apparatus 1 uses the same detection method for measuring the electric field strength distribution by the first measurement unit 21 and the detection method for measuring the electric field strength by the second measurement unit. For this reason, the correlation between the electric field intensity distribution to be judged and the acceptance rate X or the number of times threshold used for the judgment is increased, and whether the electric field intensity distribution to which the median filter is applied can be used for estimating the maximum radiation position. can be performed more accurately.

Although the embodiments of the present invention have been described above with reference to the drawings, the specific configuration is not limited to the above-described embodiments, and design changes and the like are also included within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1... Radiation interference measuring apparatus, 11... Antenna, 12... Antenna mast, 13... Turntable, 14... Drive control part, 21... First measurement part, 22... Second measurement part, 30... Control part, 301... Calculation Unit 302 Calculation unit 303 Determination unit 100 Radiation source 200 Table 310 Main control unit 320 Input device 330 Output device 340 Storage device 345 Storage medium 350 Bus , S... square

Claims (8)

A first measurement for measuring an electric field intensity distribution on a surface surrounding a radiation source of radiated interfering waves by measuring the electric field intensity in a predetermined frequency band at a plurality of measurement points set on the surface at a first sampling time. Department and
a second measurement unit that measures the electric field intensity time waveform by measuring the electric field intensity at each second sampling time at the measurement point where the predetermined electric field intensity is measured among the plurality of measurement points;
A computing unit that applies a median filter to the electric field intensity distribution;
a calculation unit that calculates a tolerance rate of spike noise with respect to the electric field strength distribution to which the median filter is applied, and calculates a probability that long-period noise is measured based on the electric field strength time waveform;
a determination unit that determines whether the probability that the long-period noise is measured is equal to or less than the allowable rate;
A radiated emission measurement device comprising The calculation unit calculates a number threshold that is the product of the allowable rate and the number of times the second measurement unit measures the electric field strength for each second sampling time,
The determination unit determines that the number of times the difference between the electric field intensity measured by the second measurement unit at each second sampling time and the statistical value of the electric field intensity at each second sampling time exceeds a predetermined difference threshold, Determining whether it is equal to or less than the number of times threshold,
The radiated emission measuring device according to claim 1. The calculation unit calculates the acceptance rate using the following formula (1):
3. The radiated emission measuring device according to claim 1 or 2.

X: Probability of measuring long-period noise P(X): Probability of observing N _S or less spike noises N _m : Total number of measurement points The predetermined electric field strength is the maximum electric field strength among the electric field strengths measured at the plurality of measurement points,
4. The radiated emission measuring device according to any one of claims 1 to 3. The measurement point where the predetermined electric field strength is measured is the measurement point where the electric field strength measured by the first measurement unit exceeds a predetermined electric field strength threshold,
The radiated emission measuring device according to any one of claims 1 to 4. the second sampling time is the same length as the first sampling time;
The radiated emission measuring device according to any one of claims 1 to 5. The frequency resolution bandwidth of the second measurement unit is the same as the frequency resolution bandwidth of the first measurement unit.
The radiated emission measuring device according to any one of claims 1 to 6. The detection method in which the second measurement unit measures the electric field strength is the same as the detection method in which the first measurement unit measures the electric field strength distribution.
The radiated emission measuring device according to any one of claims 1 to 7.

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