JP2942569B2 - EMI measurement device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an EMI measuring apparatus for measuring the spectrum of an interference wave output from a test equipment, and particularly to an EMI measuring apparatus arranged in an open field state. The present invention relates to an EMI measuring device that measures an output interference wave.

[Prior Art] In general electronic devices, high-frequency electromagnetic waves are emitted from digital circuits and the like. Since this electromagnetic wave has an adverse effect on communication radio waves, it is called an electromagnetic interference wave, and the International Commission on Radio Interference Standards (CISPR) requires that it be kept below a certain level. EMI (Electric Magnetic Inter
ferenc) Measuring devices have been developed.

When measuring electromagnetic interference waves (hereinafter abbreviated as abbreviated waves) output from these various devices in the open field,
Since external waves other than the interference wave output from the EUT are also measured at the same time, they are generally measured by the system shown in FIG. That is, the EUT 1 is placed on a turntable 3 that is driven to rotate by a motor 2, and an antenna 5 that can be moved up and down by a motor 4 is provided at a position separated from the EUT 1 by a predetermined distance. The spectrum of the interfering wave a and the foreign wave b received by the antenna 5 is measured by the analyzer 6. The measurement result is analyzed by the data processing unit 7. In addition, each motor 2,
4 is rotationally driven by the drive control device 8.

As shown in FIG. 10, the analyzer 6 includes a mixer 6a, a local oscillator 6b, a measurement controller 6c, and a BPF (bandpass filter) 6.
d, a detection unit 6e, and an evaluation circuit 6f. Where the local oscillator 6
b performs frequency sweep in response to a command from the measurement control unit 6c. The measurement control unit 6c receives the measurement condition setting information, controls the above-described units, and performs a consistent operation. The BPF 6d is configured such that its pass bandwidth (RBW: Resolution Band Width) can be varied, and determines the resolution in spectrum analysis. The detection unit 6e is a BPF 6d
To detect and output the level of the spectrum and the frequency thereof. In general, a frequency detection error occurs when detecting a frequency. If the resolution bandwidth RBW is properly set, the error range is several% of the measurement frequency range.
become. The evaluation circuit 6f includes a quasi-peak detector in this example, and detects and outputs a quasi-peak value of the spectrum.

Such an EMI measuring device performs the following spectrum measurement, and then evaluates and measures the interference wave from the EUT.

As shown in FIG. 12, a desired measurement frequency range BW1 is set in the analysis unit 6, the power of the EUT 1 is cut off, and the spectrum of only the external waves A1 and A2 when the generation of the interference wave is stopped. Is measured, and the level at that time is the predetermined threshold TH
The respective frequencies Af1 and Af2 of the spectrum which become ₁ or more are obtained.

The power of the EUT 1 is turned on, and the spectrum measurement of the mixed wave (B1 + B2 + A1 + A2) composed of the interfering waves B1 and B2 from the EUT 1 and the external waves A1 and A2 from other than the EUT 1 is performed. In this case, by performing spectrum measurement of the desired measurement frequency range BW1 all, the threshold value TH ₁ or more respective frequencies of the spectrum with a level of Af1, Af2, Bf1, Bf2
Is detected.

The frequencies Bf1, B excluding the frequencies Af1, Af2 measured from the frequencies Af1, Af2, Bf1, Bf2 measured at
Detect f2.

Turn on the power of the EUT 1, and set the frequency of the
A measurement frequency range BW2 (<BW1: evaluation bandwidth) centered on Bf1 and Bf2 and a resolution bandwidth RBW2 corresponding to this evaluation bandwidth are set in the analysis unit 6, and spectrum measurement is performed. Then, the output of the evaluation circuit 6f at that time is used for each frequency Bf
Output as evaluation measurement result (evaluation data) in 1, Bf2.

The evaluation bandwidth is defined by the international standard (CISP).
R) is the recommended bandwidth. Also, the desired measurement frequency range is often wide. For example, 30MHz-1
In the case of GMz, measurement is performed by dividing into a plurality of frequency ranges.

The elevating device for the turntable 3 and the antenna 5 is a device for receiving an interference wave radiated from the EUT 1 in the best condition via the antenna 5.

[Problems to be Solved by the Invention] However, the EMI measuring apparatus shown in FIGS. 9 and 10 also has the following problems (a) to (c) to be solved.

(A) As described above, since the measurement frequency range is wide, spectrum measurement is performed by dividing the frequency range into a plurality of frequency ranges. The frequency measurement accuracy (measurement accuracy) in the analyzer 6 is as follows.
It depends on the measurement frequency range BW (span) to be swept at a time and its resolution bandwidth RBW. Therefore, for example, the obtained frequency Bf1, in many cases, is not the correct center frequency of the spectrum B1. On the other hand, spectrum B1
The measurement frequency range BW for performing the final evaluation of the above is 1/500 or less as compared with the previous measurement frequency range. As a result, when the measurement frequency range of the final evaluation is set with the wrong frequency Bf1 as the center and the spectrum measurement is executed, the corresponding spectrum is out of the measurement range, and the spectrum B1 cannot be evaluated.

(B) In the above measurement, the reason to detect only the frequency of the spectrum with a predetermined threshold value TH ₁ or more levels, the exogenous wave or interference wave incoming noise generated in the measurement system as shown in FIG. 11 It is intended to prevent the capture as. However, lowering the threshold TH ₁ to the noise level near to sensitively measure to a lower level of the disturbing wave, the measurement erroneous will be Ho捉noise as disturbance or foreign wave. That is, there is a disadvantage that the sensitivity of measuring the interference wave cannot be increased.

(C) In addition, the spectrum of the extraneous wave that has not occurred at the time when the spectrum was measured with the power of the EUT 1 turned off (the above measurement time) is changed with the power of the EUT 1 turned on. It may occur suddenly when spectrum measurement is performed. Therefore, there is a problem that the spectrum caused by the extraneous wave that occurs only when the power of the EUT 1 is turned on cannot be specified as that of the extraneous wave. In other words, there is a problem that this extraneous wave is erroneously recognized as an interference wave.

(D) Further, the above-mentioned spectrum caused by an extraneous external wave may be generated in the process of performing the final evaluation measurement (the measurement described above). Therefore, no effective means has been developed to remove the spectrum due to the extraneous wave generated in the final evaluation stage.

As described above, in particular, as shown in (c) and (d), in each spectrum measurement stage, since there is no function of reliably identifying and removing the spectrum caused by the extraneous wave, a suspicious spectrum is generated during the spectrum measurement. Then
It is necessary for the operator to determine the type of the spectrum based on the experience from the spectrum waveform and the signal level and to perform, for example, re-measurement to determine the suspicious spectrum. Therefore, it is necessary for the operator to judge the measurement result at each stage and shift to the measurement at the next stage, so that a manual operation remains for the operator, which is very complicated.

The present invention has been made in view of such circumstances, and it is possible to accurately capture a spectrum based on an appropriate relationship between a measurement frequency range and a resolution bandwidth, and to perform average processing on measured levels. It is an object of the present invention to provide an EMI measuring device capable of increasing a sensitivity of an interference wave measurement by lowering a threshold value, preventing a measurement error due to a sudden external wave, and greatly improving a work efficiency of an interference wave measurement.

[Means for Solving the Problems] In order to solve the above problems, the present invention, as shown in FIG. 1, uses a mixed wave of an interfering wave from the EUT and an external wave from other than the EUT. An EMI measuring device that measures each spectrum in a predetermined measurement frequency range, detects and outputs the level and frequency thereof, and has an analysis unit having an evaluation circuit for evaluating the interference, and measures the interference. An averaging unit that performs an averaging process on each spectrum level to output an average value, an external wave average value output by the averaging unit when only an external wave is received, and the external wave frequency and mixed wave An interference wave detecting means for detecting and outputting the frequency of the interference wave based on the average value of the mixed wave and the frequency of the mixed wave when the signal is received, and a predetermined measurement frequency range (BW1) at the time of the first measurement. Set, then n times (n ≧ 3) The measurement is performed sequentially by setting the measurement frequency range (BWk: BW1>BWk-1>Bwk> BWn) including the frequency of the interference wave output by the interference wave detection means at the previous measurement and narrower than the previous measurement. The apparatus includes an analysis control unit and an evaluation unit that receives an output signal of the evaluation circuit at the time of n-times measurement and outputs an evaluation result of an interference wave.

Further, in another invention, as the interference wave detecting means,
Comparing means for comparing the average value of the extraneous waves or the average value of the mixed waves with a predetermined threshold value; A storage unit that stores the wave frequency; and a deletion unit that deletes the external wave frequency from the mixed wave frequency and outputs the frequency as the frequency of the interference wave.

In another aspect of the present invention, the evaluation means includes a fluctuation detecting section for detecting each fluctuation of the level and the frequency within a predetermined time from the analysis section at the time of measuring n times; Determining means for determining whether or not an interference wave based on the frequency of, and receiving and storing the output signal of the evaluation circuit after the determination means determines that the interference wave,
And an evaluation memory (212c) for an interference wave enabled to be output.

[Operation] According to the EMI measuring apparatus configured as described above, the predetermined measurement frequency range (BW1) is set in the analysis unit at the time of the first (first) measurement, and the measurement is sequentially performed until n times (n ≧ 3). Measurement frequency range (BWk: BW1> BWk−) that includes the frequency of the interference wave output by the interference wave detection means during the previous measurement and is narrower than the previous measurement
1>Bwk> BWn) to perform each spectrum measurement. Therefore, as the value of n increases,
That is, the measurement frequency range (span) BW gradually narrows as the number of measurements increases, so that the frequency measurement resolution increases.

Therefore, even if the frequency of the spectrum of the interference wave obtained in the first (first) measurement does not have a sufficient measurement resolution, the next stage span is immediately changed to the final evaluation span (n-th time). ), But instead of a narrower intermediate span, the spectrum is prevented from deviating from the measurement frequency range (span) at the time of measurement in the intermediate stage.

Also, since the averaging process averages the level that changes every moment within a certain period of time, the spectrum level of the extraneous wave and noise that can be estimated to have a large level fluctuation is
The output level is significantly reduced as compared with the peak detection processing. On the other hand, since the level fluctuation of the interference wave output from the EUT is small, the output level of the spectrum of the interference wave is not significantly reduced as compared with the peak detection processing. Therefore, by adopting this averaging process for the first measurement and the measurement in the intermediate stage, the spectrum of the extraneous wave and the noise can be more clearly distinguished from the spectrum of the interfering wave, and as shown in FIG. Threshold
Since TH ₀ can be reduced to the threshold value TH ₁ shown in FIG.
Spectrum B3 may reliably detected by the first 12 conventionally shown in FIG threshold position value TH ₀ following disturbance.

As described above, since the spectrum of the interference wave can be reliably specified by the first measurement and the measurement at each intermediate stage, the process from the first measurement to the final evaluation measurement can be completely automated.

Furthermore, even if a spectrum due to an extraneous wave suddenly appears during the final evaluation measurement, the spectrum due to the extraneous wave can be identified and removed by measuring the level fluctuation and the frequency fluctuation within a certain period of time.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a schematic diagram showing a schematic configuration of the EMI measuring device of the embodiment. The same parts as those in FIG. 9 are denoted by the same reference numerals.

An EUT 1 is mounted on a turntable 3 that is driven to rotate by a motor 2, and an antenna 5 that can be moved up and down by a motor 4 is provided at a position separated from the EUT 1 by a predetermined distance. The spectrum of the interfering wave b and the extraneous wave a received at 5 is measured by the analyzer 20. The analyzer 20 has a configuration substantially similar to that of FIG. 10, and is controlled by the measurement controller 6c. The measurement result measured by the analysis unit 20 is sent to the sub control unit 21a. The control unit 21 connected to the sub-control unit 21a is composed of a kind of personal computer, executes various data processing on the spectrum measurement result input from the analysis unit 20, and sends the data processing result to the printer 22. Print out or display on CRT display 24. The control unit 21
Controls the vertical position of the antenna 5 by driving the motor 4 via the antenna control circuit 24,
The rotation angle position θ of the turntable 3 is controlled by driving the motor 2 via the motor 25. Further, the control unit 21 controls the power supply of the EUT 1 to be turned on / off via the power supply control circuit 26.

The height (vertical position) of the antenna 5 to be controlled to obtain the best reception level when receiving the interference wave b output from the EUT 1 is theoretically related to the frequency of the interference wave b. The characteristics shown in FIG. 6 are obtained. Therefore, when the measurement frequency range is changed, the antenna 5
Must be set to the theoretical value each time. In addition,
Each theoretical value of the antenna height corresponding to each frequency is stored in the control unit 21 in advance.

FIG. 1 is a block diagram showing a schematic configuration of the analysis unit 20 and the sub control unit 21a. The analysis unit 20 has the same configuration as the conventional analysis unit 6 shown in FIG.

The sub control unit 21a includes an average processing unit 210, an interference wave detection unit 211,
It comprises an evaluation unit 212, an analysis control unit 213, and an output interface 214, and the configuration is achieved by a CPU, a ROM, a RAM, and the like.

Among them, the averaging unit 210 performs an averaging process on the level of the measurement data on the frequency and the level of the spectrum output from the detection unit 6e, and outputs the average value. Examples of the average value include an average value of an external wave when the spectrum of an external wave is measured, and an average value of a mixed wave when the spectrum of an external wave and an interference wave are measured.

In the interference wave detecting means 211, the comparing means 212a outputs the frequency of the spectrum corresponding to the average value equal to or larger than the predetermined threshold value among the average values from the averaging means 210. The first memory 211b stores an external wave average value equal to or higher than a predetermined threshold value and a spectrum frequency corresponding to the average value. Also,
The second memory 211c stores a mixed wave average value equal to or higher than a predetermined threshold value and a spectrum frequency corresponding to the average value. Further, the deleting unit 211d calculates and outputs the frequency and level of the interference wave based on the frequency and the average value stored in the first and second memories 211b and 211c. That is, the deleting unit 211d deletes the frequency of the spectrum of the foreign wave from each frequency of each spectrum of the mixed wave, and outputs the remaining frequency as the frequency of the interference wave.

In the evaluation means 212, the fluctuation amount detecting means 212a receives the frequency and level of the spectrum considered to be an interference wave output from the detection section 6c, and detects and outputs the fluctuation amount of the frequency and level within a predetermined time. The discriminating means 212b compares the frequency and level of the interfering wave detected by the interfering wave detecting means 211 with respect to each other, and if the fluctuation amount of the frequency and the level of the spectrum considered to be the interfering wave are both within a predetermined range. If this is the case, it is determined to be that of the interfering wave, and the result is output.
The evaluation memory 212c stores the frequency and level of the spectrum of the interference wave output from the detection unit 6e after the determination, and outputs it to the next output interface 214.

In the first measurement, the analysis control means 213 sets initial condition information (particularly, measurement frequency range BW1 and resolution bandwidth RBW1).
Is received by the measurement condition determining means 213b, and the analyzer 20 is controlled and measured according to the information. Further, the information is stored in the measurement condition memory 213c.

In the second to Nth measurements, measurement condition determination means
213b is based on the frequency of the interfering wave output from the interfering wave detection means 211, and the previously measured frequency range (BWk-1) and resolution bandwidth (RW) stored in the measurement condition memory 213c.
Measurement frequency range BWk (<BWk-1), narrower than BWk-1)
The frequency range including the interference wave measured last time with the resolution bandwidth RBWk (<RBWk−1) is set in the analysis unit 20 and is measured. At this time, the resolution bandwidth RBWk set by the measurement condition determination unit 213b in the BPF 6d of the analysis unit 20 at the time of the Nth measurement is 120 kHz specified in the above-described CISPR standard in this embodiment.

In the Nth measurement, when the determination by the determination unit 212b and the fluctuation amount detection unit 212a is unnecessary, that is, when it is not possible to input a sudden external wave as described later, the evaluation memory 212c The evaluation data from the circuit 6f is stored and output. In this case, the averaging means 210 and the interference wave detecting means 211 need not operate. On the other hand, in the case where the determination by the fluctuation amount detection means 212a and the determination means 212b is performed, the measurement required for the determination corresponds to the N-th measurement. Evaluation data output from 6f is stored in the evaluation memory
Store it in 212c.

Further, when the interference condition selection information is set to, for example, [2], the measurement condition determining means 213b determines that
The number of waves is selected, and the frequency is set in the analysis unit 20 as a set frequency in the next measurement.

The output interface 214 is configured to store data from the above-described units and output the data to the CRT display 23, the printer 22, and the like as necessary.

On the other hand, although not shown, each of the above units is connected to the control unit 21 via a bus line, and is controlled so that a consistent operation is performed.

When the measurement is performed over a wide frequency range such as 30 MHz to 1 GHz as shown in FIG. 4 using the EMI measuring device configured as described above, the entire measurement frequency range is divided into a plurality of divided measurement ranges. Preliminary measurement is performed for each span by dividing into frequency ranges (hereinafter referred to as spans). Each span measured in this preliminary measurement has a value of, for example, a width of 20 MHz to 150 MHz as shown in the drawing. Span 150
When the spectrum of the interfering wave and the mixed wave is specified by the preliminary measurement in MHz, the intermediate measurement (external wave and interfering wave measurement) is performed with a narrow span of, for example, 6 MHz around the frequency of each spectrum. This span is set to, for example, 4% of the span at the time of the preliminary measurement. This is because the error in the sweep frequency when the local oscillator 6b sweeps the frequency is, for example, ±
This is because 4% or less of the span at the time of the preliminary measurement is the lower limit value of the span at the time of the intermediate measurement because it is 2% or less. further,
The final inter-evaluation measurement with a span of, for example, 240 KHz is performed around the frequency of the interference wave spectrum obtained in the intermediate measurement. Each of the spans is stored in the measurement condition setting unit 213b in advance.

Here, the single measurement means that the spectrum measurement of the extraneous wave and the mixed wave is performed over the entire range of the measurement frequency (the second and subsequent times, the frequency range including the previously measured interference wave frequency), and the interference wave detection is performed. Until the means 211 outputs the frequency of a series of interference waves. In this embodiment, the above-mentioned number of measurements n is set to three times, and each measurement of n = 1, 2, and 3 is a preliminary measurement,
They are called intermediate measurement and final evaluation measurement.

First, an operation in the case of measuring a one-way interference wave among the interference waves output from the EUT 1 will be described. That is,
This is an operation example in a state where the control by the antenna control circuit 24 and the turntable control circuit 25 in FIG. 2 is fixed at a predetermined position.

FIG. 3 shows a flowchart of this operation, and the detecting unit at that time.
FIG. 4 shows a display example of the measurement data output from 6e.
This display is output via the output interface 214 to the CRT display 23.
It is an example displayed on the screen.

That is, in the flowchart of FIG. 3, the preliminary measurement is performed at P1 and P2. First, the power supply of the EUT 1 is shut off at P1. Then, as shown in FIG.
The frequency is set to MHz to 1 GHz, and the resolution bandwidth RBW1 is set to 800 kHz. Then, after averaging the measured data, the average value of the extraneous waves above the threshold value TH and the frequencies Af1, Af2
Is stored in the first memory 211b. Next, the power of the EUT 1 is turned on, and the measurement of each spectrum for the mixed wave is performed under the same conditions as the external wave measurement. Then, an averaging process is performed, and the average value of the mixed wave equal to or higher than the threshold value and the frequency thereof are stored in the second memory 211c. Then, from the respective frequency values obtained by the mixed wave measurement, the respective frequencies obtained by the previous external wave measurement are deleted, and each spectrum B of the interfering wave is deleted.
The frequencies Bf1 and Bf2 of 1, B2 are obtained and output. Finally, in P2, the number of frequencies to be selected based on the interference wave selection information is set. In the embodiment, two frequencies Bf1 and Bf2 (Af2) are selected. As shown, when Af2 and Bf2 cannot be clearly distinguished, either one of the frequencies is adopted. This completes the preliminary measurement.

Next, an intermediate measurement is performed in P3 and P4. That is, P3
Then, the power of the EUT 1 is shut off, and the external wave spectrum is measured. In this case, the span W for the frequency Bf1
B20 is ± 3 MHz around the previously selected frequency Bf1.
Also, the resolution bandwidth RBW2 is set to 300 kHz which is narrower than the preliminary measurement. The span BW21 for the frequency Bf2 is
± 3 MHz centered at. The resolution bandwidth RBW2 is the same. Then, the measurement data obtained by the two measurements is averaged, and the average value of the external wave equal to or higher than the threshold value and the frequency A′f2 thereof are stored in the first memory 211b.

Next, the power of the EUT 1 is turned on, and two measurements are performed on the mixed wave under the same conditions as described above. Then, the measurement data is averaged, and the average value of the mixed waves equal to or higher than the threshold value and the frequencies B'f1, A'f2, B'f2 are stored in the second memory 211b. Note that in this intermediate measurement, the resolution bandwidth RBW2
Is narrow, A'f2 and B'f2 can be accurately distinguished. At P4, the respective frequencies of the first memory 211b are removed from the respective frequencies of the mixed waves of the second memory 211c, and the frequencies B'f1 and B'F2 of the interfering waves are output. This completes the intermediate measurement.

Next, the final evaluation measurement is executed in P5 to P7. That is, at P5, the respective spans BW31 and BW32 are set to ± 120 kHz around the respective frequencies B'f1 and B'f2 obtained in the intermediate measurement, and the resolution bandwidth RBW3 is set to 120 kHz narrower than the intermediate measurement. Then, a spectrum measurement is performed on the interference wave, and the fluctuation amount detecting means 212a measures the fluctuation amount of the frequency and the level within a predetermined time. The determination unit 212b determines whether the variation measured in P6 is within a predetermined range. If it is within the predetermined range, the spectrum of the corresponding frequency is not due to a sudden extraneous wave, so the spectrum measurement for the interfering wave is executed again under the same conditions. Then, the evaluation data obtained from the evaluation circuit 6f is stored in the evaluation memory 212c and output via the output interface 214. Then, the evaluation data output at P7 is displayed on the CRT display 23. If the fluctuation amount exceeds the predetermined range in P6, the spectrum of the corresponding frequency is a spectrum of a sudden extraneous wave, so that the measurement is stopped and the evaluation data is not taken in. This is the end of the final evaluation measurement.

The EMI measuring apparatus of the present invention that performs measurement in such a procedure has the following features.

That is, as shown in FIG. 5, in the conventional apparatus, the threshold value TH ₀ needs to avoid the fluctuation of the noise level, but in the present invention, the fluctuation of the noise level is compressed by the averaging process. since, as shown in FIG. 5 (b), the threshold TH ₁ can be lowered, it was possible to improve the spectrum detection accuracy.

In addition, the spectrum measurement is divided into at least three stages of preliminary measurement, intermediate measurement, and final evaluation measurement, and in each measurement, the frequency measurement range (span) that falls within the error range of frequency detection in the previous measurement is set for the next measurement. And measure. Therefore, the spectrum obtained by the immediately preceding measurement can be reliably measured without overlooking the spectrum obtained by the current measurement.

Furthermore, even if a sudden extraneous wave enters the final evaluation measurement, the evaluation measurement is not performed by erroneously recognizing the spectrum of the extraneous wave as the spectrum of the interfering wave.

In the identification of the extraneous wave, the extraneous wave is generally a broadcast wave or the like, and most of the extraneous waves are modulated waves, and are affected by long-distance propagation. While there is a property that the fluctuation is large, the interference wave is distinguished between the two using the property that the level and frequency are almost stable.

Next, the control unit 21, the sub-control unit 21a, and the analysis control unit 2 included in the sub-control unit 21a when the EUT 1 is rotated on a turntable to measure omnidirectional interference waves.
Thirteen actual measurement processing operations will be described with reference to the flowcharts of FIGS. 7 and 8.

When the measurement is started in FIG. 7, S (step) 1
Then, the control unit 21 shuts off the power of the EUT 1 via the power control circuit 26. That is, a state is created in which only the external wave is received by the antenna 5. Next, the measurement condition setting means 213b sets a span number Aw assigned to each span to an initial value 1 in order to count the number of spans. Then, in S2, the measurement condition setting means
Span of span number Aw set in 213b (W span)
The theoretical value of the antenna height corresponding to the above is obtained from FIG. 6 and set to the theoretical height. Thus, the designated W span is set in the analysis unit 20, and the external wave spectrum measurement is executed. Then, storing the spectrum of the waveform of the threshold value TH ₁ or more exogenous waves preset in the resulting spectrum. Then, each spectrum of the extraneous wave is displayed on the CRT display 23. When the spectrum measurement of one W span is completed, 1 is added to the span number Aw.
If the added span number Aw does not exceed the final span number Am in S3, the process returns to S2, adjusts the antenna height, and executes spectrum measurement for the next W span.

When the span number Aw exceeds the final span number Am in S3, the measurement of all the spectrums of only the external waves in the entire measurement frequency range has been completed, so the power supply of the EUT 1 is turned on in S4. Then, the above-mentioned span number Aw is set to the initial value 1, and the antenna height is set to the theoretical value of the corresponding W span in S5. Next, the rotation angle position θ of the turntable 3 is set to the reference angle position via the turntable control circuit 25 (θ = 0).

In S6, the mixed wave spectrum measurement of the span specified by the span number Aw at the rotation angle position θ is executed. Of the threshold TH ₁ or more data containing each spectrum of the interference wave and foreign wave obtained, by deleting the data of only foreign wave even measured not turn the power of the previous EUT 1 , The remaining data, ie, only the spectrum due to the interference wave. In this case, the frequency f _{M of} each spectrum is stored. Then, the rotational angle position θ of the turntable 3 is rotated by the predetermined angle Δθ, and the spectrum measurement of the same W span is executed again in S6. And
When the rotation angle position θ after rotation reaches 2π (one rotation) in S7, the obtained measurement data is displayed on the CRT display 23.

Next, 1 is added to the span number Aw, the process returns to S5, and the corresponding W
Perform a spectrum measurement on the span. And
When the spectrum measurement for all the W spans is completed in S8, the preliminary measurement is completed, so the intermediate measurement from S9 is executed.

When the intermediate measurement is started, the power of the EUT 1 is cut off in S9, and each frequency f _M of each spectrum of the interference wave obtained in the preliminary measurement is determined. Then, a measurement point number is set for each frequency f _M , and the measurement point number P is set to the initial value 1
Set to. Then, in S10, the measurement frequency region of the P-th measurement point, that is, the span is set to (f _M ± W span 2).
%) To the N (narrow) span. Therefore, this N span is 4% of the W span. Next, the antenna height is set to a theoretical value corresponding to this N span. Then, an external wave spectrum measurement for N spans is performed. Then, if the measurement result to the threshold TH ₁ or more spectrum has occurred, the spectrum because the spectrum due to extraneous waves, and stores the waveform of the spectrum. When the spectrum measurement of one measurement point is completed, 1 is added to the measurement point number P, and the spectrum measurement for the next measurement point is executed.

Then, when the spectrum measurement for the extraneous wave at all the measurement points set in S11 is completed, S1
Turn on the power of the EUT 1 in 2. Then, a measurement point number P is set to an initial value 1, to adjust the vertical position of the antenna 5 to the theoretical height corresponding to a frequency f _M for designating the measurement point P set at S13. Then, the rotational angle position θ of the turntable 3 is set to an angular position corresponding to the maximum value obtained by the preliminary measurement. Next, an N span is set, and a mixed spectrum measurement is performed.

Of the data including the spectrum of the spectrum and the foreign wave resulting disturbance, the EUT 1 threshold TH ₁ or more of the data obtained in the measurement of the power-off, i.e. the spectrum due to external wave The frequency f _M of each spectrum is deleted and the remaining spectrum is stored as a spectrum for evaluation measurement. In this case, the number of frequencies f _M to be stored is limited to a maximum of three (N = 3) in descending order of the level, which is considered to be stochastically sufficient.
That is, if there are a large number of adjacent spectra, they are regarded as one spectrum. And S1
The evaluation measurement point number E is introduced into each frequency f _M of the spectrum for each evaluation measurement set in 4 (E ≦ 3), and E
Is set to the initial value 1.

The span in the final evaluation measurements in E th evaluation measurement points at S15 is set to (f _M ± 120KHz) (Evaluation span = 240KHz), executes the spectrum measurement with the set evaluation span. Then, the obtained fluctuations in the level and frequency of each spectrum are measured for a predetermined period of time. Then, if the fluctuation value measured in S16 is within the predetermined range, it can be determined that the corresponding spectrum is the spectrum of the interference wave. If the fluctuation value is out of the predetermined range, the corresponding spectrum can be determined to be a spectrum of an extraneous wave, so that the final evaluation measurement is not performed.

When the corresponding spectrum is determined to be the spectrum of the interfering wave, while moving the antenna height in S17 of FIG.
Set the height at which the spectrum measurement level indicates the maximum value. Similarly, the turntable 3 is rotated to set the rotation angle position at which the measured level of the spectrum shows the maximum value.

Then, in S18, the analysis unit 20 performs the final evaluation measurement on the corresponding spectrum. Then, while storing the evaluation data output from the evaluation circuit 6f, the CR
It is displayed on the T display 23.

When the final evaluation measurement of one spectrum is completed, the evaluation measurement point number E is incremented by 1 and the process returns to S15 to start the evaluation measurement processing for the spectrum of the next evaluation measurement point. When the evaluation measurement point number E exceeds the maximum value E _N (= 3) in S19, the measurement point number P
Then, the process returns to step S13 to start an intermediate measurement process for the spectrum at the next measurement point when the power of the EUT is turned on.

When the measurement point number P exceeds the maximum value Pm indicated by the number of the spectrum of the interference wave obtained at the end of the preliminary measurement in S20, a series of spectrum evaluation measurement for the interference wave output from the EUT 1 is performed. To end.

According to the EMI measuring device configured as described above, the W span, N span, and evaluation span indicating the frequency range of the measurement in the preliminary measurement, the intermediate measurement, and the final evaluation measurement have a magnitude relationship as shown in FIG. because it is set, even if they are set then narrow span around the frequency f _M of the measured spectrum with a wide span, never out of the measurement area of the next narrow span corresponding spectrum.

Incidentally, assuming that the resolution bandwidth RBW (accuracy) is 2% of the frequency bandwidth BW that can be measured at one time in the analyzer 20, and the N span is 4% of the W span, the resolution bandwidth in the W span is [W span × 0.02]. Therefore, if the W span is 150 MHz, the resolution bandwidth within the W span is ± 3 MHz. On the other hand, since the N span in this case is 6 MHz, even if an error of a maximum of 3 MHz occurs in the frequency f _M of the spectrum measured in the W span,
It does not deviate from the N span.

Next, since the N span is 6 MHz, the resolution bandwidth within the N span is 6 MHz × 0.02 = ± 120 KHz. Therefore, even if an error of 120 KHz at the maximum occurs in the frequency f _M of the spectrum measured in the N span, it does not deviate from the evaluation span of 240 KHz.

As described above, when shifting from a wide span to a narrow span, the corresponding spectrum does not go out of the measurement range, so that the span shift can be automated.

Furthermore, at the time of preliminary measurement and at the time of intermediate measurement, since the analyzer 20 is shifted from the peak processing to the averaging processing, as described above, the level of the spectrum of the extraneous wave is compared with the case where the peak processing is performed. Can be greatly reduced. Therefore, the distinction between the spectrum of the extraneous wave and the spectrum of the interfering wave becomes clearer, and the distinction in the case of turning on / off the power of the EUT 1 to distinguish the two spectra becomes clearer. Even if the judgment is automated, the probability that an erroneous judgment will occur becomes very small.

Moreover, it can be set to a lower value than the threshold value TH ₁ to the conventional value TH _0. As a result, it becomes possible to detect the spectrum of the interference wave buried in the vicinity of the threshold or the spectrum of the interference wave buried in the spectrum of the foreign wave.

Furthermore, even if a spectrum of an external wave suddenly occurs in addition to the spectrum of the interfering wave to be measured in the final evaluation measurement stage, the level fluctuation value of each spectrum and the fluctuation value of the frequency are measured to obtain the level fluctuation value. In addition, a spectrum having a small frequency fluctuation value can be specified as a spectrum of the interference wave, and only the spectrum of the interference wave can be reliably extracted. Therefore, the target spectrum can be automatically evaluated and measured even in the final evaluation measurement stage.

As described above, at each stage, the spectrum of the interfering wave can be reliably distinguished from the spectrum of the extraneous wave, so that from the preliminary measurement to the final evaluation measurement can be fully automated measurement that does not require the judgment of the operator. Becomes

[Effects of the Invention] As described above, according to the EMI measuring device of the present invention,
At least one or more intermediate measurements are inserted between the first measurement and the final evaluation measurement, and the averaging process is used instead of the peak detection process for spectrum measurement at each stage except the final evaluation measurement. Therefore, when the measurement frequency range is narrowed, the spectrum does not deviate from the narrowed measurement frequency range, and the spectrum of the interference wave output from the EUT can be reliably distinguished from the spectrum of the foreign wave. As a result, the measurement operation from the first measurement to the final evaluation measurement can be fully automated while maintaining high measurement accuracy, greatly improving the efficiency of interference wave measurement work, and significantly reducing the burden on the operator. Can be reduced.

In addition, since the level and frequency fluctuations are measured in the final evaluation measurement stage, even if a spectrum of an extraneous wave occurs in the final evaluation stage, the spectrum can be reliably removed. Therefore, the measurement accuracy can be further improved.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing the present invention, and FIGS.
FIG. 1 shows an EMI measuring apparatus according to one embodiment of the present invention. FIG. 2 is a schematic diagram showing the whole, FIGS. 3, 7, and 8 are flow charts showing the operation, and FIG. FIG. 5 is a schematic diagram showing a measurement operation at each stage, FIG. 5 is a spectrum characteristic diagram for explaining effects, FIG. 6 is a characteristic diagram showing a relationship between frequency and antenna height, and FIG. 9 is a conventional EMI measurement. FIG. 10 is a schematic diagram showing the device, FIG. 10 is a block diagram showing a general analysis unit, FIG. 11 is a characteristic diagram showing the relationship between extraneous waves, interfering waves, and noise, and FIG. 12 explains the operation of the conventional device. FIG. 1 ... test equipment, 3 ... turntable, 5 ... antenna, 6c ... measurement control unit, 6f ... evaluation circuit, 20 ... analysis unit, 21 ... control unit, 21a ... sub-control unit, 23 ... CRT display, 26 ... Power control circuit, 210 ... Averaging means, 211 ...
... interference wave detection means, 212 ... evaluation means, 213 ... analysis control means.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-3264 (JP, A) JP-A-1-191068 (JP, A) JP-A 62-75631 (JP, U)

Claims (3)

(57) [Claims] 1. A spectrum of a mixed wave comprising an interfering wave from an EUT and an external wave from a device other than the EUT is measured in a predetermined measurement frequency range, and its level and frequency are detected and output. An EMI measuring device that includes an analyzing unit having an evaluation circuit for evaluating an interference wave, and that measures the interference wave, and performs an averaging process on the level of each spectrum to output an average value. An averaging unit (210), an average value of the external wave output by the averaging unit when receiving only the external wave, an average value of the external wave and a mixed wave average value when receiving the mixed wave, and a frequency of the mixed wave Interference wave detection means (21) for detecting and outputting the frequency of the interference wave based on
1), a predetermined measurement frequency range (BW1) is set in the analysis unit at the time of the first measurement, and the frequency of the interference wave output by the interference wave detection unit at the previous measurement is sequentially set up to n times (n ≧ 3). And a narrower measurement frequency range than the previous measurement (BWk: BW1> BWk−
1>Bwk> BWn) and an analysis control means (213) for performing each measurement, and an evaluation means (212) for receiving an output signal of the evaluation circuit at the time of n times of measurement and outputting an evaluation result of the interference wave. An EMI measuring device, comprising: 2. The apparatus according to claim 1, wherein said interference wave detecting means includes a comparing means (211a) for comparing the average value of the external wave or the average value of the mixed waves with a predetermined threshold value. Storage unit (211b, 211c) for storing the extraneous wave frequency and the mixed wave frequency in the averaged extraneous wave value and the mixed wave average value
2. The EMI measuring apparatus according to claim 1, further comprising: a deletion unit (211d) for deleting the extraneous wave frequency from the mixed wave frequency and outputting the frequency as the frequency of the interference wave. 3. A fluctuation detecting section (212a) for detecting each fluctuation of a level and a frequency from the analysis section within a predetermined time at the time of measuring n times. Determining means (212b) for determining whether or not the signal is an interference signal based on the frequency of the interference signal, and receiving and storing the output signal of the evaluation circuit after the determination means determines that the signal is an interference signal; Evaluation memory (21)
The EMI measuring device according to claim 1 or 2, further comprising 2c).