JP2006084413A - Source identifying method for electromagnetic interference signal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To comparatively easily identify a source of electromagnetic interference signal in a comparatively short time. <P>SOLUTION: The source of electromagnetic interference signal is identified by collating a characteristic of an electromagnetic interference signal measured at a faraway point, or a signal corresponding to it with a characteristic of an electromagnetic interference signal of each electromagnetic interference signal source measured at a nearby point. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for specifying an electromagnetic wave interference signal generation source suitable for specifying an electromagnetic wave interference signal generation source of an electronic apparatus having a digital circuit.

  In general, most electromagnetic interference signals (EMI) generated by the operation of an electronic device having a digital circuit are caused by a fundamental wave of a rectangular wave typified by a clock signal or a digital transmission signal and its harmonics.

  An electronic device having a digital circuit in recent years is composed of a plurality of functional modules as shown in FIG. 13, and in this case, operates with clock signals having a plurality of frequencies. These clock signals having a plurality of frequencies are usually generated by multiplying or dividing one frequency.

  For this reason, the electromagnetic wave interference signal (EMI) generated by the operation of this digital circuit is often intricately superimposed with a fundamental wave or its harmonics by a clock signal having a plurality of frequencies or a digital transmission signal synchronized therewith. ing.

  In general, countermeasures against electromagnetic interference proceed while investigating the source and transmission path of the electromagnetic interference signal. As a method of investigating the source of this electromagnetic interference signal, as shown in FIG. 13, a current having a frequency that is a countermeasure against electromagnetic interference flowing on a substrate, chassis, or cable using an inspection probe 1 such as an electric field probe or a magnetic field probe. Can be used.

Further, an electromagnetic radiation measurement method as described in Patent Document 1 has been proposed.
JP 2001-343409 A

  Incidentally, for example, when investigating the generation source 2 and the transmission path of the electromagnetic wave interference signal having the frequency f1 as shown in FIG. 13, in the conventional investigation method, the function modules 3, 4 and 5 which are other electromagnetic wave interference signal generation sources are used. When the frequency of the clock signal is f2, f3 and f4 and the higher harmonics are superimposed on the frequency f1 of the electromagnetic interference signal to be investigated as f1 = 2 × f2 = 3 × f3 = 4 × f4, this electromagnetic wave The frequency f1 of the interference signal and the other harmonic frequencies 2 × f2, 3 × f3, 4 × f4 cannot be separated, and a plurality of sources and transmission paths of the electromagnetic interference signal are observed in a complex manner. It is difficult to specify the source and transmission path which are the main factors, and there is a disadvantage that it takes a long time to investigate the source of the electromagnetic interference signal.

  Moreover, although the technique of patent document 1 can measure an electromagnetic interference signal, the generation source of the electromagnetic interference signal of the electronic device which has a digital circuit cannot be specified.

  SUMMARY OF THE INVENTION In view of this point, an object of the present invention is to make it possible to identify a source of an electromagnetic wave interference signal relatively easily and in a relatively short time.

  The method for identifying the source of electromagnetic interference signal according to the present invention compares the characteristics of the electromagnetic interference signal measured in the far field or a signal corresponding thereto with the characteristics of the electromagnetic interference signal of each electromagnetic interference signal source measured in the near field. The source of the electromagnetic interference signal is specified.

  According to the present invention, the characteristics of the electromagnetic interference signal measured in the far field or a signal corresponding thereto are collated with the characteristics of the electromagnetic interference signals of the respective electromagnetic interference signal sources measured in the near field. The source of the electromagnetic wave interference signal can be specified relatively easily and in a relatively short time without requiring skill.

  Hereinafter, an example of the best mode for carrying out the electromagnetic wave interference signal generation source specifying method of the present invention will be described with reference to the drawings.

  FIG. 2 shows a configuration example for carrying out the electromagnetic wave interference signal generation source specifying method according to this example. In FIG. 2, 10 is a facility for conducting electromagnetic wave interference evaluation and electromagnetic wave interference countermeasure examination, for example, a 3 m anechoic chamber.

  In this example, an electronic device, that is, a device under test 11 that attempts to identify the source of the electromagnetic interference signal is arranged at a predetermined position in the anechoic chamber 10. In this example, the characteristics of the far-field electromagnetic interference signal of the device under test 11 are measured.

  An antenna 12 for detecting an electromagnetic interference signal generated by the device under test 11 is provided at a predetermined position in the anechoic chamber 10, and a detection signal such as an electromagnetic interference signal from the antenna 12 is transmitted to the outside of the anechoic chamber 10. To the measurement system 13 provided in

  In the study of countermeasures against electromagnetic interference, a device that indirectly evaluates electromagnetic interference signals as a common mode current or a common mode voltage, such as an evaluation device or a current probe that applies Workbench Faraday Cage, may be used instead.

  The measurement system 13 includes a spectrum analyzer, an electromagnetic wave interference signal (EMI) receiver, a high frequency (RF) amplifier, a high frequency (RF) switch, and the like, and is controlled by a control device 14 such as a computer. In this case, the interface of the measurement system 13 is often automatically controlled via a GPIB (General Purpose Interface Bus) or the like.

  The control device 14 including a computer or the like controls the anechoic chamber 10 and the measurement system 13 via the bus GPIB and the like, collects and analyzes the data measured by the measurement system 13, and uses the electromagnetic wave according to the flowchart shown in FIG. Implement a method for identifying the source of the jamming signal. In FIG. 2, reference numeral 15 denotes a monitor for performing various displays.

  FIG. 3 shows a configuration example for measuring the characteristics of the electromagnetic interference signal in the near field of the device under test 11 for implementing the electromagnetic interference signal generation source specifying method according to this example. The device under test (electronic device) 11 in the example of FIG. 3 has functional modules 16, 17, and 18 composed of three ICs (semiconductor integrated circuits) as sources of electromagnetic interference signals.

  In the example of FIG. 3, the characteristics of the electromagnetic interference signals in the near field of the respective functional modules 16, 17, 18 of the device under test 11 are measured. Reference numeral 19 denotes an inspection probe such as an electric field probe or a magnetic field probe. The inspection probe 19 is used to measure the electromagnetic wave interference signals of the functional modules 16, 17 and 18, respectively. A detection signal such as an electromagnetic wave interference signal from the inspection probe 19 is supplied to the measurement system 13 similar to FIG.

  The measurement system 13 is controlled by a control device 14 comprising a computer as in FIG. 2, and data measured by the measurement system 13 is collected and analyzed by the control device 14 comprising this computer. The control device 14 shown in FIG. 3 executes a flowchart as shown in FIG. 4 for obtaining the characteristics of the electromagnetic wave interference signal.

  In this example, in order to execute the electromagnetic wave interference signal generation source specifying method according to the flowchart shown in FIG. 1, first, after starting, the electromagnetic wave interference signal of each electromagnetic wave interference signal source measured in the near field of the device under test 11 in step S1. To get the features of each. In this example, the characteristics of the electromagnetic wave interference signals of the functional modules 16, 17 and 18 which are the electromagnetic wave interference signal generation sources as shown in FIG. 3 are obtained in advance as shown in FIG. Make it a library.

  As an example of the characteristics of the electromagnetic wave interference signal, for example, the modulation degree of the frequency domain information, the modulation frequency, the period of the time domain information, and the duty of the spectrum analyzer obtained by the flowchart of FIG.

  This flowchart of FIG. 4 will be described. In the flowchart of FIG. 4, first, after starting, in step S11, the frequency fe of the electromagnetic wave interference signal to be measured is defined (set) in the spectrum analyzer which is a measuring instrument. . The frequency fe of the electromagnetic wave interference signal is frequency data obtained from spectrum data obtained by normal evaluation based on the EMI standard as shown in FIG. FIG. 5 shows an example of spectrum data of 30 MHz to 1 GHz based on the EMI standard. In FIG. 5, line a is a standard value.

  In step S11, the spectrum analyzer defines (sets) the sideband measurement frequency upper limit fsmax and the sideband measurement frequency lower limit fsmin to determine a predetermined frequency range. The frequency upper limit fsmax and the frequency lower limit fsmin are determined from the performance of the measuring instrument and the time taken for measurement. Generally, the frequency lower limit fsmin is defined as several KHZ to several tens KHZ, and the frequency upper limit fsmax is defined as several hundred KHZ. Set).

  In step S11, the detection sideband number Ns, which is the number of sidebands to be detected, is set (defined). The number of detected sidebands Ns is counted by the number of sets of the upper and lower sidebands of the carrier wave. Since the time required for measurement becomes longer as the number of detection sidebands Ns increases, it is usually set to 1 to 4.

  In step S11, the time domain information acquisition time Tt is set (defined). This time domain information acquisition time Tt is a time during which continuous acquisition of frequency domain information (frequency domain data) is continued, and may be determined by the device under test 11. If the time domain information acquisition time Tt is set longer, the measurement time becomes longer accordingly. Usually, it is set to several seconds to several tens of seconds.

  Thereafter, the carrier frequency fc of the electromagnetic wave interference signal is measured (step S12). This carrier wave frequency fc is a center frequency of the frequency fe of the electromagnetic wave interference signal and is a frequency indicating the maximum peak value, and is obtained by measuring the frequency fe of the electromagnetic wave interference signal in detail.

Next, SPAN (frequency range for measurement) of the spectrum analyzer is set (step S13). The SPAN is a value multiplied by an arbitrary value Sn slightly larger than twice the frequency lower limit fsmin so that the frequency lower limit fsmin of the sideband measurement can be sufficiently observed when the carrier frequency fc is set as the center frequency.
SPAN = 2 × fsmin × Sn
And an arbitrary value Sn is normally set to a value of 1.5.

Next, the resolution bandwidth RBW (Resolution Band Width) of the spectrum analyzer is set (step S14). This resolution bandwidth RBW is determined based on a balance between measurement speed and measurement accuracy. When giving priority to the measurement speed, the denominator for dividing the SPAN is set small, and when giving priority to the measurement accuracy, the denominator for dividing the SPAN is set large. Generally, it is set to SPAN / 10 to SPAN / 50. In this example, RBW = SPAN / 20
And set.

  In this example, spectrum data (frequency domain information) is acquired by the control device (computer) 14 under the above conditions (step S15). This spectrum data is averaged, for example, to obtain necessary and sufficiently stable data.

  Next, peak detection is performed from the spectrum data (frequency domain information) (step S16). For example, as shown in FIG. 6, the detected peak is composed of a carrier wave, a sideband, and noise. The noise referred to here is generated from a portion unrelated to the electromagnetic interference signal whose frequency characteristics are to be analyzed, such as an external radio wave.

  Next, sidebands are selected from the detected peaks shown in FIG. 6, and the sideband frequency fs is detected (step S17). In this case, a set of peaks having an object relationship on the upper side and the lower side with respect to the carrier wave is set as a sideband. In general, since an electromagnetic wave interference signal by a digital circuit has both sidebands, it is determined that a peak that is not related to both sidebands is not a sideband. In the example of FIG. 6, there are three sidebands 1, 2 and 3.

  Next, it is determined whether or not the number of detected sidebands is equal to or greater than the number Ns set in step S1, for example, 2 (step S18), and the detected number of sidebands is set to the set number of sidebands Ns. If not, the SPAN of the spectrum analyzer is doubled (step S19), and it is determined whether the SPAN is within the frequency range fsmax × 2 (× Sn) in which the sideband measurement frequency upper limit fsmax can be sufficiently observed (step S19). S20), when it is within, step S14, step S15, step S16, step S17, step S18, step S19, and step S20 are repeated.

  If this SPAN exceeds the frequency range fsmax × 2 (× Sn) in which the SPAN can sufficiently observe the sideband measurement frequency upper limit fsmax, it is determined whether there is a number of detected sidebands (step S21). When it is determined in step S21 that there is no detection sideband, it is assumed that there is no feature of the frequency domain information (step S22).

  When the number of sidebands detected in step S18 is equal to or greater than the set number of sidebands Ns, the frequency domain data (frequency domain information) obtained by the measurement by the setting of the spectrum analyzer is set in step S1. Measurements are made during the acquisition time Tt and stored as time domain information (time domain data) (step S23). As the time domain information obtained in step S23, as shown in the example of FIG. 7, a time axis change curve of the carrier wave and sidebands during the time Tt is obtained with the horizontal axis as the time axis and the vertical axis as the level.

  In step S21, the number of detected sidebands is less than the set number of sidebands Ns, but when several sidebands are detected, the maximum frequency fs of the detected sideband of the SPAN is Slightly larger than twice and set to the maximum fs × 2 (× Sn) (step S24).

  Further, when the measurement speed decreases for the resolution bandwidth RBW, a value widened in accordance with the expansion of the SPAN is set (step S25), and the process proceeds to step S23.

  In this example, the periodicity of the temporal level change of the carrier wave and sideband of the time domain information obtained in step S23 is detected (step S26). In step S26, it is determined whether or not periodicity is detected (step S27). If it is determined that there is no periodicity, the time domain information (time domain data) is not characterized (step S28).

  When it is determined in step S27 that there is periodicity, this period and duty as shown in FIG. 7 are characteristic of the time domain information (time domain data) of this electromagnetic wave interference signal (step S29).

  Further, in this example, as shown in FIG. 7 obtained in step S23, time domain information (time domain data) is averaged, and the frequency and level of each of the carrier wave and the sideband are calculated (step S30), The respective frequencies and levels of the carrier wave and the sidebands as shown in FIG. 8 are obtained.

  Next, from the respective frequencies and levels of the carrier wave and the sidebands, for example, as shown in FIG. 8, modulation degrees ΔdB1, ΔdB2,... ), (Fc−fs3, fc + fs3) are calculated (step S31), and the modulation factor and the modulation frequency are characteristic of the frequency domain information (frequency domain data) of the electromagnetic wave interference signal (step S32).

  In this example, the characteristics of the electromagnetic wave interference signals of the functional modules 16, 17 and 18 shown in FIG. 3 are measured according to the above, and the result is used as a library.

  The measurement of the characteristics of the electromagnetic interference signals of the functional modules 16, 17, and 18 of the electronic device that is the device under test 11 for producing this library is, for example, a breadboard (for a large single substrate prototyped in the early stages of development). It is better to use a prototype for checking the operation.

  When the electromagnetic interference signal generated by the electromagnetic interference signal source is a functional module (active component) that does not depend on software, circuit configuration, etc., operate the functional module alone (peripheral to activate it) Circuits and equipment are necessary), and the characteristics of the electromagnetic interference signal may be measured to construct a library.

Here, the characteristics of the frequency domain information obtained from the flowchart of FIG. 4 of the functional module 16 of the device under test 11 of FIG. 3, ie, the characteristic data 1 consisting of the carrier wave and sideband of the spectrum data are as shown in FIG. To do. The modulation frequency ΔF1 · 1 of the first sideband of the feature data 1 is
ΔF1 · 1 = ((Fc−FSL1 · 1) + (FSU1 · 1−Fc)) / 2
And the modulation frequency ΔF1 · 2 of the second sideband is
ΔF1 · 2 = ((Fc−FSL1 · 2) + (FSU1 · 2−Fc)) / 2
And the modulation frequency ΔF1 · 3 of the third sideband is
ΔF1 · 3 = ((Fc−FSL1 · 3) + (FSU1 · 3−Fc)) / 2
It is.

  Where Fc is the carrier frequency, FSL1 · 1 is the first lower sideband frequency of feature data 1, FSU1 · 1 is the first upper sideband frequency, and FSL1 · 2 is the second lower sideband frequency. The sideband frequency, FSU1 · 2 is the second upper sideband frequency, FSL1 · 3 is the third lower sideband frequency, and FSU1 · 3 is the third upper sideband frequency. is there.

The modulation degree ΔLU1 · 1 of the first upper sideband of the feature data 1 is
ΔLU1 · 1 = LSU1 · 1−Lc1
And the modulation degree ΔLU1 · 2 of the second upper sideband is ΔLU1 · 2 = LSU1 · 2-Lc1
And the modulation degree ΔLU1 · 3 of the third upper sideband is ΔLU1 · 3 = LSU1 · 3-Lc1
It is.

Further, the modulation degree ΔLL1 · 1 of the first lower sideband of the feature data 1 is ΔLL1 · 1 = LSL1 · 1−Lc1
And the second lower sideband modulation degree ΔLL1 · 2 is ΔLL1 · 2 = LSL1 · 2-Lc1
And the third lower sideband modulation degree ΔLL1 · 3 is ΔLL1 · 3 = LSL1 · 3-Lc1
It is.

  Where Lc1 is the carrier level, LSU1 · 1 is the first upper sideband level, LSU1 · 2 is the second upper sideband level, and LSU1 · 3 is the third upper sideband level. , LSL1 · 1 is the level of the first lower sideband, LSL1 · 2 is the level of the second lower sideband, and LSL1 · 3 is the level of the third lower sideband.

  Further, it is assumed that the characteristics of the frequency domain information obtained from the flowchart of FIG. 4 of the functional module 17 of the device under test 11 of FIG. 3, that is, the characteristic data 2 including the carrier wave and sideband of the spectrum data is as shown in FIG. 9C. . The modulation frequency ΔF2 · 1 of the first sideband of the feature data 2 is ΔF2 · 1 = ((Fc−FSL2 · 1) + (FSU2 · 1−Fc)) / 2, and the second sideband Modulation frequency ΔF2 · 2 is ΔF2 · 2 = ((Fc−FSL2 · 2) + (FSU2 · 2−Fc)) / 2, and the modulation frequency ΔF2 · 3 of the third sideband is ΔF2 · 2 3 = ((Fc−FSL2 · 3) + (FSU2 · 3-Fc)) / 2.

  Where Fc is the carrier frequency, FSL2 · 1 is the first lower sideband frequency of feature data 2, FSU2 · 1 is the first upper sideband frequency, and FSL2 · 2 is the second lower sideband frequency. Side sideband frequency, FSU2 · 2 is the second upper sideband frequency, FSL2 · 3 is the third lower sideband frequency, and FSU2 · 3 is the third upper sideband frequency. is there.

The modulation degree ΔLU2 · 1 of the first upper sideband of the feature data 2 is
ΔLU2 · 1 = LSU2 · 1−Lc2
And the modulation degree ΔLU2 · 2 of the second upper sideband is ΔLU2 · 2 = LSU2 · 2−Lc2
And the modulation degree ΔLU2 · 3 of the third upper sideband is ΔLU2 · 3 = LSU2 · 3-Lc2
It is.

Further, the modulation degree ΔLL2 · 1 of the second lower sideband of the feature data 2 is ΔLL2 · 1 = LSL2 · 1−Lc2.
And the second lower sideband modulation degree ΔLL2 · 2 is ΔLL2 · 2 = LSL2 · 2−Lc2
And the third lower sideband modulation degree ΔLL2 · 3 is ΔLL2 · 3 = LSL2 · 3-Lc2
It is.

  Where Lc2 is the carrier level, LSU2 · 1 is the first upper sideband level, LSU2 · 2 is the second upper sideband level, and LSU2 · 3 is the third upper sideband level. , LSL2 · 1 is the level of the first lower sideband, LSL2 · 2 is the level of the second lower sideband, and LSL2 · 3 is the level of the third lower sideband.

  Further, it is assumed that the characteristics of the frequency domain information obtained from the flowchart of FIG. 4 of the functional module 16 of the device under test 11 of FIG. 3, that is, the characteristic data 3 including the carrier wave and sideband of the spectrum data are as shown in FIG. 9D. . The modulation frequency ΔF3 · 1 of the first sideband of the feature data 1 is ΔF3 · 1 = ((Fc−FSL3 · 1) + (FSU3 · 1−Fc)) / 2, and the second sideband The modulation frequency ΔF3 · 2 is ΔF3 · 2 = ((Fc−FSL3 · 2) + (FSU3 · 2−Fc)) / 2.

  Where Fc is the carrier frequency, FSL3 · 1 is the first lower sideband frequency of feature data 3, FSU3 · 1 is the first upper sideband frequency, and FSL3 · 2 is the second lower sideband frequency. The frequency of the side sideband, FSU3 · 2 is the frequency of the second upper sideband.

The modulation degree ΔLU3 · 1 of the first upper sideband of the feature data 3 is
ΔLU3 · 1 = LSU3 · 1−Lc3
And the modulation degree ΔLU3 · 2 of the second upper sideband is ΔLU3 · 2 = LSU3 · 2−Lc3
It is.

Further, the modulation degree ΔLL3 · 1 of the first lower sideband of the feature data 3 is ΔLL3 · 1 = LSL3 · 1−Lc3
And the second lower sideband modulation factor ΔLL3 · 2 is ΔLL3 · 2 = LSL3 · 2−Lc3
It is.

  Where Lc3 is the carrier level, LSU3 · 1 is the first upper sideband level, LSU3 · 2 is the second upper sideband level, and LSL3 · 1 is the first lower sideband level. The level, LSL3 · 2 is the level of the second lower sideband.

  The feature data 1, feature data 2 and feature data 3 as shown in FIGS. 9B, 9C and 9D are previously registered (stored) in a memory, and are read into a memory such as a RAM of the control device 14 in this step S1. .

  In step S1, the spectrum analyzer setting (RBW, SPAN, etc.) of the measurement system 13 when the electromagnetic interference signal is measured in the near field in FIG. 3 is defined, that is, the measurement conditions. In step S2, The measurement conditions of the spectrum analyzer of the measurement system 13 in FIG. 2 are set to the same conditions as defined in step S1.

  Next, as shown in FIG. 2, for example, a far-field electromagnetic interference signal is measured by an antenna 12 in a 3 m anechoic chamber 10, that is, a spectrum is measured (step S3). The problem frequency exceeding the margin is included, and the carrier wave and the sideband are detected (step S4).

  In this case, it is assumed that the detected carrier wave and sideband are measurement data as shown in FIG. 9A, for example, and there are three sidebands at the carrier frequency Fc. In this example, since the carrier wave and the sideband are present, the determination in step S5 is “Yes”, the frequency and level of this carrier wave and sideband are measured (step S6), and the modulation frequency which is the characteristic of the frequency domain information And the degree of modulation is calculated.

The modulation frequency ΔF0 · 1 of the first sideband, which is a characteristic of the frequency domain information of the measurement data in FIG.
ΔF0 · 1 = ((Fc−FSL0 · 1) + (FSU0 · 1−Fc)) / 2, and the modulation frequency ΔF0 · 2 of the second sideband is
ΔF0 · 2 = ((Fc−FSL0 · 2) + (FSU0 · 2−Fc)) / 2, and the modulation frequency ΔF0 · 3 of the third sideband is
ΔF0 · 3 = ((Fc−FSL0 · 3) + (FSU0 · 3-Fc)) / 2.

  Where Fc is the carrier frequency, FSL0 · 1 is the first lower sideband frequency of the measurement data, FSU0 · 1 is the first upper sideband frequency, and FSL0 · 2 is the second lower sideband. Sideband frequency, FSU0 · 2 is the second upper sideband frequency, FSL0 · 3 is the third lower sideband frequency, and FSU0 · 3 is the third upper sideband frequency .

The modulation degree ΔLU0 · 1 of the first upper sideband of this measurement data is
ΔLU0 · 1 = LSU0 · 1−Lc0
And the modulation degree ΔLU0 · 2 of the second upper sideband is ΔLU0 · 2 = LSU0 · 2−Lc0
And the third upper sideband modulation degree ΔLU0 · 3 is given by ΔLU0 · 3 = LSU0 · 3-Lc0
It is.

Further, the modulation degree ΔLL0 · 1 of the first lower sideband of the measurement data is ΔLL0 · 1 = LSL0 · 1−Lc0
And the second lower sideband modulation degree ΔLL0 · 2 is ΔLL0 · 2 = LSL0 · 2−Lc0
And the third lower sideband modulation degree ΔLL0 · 3 is ΔLL0 · 3 = LSL0 · 3-Lc0
It is.

  Where Lc0 is the carrier level, LSU0 · 1 is the first upper sideband level, LSU0 · 2 is the second upper sideband level, and LSU0 · 3 is the third upper sideband level. , LSL0 · 1 is the level of the first lower sideband, LSL0 · 2 is the level of the second lower sideband, and LSL0 · 3 is the level of the third lower sideband.

  Next, the electromagnetic wave interference signal measured in the far field of the device under test 11 or the modulation frequency and modulation factor of the measurement data, which is a characteristic of the signal corresponding thereto, and each electromagnetic wave interference signal source measured in the near field of the device under test Then, the modulation frequency and the modulation degree of the characteristic data 1, 2, 3 which are the characteristics of the electromagnetic wave interference signals of the functional modules 16, 17, 18 are collated respectively (step S7).

  This verification of the modulation frequency is performed in consideration of the measurement accuracy and the like in the difference between the measurement data and the feature data 1, 2 and 3. Further, the modulation degree is collated by the difference between the measurement data and the feature data 1, 2, and 3.

Next, the coincidence ratio between the measurement data and the feature data 1, 2, 3 is calculated (step S8). An example of the calculation formula for the coincidence ratio of the modulation frequency between the measurement data and the feature data 1, 2 and 3 is shown by taking the first sideband of the frequency closest to the carrier waves of the feature data 1 and the measurement data as an example. . The modulation frequency matching rate AF is AF = 100− | ΔF1 · 1−ΔF0 · 1 / (α × RBW) × 100 (%)
It is. α is a weighting factor for measurement accuracy. 0% or less shall be 0%. Generally, α is set in the range of 1 to 4. The same applies to other cases.

An example of a calculation formula for the modulation rate coincidence rate is shown by taking the first lower sideband of feature data 1 and measurement data as an example.
Modulation degree matching rate AL is AL = 100− | ΔLL1 · 1−ΔLL0 · 1 | / β × 100 (%)
It is. β is a weighting factor for measurement accuracy. 0% or less shall be 0%. β means that the match rate is 0% when the modulation degree difference exceeds β (dB). β is generally set in the range of 5 to 10 dB. The same applies to other cases.

Further, in this example, an example of an expression for obtaining the matching rate Areg of the frequency domain information from the matching rate AF of the modulation frequency and the matching rate AL of the modulation degree is shown below.
Afreg = √ (AF × AL)
In this example, the function module 16 having the highest frequency domain information match rate Areg is used as the generation source of the electromagnetic wave interference signal.

  Thereafter, the result of the match rate is output (step S9), and the function module 16 that can obtain the feature data 1 having a high match rate with respect to the measurement data is specified as the source of the electromagnetic wave interference signal.

  In step S5, when there is no carrier wave and sideband, the match rate is set to 0% (step S10), and the match rate is set to 0% (step S9).

  According to this example, the function module which is an electromagnetic wave interference signal generation source measured in the modulation frequency and modulation degree obtained from the frequency domain information which is the characteristic of the electromagnetic wave interference signal measured in the far field or the signal corresponding thereto, and the near field. Since the respective modulation frequencies and modulation degrees of the respective feature data 1, 2, and 3 of 16, 17, and 18 are collated, the collation result can be converted into a numerical value and can be compared relatively easily without requiring skill. The source of the electromagnetic interference signal can be identified in a short time.

In addition, according to the present example, the source of the electromagnetic interference signal is specified based on the modulation frequency and the modulation factor that are characteristic of the frequency domain information, so that the frequency of the electromagnetic interference signal and the frequency of the clock signal of another functional module are higher Even when the frequency of the wave is superimposed, the source of the electromagnetic interference signal can be distinguished.
Further, in this example, the feature data 1, 2 and 3 measured in the near field are registered in advance, so that the measurement data can be collated in real time, and the source of the electromagnetic interference signal can be specified in a relatively short time.

  In this example, since a plurality of feature data 1, 2 and 3 measured in the near field are registered in advance, measurement data obtained by one measurement and a plurality (for example, three) of electromagnetic wave interference signal sources 16 and 17 are obtained. And the source of the electromagnetic interference signal can be identified efficiently.

  In the above-described example, the modulation frequency and the modulation degree of the frequency domain information are collated as the characteristics of the electromagnetic interference signal. Instead, the period of the time domain information that is the characteristic of the electromagnetic interference signal obtained in step S29 of FIG. You may make it collate a duty.

  This collation of time domain information is basically the same as the collation of frequency domain information described above.

An example of a calculation formula for obtaining this match rate is shown below.
The cycle match rate AT is
AT = 100− | T1−T0 | / J × 100 (%)
Duty match rate AD is
AD = 100− | D1−D0 | / K × 100%
The time domain information match rate Atime is
Atime = (AT + AD) / 2
It is.

  Here, T1 is the period of measurement data measured in the far field (seconds), T0 is the period of feature data measured in the near field, D1 is the on-duty (%) of measurement data measured in the far field, and D0 is the near field. On-duty (%) of the characteristic duty measured in J. K is a weighting factor, which determines how much the difference between the measurement data and the feature data is 0%.

  In this time domain information, J is generally set in the range of SWT / 50 to SWT / 20, and K is generally set in the range of 5% to 15%.

  According to this example, since the generation source of the electromagnetic interference signal is specified based on the period and duty of the time domain information that is a characteristic of the electromagnetic interference signal, it can be easily understood that the same effect as the above example can be obtained. .

  Further, the modulation information obtained in the flowchart shown in FIG. 10 can be used as a feature of the electromagnetic wave interference signal.

  That is, in the flowchart of FIG. 10, after the start, first, in step S41, the frequency fe of the electromagnetic wave interference signal to be measured is defined (set) in the spectrum analyzer which is a measuring instrument. The frequency fe of the electromagnetic wave interference signal is frequency data obtained from spectrum data obtained by normal evaluation based on the EMI standard as shown in FIG.

  In step S41, the spectrum analyzer defines (sets) the sideband measurement frequency upper limit fsmax and the sideband measurement frequency lower limit fsmin. The frequency upper limit fsmax and the frequency lower limit fsmin are determined from the performance of the measuring instrument and the time taken for measurement. Generally, the frequency lower limit fsmin is defined as several KHZ to several tens KHZ, and the frequency upper limit fsmax is defined as several hundred KHZ. Set).

  Thereafter, the carrier frequency fc of the electromagnetic wave interference signal is measured (step S42). This carrier frequency fc is the center frequency of the frequency fe of the electromagnetic interference signal, and can be obtained by measuring the frequency fe of the electromagnetic interference signal in detail.

  Next, in step S43, the SPAN (span, measurement frequency range) of the spectrum analyzer is set to “0” at the frequency fe of the electromagnetic wave interference signal to be measured to specify the frequency, and the scanning time SWT (Sweep Time) Is set to an arbitrary time during which the frequency upper limit fsmax can be sufficiently measured. For example, 1 / (2 × fsmax) or more.

  This is because, in this example, the frequency upper limit fsmax is changed from the scan time SWT at which the frequency lower limit fsmin can be measured to the scan time SWT at which the frequency lower limit fsmin can be measured. First, the frequency lower limit fsmin is set to a scanning time SWT at which sufficient measurement is possible.

  Next, the resolution bandwidth (Resolution Band Width) of the spectrum analyzer which is a measuring instrument is adjusted to a value at which the electromagnetic wave interference signal to be measured can be best measured (step S44).

  Next, in order to remove noise from the measurement waveform, the VBW (Video Band Width) of this spectrum analyzer is set to 20 ÷ SWT, for example. This means 20 times the 1 / SWT (HZ), and is generally set to about 10 to 40 times (step S45).

  The time domain information (time domain data) of the electromagnetic wave interference signal is acquired by the spectrum analyzer in the above state (step S46). The time width measured in step S46 is set so that the set frequency lower limit fsmin and frequency upper limit fsmax can be measured.

  The shortest time width is set to a range that can sufficiently cover the frequency fe of the electromagnetic wave interference signal to be measured, for example, 1 / fsmax × 0.8, and the longest time width, for example, 1 / fsmin × 1.5.

  In this case, when a measuring instrument (spectrum analyzer) capable of simultaneously measuring both the lower frequency limit fsmin and the upper frequency limit fsmax can be used, one measurement may be performed if there is little variation.

  However, if this cannot be realized, the observation time region is divided into a plurality of times with a time width corresponding to the electromagnetic wave interference signal frequency to be measured.

  For the time domain information of the electromagnetic wave interference signal obtained in step S46, for example, an electromagnetic wave interference signal with the horizontal axis as the time axis and the vertical axis as the level as shown in FIG. 11 is obtained.

Next, it is judged (detected) whether or not the time domain information of the electromagnetic wave interference signal as shown in FIG. 11 acquired in step S46 has periodicity (step S47).
When periodicity is detected in step S47, frequency information 1 / TS = fs of the period TS can be calculated to obtain frequency information of amplitude modulation, and this frequency information is stored as periodic data (step S48). . In this case, there may be a plurality of periods TS. In this way, it is possible to recognize the modulation frequency (possibly multiple) originating from the same source.

  When the time domain information of the electromagnetic wave interference signal is the example of FIG. 11, there are two periods of TS1 and TS2, and the modulation frequencies fs1 = 1 / TS1 and fs2 = 1 / TS2 of the periods TS1 and TS2 are calculated. Is stored in memory.

  Thereafter, the scanning time SWT of the spectrum analyzer is doubled (step S49). If no periodicity is detected in the time domain information (time domain data) of the electromagnetic wave interference signal in step S47, the process proceeds to step S49, and then it is determined whether or not the doubled scanning time SWT is smaller than 1 / fsmin. If it is smaller (step S50), step S45, step S46, step S47, step S48, step S49, and step S50 are repeated, and the modulation frequency fs = 1 / TS of the period TS is stored.

  When the spectrum analyzer scanning time SWT is greater than 1 / fsmin in step S50, it is determined whether there is periodic data stored in step S48 (step S51). If there is no stored periodic data, The process ends with no modulation information (step S52).

  When there is a modulation frequency fs = 1 / TS of amplitude modulation which is the periodic data of the period TS stored in step S51, the SPAN of this spectrum analyzer is set slightly larger than 2 × fs and the resolution bandwidth RBW is set to SPAN / 20. (Step S53), and then, with this spectrum analyzer, as shown in FIG. 12, the narrow-band frequency domain information of the electromagnetic wave interference signal is captured, and the sideband corresponding to the frequency fs of the period TS is extracted, It is confirmed whether or not the modulation frequency fs stored in step S48 on the acquired electromagnetic wave interference information, in the example of FIG. 11, the modulation frequencies fs1 and fs2 exist in the frequency domain information of the electromagnetic wave interference signal as shown in FIG. S54).

  That is, it is matched whether or not the sidebands indicating the modulation frequencies obtained from the time domain information, for example, the modulation frequencies fs1 and fs2 are present in the frequency domain information. In the example of FIG. 12, it can be confirmed that sideband 1 (fc−fs1, fc + fs1) and sideband 2 (fc−fs2, fc + fs2) exist.

  Thus, by extracting the frequency domain information and the modulation frequency fs of the measurement result of the time domain information, it is possible to improve the extraction accuracy of the modulation frequency of the electromagnetic wave interference signal.

  In step S54, when the sideband indicating the modulation frequency fs obtained from the time domain information of the electromagnetic interference signal is also present on the frequency domain information of the electromagnetic interference signal, the sideband (fc-fs, fc + fs) and the frequency and level of the carrier wave fc are measured in detail, and the modulation degree and modulation frequency, which are modulation information, are converted (step S55).

  The modulation degree and the modulation frequency, which are the modulation information of the electromagnetic wave interference signal, are obtained, and the extraction of the modulation information is completed (step S56).

  Modulation information using a flowchart as shown in FIG. 10 can be used as a feature of the electromagnetic interference signal, and the same effect as the above-described example can be obtained when this modulation information is used as a feature of this electromagnetic interference signal. It will be easy to understand.

  In the above example, the feature data 1, 2, and 3 measured in the near field are registered in advance (library). However, every time the measurement data obtained by measuring the feature data 1, 2, and 3 in the far field is obtained. Of course, it may be obtained.

  Further, the present invention is not limited to the above-described examples, and various other configurations can be adopted without departing from the gist of the present invention.

It is a flowchart with which description of the example of the best form for implementing the source identification method of the electromagnetic wave interference signal of this invention is provided. It is a block diagram which shows the example of the structure system for implementing FIG. It is a block diagram which shows the example of the structure system for implementing FIG. 6 is a flowchart illustrating an example of a method for obtaining an example of characteristics of an electromagnetic interference signal. It is a diagram with which it uses for description of this invention. It is a diagram with which it uses for description of FIG. It is a diagram with which it uses for description of FIG. It is a diagram with which it uses for description of FIG. It is a diagram with which it uses for description of the example of this invention. It is a flowchart which shows the example of the method of obtaining the other example of the characteristic of an electromagnetic wave interference signal. It is a diagram with which it uses for description of FIG. It is a diagram with which it uses for description of FIG. It is a block diagram with which it uses for description of the conventional example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Electromagnetic anechoic chamber, 11 ... Device under test, 12 ... Antenna, 13 ... Measurement system, 14 ... Control device, 15 ... Monitor, 16, 17, 18 ... Functional block, 19 ... Inspection probe

Claims (5)

  The source of the electromagnetic interference signal is identified by comparing the characteristics of the electromagnetic interference signal measured in the far field or the equivalent signal with the characteristics of the electromagnetic interference signal of each electromagnetic interference signal source measured in the near field. A method for identifying a source of an electromagnetic interference signal, characterized by comprising: In the electromagnetic wave interference signal generation source identifying method according to claim 1,
An electromagnetic interference signal generation source specifying method, wherein the characteristics of the electromagnetic interference signal of each electromagnetic interference signal generation source measured in the near field are registered in advance. In the electromagnetic wave interference signal generation source specifying method according to claim 1 or 2,
The characteristic of the electromagnetic interference signal is to detect the sideband by detecting the peak of the frequency domain information of the predetermined frequency range of the electromagnetic interference signal, to detect the frequency and level of the detected sideband,
An electromagnetic wave interference signal generation source specifying method, characterized by a modulation degree and a modulation frequency of frequency domain information of the electromagnetic wave interference signal obtained by calculation from the detected frequency and level of the sideband. In the electromagnetic wave interference signal generation source specifying method according to claim 1 or 2,
The electromagnetic interference signal is characterized in that a sideband is detected by detecting a peak of frequency domain information in a predetermined frequency range, the detected sideband is acquired for a predetermined time, and the time of the sideband acquired for the predetermined time is obtained. An electromagnetic interference signal generation source specifying method, characterized by the period and duty of time domain information of the electromagnetic interference signal obtained by detecting periodicity of level change. In the electromagnetic wave interference signal generation source specifying method according to claim 1 or 2,
The electromagnetic interference signal is characterized in that the periodicity is detected from the time domain information of the electromagnetic interference signal, the frequency of the period is calculated, and the modulation information of the frequency domain information obtained from the frequency of the period is characterized. To identify the source of electromagnetic interference signal.

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