JP2006258756A - Device and method for measuring electromagnetic field - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To securely measure the electromagnetic field, even in an apparatus in which a packet communication system or the like is adopted and the variations in radio wave radiation state is large. <P>SOLUTION: When measuring the electromagnetic field, by continuously receiving the electromagnetic wave radiated from the apparatus under test, the electromagnetic wave radiated from the apparatus under test is received by a receiving antenna 14, while changing the height. The height of the receiving antenna, when the maximum value of the electromagnetic wave is received by the receiving antenna 14, is compared with electromagnetic propagation characteristics made into a database in terms of frequencies and polarization waves, to verify the reliability whether the maximum value is properly acquired, on the basis of the comparison result. For example, when an intermittent wave, in which the receiving level suddenly increases cannot be measured or the like, remeasurement is performed so that precise measurement can be performed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electromagnetic field measurement apparatus and an electromagnetic field measurement method that continuously receive electromagnetic interference (EMI) radiated from an electronic device or the like and measure an electromagnetic field.

  In many electronic devices, electromagnetic waves radiated from a clock oscillation circuit or the like for driving a CPU, a bus, an external memory, etc. are interference electromagnetic waves (EMI: Electro-magnetic Interference) that interfere with the functions of other electronic devices. EMI-related industrial standards have been established by government agencies such as the American National Standards Institute (ANSI) and the International Special Committee on Radio Interference (CISPR), and the government The emission level is regulated by an organization such as the US Federal Communications Commission (FCC). For this reason, generally, the peak value (PK: Peak) or quasi-peak value (QP) of EMI radiated from an electronic device or the like is the limit value of the radiation level defined in the FCC rule, CISPR22 standard, etc. Standard conformance judgment is performed as to whether or not (limit) is satisfied.

  In addition, in order to prevent the occurrence of non-conforming products due to product variations, there is a case where a predetermined margin conformity evaluation is performed to determine whether or not a predetermined margin according to internal regulations on product management is satisfied.

  Measurement of EMI radiated from electronic devices usually uses an electromagnetic field measurement system in an anechoic chamber in which an electromagnetic wave absorber is laid on the inner wall of the shield room in order to avoid the influence of communication waves such as broadcast waves and mobile phones. Often done.

  A turntable is installed inside the anechoic chamber, and an electronic device under test (EUT: Equipment Under Test) and its peripheral devices are placed on this turntable and rotated 360 degrees, and a receiving antenna is installed. By vertically moving in the range of 1m to 4m and continuously receiving EMI from the EUT, the electromagnetic field caused by the EMI radiated from this EUT can be measured using a spectrum analyzer and EMI receiver Is done.

  Then, the EMI radiated from the EUT is received by the receiving antenna in the anechoic chamber. The receiving antenna is measured while moving in the vertical direction under the control of a computer. The maximum value (PK: Peak value) of the EMI level received by the receiving antenna is measured with a spectrum analyzer. The spectrum analyzer has a function of holding the maximum value to be held and recorded for each frequency, a function of recording the reception level of EMI by the receiving antenna for each frequency, and the like. This spectrum analyzer acquires the EMI received by the receiving antenna through the RF amplifier, and generates the maximum value of the reception level for each frequency.

  The EMI receiver acquires a QP value that defines an allowable value of EMI. Then, the computer apparatus adds necessary correction values (cable loss, antenna factor, etc.) to the data acquired by the spectrum analyzer and the EMI receiver, and performs analysis such as margin calculation for the level and limit.

  The flowchart of FIG. 17 shows a conventional process example in which electromagnetic field measurement is performed by the electromagnetic field measurement system configured as described above. Referring to FIG. 17, first, the maximum value of EMI radiated from the EUT is obtained by rotating the turntable 360 degrees and vertically moving the receiving antenna in the range of 1 m to 4 m, and using the maximum value hold function of the spectrum analyzer. Are obtained for each frequency (step S1). Next, it is verified whether or not the maximum value acquired in step S1 satisfies a limit (or a predetermined margin) (step S2). If all the frequencies satisfy the limit (or the predetermined margin), the measurement is terminated. If there is a frequency that does not satisfy the limit (or the predetermined margin), the process proceeds to step S3.

  Next, all frequencies that do not satisfy the limit (or predetermined margin) are extracted from the maximum value acquired in step S1 (step S3). For each frequency extracted in step S3, the frequency is manually fine-tuned so that the reception level is maximized, and the frequency accuracy is increased (step S4). In the following description, the frequency after fine adjustment is referred to as the maximum radiation frequency.

  Thereafter, the antenna height and turntable angle at which the reception level is maximized are manually specified for each maximum radiation frequency finely adjusted in step S4 (step S5). In the following description, the antenna height and the turntable angle at which the reception level is maximum are collectively referred to as the maximum radiation direction.

  Then, the EMI QP value is acquired in the QP detection mode of the EMI receiver at the maximum radiation frequency finely adjusted in step S4 and the maximum radiation direction specified in S5 (step S6). Further, it is determined for each frequency whether or not the EMI QP value acquired in step S6 satisfies a limit (or a predetermined margin), and the measurement is terminated (step S7).

Japanese Patent Application Laid-Open No. H10-228561 discloses a technique for performing this type of electromagnetic field measurement.
JP 2001-343409 A

  Such conventional electromagnetic field measurement has various problems. That is, as a first problem, due to the diversification of technologies of digital electronic devices, packet communication methods (dividing data in a certain unit) are often adopted between device internal modules and recording media. Intermittent waves have increased in comparison.

  When the EMI is an intermittent wave, the method of obtaining the maximum value of the EMI while moving the turntable and the receiving antenna is such that the probability that the maximum value can be obtained in the maximum radiation direction is the radiation period of the intermittent wave and the sweep timing of the spectrum analyzer ( Sweep time, frequency span setting, etc.). If this probability is low, the measurement error increases, and it is often impossible to correctly determine the effect of EMI countermeasures. For this reason, the EMI countermeasure study time tends to increase as compared with the prior art, which is a heavy load on the designer in charge of EMI countermeasures. In addition, it is difficult to determine conformity with standards, and in some cases, there is a possibility of overlooking a nonconforming product by mistake.

  As the second problem, the EMI countermeasure effect determination and the standard conformance determination measure a plurality of EUTs and evaluate the variation of the radiation level of each EUT, but in the case of intermittent waves, it was described in the first problem. As described above, since the measurement error is large, it is a very small number of measurers who have advanced evaluation techniques that can correctly determine the variation. Therefore, the measurement error may be misrecognized as a variation in the radiation level of each EUT, leading to an increase in the examination time of the EMI countermeasure unit and the number of EMI countermeasure parts, which may increase the product cost.

  As a third problem, in order to correctly perform EMI countermeasure effect determination and standard conformity determination, it is determined whether or not the EMI is an intermittent wave, and in the case of an intermittent wave, the maximum EMI is obtained by observation over a long time according to the radiation period. The radiation direction must be specified and the maximum value obtained. Therefore, it is necessary to train full-time measurement specialists who have sufficient knowledge and experience about measurement to be able to do this accurately.

  The present invention has been made in view of such a point, and an object thereof is to ensure that electromagnetic field measurement can be performed even in the case of a device that employs a packet communication method or the like and has a large fluctuation in radio wave radiation state.

  In the present invention, when electromagnetic waves radiated from a device under measurement are continuously received to measure an electromagnetic field, the electromagnetic waves radiated from the device under measurement are received by a receiving antenna while changing the height, and received. Check whether the receiving antenna height when the maximum value of the electromagnetic wave received by the antenna was obtained was compared with the radio wave propagation characteristics stored in the database for each frequency and polarization, and the maximum value was obtained appropriately based on the comparison result. The reliability of whether or not is verified.

  By doing in this way, for example, it can be determined whether or not an intermittent wave whose reception level suddenly increases can be measured correctly.

  According to the present invention, for example, it can be determined whether or not an intermittent wave whose reception level suddenly increases can be measured correctly, and electromagnetic field measurement can be performed even in the case of a device that adopts a packet communication method or the like and has a large fluctuation in radio wave radiation state. It will surely be possible.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 shows a configuration example of the electromagnetic field measurement system of this example, and FIG. 2 shows a device arrangement example. In this example, in order to avoid the influence of communication waves such as broadcast waves and mobile phones, the EMI radiated from the electronic device or the like as the object to be measured in the anechoic chamber in which the electromagnetic wave absorber is laid on the inner wall of the shield room. It is configured to measure. FIG. 1 shows the configuration of the anechoic chamber. In the anechoic chamber, a metal reference ground plane 10 having a predetermined range is installed, and a turntable 11 is installed in the reference ground plane 10. An electronic device under test (EUT: Equipment Under Test) 21 and its peripheral devices 22 and 23 are placed on the turntable 11 and rotated 360 degrees by the turntable 11 during measurement.

  A receiving antenna 14 is installed within the range of the reference ground plane 10 and receives EMI radiated from the EUT 21. The receiving antenna 14 is mounted on a vertically installed antenna mast 13 via an antenna positioner, and is installed inside a pit 31 provided below the reference ground plane 10 as shown in FIG. The height can be changed by the antenna positioner driving device 35. Specifically, it is configured to vertically move within a range of 1 m to 4 m and continuously receive EMI from the EUT. The receiving antenna 14 is configured to receive, for example, horizontal polarization and vertical polarization separately.

  As shown in FIG. 2, the signal received by the receiving antenna 14 is detected and held by a spectrum analyzer 32 or the like installed inside the pit 31 of the anechoic chamber 30. An RF amplifier or the like may be connected. Data held by the spectrum analyzer 32 or the like is sent to a measurement room 40 separate from the anechoic chamber 30 by a cable (such as an optical fiber cable) connected to a GPIB (General Purpose Interface Bus) extender 34 as a transmission device. The data is received by the GPIB extender 41 and analyzed by the computer apparatus 2 or the like.

  FIG. 3 is a diagram illustrating an example of a connection configuration of measurement devices in the anechoic chamber 30 and the measurement chamber 40. The spectrum analyzer 32 in the pit 31 includes a maximum value hold (MaxHold) function for holding and recording the maximum value (PK: peak value) of the EMI level received by the reception antenna 14 for each frequency, and the reception antenna 14. A clear / write function for recording the EMI reception level for each frequency for each sweep is provided. The spectrum analyzer 31 acquires EMI received by the receiving antenna via an RF amplifier (not shown), and generates a maximum value of the reception level for each frequency. A coaxial relay switch matrix 33 is installed in the pit 31.

  In the measurement chamber 40, a computer device 42, a turntable controller 43, an antenna position controller 44, a signal generator 45, and an EMI receiver 46 are prepared. The GPIB extender 41 on the measurement room 40 side is connected to the first GPIB board 42a of the computer apparatus 42, and the other devices 43 to 46 in the measurement room 40 are connected to the second GPIB board 42b of the computer apparatus 42. It is.

  The EMI receiver 46 has a QP detection mode and acquires a QP value that defines an allowable value of EMI. The computer device 42 controls the operation of the electromagnetic field measurement system, and adds necessary correction values (cable loss, antenna factor, etc.) to the data acquired by the spectrum analyzer 32 and the EMI receiver 46, and controls the level and limit. Used for analysis such as margin calculation.

  Note that it is desirable for the EMI measuring device and the drive device to have a short communication time and data processing time with the computer device 42. The position information of the receiving antenna driving device 35 may be configured to output a binary coded code (BCD) from a sequencer or the like and directly import it into a computer.

  Next, a processing example in which electromagnetic field measurement is performed in the electromagnetic field measurement system of this example will be described with reference to the flowchart of FIG. In the following description, processes such as arithmetic processing and data analysis are executed in the computer device 42 unless otherwise specified.

  First, using the clear / write function of the spectrum analyzer, the EMI analysis data A in which the level data for each sweep and the position data of the drive system are associated by frequency is acquired (step S8). The process for acquiring EMI analysis data will be described later. Then, the maximum value A of the EMI analysis data acquired in step S8 is calculated for each frequency (step S9). Here, it is verified whether or not the maximum value A calculated in step S9 satisfies a limit (or a predetermined margin) (step S10). If the maximum value A satisfies the limit (or predetermined margin) at all frequencies, the measurement is terminated. If there is a frequency at which the maximum value A does not satisfy the limit (or predetermined margin), the process proceeds to step S11.

  In step S11, all frequencies for which the maximum value A did not satisfy the limit (or predetermined margin) in step S10 are extracted. Further, the maximum radiation direction is extracted for each frequency extracted in step S11 (step S12). Then, when the evaluation accuracy is improved for all the frequencies extracted in step S11, the process proceeds to step S17, and when the evaluation accuracy is improved only for the intermittent wave, the process proceeds to step S14.

  By proceeding to step S14, the maximum value of the intermittent wave, which has been a problem in the prior art, is acquired correctly, and both the creation of EMC quality and the reduction of the burden on the measurer by shortening the time for studying countermeasures are achieved. Specifically, it is determined whether the frequency extracted in step S11 is an intermittent wave for each frequency (step S15). If there is a frequency determined to be an intermittent wave, the process proceeds to S16, where the intermittent wave If no frequency is determined, the process proceeds to S18. The process of determining whether or not the frequency is an intermittent wave will be described later with reference to the flowchart of FIG. 5 or FIG.

  Thereafter, the frequency determined as an intermittent wave in step S14 is extracted (step S16). In step S13, if the evaluation accuracy improvement is selected for all the frequencies extracted in step S11, and the evaluation accuracy analysis method is performed for all the frequencies extracted in step S11, the intermittent wave When only the evaluation accuracy improvement implementation is selected, the evaluation accuracy analysis method is performed on the frequency extracted in step S16 (step S17). Details of the evaluation accuracy analysis will be described later (FIG. 7).

  Then, the maximum radiation frequency is specified in the frequency extracted in step S11 (step S18), and the EMI test receiver is classified according to the maximum radiation frequency specified in step S18 in the maximum radiation direction extracted in step S12 or step S18. The QP value is acquired in the QP detection mode (step S19). Then, it is determined whether or not the QP value acquired in step S19 satisfies a limit (or a predetermined margin), and the measurement ends. When the evaluation accuracy analysis, which is the result of verification of measurement reliability, is lower than a predetermined value, the maximum value of the radio wave propagation characteristics stored in the database is reacquired by the receiving antenna within the range of the receiving antenna height. Processing may be performed.

  Next, each data used for measurement will be described. First, the EMI analysis data shown in step S8 of the flowchart of FIG. 4 will be described. The time domain used for obtaining the data (Time-domain) The analysis will be described first. Time domain analysis is performed by converting level data for each sweep continuously acquired by the clear / write function of the spectrum analyzer into time-series data (Time-Domain data) for each frequency. It means to expand and analyze the temporal level change of that data.

  In order to perform analysis such as intermittent wave determination and automatic extraction of the maximum radiation direction by the time domain analysis, level data and level data are acquired for each sweep of the spectrum analyzer using the clear / write function of the spectrum analyzer. The time turntable angle data and the receiving antenna height data (hereinafter referred to as drive system position data) are obtained in association with each other. The data acquired in this way is used as EMI analysis data. The data for EMI analysis being measured is temporarily managed on the memory of the computer device 42, taken into the computer device 42 after a series of measurements, and stored in a storage device such as a hard disk.

  Next, the intermittent wave determination parameters shown in steps S14 and S15 of the flowchart of FIG. 4 will be described. By performing time domain analysis for each frequency from the EMI analysis data acquired in step S8 of the flowchart of FIG. It is determined for each frequency whether or not the received EMI is an intermittent wave. As for the intermittent wave, for example, as shown in FIG. 8, the reception level suddenly increases with the periodicity and the reception level suddenly increases. For example, as shown in FIG. In this example, both cases are included. In this example, the subjective determination of a measurement expert is quantitatively determined by employing the following parameters.

Next, parameters for intermittent wave extraction will be described with reference to FIGS.
L (f_t): reception level at time t of time domain data at frequency f L (f_Max): maximum value of time domain data at frequency f L (f_Ave): average value of time domain data at frequency f (F_t_moving average): L (f_t) of the time domain data at the frequency f and an average value of A reception levels (A is arbitrary) before and after the time at the same frequency f (for example, when A = 2, 5 (This is the average of the received levels)
L (f_increment): value obtained by subtracting the minimum value from the maximum value of L (f_t) continuously increasing in the time domain data at frequency f. L (f_decrease): time domain at frequency f A value obtained by subtracting the maximum value from the minimum value of L (f_t) that is continuously decreasing in data. L (f_difference): In the change of L (f_increment) from continuous L (f_decrease) , L (f_decrement) plus L (f_increment)

  Using these parameters, time domain analysis is performed for each frequency from the EMI analysis data acquired in step S8 of the flowchart of FIG. 4, and it is determined whether the acquired EMI is an intermittent wave or not. 6 is performed according to the flowchart shown in FIG.

  Next, details of the first intermittent wave determination method shown in FIG. 5 will be described. First, as step S21, L (f_increment) is calculated from time domain data calculated for each frequency from the EMI analysis data A acquired in step S8 of the flowchart of FIG. 4 (see FIG. 11).

  Next, L (f_decrease) is calculated from the time domain data calculated for each frequency from the EMI analysis data A acquired in step S8 of the flowchart of FIG. 4 (step S22: see FIG. 11). Then, L (f_difference) is calculated from L (f_increment) and L (f_decrement) calculated in step S21 and step S22 (step S23: see FIG. 11).

  After that, it is determined whether or not L (f_difference) calculated in step S23 is equal to or greater than an arbitrary threshold B (for example, B = 10 dB) (step S24). It determines with it being a wave (step S25), and when it is less than the threshold value B, it determines with the frequency f not being an intermittent wave (step S26).

  Next, details of the second intermittent wave determination method shown in FIG. 6 will be described. First, in step S27, the maximum value L (f_Max) is calculated from the time domain data calculated for each frequency from the EMI analysis data A acquired in step S8 of the flowchart of FIG. 4 (see FIG. 10).

  Then, an average value L (f_Ave) is calculated from the time domain data calculated for each frequency from the EMI analysis data A acquired in step S8 of the flowchart of FIG. 4 (step S28: see FIG. 10). Further, the moving average value L (f_t_moving average) is calculated from the time domain data calculated for each frequency from the EMI analysis data A acquired in step S8 of FIG. 2 (step S29: see FIG. 10).

  Further, L (f_t) is a value obtained by subtracting an arbitrary threshold C (for example, C = 10 dB) from L (f_Max) calculated in step S27, and an arbitrary threshold is added to L (f_Ave) calculated in step S28. All the conditions equal to or greater than the value obtained by adding D (for example, D = 5 dB) and the value obtained by adding an arbitrary threshold E (for example, E = 5 dB) to L (f_t_moving average) calculated in step S29 are satisfied. (Step S30), if satisfied, it is determined that the frequency f is an intermittent wave (step S31), and otherwise, it is determined that it is not an intermittent wave (step S32).

  In this example, the radio wave propagation characteristic database is stored in the computer device 42 and the like. In order to determine whether or not the maximum value of EMI, in particular, the maximum value of the intermittent wave, which has been a problem in the conventional processing, can be acquired correctly, the EMI analysis acquired in step S8 of the flowchart of FIG. In the data, it has theoretical radio wave propagation characteristics and measured radio wave propagation characteristics that make the database of the maximum reception height for each frequency and polarization, receiving antenna height at the time of maximum value acquisition (hereinafter referred to as maximum reception height) Use a database. FIG. 15 shows an example of theoretical radio wave propagation characteristics, and FIG. 16 shows an example of actually measured radio wave propagation characteristics.

  The radio wave propagation characteristics used to determine whether or not the maximum value has been correctly acquired is not a point distribution of the maximum value reception height as shown in FIGS. 13 and 14, but the maximum value reception as shown in FIG. A surface distribution with a range in height is used. This is because, for example, FIG. 12 shows a measurement example of the actually measured radio wave propagation characteristics. When the transmission antenna height h1 and the distance R between the transmission and reception antennas change, the direct wave and reflected wave reception antennas 13 radiated from the transmission antenna 53 are received. This is because the phase in FIG. 6 changes and the maximum reception height differs as shown in the example of FIG. 13 and the example of FIG. FIG. 13 shows an example of theoretical radio wave propagation characteristics when the transmitting antenna height is 90 cm and the distance between the transmitting and receiving antennas is 300 cm, and FIG. 14 is an example of theoretical radio wave propagation characteristics when the transmitting antenna height is 120 cm and the distance between the transmitting and receiving antennas is 300 cm.

  The measurement example of the actually measured radio wave propagation characteristic shown in FIG. 12 will be described. In this example, the signal from the signal source 51 (broadband signal generator or tracking generator) is attached to the antenna mast 52 so that the height can be adjusted. The transmission antenna 53 is configured to transmit. In this case, the transmitting antenna 53 and the receiving antenna 13 are arranged on the same reference ground plane.

  As such a configuration, the theoretical radio wave propagation characteristics are calculated for each transmission antenna height h1 and for each transmission / reception antenna distance R using the calculation formula described in ANSI C63.5 Appendix A A1, Maximum Received Field and the like.

  As shown in FIG. 12, the measured radio wave propagation characteristic example is calculated by radiating the output of the wideband signal generator 51 from the transmission antenna 53 and moving the reception antenna 13 in the vertical direction from 1 m to 4 m while moving the spectrum analyzer 32 (or The reception antenna height when the reception level acquired by the receiver) reaches the maximum value is determined for each polarization, for each frequency, for each transmission antenna height h1, and for each distance R between transmission and reception antennas.

  Next, the evaluation accuracy analysis method in this example will be described. This evaluation accuracy analysis method is a technology for improving the conformity of standards. In this example, an evaluation accuracy analysis as to whether or not the maximum value of EMI, in particular, the maximum value of intermittent waves has been correctly acquired, is performed according to the flowchart shown in FIG. When the evaluation accuracy analysis method is applied only to intermittent waves, it is possible to achieve both a reduction in evaluation error and a reduction in evaluation time.

  Next, the flowchart of the evaluation accuracy analysis method shown in FIG. 7 will be described. First, for each frequency that does not satisfy the limit (or a predetermined margin) extracted in step S11 in the flowchart of FIG. 4, the maximum reception height A is calculated from the EMI analysis data A acquired in step S8 of FIG. (Step S33).

  Next, it is determined for each frequency whether or not the maximum reception height A calculated for each frequency in step S33 is within the maximum reception height range in the actually measured radio wave propagation characteristics (step S34). Advances to step S37, and if not within the range, advances to step S35. In step S35, EMI analysis data B is acquired within the maximum reception height range in the actually measured radio wave propagation characteristics, and the maximum value B is calculated in step S36.

  Thereafter, it is determined for each frequency whether or not the maximum reception height A calculated for each frequency in step S33 is within the maximum reception height range in the theoretical radio wave propagation characteristics (step S37). The process proceeds to step S40, and if not within the range, the process proceeds to step S38. In step S38, the EMI analysis data C is acquired within the maximum reception height range in the theoretical radio wave propagation characteristics, and in step S39, the maximum value C of the EMI analysis data C is calculated.

  Then, in the maximum value B and the maximum value C acquired in step S36 and step S39 and the maximum value A extracted in step S9 and step S11 of the flowchart of FIG. (Step S40).

By measuring as described above, the following effects can be obtained.
That is, first, the reliability of the standard conformity determination is improved. For example, the reliability of whether or not the measurement data is the maximum value can be verified by comparing the reception antenna height at the time of obtaining the maximum value of EMI with the radio wave propagation characteristics stored in the database. When doubt arises in the verification result, the re-acquisition of the maximum value is executed within the maximum value reception height range created in the database. By doing so, the data accuracy and reliability at the time of conformance judgment are dramatically improved, and it effectively eliminates the production of non-conforming products due to errors in conformity judgment and the shipment of non-conforming products. can do.

  Secondly, skillless evaluation of intermittent waves can be realized. That is, time domain analysis is performed using EMI analysis data acquired for each sweep of the spectrum analyzer, and intermittent waves are extracted. The height of the receiving antenna at the time of obtaining the maximum value of those intermittent waves is collated with the radio wave propagation characteristics made in the database. If the receiving antenna height at the time of obtaining the maximum value is not within the maximum value receiving height range of the radio wave propagation characteristics, remeasurement is performed within the maximum value receiving height range. By implementing this evaluation process and function in EMI evaluation software and automatically executing it, a skillless evaluation of intermittent waves can be realized.

  Third, it is possible to achieve both short-time evaluation of EMI countermeasures and evaluation accuracy. When the receiving antenna is scanned at a predetermined height, for example, 1 m to 4 m, it takes a measurement time. In particular, in the case of EMI (intermittent wave) generated every tens of seconds, it is necessary to fix the positions of the turntable and the antenna mast until the reception level is strongly observed. It will take time.

  For example, assuming that EMI generated at 10-second intervals is measured by dividing the measurement frequency band (30-1000MHz, etc.) into three, 10 degree steps, 10 cm height steps, and both horizontal and vertical polarization, the measurement time is at least 18 hours. It is. If such an amount of time is spent for each EMI countermeasure plan, the work efficiency is very poor. In the worst case, it may be impossible to manufacture and ship products as planned.

  Here, in the case of this example, when determining the EMI countermeasure effect of the intermittent wave, it is limited to the maximum radiation height range of one or both of the theoretical radio wave propagation characteristic and the actual radio wave propagation characteristic which are made into a database. Can be measured and the effect can be evaluated. Assuming that all frequencies are evaluated without degrading the evaluation accuracy, the EMI countermeasure effect can be determined in a significantly shorter time than the conventional method in a maximum of 9.4 hours.

  Fourthly, EMI evaluation engineer education and its technical level can be improved. According to this example, the EMI evaluation accuracy of intermittent waves can be increased in a short time. However, because EMI is accompanied by complex phenomena with new digital technology, EMI with a phenomenon outside the scope of this example is handled by a highly skilled EMI evaluation engineer. Evaluation / judgment is required.

  Generally, excellent trainers tend to be short. Therefore, it is used for self-training as an object competing for the evaluation accuracy and evaluation time of the EMI evaluation software in which the processing of this example is implemented, or used as a tool for determining the progress of EMI evaluation technology. Thereby, it can lead to improvement of EMI evaluation technical capability. In particular, the effect can be expected when specifying intermittent waves and specifying the maximum radiation height.

  Fifth, the measurement skill can be made unquestioned. According to this example, it is possible to automatically perform EMI standard conformity determination with high accuracy and high reliability. Therefore, in general, it is possible to easily create EMC quality of a developed product by a product designer who does not have evaluation skills as compared with the conventional technology. Furthermore, it is possible to avoid repeated EMI countermeasure examination work and standard conformity determination due to omission of EMI countermeasures, thereby realizing product shipment as planned.

  For the purpose of studying countermeasures for EMI, the range of movement of the receiving antenna is limited to measurement within the maximum reception height range of either the theoretical radio wave propagation characteristics or actual radio wave propagation characteristics in the database, or both. In addition, the EMI countermeasure study time may be shortened.

  Also, an electronic device that emits EMI with a long periodicity (for example, every 10 seconds) by calculating the periodicity of intermittent waves and obtaining the maximum value by varying the turntable angle and antenna height while maintaining synchronization Automatic evaluation can be realized. Thereby, for example, the EUT is set in the evening, and the result can be obtained the next day.

It is a perspective view which shows the example of a measurement system by one embodiment of this invention. It is a block diagram which shows the example of apparatus arrangement | positioning of the measurement system by one embodiment of this invention. It is a block diagram which shows the apparatus structural example of the measurement system by one embodiment of this invention. It is a flowchart which shows the example of an electromagnetic field measurement by one embodiment of this invention. It is a flowchart which shows the intermittent determination process example (example 1) by one embodiment of this invention. It is a flowchart which shows the intermittent determination process example (example 2) by one embodiment of this invention. It is a flowchart which shows the example of evaluation accuracy analysis by one embodiment of this invention. It is a wave form diagram which shows the example of a periodic intermittent wave. It is a wave form diagram which shows the example of the intermittent wave without periodicity. It is a wave form diagram which shows the example (example 1) of the parameter for intermittent wave determination. It is a wave form diagram which shows the example (example 2) of the parameter for intermittent wave determination. It is a block diagram which shows the example of a measurement of measured radio wave propagation characteristic. It is a wave form diagram which shows the example of theoretical radio wave propagation. It is a wave form diagram which shows the example of theoretical radio wave propagation. It is a wave form diagram which shows the example of theoretical radio wave propagation. It is a wave form diagram which shows the example of measurement radio wave propagation. It is a flowchart which shows the example of the conventional electromagnetic field measurement.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Reference ground plane, 11 ... Turntable, 12 ... Stand, 13 ... Antenna mast, 14 ... Receiving antenna, 15 ... Radio wave absorber, 21 ... Electronic device under test (EUT), 22, 23 ... Peripheral device, 31 ... Pit, 32 ... Spectrum analyzer, 33 ... Coaxial relay switch matrix, 34 ... GPIB extender, 40 ... Measurement room, 41 ... GPIB extender, 42 ... Computer device, 42a, 42b ... GPIB board, 43 ... Turntable controller, 44 ... Antenna Position controller, 45 ... signal generator, 46 ... EMI receiver, 51 ... signal generator, 52 ... antenna mast, 53 ... transmitting antenna

Claims (4)

In an electromagnetic field measurement device that continuously receives electromagnetic waves radiated from a device under test and measures the electromagnetic field,
A receiving antenna that receives electromagnetic waves radiated from the device under test while changing the height;
A collation unit that collates the reception antenna height when obtaining the maximum value of the electromagnetic wave received by the reception antenna with the radio wave propagation characteristics databased by frequency and polarization,
An electromagnetic field measurement apparatus comprising: a processing unit that determines reliability of whether or not the maximum value has been appropriately acquired based on the collation result. The electromagnetic field measurement apparatus according to claim 1,
When the verification result of reliability in the processing unit is lower than a predetermined value, the maximum value is re-acquired by the receiving antenna within the maximum receiving antenna height range of the radio wave propagation characteristics created in the database. An electromagnetic field measuring device. The electromagnetic field measurement apparatus according to claim 1,
A plurality of level data received and acquired by the receiving antenna is expanded into time-series data for each frequency, and the temporal level change of the data is analyzed to generate an intermittent wave whose reception level suddenly increases. An electromagnetic field measurement apparatus characterized by extracting and setting the extracted intermittent wave as the maximum value. In the electromagnetic field measurement method for continuously receiving the electromagnetic wave radiated from the device under test and measuring the electromagnetic field,
The electromagnetic wave radiated from the device under test is received by the receiving antenna while changing the height,
Receiving antenna height at the time of obtaining the maximum value of the electromagnetic wave received by the receiving antenna, collated with the radio wave propagation characteristics databased by frequency and polarization,
An electromagnetic field measurement method comprising: determining whether or not a maximum value has been appropriately acquired based on a result of the collation.