JP2005233833A - Electromagnetic interference measuring system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily measure EMI radiated from an object to be measured having cable terminals as necessary at any time by eliminating the need for the selection of measuring environment even if the object to be measured is in a state communicating with peripheral equipment or in a state supplied with electric power. <P>SOLUTION: By connecting a cable 51 for communications and a power cord 52, to which common mode filters 47 and 48 and a shield cover 49 are applied, via through-tubes 114 to the object to be measured (EUT) 12 housed in an electrically conductive case 11 and any sections to be measured (EMI extraction ports) in the object to be measured 12 each to a nearby cable 16 incorporating a resistor via a flexible cable (EMI extraction lead) 41, a common mode current is generated between an absolute reference electric potential of the case 11 and a reference electric potential of the object to be measured 12. The common mode current is detected, and frequency analysis is performed on its level by a spectrum analyzer etc. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention eliminates the need to select a measurement environment, and allows a relatively small electrical / electronic device or the like as a measurement object to be measured from the measurement object having the cable terminal in a state where the measurement apparatus is accommodated inside the conductive casing. The present invention relates to an electromagnetic wave measurement system in which the level of radiated electromagnetic waves can be easily measured.

  In the past, in order to measure or evaluate electromagnetic waves (hereinafter referred to as EMI: Electro Magnetic Interference) radiated from electrical / electronic devices, EMI evaluation facilities and relatively large G-TEM cells (TEM (TEM There is a need for a measurement device such as a confined test vessel that propagates EMI in a transverse electromagnetic mode.

  Here, if we briefly explain the evaluation of electrical and electronic equipment in EMI evaluation facilities such as an anechoic chamber and an open site, not only the object to be measured (hereinafter referred to as EUT (Equipment Under Test)) but also its vicinity. EMI from the EUT is evaluated as a state including peripheral devices arranged and communication cables and power cords connected thereto. An example of the setup at that time is shown in FIG. Incidentally, the setup mentioned here is defined as processing such as the relative positional relationship between the EUT and the peripheral device, how to cross and bundle various cables, and the like.

  As shown in FIG. 22, the EUT 221 is placed on a turntable (not shown) via an inclusion (non-conductive) 225. Peripheral devices 222 to 224 that perform data communication with the EUT 221 via the digital communication cable 226 are also arranged on the inclusions 225 around the EUT 221, and the EUT 221 can be rotated in the horizontal plane together with the peripheral devices 222 to 224. The On the other hand, an antenna mast (not shown) to which a receiving antenna 227 is attached is erected at a position away from the turntable by a certain distance, and the receiving antenna 227 is moved up and down in the vertical direction. It can also be raised and lowered. As a result, the receiving antenna 227 can detect the EMI according to the lift position and the turntable rotation position.

  FIG. 23 also shows a simplified diagram of the setup at that time. From this figure, it can be seen that three digital communication cables 226 and one power cord 228 are connected to the EUT 221. I understand. EMI radiated directly from the EUT 221 and peripheral devices 222 to 224 or EMI radiated through various cables (digital cable, power cord, analog cable) connected to the EUT 221 are in a combined state. This is detected by the receiving antenna 227. Furthermore, a schematic diagram of the setup is shown as FIG. 24. In general, considering that radiation from various cables connected to the EUT is dominant, these cables are connected as antennas. It is possible to replace the existing port with an EMI supply source. It can be said that the change in the EMI level in the EMI evaluation facility is the change in the common mode current in the port. Eventually, EMI is emitted by using the EMI measurement point as an EMI supply source and the digital communication cable 226 and the power cord 228 function as an antenna, and the signal is detected by the receiving antenna 227 as a combined state, and the level is spectrum. Frequency analysis is performed with an analyzer.

Incidentally, in the thing of patent document 1, in order to measure the electromagnetic waves radiated | emitted from the to-be-measured object in which at least any one is provided among an input / output signal line and a power supply line, on an input / output signal line The frequency component superimposed on the signal potential or the power supply potential on the power supply line is extracted, and the intensity of the radiated electromagnetic wave is determined based on the level of the frequency spectrum of the frequency component. Moreover, in the thing of patent document 2, a measuring object (rectangular board | substrate) is accommodated in an electroconductive housing | casing, The reference potential of the measuring object (rectangular board | substrate) with respect to the absolute reference potential of the housing | casing In order to measure the electromagnetic wave noise appearing in, a radio wave absorber having a radio wave absorption characteristic at a frequency higher than the measurement frequency range and having a dielectric constant of a predetermined condition in the measurement frequency range is provided inside the housing.
JP 2001-289895 A Japanese Patent Laid-Open No. 2002-181863

As described above, since the EMI measurement so far requires a simple measuring device such as an EMI evaluation facility and a relatively large G-TEM cell, there are the following problems. .
1) When measurement is performed at an EMI evaluation facility, generally 1 to 2 hours are required for each measurement, and it takes a lot of time to evaluate EMI countermeasure effects and EMI quality of mass-produced products. It will take.
2) In the EMI evaluation facility, the radiation level changes depending on the positional relationship between the EUT and peripheral devices, the arrangement conditions of the connection cables, etc., so the reproducibility of the EMI evaluation is poor and the EMI countermeasure effect etc. cannot be accurately grasped. There are many cases.
3) In the EMI evaluation facility, measurement is performed using a drive system (antenna mast and turntable). However, for EMI whose radiation level fluctuates with time, a different result is obtained for each measurement.
4) Measurement with an EMI evaluation facility requires experience, knowledge, and skills, and results often differ depending on the measurer.

5) When using an EMI evaluation facility, a reservation is generally required, and it is impossible to make measurements as needed.
6) New installation of EMI evaluation equipment generally requires investment of tens of millions to hundreds of millions of yen, and also requires maintenance costs and specialized management personnel.
7) In the case of a measuring apparatus that evaluates a substrate constituting an EUT, the evaluation cannot be performed in a state where the mechanical chassis is mounted. In general, a relatively small mechanical chassis for electrical and electronic equipment is used as a reference potential. Therefore, in a state where only the board is in a state where the mechanical chassis is removed or a screw stopper is loosened. The EMI level in the EMI evaluation facility is different.
8) In some measuring devices, a common mode filter is not attached to a digital interface bus such as USB (Universal Serial Bus) or IEEE (Institute of Electrical and Electronics Engineers) 1394, Under the influence of peripheral noise (hereinafter referred to as external noise) such as EMI, broadcast wave, city noise, etc., the peripheral device cannot be evaluated in communication with the peripheral device.

  The object of the present invention is to make it unnecessary to select a measurement environment, and even when the EUT is in communication with a peripheral device, the level of EMI radiated from the EUT having the cable terminal as needed. It is an object of the present invention to provide an electromagnetic wave measurement system that can be easily measured.

  The electromagnetic wave measurement system according to the present invention detects a common mode current generated between the absolute reference potential of the casing and the measured part of the EUT in a state where the EUT is accommodated in the conductive casing. The level is subjected to frequency analysis, and the casing as a constituent element includes at least a cable for data communication with a peripheral device installed outside the casing and an object to be measured from outside the casing. A through-pipe for drawing the power cord for supplying power to the outside of the housing and a resistor for adding output impedance are inserted inside, and one end is indirectly connected to any part to be measured in the EUT The other end is provided with one or more resistors with a built-in resistor connected to a coaxial cable, a bottom surface of the casing, and a non-conductor for isolating the object to be measured.

  The conductive casing has a size that is not limited by the installation environment such as space and load resistance, for example, a size that can be easily installed on a desk in an office. Further, the casing is provided with a through pipe, and a communication cable for the EUT to perform data communication with an external peripheral device is drawn out of the casing through the through pipe, and the common mode filter And connected to a peripheral device through a shield cover. Therefore, even when the EUT is in communication with the peripheral device, the EMI radiated from the EUT having the cable terminal without being affected by the EMI from the peripheral device and external noise is It becomes possible to measure at any time.

  According to the electromagnetic wave measurement system according to the present invention, selection of a measurement environment is unnecessary, and even when the EUT is in communication with an external peripheral device or in a state where power is supplied, the cable terminal is held at any time. The level of EMI emitted from the EUT can be easily measured.

An embodiment of the present invention will be described below with reference to FIGS.
First, the measurement principle in the present invention will be described. As shown in FIG. 1, a non-conductive body (not shown) is provided on the inner bottom surface of the conductive casing 11 so as to isolate the bottom surface from the EUT 12, and the EUT 12 is placed on the non-conductive body. Placed. As a result, a stray capacitance 13 is generated between the reference potential of the EUT 12 and the bottom surface of the housing 11. Accordingly, a measurement site (hereinafter referred to as an EMI extraction port) 14 in the EUT 12 is passed through a flexible cable (hereinafter referred to as an EMI extraction lead) 15 and a resistor built-in connector 16 so that a loop circuit is formed. If connected to the bottom surface of the housing 11, a common mode current flows in the formed loop circuit. If this common mode current is extracted and then subjected to frequency analysis using a 50Ω EMI measuring device (spectrum analyzer / EMI receiver or the like) 17, EMI can be measured or evaluated.

  Now, the present invention will be specifically described. First, the perspective external appearance of the housing according to the present invention is shown in FIG. 2, the plane state thereof is shown in FIG. 3, and the entire electromagnetic wave measuring system according to the present invention is shown as an example. The configuration is shown as FIG. As shown in the figure, the casing 11 itself is made conductive so that a relatively small electric / electronic device can be accommodated therein, and is not limited by the installation environment such as space and load resistance. Thus, it is configured as a size that can be easily installed on a desk or the like in an office. The size is, for example, an inner dimension of 450 mm (W) × 700 mm (D) × 150 mm (H). By making the casing 11 conductive, external noise can be blocked.

The housing 11 is composed of the following elements.
Gasket: A gasket (for example, a shield finger) 113 is installed on the edge of the top plate in the housing 11 in order to block external noise (see FIG. 2).
Through pipe: A cable (digital system cable (communication cable 51), power cord 52) connected to the EUT 12 is pulled out of the housing 11 to perform data communication with the peripheral device 46 and supply power to the EUT 12. A through pipe 114 is installed on the wall surface of the housing 11. The number of installation is arbitrary, but normally four are installed on the wall surface in front of the housing 11 and four are installed on the inner wall surface (see FIGS. 2 to 4). However, not all of the penetrating pipes 114 are actually used, and the penetrating pipes that are not used need to be covered with a conductive cap in order to block external noise.
Non-conductor (No. 1): Non-conductive between the inner bottom surface and the EUT 12 in order to extract a stable common mode current while keeping the stray capacitance between the inner bottom surface of the housing 11 and the EMI extraction port of the EUT 12 constant. A body (not shown) is installed. The height of this non-conductor is usually set to 30 mm.

Resistor-incorporated connector: A resistor-incorporating connector 16 (which will be described in detail later) with a built-in resistor that maintains stable output impedance characteristics and improves the reproducibility of measurement is installed. The resistance value and type of the resistor are arbitrary, but normally a 100Ω metal film resistor or one chip resistor is incorporated. The installation site and the number of the connectors with built-in resistors 16 are arbitrary, but usually three are installed in front of the housing 11 and three in the back (see FIGS. 2 to 4). The resistor built-in connector 16 is detachably connected to an EMI extraction lead 41, which will be described in detail later, via a connector pin, thereby realizing easy operability and improved reproducibility.
Handle (No. 1): Various handles 111 are installed on the outer wall of the casing 11 in order to smoothly and safely move the casing 11 itself (see FIGS. 2 and 3).
Handle (No. 2): In order to smoothly open and close the top plate, a handle 115 is installed on the outer top plate of the housing 11 (see FIG. 3).
Damper: A damper 112 is installed on the outer wall of the housing 11 in order to smoothly open and close the top plate (see FIGS. 2 and 3).
Non-conductor (No. 2): Non-conductor (this will also be described later) in order to prevent the contact of the EMI extraction lead to the inner wall surface of the housing 11 and to prevent the measurement data error rate from deteriorating due to resonance or the like Is installed on the inner wall surface of the housing 11 around the connector 16 with built-in resistor.
Radio wave absorber: A radio wave absorber (not shown) is installed inside the housing 11 in order to suppress reflection of EMI generated from the EUT 12, the communication cable 51, and the power cord 12 in the housing 11. . Usually, it is installed on the inner wall of the housing 11.

The constituent elements of the casing have been described above. Hereinafter, constituent elements other than the casing will be described.
EMI extraction lead: The EMI extraction lead 41 is a flexible cable for connecting between the EMI extraction port 14 and the resistor built-in connector 16 as shown in FIG. In general, a flexible insulator can be used), a conductive wire mesh covering this insulating tube, a hook clip as one end for clipping the EMI extraction port, and a connector pin as the other end (operability) (This will also be described later).
50Ω EMI measuring device: a measuring device for analyzing the frequency of the extracted common mode current level. As the 50Ω EMI measuring device 17, a spectrum analyzer, an EMI receiver, or the like is used (see FIG. 4). ).
RF amplifier: An amplifier that amplifies the extracted common mode current. As the RF amplifier 42, an amplifier built in the EMI measuring device can be substituted (see FIG. 4).

Computer etc .: Used for collection / management and calculation processing of measurement data acquired by the 50Ω system EMI measuring device 17 and control of the 50Ω system EMI measuring device 17. A personal computer is used (see FIG. 4).
50Ω coaxial cable: a 50Ω coaxial cable for connecting between the resistor built-in connector 16 installed in the housing 11 and the 50Ω EMI measuring device 17, and the 50Ω coaxial cable 44 Since the RF amplifier 42 is interposed between the two, two are required (see FIG. 4).
GPIB (General Purpose Interface Bus) cable: EMI measuring device control communication cable, and the GPIB cable 45 connects the computer 43 and the 50Ω EMI measuring device 17 (see FIG. 4). reference).
Common mode filter: A communication common mode filter 47 is used to block EMI from the outside of the housing 11, that is, EMI from the peripheral device 46, external noise, and the like and pass only necessary signals. For the power source 50, a power source common mode filter 48 is used (see FIG. 4). As the structure of this common mode filter, for example, a cable (digital cable, power cord, etc.) is bifilar wound around a magnetic material (ferrite ring or the like) and accommodated in a conductive casing.
Shield cover: A shield cover 49 is used to block external noise superimposed on the cable between the through pipe 114 and the common mode filters 47 and 48 (see FIG. 4).

  Here, a supplementary explanation will be given for further necessary components among the components described above. First, a supplementary description of the resistor built-in connector will be described. As shown in FIGS. 5A and 5B, the resistor built-in connector 16 is configured as a cylinder 161 having one end formed as a flange 162. The male connector pin 163 is attached to the inside of the cylinder 161 so as to partially protrude to the outside. One end of a resistor 164 is also connected to the other end of the male connector pin 163, and the other end of the resistor 164 is also connected to a 50Ω coaxial cable to the RF amplifier. The resistor built-in connector 16 configured in this way is attached and fixed to the wall surface of the housing 11 with screws by screw fixing holes 165 formed in the flange 162, and the male connector pin 163 is By fitting with a female connector pin as one end of the EMI extraction lead, it is connected to the EMI extraction port.

  Next, a non-conductor for preventing the EMI extraction lead from contacting the inner wall surface of the housing will be supplementarily described. An example of the attachment state of the non-conductor as the contact preventing jig 61 is shown in FIG. As shown in FIG. 6, the shape of the contact preventing jig 61 is arbitrary. However, the contact prevention jig 61 is entirely connected so that the resistor built-in connector 16 is surrounded by the inner wall surface of the housing 11 in the vicinity of the resistor built-in connector 16. Mounted as a letter.

  Further, a supplementary explanation of the EMI extraction lead will be given. The overall appearance of the EMI extraction lead is shown in FIG. As can be seen from FIG. 7, the EMI extraction lead 41 has a flexible insulator (not shown) (rubber tube, urethane foam, etc.) whose outer surface is covered with a wire mesh 412 and one end of which is female. The mold connector pin 411 and the other end are configured as a hook clip 413. In this use, the EMI extraction port is clipped by the mouth clip 413 and the female connector pin 411 is fitted to the male connector pin in the nearest resistor built-in connector 16. For reference, FIG. 8 shows an overview of the male resistor built-in connector 16 and the female connector pin 411, and FIG. 9 shows the connection state of the EMI extraction lead 41 to the resistor built-in connector 16.

  By the way, the above-mentioned resistor built-in connector and EMI extraction lead are respectively provided with a male connector pin and a female connector pin, but in the opposite case, that is, a female connector pin and a male connector pin, respectively. Needless to say, the same connection function can be obtained even if the device is provided. The overall appearance of the EMI extraction lead in this case is shown in FIG. 10 together with the resistor built-in connector. As shown in the figure, one end of the EMI extraction lead 41 is replaced with a male connector pin 414, and a female connector pin (not shown) is provided in the resistor built-in connector 16 instead of the male connector pin. Is provided. When this is used, the EMI extraction port is clipped by the mouth clip 413 and the male connector pin 414 is fitted to the female connector pin in the nearest resistor built-in connector 16. For reference, FIG. 11 shows the general appearance of the female resistor connector 18 and the male connector pin 414, and FIG. 12 shows the connection state of the EMI extraction lead 41 to the resistor connector 16.

As described above, it can be said that the change in the EMI level in the EMI evaluation facility is the change in the level of the common mode current in the port to which various cables are connected. Therefore, in order to quantitatively evaluate changes in EMI characteristics (such as EMI countermeasure effects and variations) in digital and analog systems, such as the communication status with peripheral devices and the power supply status, the optimal point for measuring common mode currents, That is, examples of the EMI extraction port include the following.
1) Reference potential portion in a digital cable connected to the EUT (described later)
2) Reference potential part of I / O Port (input / output port) in EUT to which digital cable is connected 3) Skin part of power supply (DC power supply and AC power supply) 4) Power supply (DC power supply) cord is connected 5) Reference potential portion of the analog cable connected to the EUT 6) Reference potential portion of the EUT to which the analog cable is connected 7) Reference potential portion of the attachment with the rated termination resistor (described later)

  Next, a supplementary explanation of the attachment with the rated termination resistor will be given. This is configured as an analog connector to which a rated termination resistor is attached in order to evaluate an analog system (a system that does not communicate with peripheral devices such as headphones and microphones). This is attached to an analog input / output signal connector in the EUT, and measurement is performed as an EMI extraction port. An example of the attachment with the rated termination resistance is shown in FIG. As shown in the drawing, the attachment 52 with the rated termination resistor is such that the reference potential conductor 523 is easily clipped by the incision clip among the left channel conductor 521, the right channel conductor 522 and the reference potential conductor 523. Further, it is provided in a state protruding more in the direction opposite to the insertion direction. A load resistor 524 is provided between the reference potential conductor 523 and the left channel conductor 521 and the right channel conductor 522. As a result, changes in the EMI level due to handling conditions such as the arrangement of analog cables connected to the EUT and how to bundle the cables are suppressed.

  Next, a digital cable in which a connector portion connected to the EUT is processed in order to evaluate a digital system in a communication state with a peripheral device will be described. The reference potential (metal part) at the connector part of the digital cable is processed so as to be exposed. An example of the processing is shown in FIG. As shown in the figure, in the communication cable 51, the connector portion to the EUT is normally in a state where only the reference potential conductor 512 is exposed, but the insulating coating 511 in the vicinity thereof is removed. By this removal, the reference potential conductor 513 is newly stripped. Therefore, when the connector portion is connected to the EUT, the reference potential conductor 513 is exposed to the outside, and can be easily clipped by the hook clip. Thereby, the contact resistance when clipped as an EMI extraction port is stabilized, and the evaluation can be performed with good reproducibility while maintaining the communication state with the peripheral device.

  Next, based on FIG. 15, a measurement flow when performing EMI measurement in a state where one end of the EMI extraction lead is connected to the resistor built-in connector will be described. This measurement is performed each time the EMI extraction port is clipped by the incision clip. First, the EUT is installed near the center in the housing (step S1). Next, the communication cable and the power cable (power cord) are connected to the EUT (step S2). In step S2, the cable is drawn out of the housing from the through pipe, and connected to a peripheral device or a power source through the common mode filter and the shield cover. Thereafter, it is determined whether or not the evaluation in the communication state is performed (step S3). If it is determined in this determination that the evaluation in the communication state is performed, both the EUT and the peripheral device are powered on (step S4). If it is determined that the evaluation in the communication state is not performed, only the EUT is powered on (step S5).

  As described above, after the power is turned on, it is determined whether or not the evaluation is performed in consideration of the analog system (step S6). If it is determined in this determination that the evaluation is performed with the analog system taken into account, the attachment with the rated termination resistor is attached to the analog port (step S7). Thereafter, the EMI extraction port is clipped by the EMI extraction lead, and the connector pin of the EMI extraction lead is connected to the nearest resistor built-in connector as necessary (step S8). On the other hand, if it is determined in step S6 that the analog system is not evaluated, the EMI extraction port is clipped by the EMI extraction lead and, if necessary, the connector of the EMI extraction lead. The pin is connected to the nearest resistor built-in connector (step S8). Thereafter, the top plate of the housing is closed (step S9), and acquisition of spectrum data (measurement data) is started using the EMI measuring device, but the acquired spectrum data is stored in a computer or the like ( Step S10). After acquiring the spectrum data, it is determined whether or not all the EMI extraction ports have been measured (step S11). If all the measurements have been made in this determination, the series of processing ends. If not all have been measured, the top plate of the housing is opened until all are measured (step SS12), and the process returns to step S8. Then, a new EMI extraction port is clipped by the EMI extraction lead, and the connector pin of the EMI extraction lead is connected to the nearest resistor built-in connector as necessary, and the same processing is repeated. ing.

  Although the measurement flow has been described above, the number of EMI extraction leads used at that time is one, and the common mode current is sequentially extracted from each of the EMI extraction ports. As a result, it is possible to verify the change and concentration of the common mode current level at each EMI extraction port, and it is possible to evaluate the EMI level change such as the EMI countermeasure effect and to specify the radiation source (radiation route). Incidentally, how the EMI level changes before and after the countermeasure against the EMI for the same EUT is shown in FIG. 16 for the anechoic chamber and FIG. 17 for the present invention.

  When evaluating the effect of EMI countermeasures (change in EMI characteristics), in principle, the maximum values at all EMI extraction ports are calculated for each frequency and then evaluated. However, in the measurement at the EMI evaluation facility, the radiation efficiency of the cable itself changes depending on the arrangement conditions of the cable etc. connected to the EUT, so the EMI extraction port to which the high radiation efficiency cable is connected (specified in the EMI evaluation dedicated facility) May be evaluated with a priority.

  Since the electromagnetic wave measurement system according to the present invention is configured as described above, it is possible to analyze and grasp the time variation characteristics of EMI. In other words, if it is combined with software that has a function to continuously acquire the data of the measuring instrument (for example, acquire all the data for each sweep (sweep) in the spectrum analyzer), the time fluctuation of the level of each frequency Characteristics (stable EMI, intermittent level fluctuation EMI (EMI in which the level intermittently fluctuates in time)), temperature characteristics, and the like can be quantitatively evaluated. For reference, the two-dimensional time domain (20 minutes) at a specific frequency is shown in FIG. 18, the three-dimensional time domain (20 minutes) in all measurement frequency bands is shown in FIG. FIG. 20 shows (30 seconds intermittent EMI), and FIG. 21 shows a two-dimensional time domain (30 seconds stable EMI) at a specific frequency.

Further, from the time domain data acquired by the software having the time domain analysis function, the QP value acquired by the QP detection mode of the EMI receiver is estimated using a function that simulates the response characteristic of the QP detection circuit. It becomes possible.
Further, when a plurality of EMI extraction leads are used at the same time, the top plate can be opened and closed accordingly, so that the maximum EMI level is evaluated in a short time. For example, when the same number of extraction leads as the number of EMI extraction ports are used, all the EMI extraction ports are collectively evaluated.

As described above, according to the electromagnetic wave measurement system of the present invention, the examination of EMI countermeasures for a relatively small electric / electronic device having a cable terminal is affected by external noise at the design office (design bench). It can be done without. As a result, unlike the conventional EMI evaluation facility using EMI evaluation equipment, which is generally used by advance reservation, timely examination can be performed as needed. In addition, an increase in the number of EMI evaluation facilities (such as an anechoic chamber) that involves an investment of tens of millions of yen to several hundreds of millions of yen will be avoided or suppressed.
Further, EMI countermeasures can be examined and evaluated in a time of 1/10 or less as compared with the conventional case. For example, if the estimation time (excluding the time required for setup) when the measurement frequency range is 30 MHz-1 GHz and the number of interfaces (the number of Ports) is 6 as a trial calculation condition, Measurement) takes more than 1 hour, but in the case of the present invention (no place restrictions), it takes only 6 minutes (= 1 minute × 6 Port).

Furthermore, the effect of EMI countermeasures for each EMI extraction port can be evaluated based on the communication status with peripheral devices (one condition of the system configuration defined in the EMI measurement standard), and the main radiation route (EMI-like antenna) can be evaluated. It becomes possible to accurately grasp the level change.
In addition, since the EMI and external noise from peripheral devices are blocked and there is no drive system, that is, the evaluation can be performed in a stable measurement environment, the error rate of the entire measuring apparatus can be suppressed to 1 dB or less. It becomes. By taking advantage of this feature, it is possible to quantitatively evaluate reproducibility and repeatability, level variations among a plurality of EUTs, EMI countermeasure effects of intermittent level fluctuation EMI, and the like.
In addition, the measurement environment is easy to set and no special evaluation skills are required, so that no expert measurement personnel are required. That is, it becomes easy to examine EMI countermeasures by a measurer (for example, a designer) having insufficient evaluation skills.

  Although the invention made by the present inventor has been specifically described based on one embodiment, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

It is a figure which shows the electromagnetic wave measurement principle of this invention. It is a figure which shows the isometric view external appearance of the housing | casing which concerns on this invention. Similarly, it is a figure which shows the planar state. It is a figure which shows the whole structure in an example of the electromagnetic wave measurement system by this invention. It is a figure which shows the front state by which some resistors built-in connectors based on this invention were made into the cross section, and the left side surface state. It is a figure which shows the attachment state to the inner wall surface of the nonconductor for preventing the EMI extraction lead contact to the inner wall surface of a housing | casing. It is a figure which shows the whole external appearance of EMI extraction lead | read | reed (the 1) with a connector with a built-in resistor. It is a figure which shows the external appearance of a resistor built-in connector and a female connector pin. It is a figure which shows the connection state of the EMI extraction lead to the resistor built-in connector. It is a figure which shows the whole external appearance of the EMI extraction lead | read | reed (the 2) with a connector with a built-in resistor. It is a figure which shows the external appearance of a resistor built-in connector and a male connector pin. It is a figure which shows the connection state of the EMI extraction lead to the resistor built-in connector. It is a figure which shows the general appearance in an example of an attachment with a rated termination resistance. It is a figure which shows the example of a process with respect to the connector part connected to EUT. It is a figure which shows an example of the EMI measurement flow which concerns on this invention. It is a figure which shows how an EMI level changes before and after the countermeasure by an EMI countermeasure as an anechoic chamber. It is a figure which shows how the EMI level changes before and after the countermeasure by the EMI countermeasure as in the present invention. It is a figure which shows the two-dimensional time domain (20 minutes) in a certain specific frequency. It is a figure which shows the three-dimensional time domain (20 minutes) in all the measurement frequency bands. It is a figure which shows the two-dimensional time domain (30 second intermittent EMI) in a certain specific frequency. It is a figure which shows the two-dimensional time domain (30 second stable EMI) in a certain specific frequency. It is a figure which shows the example of a setup in an EMI evaluation installation. It is a figure which shows the simple figure of the setup. It is a figure which shows the schematic diagram of the setup.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... (Conductive) housing | casing, 12 ... EUT (measurement object), 114 ... Through pipe, 16 ... Resistor built-in connector, 15, 41 ... EMI extraction lead (flexible cable), 51 ... Communication cable, 52 ... Power cord, 47 ... Communication common mode filter, 48 ... Power common mode filter, 49 ... Shield cover, 411,414,163 ... Connector pin, 61 ... (EMI extraction lead) Contact prevention jig, 52 ... Attachment with rated termination resistor

Claims (7)

In a state where the object to be measured is accommodated in the conductive casing, the level is detected after detecting the common mode current generated between the absolute reference potential of the casing and the portion to be measured of the object to be measured. An electromagnetic wave measurement system for frequency analysis,
The housing as a component is at least
A cable for data communication with peripheral devices installed outside the housing, and a through pipe for pulling out a power cord for supplying power to the object to be measured from outside the housing;
One or more resistors in which a resistor for adding output impedance is inserted, one end of which is indirectly connectable to an arbitrary measured portion of the measured object, and the other end is connected to a coaxial cable A built-in connector;
An electromagnetic wave measurement system comprising a bottom surface of the housing and a non-conductor for isolating the object to be measured. The electromagnetic wave measurement system according to claim 1,
The electromagnetic wave measurement system, wherein any one of the measurement target parts and the one of the built-in resistors are connected via a flexible cable. The electromagnetic wave measurement system according to claim 1,
A common mode filter is provided for each of the data communication cable and power cord existing outside the casing, and a shield cover is provided between the common mode filter and the through pipe. An electromagnetic wave measurement system characterized by that. The electromagnetic wave measurement system according to claim 1,
An electromagnetic wave measurement system, wherein an electromagnetic wave absorber is provided on an inner wall surface of the casing. The electromagnetic wave measurement system according to claim 1,
In the digital system, when the reference potential portion at the input / output port is the part to be measured and the connector as one end of the communication cable is inserted and connected to the object to be measured, The processed reference potential metal surface part is taken as the measurement site,
In the analog system, the reference potential part in the connector with the rated termination resistor inserted and connected to the analog signal input / output terminal is the part to be measured. In the power cord, the insulation skin part is the part to be measured. An electromagnetic wave measurement system characterized by that. The electromagnetic wave measurement system according to claim 2,
The electromagnetic wave measurement system, wherein the flexible cable and the resistor built-in connector are detachably connected via a connector pin. The electromagnetic wave measurement system according to claim 2,
An electromagnetic wave measurement system, wherein a non-conductor for preventing contact of the flexible cable to the housing is provided on the inner wall surface of the housing in the vicinity of each of the connectors with built-in resistors.