JP2003294706A - Device for estimating electromagnetic wave shielding performance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a device for estimating electromagnetic wave shielding performance, which is shortened in construction period and reduced in cost by detecting, during construction, a defect of an electromagnetic wave shield at a wall or the like of a building, and taking a measure at that time. <P>SOLUTION: The device for estimating electromagnetic wave shielding performance which passes AC current through a wall surface made of a conductive material inside a building to which an electromagnetic wave shield is applied, thereby evaluating the shielding performance at a connecting portion 4 of the wall, comprises a computing function block which estimates the shielding performance in a place wave according to detected quantities of two radiation magnetic fields in a horizontal direction corresponding to a face current around the shielding performance evaluating portion and is a vertical direction with respect to a wall surface at the shielding performance evaluating portion. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic wave shield performance estimating device for estimating and evaluating the effect of electromagnetic wave leakage prevention measures for reducing electromagnetic wave leakage to the outside of an electronic device which is carried out at the place where the electronic device is installed. is there.

[0002]

2. Description of the Related Art A conventional electromagnetic wave shield evaluation method is, for example, as shown in Japanese Patent Laid-Open No. 8-68815, after completion of a building having electromagnetic wave shield measures, an electronic device in the building is actually driven. The effect of electromagnetic wave shielding measures outside the building was evaluated by measuring with an antenna.

[0003]

Since the conventional electromagnetic wave shield performance estimating device is constructed as described above, the electronic device is actually driven in the building to perform the evaluation. After the completion of the work, even if a failure of the shield is detected, construction work for the repair is required again, which is disadvantageous in terms of construction period and cost.

The present invention has been made in order to solve the above problems. By detecting a failure of an electromagnetic wave shield on a wall of a building during construction and taking countermeasures at that time, the construction period can be shortened and the cost can be reduced. The purpose of the invention is to obtain an electromagnetic wave shield performance estimation device that saves

[0005]

SUMMARY OF THE INVENTION An electromagnetic wave shield performance estimating apparatus according to the present invention has a horizontal radiated magnetic field corresponding to a surface current around a shield performance evaluation section by passing an alternating current through a wall surface, and a shield performance. It is provided with a calculation function block for estimating the shield performance in a plane wave in accordance with two detection amounts of a radiated magnetic field in the direction perpendicular to the wall surface in the evaluation section.

According to the electromagnetic wave shield performance estimating apparatus of the present invention, the shield performance evaluating unit detects the amount of the radiant magnetic field in the vertical direction with respect to the wall surface from the vertical radiating magnetic field in the shield performance evaluating unit. The detection amount obtained by subtracting the radiated magnetic field in the vertical direction at the distant portion is used.

In the electromagnetic wave shield performance estimating apparatus according to the present invention, in the arithmetic function block, a horizontal radiating magnetic field and a vertical radiating magnetic field obtained by passing an AC current through a conductive plate having a known shield performance and a gap. The two detection amounts of the magnetic field are used as reference values.

The electromagnetic wave shield performance estimating apparatus according to the present invention includes, in the arithmetic function block, a logarithmic amplifier for converting two detection amounts of a horizontal radiating magnetic field and a vertical radiating magnetic field into a logarithmic quantity.

In the electromagnetic wave shield performance estimating apparatus according to the present invention, in the arithmetic function block, the logarithmic quantity corresponding to the two detection quantities detected as the reference value and the two detection quantities detected for the shield performance evaluation are used. It is provided with two differential amplifiers that convert the corresponding logarithmic quantity into a difference corresponding to each detected magnetic field direction.

The electromagnetic wave shield performance estimating apparatus according to the present invention includes, in the arithmetic function block, an adder for adding two differences respectively corresponding to the detected magnetic field directions.

In the electromagnetic wave shield performance estimating device according to the present invention, the arithmetic function block converts the reference value corresponding to the ratio of the frequency required for shield performance estimation and the frequency at the time of measurement into a logarithmic quantity, and the frequency correction amount. And a differential amplifier that takes the difference between the frequency correction amount converted by the logarithmic amplifier and the added value of the two differences.

In the electromagnetic wave shield performance estimating apparatus according to the present invention, in the arithmetic function block, a constant voltage amount is set in order to make the difference between the frequency correction amount and the added value of the two differences correspond to the amount indicating the shield performance in a plane wave. It is equipped with a level shifter that shifts only.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below. Embodiment 1. 1 is a block diagram showing an electromagnetic wave shielding performance (SE) estimating apparatus according to Embodiment 1 of the present invention,
FIG. 2 is a partially enlarged view of the electromagnetic wave shielding performance (SE) estimating device. In FIG. 1, 1 is an electromagnetic field probe for detecting a vertical radiated magnetic field, 2 is an electromagnetic field probe for detecting a horizontal radiated magnetic field, 3 is a conductor wall (or plate) made of a conductive material, and 4 is its It is a connection part (or a gap) existing on the wall surface. Reference numeral 5 is a signal line for transmitting a detection signal of the electromagnetic field probe 2 for detecting a radiation field in the horizontal direction, 6
Is a signal line for transmitting the detection signal of the electromagnetic field probe 1 for detecting the radiation field in the vertical direction, 7 is a logarithmic amplifier for converting the signal on the signal line 6 into a logarithm, and 8 is a signal for converting the signal on the signal line 5 into a logarithm. A logarithmic amplifier, 9 is a signal line for transmitting the output signal of the logarithmic amplifier 7, and 10 is a signal line for transmitting the output signal of the logarithmic amplifier 8. Reference numeral 11 is a reference voltage terminal for giving a prescribed reference voltage, 12 is also a reference voltage terminal for giving a prescribed reference voltage, 13 is a differential amplifier for obtaining a differential signal between the voltage of the signal line 10 and the voltage of the reference voltage terminal 11, and 14 is A voltage generation circuit for applying a specified voltage to the reference voltage terminal 11, 15 is a differential amplifier for obtaining a differential signal between the signal line 9 and the voltage of the reference voltage terminal 12, 1
6 is a voltage generation circuit for applying a specified voltage to the reference voltage terminal 12, 17 is a signal line for transmitting the output signal of the differential amplifier 13, 18 is a signal line for transmitting the output signal of the differential amplifier 15, and 19 and 20 are These are changeover switches for turning on / off the connection between the output signals of the differential amplifiers 13 and 15 and the next block. Reference numerals 21 and 22 are signal lines connected to the outputs of the changeover switches 19 and 20, respectively, and 23 is an adder connected to the signal lines 21 and 22 and taking a sum signal of the two.
4 is a signal line for transmitting the output of the adder 23, 25 is a reference voltage terminal for giving a prescribed reference voltage, and 26 is a reference voltage terminal 2
5 is a logarithmic amplifier for converting the reference voltage value into a logarithmic value; 27 is a signal line for transmitting the output signal of the logarithmic amplifier 26; An amplifier, 29 is a voltage generating circuit for applying a specified voltage to the reference voltage terminal 25, 30 is a signal line for transmitting the output signal of the differential amplifier 28, 31 is a level shifter for adjusting the DC level of the output signal of the differential amplifier 28, Reference numeral 32 is a signal line for transmitting the output signal of the level shifter 31, and 33 is an output terminal. In FIG. 2, 34 is an alternating current (Is) flowing through the conductor wall 3, and 35 is a horizontal magnetic field (H) generated by the alternating current 34 flowing through the conductor wall 3.
v) and 36 are vertical magnetic fields (Hp) generated from the connecting portion (gap) 4 of the conductor wall 3.

Next, the operation will be described. When a plate member (wall, etc.) made of a conductor has a gap due to the connecting portion 4 or welding, when an alternating current is supplied to this plate member by some method, a surface current (Is) bypasses the gap part. As a result, a magnetic field (Hp) perpendicular to the plate material is generated in the gap and its vicinity. In addition, the surface current (I
A magnetic field (Hv) in the parallel direction is generated in the plate material by s).
At this time, it is easily derived that the surface current (Is) and the parallel magnetic field (Hv) have a substantially proportional relationship. Further, the shield amount (SE) in the plane wave is given by the following equation (1). SE = 20 log (Hin / Hout) (dB) (1) where Hin is the incident magnetic field on the sample to be measured, Hou
Similarly, t is a transmitted magnetic field. For plane waves (far field),
Even if Expression (1) is expressed by the electric field amounts (Ein, Eout), the values are the same.

When a plate material made of a conductive material has a gap, when an electromagnetic wave is incident (Hin) on the plate material, an induced current is induced on the surface of the plate material by the incident wave, and this surface current is generated. As in the case of the above-described current drive, since a vertical magnetic field (both sides of the plate material) is generated by bypassing the gap, it is considered that the incident wave is transmitted (Hout) through the plate material. From this, the following correspondence is approximately given to the electromagnetic field when an alternating current is applied to the plate material made of a conductive material and when an electromagnetic wave is incident from the outside. Hin → Hv, Hout → Hp (2) Further, Donald R. J. “El” by White
According to "electromagnetic shielding", when a plate material (a sufficiently large area) made of a conductive material has a gap as described above, the shield amount (SE) in a plane wave of the plate material is determined by electromagnetic field analysis. It is known to be approximated as follows: SE = 97−20 log (L · f) +20 log {1 + ln (L / s)} (dB) (3) where L is the length of the gap between the plate materials ( mm), f is the frequency (MHz), and s is the width of the gap (mm).

From the above, by combining the formulas (1) and (2) and further applying the approximate formula of the formula (3), an alternating current is applied to a plate material having a gap made of a conductive material. The magnetic field (Hp, Hv) generated when
It can be easily derived that the approximate expression of the shield amount (SE) in the plane wave of the plate material can be expressed as follows. SE = SEref−20log (Hv, ref / Hv, m) + 20log (Hp, ref / Hp, m) + 20log (fref / fm) (dB) (4) where SEref, Hv, ref, Hp, ref, f
ref is the reference value of the shield amount of the conductive plate with the gap obtained by the formula (3), the horizontal magnetic field measurement value of the conductive plate, and the vertical magnetic field measurement value of the conductive plate with the gap. Frequency. Also, Hv, m, Hp,
m and fm are frequencies at which the horizontal magnetic field measured value, the vertical magnetic field measured value, and the shield amount at the connection portion (not necessarily a simple gap) in the sample to be measured are to be obtained. From the above equation (4), the reference value (the shield amount SEref in the actual plane wave, or the value SEre according to the equation (3) of the simple slot model)
f) is required, even in the general case of the connection part 4 (bolting, welding, crimping, etc.), the magnetic field in the direction parallel to the surface near the shield surface connection part 4 and the connection part 4 It is possible to obtain an estimated value of the shield amount in a plane wave (far field) by the connecting portion 4 of the entire conductive plate simply by measuring the vertical magnetic field.

In the partially enlarged view of the electromagnetic wave shielding performance (SE) estimating apparatus according to the first embodiment of the present invention shown in FIG. 2, when an alternating current 34 is applied to a plate material made of a conductive material and having a gap, A vertical magnetic field (Hp) 36 is generated in the connection portion (gap) 4. The vertical magnetic field (Hp) 36 is generated when the AC current 34 near the connecting portion 4 bypasses the connecting portion 4, so that the horizontal magnetic field (Hv) near the connecting portion 4 is generated.
35 is due to the vertical magnetic field (Hp) 36. From this, both magnetic field components (Hp and H, respectively)
The shield amount (SE) in the plane wave can be obtained by measuring v) and performing the calculation represented by the equation (4). This is shown in the block diagram of FIG. Figure 1
In, the measured amount of the sample to be measured (including the reference amount)
Horizontal magnetic field (Hv) 35 and vertical magnetic field (Hp) 3
Each of 6 is input to logarithmic amplifiers 7 and 8 and converted into logarithmic quantities (logHv and logHp, respectively). The first measurement is input to the differential amplifiers 13 and 15 as reference quantities, and the outputs 17 and 18 (A · logHv, ref, A, respectively) of the differential amplifiers 13 and 15 are respectively input.
The voltage generation circuit 1 so that the logHp, ref) becomes a balanced voltage (the intermediate value of the output voltage of the differential amplifier).
4 and 16 are adjusted, and the changeover switches 19 and 20 are closed (at the start of measurement, the changeover switches 19 and 20 are changed).
Is open). Next, the horizontal magnetic field (Hv) and the vertical magnetic field (Hp) are similarly measured in the unknown sample to be measured, and the measured values are input to the logarithmic amplifiers 7 and 8, respectively, and further input to the differential amplifiers 13 and 15. . As a result, the outputs 17 and 18 of the differential amplifiers 13 and 15 are respectively A · logH
p, m-A · logHp, ref, A · logHv, r
ef-A · logHv, m. By inputting the respective outputs to the adder 23, the sum of the two is calculated and input to the differential amplifier 28. On the other hand, the voltage corresponding to fref / fm is input to the logarithmic amplifier 26, and its output 27 is also input to the other input terminal of the differential amplifier 28.
Further, the output 30 of the differential amplifier 28 is connected to the level shifter 31.
By inputting to, the voltage is changed by a constant level. By these operations, the output from the output terminal 33 as a whole is as follows. Vsft-AB (Vv, ref-logHv, m) + AB (Vp, ref-logHp, m) + B * log (fref / fm) (5) where Vsft is the shift voltage of the level shifter 31,
A is the gain of the differential amplifiers 13 and 15, and B is the gain of the differential amplifier 28. Further, according to the above description, Vv, r
ef, Vp, and ref are as follows. Vv, ref = logHv, ref Vp, ref = logHp, ref (6) Furthermore, in the formula (5), A = 1, B = 20, and
By setting Vsft = SEref (known), Expression (5) becomes the same as Expression (4). That is, with the configuration shown in FIG.
By adjusting the gain of 8 and the level of the level shifter 31 appropriately, the horizontal magnetic field (H
Therefore, the shield amount (SE) can be directly obtained from the measured values of v) and the vertical magnetic field (Hp).

As described above, according to the first embodiment, in order to estimate the shield performance on the surface on which the electromagnetic wave is shielded, an AC current is caused to flow through the wall 3 made of a conductor by any method, An amount corresponding to the shield performance (SE) in a normally used plane wave can be directly derived from the detected amount by the magnetic field generated by this current and the radiated magnetic field amount generated in the connection portion 4, and the shield performance is deteriorated on the electromagnetic shield surface. Can be handled according to the actual quantity. In addition, the shielding performance can be evaluated by a simple method even during construction in a building provided with an electromagnetic wave shield. Furthermore, the electromagnetic wave shield amount (SE) can be easily measured regardless of whether it is an open space or a closed space (such as an anechoic chamber).

Embodiment 2. 3 is a block diagram showing an electromagnetic wave shielding performance (SE) estimating apparatus according to Embodiment 2 of the present invention. In FIG. 3, the same reference numerals as those in FIGS. It is the same. In FIG.
Reference numeral 37 is an electromagnetic field probe for measuring a vertical magnetic field in the vicinity of the connection portion 4 existing on the wall (or plate material) made of a conductive material, 38 is a signal line for guiding the electromagnetic field probe 37 to the next stage, and 39 is A differential amplifier that obtains a differential signal between the outputs of the electromagnetic field probe 1 and the electromagnetic field probe 37, and 40 is a signal line that guides the output signal of the differential amplifier 39 to the next stage.

Next, the operation will be described. In FIG. 3, when an alternating current is applied to a plate material such as a wall made of a conductive material, a vertical magnetic field component as background noise is generally present in addition to the vertical magnetic field due to the current in the connecting portion 4 of the plate material. Exists in. In order to reduce the influence of this background noise, in addition to the vertical magnetic field at the connecting portion 4 of the plate material, the connecting portion 4
The vertical magnetic field (background noise component) at a portion away from is measured by the electromagnetic field probe 37, and this amount is input to one of the input terminals of the differential amplifier 39. Further, the output from the electromagnetic field probe 1 which measures the vertical magnetic field at the connecting portion 4 of the plate material is input to the other input terminal of the differential amplifier 39 as well. As a result, the output of the differential amplifier 39 becomes a value obtained by subtracting the background noise component from the vertical magnetic field at the connection portion 4. By converting this output into a logarithmic quantity by the logarithmic amplifier 7, the shield amount (SE) in the plane wave when the plate material is used as the measurement sample is directly obtained by the same operation as in the first embodiment. You can The measurement with the configuration shown in FIG. 3 is a more accurate measurement value because the influence of background noise is removed.

The present invention has been described above with reference to FIGS. 1, 2 and 3.
However, it is not necessary to completely match the mathematical formula shown in the formula (5) with the formula (4), and the shield amount is derived even in the case of the proportional relationship (mutual multiplication of each other). be able to. That is, regarding the gain A of the differential amplifiers 13 and 15 shown in FIGS. 1, 2 and 3 as well as the gain B of the differential amplifier 28 and the adjustment level Vsft of the level shifter 31, the following equations should be satisfied. To do. Vsft = K · SEref, B = 20 · K, A = 1 (7) Here, K is a positive real number. Further, in FIGS. 1, 2 and 3, the output of the logarithmic amplifier 26 is given as one input of the differential amplifier 28 in the figures, but l is applied to one input terminal of the differential amplifier 28.
The voltage obtained by og (fref / fm) is directly given,
The same effect can be achieved by omitting the logarithmic amplifier 26.

As described above, according to the second embodiment, it is possible to remove the influence of the background noise caused by the current flowing through the wall surface, and the shield performance (SE) in the plane wave.
The amount corresponding to can be derived more accurately.

[0023]

As described above, according to the present invention, the horizontal radiated magnetic field corresponding to the surface current in the vicinity of the shield performance evaluation section by passing an alternating current on the wall surface, and the shield performance evaluation section. Since it is equipped with a calculation function block that estimates the shield performance in a plane wave according to the two detection amounts of the radiated magnetic field in the direction perpendicular to the wall surface, the building with the electromagnetic wave shield can be used regardless of whether it is an open space or a closed space. , It is possible to estimate the electromagnetic wave shield performance, detect the failure of the electromagnetic wave shield on the wall of the building during construction, and take measures at that time to shorten the construction period and reduce the cost. .

According to the present invention, the detected amount of the radiated magnetic field in the vertical direction with respect to the wall surface in the shield performance evaluation unit is the amount in the portion distant from the vertical radiated magnetic field in the shield performance evaluation unit. Since it is configured to use the detection amount with the radiated magnetic field in the vertical direction subtracted, it is possible to remove the influence of background noise caused by passing a current on the wall surface and to more accurately derive the amount corresponding to the shield performance in plane waves. effective.

According to the present invention, in the arithmetic function block, two detections of a horizontal radiating magnetic field and a vertical radiating magnetic field, which are obtained by passing an alternating current through a conductive plate having a known shield performance and having a gap, are provided. Since the quantity is used as the reference value, there is an effect that the electromagnetic wave shielding performance can be accurately estimated.

According to the present invention, the arithmetic function block is provided with a logarithmic amplifier for converting two detection amounts of the radiated magnetic field in the horizontal direction and the radiated magnetic field in the vertical direction into a logarithmic quantity. This has the effect of enabling accurate estimation.

According to the present invention, the logarithmic quantity corresponding to the two detected amounts detected as the reference value and the logarithmic quantity corresponding to the two detected amounts detected for the evaluation of the shield performance in the arithmetic function block. Is configured so as to include two differential amplifiers that convert into a difference corresponding to each detected magnetic field direction, so that there is an effect that the electromagnetic wave shield performance can be accurately estimated.

According to the present invention, since the arithmetic function block is provided with the adder for adding two differences respectively corresponding to the detected magnetic field directions, it is possible to accurately estimate the electromagnetic wave shielding performance. is there.

According to the present invention, in the arithmetic function block, the reference value corresponding to the ratio of the frequency required for the shield performance estimation and the frequency at the time of measurement is converted into a logarithmic quantity,
Since it is configured to include a logarithmic amplifier that outputs as a frequency correction amount and a differential amplifier that takes the difference between the frequency correction amount converted by the logarithmic amplifier and the added value of the two differences, the electromagnetic wave shield performance is accurately estimated. There is an effect that can be.

According to the present invention, in the arithmetic function block, the difference between the frequency correction amount and the added value of the two differences is
Since the level shifter that shifts by a constant voltage amount is provided in order to correspond to the amount indicating the shield performance in a plane wave, the electromagnetic wave shield performance can be estimated accurately.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electromagnetic wave shielding performance (SE) estimating device according to a first embodiment of the present invention.

FIG. 2 is a partially enlarged view of the electromagnetic wave shielding performance (SE) estimating device.

FIG. 3 is a block diagram showing an electromagnetic wave shielding performance (SE) estimating device according to a second embodiment of the present invention.

[Explanation of symbols]

1,2,37 Electromagnetic field probe, 3 Conductor wall, 4 Connection part, 5,6,9,10,17,18,21,22,2
4, 27, 30, 32, 38, 40 signal lines, 7, 8,
26 logarithmic amplifier, 11, 12, 25 reference voltage terminals,
13,15,28,39 Differential amplifier, 14,16,2
9 voltage generation circuit, 19, 20 changeover switch, 2
3 adders, 31 level shifters, 33 output terminals, 3
4 AC current, 35 horizontal magnetic field, 36 vertical magnetic field.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takashi Kanemoto             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. F-term (reference) 2G036 AA10 AA24 BA45 CA06                 2G053 AA00 AB01 BA02 BA15 BA21                       BB11 BC02 CA19 CB01 CB21                       DA01 DB02

Claims (8)

[Claims] 1. An electromagnetic wave shield performance estimation device for evaluating the shield performance at a connection part of a wall by applying an alternating current to a wall surface or a plate surface made of a conductive material such as a building having an electromagnetic wave shield, Estimate the shield performance in a plane wave according to the two detection amounts of the horizontal radiated magnetic field corresponding to the surface current around the shield performance evaluation section and the radiated magnetic field perpendicular to the wall surface in the shield performance evaluation section An electromagnetic wave shield performance estimation device comprising a calculation function block for 2. The detection amount of the radiated magnetic field in the vertical direction with respect to the wall surface in the shield performance evaluation section is such that the radiated magnetic field in the vertical direction at a portion distant from the vertical radiated magnetic field in the shield performance evaluation section. The electromagnetic wave shield performance estimation device according to claim 1, wherein a detection amount obtained by subtracting a magnetic field is used. 3. The arithmetic function block is a horizontal radiation corresponding to a surface current around a gap in a conductive plate, which is obtained by passing an alternating current through a conductive plate having a known shield performance and a gap. The electromagnetic wave shield performance estimating device according to claim 1 or 2, wherein two detection amounts of a magnetic field and a radiation magnetic field in a gap portion of the conductive plate in a direction perpendicular to the plate surface are used as reference values. 4. The arithmetic function block comprises a logarithmic amplifier for converting two detection quantities of a radiated magnetic field in the horizontal direction and a radiated magnetic field in the vertical direction into logarithmic quantities, respectively. Item 4. The electromagnetic wave shield performance estimation device according to any one of item 3. 5. The arithmetic function block includes a pair quantity corresponding to each of the two detection amounts detected as a reference value and a pair quantity corresponding to each of the two detection amounts detected for evaluating the shield performance. The electromagnetic wave shield performance estimation device according to claim 4, further comprising two differential amplifiers for converting into a difference corresponding to each detected magnetic field direction. 6. The electromagnetic wave shield performance estimation device according to claim 5, wherein the arithmetic function block includes an adder that adds two differences corresponding to the detected magnetic field directions. 7. The arithmetic function block converts a reference value corresponding to a ratio of a frequency required for shield performance estimation and a frequency at the time of measurement into a logarithmic quantity and outputs the logarithmic quantity as a frequency correction amount, and the logarithmic amplifier. 7. The electromagnetic wave shield performance estimation device according to claim 6, further comprising a differential amplifier that takes a difference between the frequency correction amount converted by the amplifier and the added value of the two differences. 8. The arithmetic function block is provided with a level shifter for shifting a difference between the frequency correction amount and the added value of the two differences by a constant voltage amount in order to correspond to the amount representing the shield performance in a plane wave. The electromagnetic wave shield performance estimating device according to claim 7, which is characterized in that.