JP2012145456A - Electromagnetic wave shield performance evaluation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable evaluating electromagnetic wave shield performance of a three-dimensional electromagnetic wave shield material and to evaluate electromagnetic wave shield performance up to a GHz band.SOLUTION: In an electromagnetic wave shield performance evaluation method for evaluating electromagnetic wave shield performance of a three-dimensional electromagnetic wave shield material, a shield box with an opening, which has a transmission antenna installed inside and the opening being able to be closed with a closing member, and a reception antenna connected to a receiver capable of receiving a signal from the transmission antenna, are set in an anechoic chamber. And the electromagnetic wave shield performance of the electromagnetic wave shield material is evaluated through receiving the signal with the receiver in such a condition that the signal from the transmission antenna inside is blocked by inserting the electromagnetic wave shield material between the closing member and the shield box, as the opening of the shield box is closed with the closing member.

Description

  The present invention relates to an electromagnetic shielding performance evaluation method capable of evaluating the electromagnetic shielding performance of a three-dimensional electromagnetic shielding material.

The electromagnetic shielding material includes a planar sheet type and a three-dimensional gasket type in which a core material made of a flexible material such as urethane foam is covered with a conductive cloth or the like.
The so-called KEC method of the general incorporated association KEC Kansai Electronics Industry Promotion Center evaluates the sheet-type electromagnetic shielding performance.

Kansai Electronics Industry Promotion Center website (http://www.kec.jp/emc/kec-method.html)

In the KEC method described above, only the electromagnetic wave shielding performance of the sheet-like electromagnetic wave shielding material can be evaluated. For this reason, in the three-dimensional gasket type electromagnetic shielding material, the electromagnetic shielding performance of a conductive cloth as a component is evaluated, or when a flexible material such as sponge has electromagnetic shielding performance, The electromagnetic shielding performance was measured in a sheet form.
That is, in the KEC method, the three-dimensional gasket type electromagnetic shielding material cannot directly evaluate the electromagnetic shielding performance.

In addition, in the KEC method, only the electromagnetic shielding performance up to the MHz band could be evaluated.
However, at present, evaluation of electromagnetic wave shielding performance up to the GHz band is required for speeding up the CPU and the like.

  The present invention was created in view of the above circumstances, and can evaluate the electromagnetic shielding performance of a three-dimensional electromagnetic shielding material such as a gasket type, and can also evaluate the electromagnetic shielding performance up to the GHz band. The object is to provide an electromagnetic shielding performance evaluation method.

  An electromagnetic wave shielding performance evaluation method according to the present invention is an electromagnetic wave shielding performance evaluation method for evaluating electromagnetic wave shielding performance of a three-dimensional electromagnetic wave shielding material, which has an opening, a transmission antenna is installed inside, and the opening is closed. When setting a shield box that can be closed with a member and a receiving antenna connected to a receiver that can receive a signal from the transmission antenna in an anechoic chamber, and closing the opening of the shield box with a closing member, The electromagnetic shielding performance of the electromagnetic shielding material is evaluated by receiving the signal with a receiver in a state where the signal from the internal transmitting antenna is blocked by sandwiching the electromagnetic shielding material between the blocking member and the shielding box. .

In the electromagnetic wave shielding performance evaluation method according to the present invention, the opening of the shield box is closed by the front panel, and the electromagnetic wave shielding material is sandwiched between the two, so that the three-dimensional electromagnetic wave which is impossible with the conventional KEC method It became possible to evaluate the electromagnetic shielding performance of shielding materials.
In addition, since it is possible to evaluate the shielding performance of various bands by selecting the transmitting antenna and the receiving antenna, it is possible to evaluate the electromagnetic shielding performance up to the GHz band, which was impossible with the conventional KEC method. .

BRIEF DESCRIPTION OF THE DRAWINGS It is drawing of the shield box and obstruction | occlusion member used for the electromagnetic wave shielding performance evaluation method based on this invention, Comprising: The figure (A) is a schematic perspective view, The figure (B) is a schematic sectional drawing of a shield box. . It is a schematic block diagram for the electromagnetic wave shielding performance evaluation method according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS It is drawing which shows the set to the shield box of the electromagnetic shielding material at the time of implementing the electromagnetic wave shielding performance evaluation method based on this invention, Comprising: The figure (A) is a schematic sectional drawing, The figure (B) is a schematic front. FIG. It is a schematic perspective view of the electromagnetic shielding material which tested the electromagnetic shielding performance evaluation method based on this invention. It is a graph which shows the evaluation result in the electromagnetic wave shielding performance evaluation method based on this invention, Comprising: The same figure (A) is 1000MHz-6000MHz (6GHz) in the state which has a 5 mm clearance gap between a shield box and a closure member. (B) is a graph comparing the intensity of the electromagnetic wave and the noise floor, and the electromagnetic wave intensity of 1000 MHz to 6000 MHz (6 GHz) and 5 mm with an electromagnetic shielding material interposed between the shield box and the closing member. It is the graph which compared with the state which has a gap | interval of. It is a schematic front view of the front panel used when measuring the electromagnetic wave shielding performance of a sheet-like electromagnetic shielding material.

  The electromagnetic wave shielding performance evaluation method according to the embodiment of the present invention is an electromagnetic wave shielding performance evaluation method for evaluating the electromagnetic wave shielding performance of the three-dimensional electromagnetic wave shielding material 500, which has an opening 110, and the transmitting antenna 300 is provided inside. The anechoic chamber 400 includes a shield box 100 installed and capable of closing the opening 110 with a closing member 200 and a receiving antenna 310 connected to an evaluation device 320 that can receive and evaluate a signal from the transmitting antenna 300. When the opening 110 of the shield box 100 is closed by the closing member 200, the electromagnetic wave shielding material 500 is sandwiched between the closing member 200 and the shield box 100 to block the signal from the internal transmitting antenna 300. In the state, the signal is received by the evaluation device 320 and the power It is adapted to evaluate the electromagnetic wave shielding performance of the wave shield material 500.

  Note that the three-dimensional electromagnetic shielding material 500 whose electromagnetic shielding performance is evaluated by this electromagnetic shielding performance evaluation method includes a core material 510 having a rectangular cross section such as urethane foam and the core material 510 as shown in FIG. And a conductive cloth 520 having conductivity that is wound around, for example, sandwiched between a casing of an electronic device and a lid that closes the casing to shield the inside of the casing from electromagnetic waves It is used for this purpose. In addition, as what is wound around the core material 510, it is not restricted to the electroconductive cloth 520 which has electroconductivity, The cloth and film which do not have electroconductivity may be sufficient.

First, as shown in FIG. 1 and the like, the shield box 100 has five square plate members and one plate member having the same outer shape as the plate member and having an opening 110 formed in a cubic shape. It is a combination. As the plate material, for example, a plate material made of a conductor having a thickness of 1.5 mm, for example, a stainless steel plate material is used.
A transmitting antenna 300 connected to the transmitter 330 is installed in the space inside the shield box 100.
On the surface of the space where the opening 110 is formed, a box-side screw hole 120 is formed so as to surround the opening 110. The box side screw hole 120 is for attaching a closing member 200 described later.

The closing member 200 for closing the opening 110 of the shield box 100 is set to have the same shape and size as the plate material on which the opening 110 is opened, and the closing side screw hole is located at a position corresponding to the box side screw hole 120. 220 has been established. The closing member 200 is made of a 1.5 mm thick stainless steel plate like the shield box 100.
A screw 250 for attaching the closing member 200 to the shield box 100 is also made of stainless steel.
In the above description, the shield box 100, the closing member 200, and the screw 250 connecting them are all made of stainless steel. However, the present invention is not limited to this and may be a metal.

A transmission antenna 300 is provided inside the shield box 100. The transmission antenna 300 is configured to transmit a signal from the transmitter 330 via the transmitter-side attenuator 340.
The transmitter-side attenuator 340 is set inside the anechoic chamber 400, and the transmitter 330 is set outside the anechoic chamber 400.

On the other hand, the receiving antenna 310 is set in the anechoic chamber 400. A signal received by the reception antenna 310 is input to an evaluation device 320 such as a spectrum analyzer via the receiver-side attenuator 350 and the amplifier 360.
The receiver side attenuator 350 is set inside the anechoic chamber 400.
However, the amplifier 360 connected to the receiver-side attenuator 350 is set inside the anechoic chamber 400 when evaluating the GHz band, but is set outside the anechoic chamber 400 when evaluating the MHz band. Is done. FIG. 2 is for evaluation in the GHz band.
The amplifier 360 is not essential and may not be used.

When the closing member 200 is attached to the shield box 100, the electromagnetic shielding material 500 is attached to the shield box 110 so as to surround the opening 110 as shown in FIG. Note that the electromagnetic wave shielding material 500 is attached to the shield box 100 using an adhesive similar to that used when the electromagnetic wave shielding material 500 is actually incorporated into a product or the like. Note that this adhesive may not be used for measurement, and as long as the influence on measurement is kept to a minimum, it is not necessary to limit to the adhesive and any adhesive can be used.
In FIG. 3, the electromagnetic shielding material 500 is arranged inside the screw 250, but the electromagnetic shielding material 500 can be arranged outside the screw 250 and on both inside and outside.

The closing member 200 that closes the opening 110 is attached to the shield box 100 to which the electromagnetic wave shielding material 500 is attached with the screw 250. At this time, the electromagnetic shielding material 500 is deformed when the blocking member 200 is pressed, but is pressed in the same manner as when the electromagnetic shielding material 500 is actually used.
In FIG. 3A, the electromagnetic wave shielding material 500 is not deformed for convenience of drawing.
The closing member 200 is attached to the shield box 100 with screws 250 at this time, but the state in which the box-side screw hole 120 does not exist in the shield box 100 is most suitable for measurement, and the closing member 200 is attached to the shield box 100 with a jig or the like. It only has to be attached.

In this manner, the electromagnetic wave shielding material 500 sandwiched between the shield box 100 and the closing member 200 is set in the anechoic chamber 400. Then, the receiving antenna 310 is set at a position 3 m away from the front side of the opening 110.
The receiving antenna 310 is set at a position 3 m away from the front side of the opening 110, but the present invention is not limited to this.

In this state, a signal is transmitted from the transmitter 330. For example, when the noise floor is as shown in FIG. 5A, electromagnetic waves of 1000 MHz to 6000 MHz (6 GHz) with a gap of 5 mm between the shield box 100 and the closing member 200 (see FIG. 5 (A)) was 80 to 120 dBμV in any range.
In this experiment, the gap between the shield box 100 and the closing member 200 is 5 mm. However, the present invention is not limited to this.

  On the other hand, when the electromagnetic shielding material 500 is interposed between the shield box 100 and the closing member 200, as shown in FIG. 5 (B), the frequency is reduced to about 60 dBμV in any frequency band. confirmed.

  That is, according to this electromagnetic wave shielding performance evaluation method, it is possible to measure the electromagnetic wave shielding performance of the three-dimensional gasket type electromagnetic wave shielding material 500, which was impossible with the conventional KEC method, and to the GHz band. Turns out to be possible.

In the case of measuring a sheet-like electromagnetic shielding material, a front panel 270 having an opening 271 is used as shown in FIG. The front panel 270 has the same outer shape as the front panel 200 used when measuring the electromagnetic wave shielding performance of the above-described three-dimensional electromagnetic wave shielding material 500, and only has an opening 271 at the center. Different.
When such a front panel 270 is used, the opening 271 of the front panel 270 is covered with a sheet-like electromagnetic shielding material.

  The schematic block diagram for the electromagnetic wave shielding performance evaluation method shown in FIG. 2 used in the above description is merely an example, and the present invention is not limited to this.

DESCRIPTION OF SYMBOLS 100 Shield box 110 Opening 200 Closure member 300 Transmitting antenna 310 Receiving antenna 320 Evaluation apparatus 330 Transmitter 500 Electromagnetic wave shielding material

Claims (1)

  In the electromagnetic wave shielding performance evaluation method for evaluating electromagnetic wave shielding performance of a three-dimensional electromagnetic wave shielding material, a shield box having an opening, a transmission antenna installed therein, and capable of closing the opening with a closing member, and the transmission When a receiving antenna connected to a receiver capable of receiving a signal from the antenna is set in an anechoic chamber and the opening of the shield box is closed with a closing member, the electromagnetic shielding material is sandwiched between the blocking member and the shield box. Thus, the electromagnetic wave shielding performance evaluation method of evaluating the electromagnetic wave shielding performance of the electromagnetic wave shielding material by receiving the signal with a receiver in a state where the signal from the internal transmitting antenna is blocked.

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