JP2008267912A - Underwater anechoic chamber and electromagnetic noise measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive underwater anechoic chamber capable of satisfactorily shielding electromagnetic noise to obtain high reliability in measurement accuracy and easily located with satisfactory convenience. <P>SOLUTION: An inner circumferential surface of an anechoic chamber body 2 having polyhedral container shape with pressure resistance is covered with an electromagnetic wave absorbing body 3. The underwater anechoic chamber is sunk into the water so that the electromagnetic noise of a sample to be tested, accommodated in the underwater anechoic chamber, is measured. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an underwater anechoic chamber and an electromagnetic noise measurement method that are less affected by electromagnetic noise from the outside.

  Electromagnetic compatibility, that is, electromagnetic noise emitted from electrical / electronic equipment does not affect any other equipment / system, and even if it receives electromagnetic noise from other equipment / system, electronic / electrical Conventionally, an anechoic chamber for storing electrical and electronic devices as test specimens has been used to test the resistance of the devices to operate without hindrance.

Thus, such an anechoic chamber is conventionally installed in a mountain (Tanzawa etc.) where there is little electromagnetic noise, or a dark room is provided in an urban area, and the walls and ceiling surface of the dark room building are covered with an electromagnetic wave absorber, The level of electromagnetic noise is reduced. Moreover, as prior art documents of the anechoic chamber, there are, for example, Patent Documents 1 to 4 and the like.
JP 2001-244686 A JP 2002-57487 A JP 2005-347524 A JP 2007-27274 A

  When installing an anechoic chamber in the mountains, it is difficult to secure a place and the convenience of transportation is poor. Also, when an anechoic chamber is installed in an urban area, it is difficult to avoid electromagnetic noise of strong electric fields, such as utility poles, buried transmission lines, trains, factories, etc., and it is difficult to obtain an anechoic chamber that can completely shield electromagnetic noise. . The inventors of the present application installed an electromagnetic anechoic chamber with a well-known structure in an urban area and completely shielded it, and turned off all power to measure how much stationary electromagnetic noise enters the anechoic chamber from the outside. It was. The measurement results are shown in FIGS. 3 to 5, the horizontal axis represents frequency (Hz), the vertical axis represents electromagnetic noise intensity (dBμV / m), a is electromagnetic noise, and b is allowed by international standards in NB (narrow band). Electromagnetic noise threshold, C is the peak value (peak value) of electromagnetic noise allowed by international standards in BB (broadband), and d is the quasi-peak value of electromagnetic noise allowed by international standards in BB (broadband) ( QP value). The graphs in FIGS. 3 to 5 are measured at different times on different days.

  From the graphs of FIGS. 3 to 5, the use of the anechoic chamber can considerably reduce the total external electromagnetic noise, but it cannot be completely eliminated. In addition, when electrical and electronic equipment needs to completely prevent malfunctions, such as in-vehicle equipment, it is required to have high resistance against self-radiated electromagnetic noise and external electromagnetic noise, and the demand for threshold is high. It is necessary to further reduce electromagnetic noise and increase measurement accuracy. Furthermore, the measurement results of electromagnetic noise differ depending on the day due to the difference in the environment outside the anechoic chamber. Therefore, in such an anechoic chamber, it is not possible to obtain high reliability with respect to measurement accuracy regarding electromagnetic compatibility.

  Furthermore, whether it is installed in the mountains or in the city, the building facilities for dark rooms are expensive. The anechoic chambers of Patent Documents 1 to 4 have the same problem as described above.

  In view of such circumstances, the present invention can well shield external electromagnetic noise, obtain high reliability with high measurement accuracy, and can easily secure a place, is convenient, and is inexpensive. The object is to provide an underwater anechoic chamber and an electromagnetic noise measurement method.

  The underwater anechoic chamber of the present invention is characterized in that the inner peripheral surface of a water-resistant darkroom body is covered with an electromagnetic wave absorber. The dark room body is preferably a polyhedral container.

  In the present invention, it is possible to measure the electromagnetic noise of a specimen that has been submerged in an underwater anechoic chamber and stored in the underwater anechoic chamber.

According to the underwater anechoic chamber and the electromagnetic noise measurement method of the present invention, various excellent effects as described below can be obtained.
I) Since water is grounded (earth) and surrounds the entire underwater anechoic chamber, it serves as a shield, and most of the electromagnetic noise radiated from the air toward the water surface is reflected by the water surface. It is not incident on the water, and even if it is incident on the water, it is greatly suppressed from rapidly attenuating and reaching the underwater anechoic chamber. As a result, a good underwater anechoic chamber can be realized.
II) Since part of the electromagnetic noise emitted from the specimen is absorbed by the electromagnetic wave absorber, no electromagnetic noise is emitted from the electromagnetic wave absorber toward the specimen. Therefore, the electromagnetic noise emitted by the specimen is not generated. Can be measured accurately, and the measurement accuracy is high and the reliability is good.
III) When electromagnetic noise is absorbed by the electromagnetic wave absorber, heat is generated and the temperature of the electromagnetic wave absorber rises. However, since the dark room body is immersed in water, heat is transferred from the dark room body to the water and cooled. Therefore, as a result of maintaining the inside of the dark room main body at a constant temperature, the specimen is not affected by the temperature of the electromagnetic wave absorber or the dark room main body.
IV) Since the anechoic chamber is installed underwater, it is not subject to location restrictions as in the case of installation in the mountains, and the convenience of transportation and the like is much better.
VI) When used in the sea, it is possible to effectively utilize idle hull dogs, harbor warehouse areas, fishing ports, etc.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
1 and 2 are examples of embodiments for carrying out the present invention. In the figure, reference numeral 1 denotes an underwater anechoic chamber, which is made of a conductive material, for example, steel, in a polyhedral container-like water-resistant darkroom body (in the illustrated example, an octagonal cross section) 2 and the darkroom body 2 A large number of electromagnetic wave absorbers 3 are provided so as to cover the entire inner peripheral surface. The darkroom body 2 is provided with an opening / closing door 2a, and a radio wave absorber 3 is also attached to the inner surface of the opening / closing door 2a. The electromagnetic wave absorber 3 has a quadrangular pyramid shape, and is made of, for example, ferrite. The dark room body 2 has a nearly spherical polyhedral container shape. In water, the closer to a spherical shape, the stronger the pressure resistance strength, and in order to lay the electromagnetic wave absorber 3 inside, it is necessary to flatten the inner peripheral pasting surface. Because there is. A leg 4 is fixed to the lower part of the dark room main body 2 so that the dark room main body 2 sinking to the seabed 5 can be supported.

  In FIG. 1, 6 is a specimen that is an electrical / electronic device housed in the darkroom body 2, 7 is an antenna housed in the darkroom body 2 so as to capture electromagnetic noise generated from the specimen 6, and 8 is A structure built in the seawater to which the underwater anechoic chamber 1 is fastened, 9 is a seafloor measurement room on the sea surface supported by the structure 8, 10 is a power source installed in the seafloor measurement room 9, 11 is A measuring unit 12 for receiving electromagnetic noise captured by the antenna 7 is electromagnetic noise. Examples of the specimen 6 include an inverter and a high frequency circuit.

Next, the operation of the above-described embodiment will be described.
For example, when measuring electromagnetic noise emitted from the specimen 6, the specimen 6 is operated by supplying power from the power source 10 to the specimen 6 with the open / close door 2a completely closed. The electromagnetic noise emitted from 6 is captured by the antenna 7 and transmitted to the measuring unit 11 to measure the frequency and the intensity of the electromagnetic noise.

  At this time, since the seawater is in a grounded state (earth) and surrounds the entire underwater anechoic chamber 1, it serves as a shield, and electromagnetic noise 12 radiated from the sea toward the seawater is reflected by the sea surface. It is not incident on the sea and attenuates rapidly even if it enters the sea. For this reason, electromagnetic noise is significantly suppressed from reaching the underwater anechoic chamber 1, and a good underwater anechoic chamber 1 can be realized.

  The electromagnetic noise emitted from the specimen 6 is captured by the antenna 7 as described above, but the electromagnetic noise that has not been captured by the antenna 7 hits the electromagnetic wave absorber 3 and is absorbed. For this reason, electromagnetic noise is not radiated from the electromagnetic wave absorber 3 toward the specimen 6. Therefore, the electromagnetic noise of the specimen 6 measured by the measuring unit 11 has high measurement accuracy and good reliability.

  When electromagnetic noise is absorbed by the electromagnetic wave absorber 3, heat is generated and the temperature of the electromagnetic wave absorber 3 rises. However, since the darkroom body 2 is immersed in seawater, heat is transferred from the darkroom body 2 to seawater. To be cooled. Therefore, as a result of maintaining the inside of the dark room main body 2 at a constant temperature, the specimen 6 is not affected by the temperature of the electromagnetic wave absorber 3 or the dark room main body 2.

  Further, since the underwater anechoic chamber 1 is installed in the sea, it is not subject to location restrictions as in the case of being installed in the mountains, and is convenient for transportation and the like. Dogs, port warehouse areas, fishing ports, etc. can be used effectively.

  Although the underwater anechoic chamber of the present invention has been described for installation in the sea, it can be implemented even when installed in fresh water, and various changes can be made without departing from the scope of the present invention. is there.

It is a schematic diagram for demonstrating the underwater anechoic chamber and the electromagnetic noise measuring method of this invention, and is a schematic diagram which shows the state which the underwater anechoic chamber sank on the seabed. It is a perspective view of the electromagnetic wave absorber used for the underwater anechoic chamber of FIG. It is a graph which shows an example of the electromagnetic noise measured in the anechoic chamber installed in the conventional city area. It is a graph which shows the other example of the electromagnetic noise measured in the anechoic chamber installed in the conventional city area. It is a graph which shows the further another example of the electromagnetic noise measured in the conventional anechoic chamber installed in the urban area.

Explanation of symbols

1 Underwater Anechoic Chamber 2 Darkroom Body 3 Electromagnetic Wave Absorber 6 Specimen

Claims (3)

  An underwater anechoic chamber characterized in that the inner peripheral surface of a water-resistant darkroom body is covered with an electromagnetic wave absorber.   The underwater anechoic chamber according to claim 1, wherein the darkroom body has a polyhedral container shape. An electromagnetic noise measuring method, comprising: measuring an electromagnetic noise of a specimen stored in a dark room body by submerging the underwater anechoic chamber according to claim 1 or 2 in water.

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