JPH1093286A - Simple measurement radio-wave dark box - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small and inexpensive measurement empty space where a simple measurement test can be carried out, corresponding to a designated frequency band for a target test equipment that operates on specific frequencies. SOLUTION: A dedicated radio-wave dark box is capable of dealing with a designated frequency band, adjacent to frequencies on which a target measurement equipment operates, formed as a rectangular parallelepiped prescribed in dimensions corresponding to the designated frequency band, and provided with a door 12 through which the target measurement equipment is loaded in or unloaded from it and a data communication section (connecting section) through which data are transmitted to or from the target measurement requirement. The dedicated radio-wave dark box is formed in such a manner that a radio-wave absorbing sheet 16, which has radio wave absorbing properties corresponding to the designated frequency, bond is pasted over the entire inner surface of a metal body 10, superior in electromagnetic shielding properties, and a transmitter 20 and a receiver 22 are installed in the metal box 10. A partitioning plate with an opening at its center may be provided between the transmitter 20 and the receiver 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dedicated simple measurement anechoic box for a designated frequency band in the vicinity of a frequency used in various devices to be measured. The present invention relates to a radio wave anechoic box in which a radio wave absorbing sheet corresponding to the specified frequency band is attached to the entire inner surface of a rectangular parallelepiped metal casing having a height and width. The anechoic box is useful for simple measurement tests and inspections of small, especially portable various wireless devices.

[0002]

2. Description of the Related Art In recent years, various communication devices utilizing ultra high frequency (UHF) have been put into practical use, and in research and development and manufacture thereof, it is necessary to frequently perform electromagnetic wave performance tests and sensitivity tests. . Traditionally, these tests have been performed in an anechoic chamber. The anechoic chamber has a special structure in which radio wave absorbers are attached to the walls, ceiling, and floor all around the electromagnetically shielded room to block electromagnetic waves entering from the outside and absorb electromagnetic waves generated inside. Room. Even in a simple case, the height and width are all about several meters (for example, 5 m ×
It is a rather large measuring space (8m x 4m), and is a large-sized facility where workers can enter inside. As the electromagnetic wave absorber, for example, a ferrite tile (a flat sintered product of ferrite) or a pyramid-shaped dielectric is used.

As is well known, recently, various small wireless devices have been developed and manufactured. For example, an analog mobile phone in the 800 MHz band, a GPS (Global Positioning System) antenna in the 1.5 GHz band, and a digital mobile phone have been developed. Phone, 1.9G
There are a PHS (simplified mobile phone) in the Hz band, a wireless LAN in the 2.5 GHz band, a VICS (road traffic information communication system), a wireless card, and the like. In the prior art, they are all tested in the same anechoic chamber.

[0004]

The anechoic chamber has the advantage of being able to measure with high accuracy any of the above-mentioned devices under measurement in various frequency bands, regardless of their size, and provides an extremely important measurement space. doing. However, it is necessary to attach thick ferrite tiles or bulky pyramid-shaped radio wave absorbers to the entire inner wall to maintain high measurement accuracy and to support a wide frequency band. There is a drawback that it requires space and requires time and cost in construction. In particular, when the number and types of devices that need to be measured increase, a large number of anechoic chambers must be provided, and the above drawbacks become extremely serious.

However, in actual research and development, improvement of manufacturing technology, product inspection, etc., it is not necessary to obtain very strict measurement results for devices to be measured that use a specific frequency band and are mass-produced. For the time being, it is often sufficient to perform simple measurement tests and inspections and to know the approximate measurement level or relative values and trends. In such an application, a small and inexpensive measurement space is required instead of a large and expensive measurement space such as an anechoic chamber.

SUMMARY OF THE INVENTION An object of the present invention is to provide an anechoic chamber which is a small and inexpensive measurement space for a device under test using a specific frequency, which corresponds to the designated frequency band and can perform simple measurement tests and inspections. To provide.

[0007]

SUMMARY OF THE INVENTION The present invention is a dedicated simple measurement anechoic box corresponding to a designated frequency band near the frequency used by a device under test. This anechoic box has a rectangular parallelepiped shape with height and width corresponding to the specified frequency band,
Radio wave absorption having radio wave absorption characteristics corresponding to the specified frequency band over the entire inner surface of a metal case having a good shield property provided with an opening / closing door portion for taking in and out of the device under test and a data transfer portion with the device under test. This is a structure in which a sheet is attached and a transmitting unit or a receiving unit is installed in an internal measurement space. The term anechoic box rather than anechoic chamber is used here to clarify that it is not a large facility such as a room, but a small device that can be placed on a workbench. .

The metal casing is preferably made of a conductive and magnetic material such as an iron plate or a stainless steel plate. By having magnetism, the function of a magnetic shield can be fulfilled. The radio wave absorption sheet is a sheet formed by mixing ferrite powder and EPDM (ethylene / propylene diene monomer) rubber at a predetermined ratio corresponding to the specified frequency band, and molding the mixture to a predetermined thickness. A transmitter and a receiver are provided on both sides in the measurement space so as to face each other. In an actual test, one of the transmitter and the receiver is the device to be measured. One or more perforated partition plates having an opening at the center may be provided between the position of the transmitting unit and the position of the receiving unit in the measurement space. The perforated partition plate has a function of suppressing a mode caused by reflection on a wall surface and allowing only a wave to directly travel from the transmission unit to the reception unit. It is preferable that the metal housing has a structure in which one surface is removable. By removing it, it is possible to easily adjust the attachment / detachment and position / direction of the internal transmission unit or reception unit.
In that case, it is necessary to prevent electromagnetic wave leakage.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As an anechoic box according to the present invention, for example, an 800 MHz anechoic box for testing an analog mobile phone in the 800 MHz band, a GSP antenna or a 1.5 GHz digital mobile phone is tested. 1.5GHz band anechoic box for PHS test
There are a 9 GHz band anechoic box, a 2.5 GHz band anechoic box for testing wireless LAN, VICS, and wireless cards. The designated frequency band of each anechoic box is as follows. Anechoic box for 800 MHz band: 700 MHz to 900 MHz Anechoic box for 1.5 GHz band: 1.4 GHz to 1.65 GHz Anechoic box for 1.9 GHz band: 1.75 GHz to 2.0 GHz Anechoic box for 2.5 GHz band: 2.35 GHz Each of the anechoic boxes of 2.65 GHz to 2.65 GHz is constituted by an inner wall surface having characteristics capable of sufficiently absorbing electromagnetic waves in the frequency band designated therein.

Therefore, each anechoic box has a housing internal dimension within the following range corresponding to the designated frequency band (wavelength). Each numerical value represents the minimum and maximum length of one side of the rectangular parallelepiped. Anechoic box for 800 MHz band: minimum 75 cm to maximum 225 cm 1.5 GHz band anechoic box: minimum 40 cm to maximum 120 cm 1.9 GHz band anechoic box: minimum 32 cm to maximum 95 cm Anechoic box for 2.5 GHz band: minimum 24 cm to maximum 72 cm Therefore, a housing having a different internal size may be manufactured for each of the designated frequency bands, but it is also possible to use a common case in which several types of designated frequency bands use the same inner size of the housing.

The radio wave absorbing sheet used in each anechoic box is as follows. 800 MHz band anechoic box: 1200 g ± 10 g of Mn-Zn ferrite powder per 100 g of EPDM rubber
What was mixed and formed into a sheet having a thickness of 6.7 mm ± 0.1 mm. 1.5 GHz band anechoic box: A 6.3 mm ± 0.1 mm thick sheet formed by mixing 650 g ± 10 g of Mn—Zn ferrite powder with 100 g of EPDM rubber. 1.9 GHz band anechoic box: A 6.3 mm ± 0.1 mm thick sheet formed by mixing 500 g ± 10 g of Mn—Zn ferrite powder with 100 g of EPDM rubber. 2.5 GHz band anechoic box: A 6.3 mm ± 0.1 mm thick sheet formed by mixing 360 g ± 10 g of Mn—Zn ferrite powder with 100 g of EPDM rubber.

FIG. 1 shows an example of an anechoic box according to the present invention, and FIG. 2 shows a cross section thereof. This anechoic box has a vertical dimension a, a horizontal dimension b, and a height dimension h corresponding to a designated frequency band.
A metal casing 10 having a rectangular parallelepiped shape (all of which have inner dimensions) and good shielding properties is used. The metal housing 10 is provided with an opening / closing door section 12 for taking in and out the device to be measured, and a connection portion (connector) 14 for exchanging data with the device to be measured. A radio wave absorbing sheet 16 having radio wave absorption characteristics corresponding to the specified frequency band is attached to the entire inner surface of the metal casing 10 (including the inner surface of the door unit 12 and the like). Then, the transmitting unit 20 and / or the receiving unit 22 are installed in the internal measurement space. One of the transmission unit 20 and the reception unit 22 is a device to be measured, and performs various tests and inspections.

Here, one of the six surfaces (upper panel 10a) of the metal housing 10 is configured to be removable. A hook 24 for lifting is provided on the upper panel 10a, and the hook 24 is a screw-in type, which also serves as a screw for attaching to the main body of the metal housing 10. When the upper panel 10a is detachable as described above, there is an advantage that the attachment and detachment of the transmission unit 20 and the reception unit 22 and the adjustment of the installation position and the direction can be easily performed. In order to prevent leakage of electromagnetic waves, the door unit 12 and the upper panel 10a
A conductive elastic contact member such as a shield finger is attached to a joint part of the metal housing 10 with the main body part to improve the shielding performance. Also, the connection part 14 for data transmission / reception with the device under test uses a shielded wire or a shielded connector to prevent radio wave leakage. Note that a structure in which the connector is directly drawn out with a shielded wire without using a connector may be employed.

Since such an anechoic box is small (for example, the maximum size for the 800 MHz band is 225 cm),
As shown in FIG. 1, the work table 30 can be placed on the work table 30, and if the work table 30 with casters is used, it can be freely moved in a laboratory or the like to perform necessary measurements.

FIG. 3 shows the internal structure of another example of the anechoic box. Here, one perforated partition plate 26 is provided between the position of the transmitting unit 20 and the position of the receiving unit 22 in the measurement space. The partition plate 26 is made of the same metal plate as the housing, and has a structure in which a rectangular opening 27 having a side of about 30 to 45 cm is formed in the center. A radio wave absorbing sheet may be attached to the metal plate. Further, a configuration may be employed in which a plurality of perforated partition plates are provided at intervals. The perforated partition plate 26 reduces the wall reflection of the electromagnetic wave on the transmitting side, and allows only the direct wave to be received on the receiving side, thereby enabling measurement in a stable environment.

[0016]

[Embodiment] An iron plate is welded and the height and width are 80 x 160 x 8
A rectangular parallelepiped casing having a size of 0 cm was assembled, and an 800 MHz band electromagnetic wave absorbing sheet was attached to the entire inner surface of the case, thereby producing an 800 MHz band electromagnetic wave anechoic box having a structure as shown in FIG.
Shield fingers were attached to the door and the part of the panel that contacted the housing body. The 800 MHz band electromagnetic wave absorbing sheet is a sheet obtained by mixing Mn-Zn based ferrite powder at a rate of 1200 g ± 10 g with 100 g of EPDM rubber to form a sheet having a thickness of 6.7 mm ± 0.1 mm. Yes,
It was cut into squares of 25 cm in length and width and used. Using this anechoic box, various tests such as a performance test and an operation check of an 800-MHz-band analog mobile phone were performed, and good measurement data was obtained.

The height and width are 50 × 100 × by welding an iron plate.
A rectangular parallelepiped casing measuring 50 cm was assembled, and a 1.5-GHz band radio wave absorbing sheet was attached to the entire inner surface thereof.
An anechoic box for 1.5 GHz band having the structure shown in FIG. Shield fingers were attached to the door and the part of the panel that contacted the housing body. The electromagnetic wave absorbing sheet for 1.5 GHz band was formed by mixing 650 g ± 10 g of Mn—Zn ferrite powder with 100 g of EPDM rubber to form a sheet having a thickness of 6.3 mm ± 0.1 mm. Things,
It was cut into squares of 25 cm in length and width and used. Using this anechoic box, various tests such as a performance test and an operation check of a GPS antenna and a 1.5-GHz band digital mobile phone were performed, and good measurement data was obtained.

Iron plate is welded and height and width are 50 × 100 ×
A rectangular parallelepiped casing measuring 50 cm was assembled, and a radio wave absorbing sheet for 1.9 GHz band was attached to the entire inner surface of the casing.
An anechoic box for the 1.9 GHz band having the structure shown in FIG. Shield fingers were attached to the door and the part of the panel that contacted the housing body. The radio wave absorption sheet for 1.9 GHz band was mixed with 100 g of EPDM rubber and 500 g ± 10 g of Mn—Zn ferrite powder to form a sheet having a thickness of 6.3 mm ± 0.1 mm. Things,
It was cut into squares of 25 cm in length and width and used. Using this anechoic box, various tests such as a PHS performance test and product inspection were performed, and good measurement data was obtained.

Iron plate is welded and height and width are 50 × 100 ×
A rectangular parallelepiped casing measuring 50 cm is assembled, and a radio wave absorbing sheet for the 2.5 GHz band is stuck on the entire inner surface thereof.
An anechoic box for 2.5 GHz band having the structure shown in FIG. Shield fingers were attached to the door and the part of the panel that contacted the housing body. The radio wave absorption sheet for the 2.5 GHz band was prepared by mixing Mn-Zn based ferrite powder at a rate of 360 g ± 10 g with 100 g of EPDM rubber to form a sheet having a thickness of 6.3 mm ± 0.1 mm. Things,
It was cut into squares of 25 cm in length and width and used. Using this anechoic box, various tests such as a next-generation wireless card (highway, commuter pass, entrance certificate, etc.) and a wireless LAN performance test and operation check were performed, and good measurement data was obtained.

[0020]

According to the present invention, for a device under test using a specific frequency, a dedicated anechoic box corresponding to the designated frequency band is used, and a thin radio wave absorbing sheet is used to prevent internal reflection. Thus, the housing can be miniaturized while securing an effective space for internal measurement. Therefore, simple measurement tests and inspections can be easily performed,
Even when a large number of measurement spaces are required, there is an effect that the installation space is small and the equipment can be installed at low cost.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of an anechoic box according to the present invention.

FIG. 2 is a cross-sectional view thereof.

FIG. 3 is a cross-sectional view of another example of the anechoic box according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Metal housing 12 Opening / closing door part 14 Connecting part 16 Radio wave absorption sheet 20 Transmitting part 22 Receiving part 26 Perforated partition plate 30 Work table

Claims (7)

[Claims] 1. An anechoic box for simple measurement corresponding to a designated frequency band in the vicinity of a frequency used by a device under test, comprising a rectangular parallelepiped having a height and width corresponding to the designated frequency band. A radio-absorbing sheet having radio-wave absorption characteristics corresponding to the specified frequency band is provided on the entire inner surface of a metal housing having a good shielding property with a door for opening and closing the device and a data transfer unit with the device under test. An electromagnetic anechoic box for simple measurement, characterized in that a transmitter or a receiver is attached in an internal measurement space. 2. The anechoic box for simple measurement according to claim 1, wherein a perforated partition plate having an opening at a central portion is provided between a position of the transmitting unit and a position of the receiving unit in the measuring space. 3. A radio wave absorbing sheet comprising a ferrite powder and E
3. The anechoic box for simple measurement according to claim 1, wherein the sheet is a sheet formed by mixing a PDM-based rubber to a thickness corresponding to a specified frequency band. 4. An EPD as an anechoic box for the 800 MHz band.
Mn-Zn-based ferrite powder is mixed with 1200 g ± 10 g with 100 g of M-based rubber to a thickness of 6.7 mm ± 0.1 mm.
2. A radio wave absorbing sheet formed into a sheet shape according to claim 1.
Or the anechoic box for simple measurement according to 2. 5. An EPD as an anechoic box for 1.5 GHz band.
The simple measurement according to claim 1 or 2, wherein a radio wave absorbing sheet formed by mixing 650 g ± 10 g of Mn-Zn based ferrite powder with 100 g of the M rubber to form a sheet having a thickness of 6.3 mm ± 0.1 mm is used. Anechoic box. 6. An EPD as an anechoic box for the 1.9 GHz band.
The simple measurement according to claim 1 or 2, wherein a radio wave absorbing sheet formed by mixing 500 g ± 10 g of Mn-Zn based ferrite powder with 100 g of the M rubber to form a sheet having a thickness of 6.3 mm ± 0.1 mm is used. Anechoic box. 7. An EPD as an anechoic box for 2.5 GHz band
The simple measurement according to claim 1 or 2, wherein a radio wave absorbing sheet formed by mixing 360 g ± 10 g of Mn-Zn ferrite powder with 100 g of the M rubber to form a sheet having a thickness of 6.3 mm ± 0.1 mm is used. Anechoic box.