JP2005061949A - Electromagnetic wave measurement dark box - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic wave measurement dark box in which the electromagnetic field intensity distribution in a shield room is made uniform, the influence of unnecessary reflected waves is suppressed, the measurement accuracy is improved, and the apparatus can be miniaturized.
An electromagnetic wave measurement dark box for installing an antenna under test 3 and a measurement antenna 4 in a shield room 2 to measure radiation characteristics or reception characteristics of an electromagnetic wave, and the inside of the shield room 2 is spherical. The electromagnetic wave absorber 1 was provided on the entire inner surface. The space of the shield chamber 2 is covered with a radio wave reflector 8 so that the central axis P of each cone 1a is directed to the approximate center O of the shield chamber 2 of the electromagnetic wave absorber 1 composed of a large number of cones 1a. Provided.
[Selection] Figure 1

Description

  The present invention relates to an electromagnetic wave measurement dark box that measures the radiation characteristic or reception characteristic of an electromagnetic wave to be tested, and in particular, makes the electromagnetic field intensity distribution in a shield room uniform and suppresses the influence of unnecessary reflected waves to improve measurement accuracy. The present invention relates to an electromagnetic wave measurement dark box which is improved and can be downsized.

As shown in FIG. 7, a conventional dark box for measuring electromagnetic waves is formed in a parallelepiped shape with a shield chamber 2 electromagnetically shielded from the outside with metal or the like, and a large number of cones on each inner side surface 2a (wall surface, ceiling, floor). An electromagnetic wave absorber 1 made of 1a is provided to form a stable electromagnetic wave measurement environment, and the antenna under test 3 and the antenna for measurement 4 are installed inside the shield chamber 2 to emit electromagnetic waves from the antenna under test. The characteristic or the reception characteristic is measured (for example, refer to Patent Document 1).
Japanese Patent Publication No. 2002-107398

  However, in such a conventional electromagnetic wave measurement dark box, the inside of the shield chamber 2 has a parallelepiped shape as shown in FIG. 7, and each cone 1a of the electromagnetic wave absorber 1 is arranged on each inner side surface 2a with its central axis. Since P is provided so as to be perpendicular to each inner surface 2a, there are many electromagnetic waves incident obliquely with respect to the central axis P of the cone 1a as shown in FIG.

  In general, the cone-shaped electromagnetic wave absorber 1 prevents reflection by matching the input impedance of the electromagnetic wave incident from the direction of the central axis P in front of the cone 1a with free space impedance, for example, electromagnetic wave absorption made of polyurethane or the like. The energy of the electromagnetic wave that has entered the body 1 is converted into heat loss by carbon or ferrite contained therein and absorbed, and when the incident direction of the electromagnetic wave deviates from the central axis P direction of the electromagnetic wave absorber 1, That is, when the incident angle of the electromagnetic wave increases, impedance matching is lost and unnecessary reflected waves of the electromagnetic wave increase. Therefore, in the electromagnetic wave measuring dark box composed of the conventional parallelepiped shield chamber 2, the influence of the unnecessary reflected wave of the electromagnetic wave on the surface of the electromagnetic wave absorber 1 cannot be ignored, and a uniform electromagnetic wave intensity distribution can be obtained. There wasn't. For this reason, the measurement accuracy of the electromagnetic wave of the antenna under test 3 has been deteriorated.

  For example, FIG. 9 shows the measurement of the electromagnetic wave intensity distribution of the dipole antenna in the parallelepiped shield chamber 2. Specifically, 2.4GHz was used as the frequency of the test signal, and the measurement was performed by changing the distance between the antennas from 300mm to 700mm at regular intervals with the test and measurement dipole antennas arranged horizontally. It is. The electromagnetic wave intensity distribution in the portion indicated by arrow A in the figure is disturbed, the dip position shift in the intensity distribution in the portion indicated by arrow B in the figure, and the intensity distribution in the portion indicated by arrow C in the figure is uniform. The lack is due to the influence of unnecessary reflected waves.

  In such a case, in order to suppress the influence of unnecessary reflected waves, the distance between the antennas 3 and 4 and the inner surface 2a of the shield chamber 2 should be made relatively large with respect to the distance between both antennas 3 and 4. The incident angle of electromagnetic waves to the electromagnetic wave absorber 1 can be reduced, and unnecessary reflected waves can be reduced. However, in this case, there is a problem that the shield chamber 2 becomes large.

  Therefore, the present invention has been made paying attention to the above-mentioned problems. The electromagnetic field intensity distribution in the shield chamber is made uniform, and the influence of unnecessary reflected waves is suppressed to improve the measurement accuracy, thereby reducing the size of the apparatus. An object of the present invention is to provide an electromagnetic wave measurement dark box that is made possible.

  To this end, the invention of claim 1 is an electromagnetic wave measurement dark box for measuring a radiation characteristic or a reception characteristic of an electromagnetic wave by installing a device under test and a measurement antenna in a shield room, It was formed in a spherical shape and an electromagnetic wave absorber was provided on the entire inner surface.

  With such a configuration, the electromagnetic wave radiation characteristic or reception characteristic of the device under test is measured in a shield chamber formed by providing an electromagnetic wave absorber on the entire spherical inner surface.

  In this case, the shield room space may be covered with a radio wave reflector as in claim 2. In addition, the electromagnetic wave absorber may be formed of a large number of cones as in the third aspect, and the central axis of each cone may be provided so as to be directed to the approximate center of the shield chamber.

  Specifically, the electromagnetic wave measurement dark box according to the present invention can be configured such that either one of the device under test or the antenna for measurement can be installed at a substantially central portion of the shield chamber, and the other is around the shield chamber. It is good to have a configuration that can be installed in the section. In this case, as shown in claim 5, the device under test or the measurement antenna installed in the substantially central portion of the shield chamber may be configured to be rotatable about the vertical rotation axis. In addition, the device under test and the measurement antenna may be configured to be held at the tip of a holding mechanism that extends from the outside of the shield chamber toward the center, respectively.

  Here, as in claim 7, a positioner configured to hold either one of the device under test and the antenna for measurement and move in the circumferential direction of the shield chamber may be provided integrally.

  In the configuration of claim 8, the shield chamber is formed by connecting the half bodies formed by dividing the shield chamber into two in the vertical direction so as to be openable and closable. In this case, a moving roller may be provided in the lower half of the half body as in the ninth aspect.

  Further, the shield chamber may be formed of the electromagnetic wave reflector itself as in claim 10, or may be formed of a resin material as in claim 11, and the metal may be adhered to the entire inner surface.

  According to the electromagnetic wave measurement dark box of the present invention, the inside of the shield chamber is formed in a spherical shape, and an electromagnetic wave absorber made up of a large number of cones is provided on the inner surface thereof so that the central axis of the cone is directed to the approximate center of the shield chamber. As a result, the unnecessary reflected wave of the radiated electromagnetic wave on the surface of the electromagnetic wave absorber can be suppressed more than before, so that the electromagnetic wave intensity distribution in the shield chamber can be made uniform. Therefore, the electromagnetic wave measurement accuracy is improved, the inside of the shield chamber can be made small, and the electromagnetic wave measurement dark box can be downsized.

  Further, by providing an electromagnetic wave absorber covering the shield room space, it is possible to prevent the intrusion of unnecessary electromagnetic waves from the outside, and to further improve the electromagnetic wave measurement accuracy.

  Furthermore, either one of the device under test or the antenna for measurement can be installed at the approximate center of the shield room, and can be rotated around the vertical rotation axis, and the other can be installed at the periphery of the shield room. Thus, two-dimensional radiated electromagnetic wave characteristics can be measured.

  In addition, since each antenna is held at the tip of the holding mechanism extending from the outside of the shield chamber toward the center, generation of unnecessary reflected waves by the holding mechanism can be suppressed, and electromagnetic wave measurement accuracy can be suppressed. Can be improved.

  In addition, either one of the device under test or the antenna for measurement is installed in the center of the shield chamber, and the other is configured to be movable in the circumferential direction by a positioner formed integrally with the shield chamber. If the body or the measurement antenna is rotated, the spherical radiation electromagnetic wave characteristic can be measured.

  Further, the shield chamber is configured by connecting the half halves formed in the vertical direction so as to be openable and closable, thereby facilitating the attachment and replacement of the DUT and the measurement antenna.

  Since the moving rollers are provided in the lower part of each half body, the opening and closing operation of the shield chamber is facilitated, and the attachment and exchange work of the DUT and the measurement antenna can be performed more easily.

  Further, if the shield chamber is formed of the electromagnetic wave reflector itself, a spherical half can be formed by drawing a metal plate, and an operation of separately attaching the electromagnetic wave reflector can be omitted, which facilitates manufacture.

  If the shield chamber is formed of a resin material and the electromagnetic wave reflector is formed by metal plating, vapor deposition, or the like, resin molding can be performed, and weight reduction and manufacturing can be facilitated.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, about the same element as FIG. 7, it shows using the same code | symbol.
FIG. 1 shows a cross-sectional view of a first embodiment of an electromagnetic wave measurement dark box according to the present invention.
In FIG. 1, the electromagnetic wave measurement dark box according to the first embodiment measures, for example, the radiation characteristics and reception characteristics of an electromagnetic wave of an antenna, and includes a spherical shield chamber 2 and an electromagnetic wave absorber 1. The holding chambers 6 and 7 for installing the antenna under test 3 and the antenna for measurement 4 are provided inside the shield chamber 2 so that the electromagnetic wave characteristics of the antenna under test 4 can be measured. Here, a case where the antenna under test 3 is a transmission antenna and the measurement antenna 4 is a reception antenna will be described as an example.

  The shield chamber 2 is for forming a stable electromagnetic wave measurement environment, and is formed in a spherical shape by an electromagnetic wave reflector 8 such as a metal, and prevents unnecessary electromagnetic waves from entering the room from the outside. The electromagnetic wave radiated from the outside of the shield chamber 2 is prevented from leaking out. As shown in FIG. 2, hemispheres 2a and 2b as halves formed by being divided into two in the vertical direction are connected in a state that can be opened and closed by a hinge 9, and each hemisphere 2a and 2b Moving rollers 10a and 10b are provided at the lower portion to facilitate opening and closing operations. The shield chamber 2 is not limited to the one formed by the electromagnetic wave reflector 8 itself, and it is sufficient that the electromagnetic wave reflector 8 is provided so as to cover at least the space of the shield chamber 2, and is formed of a resin material such as plastic, for example. The electromagnetic wave reflector 8 may be formed on the entire inner surface of the capsule by metal plating or vapor deposition. The electromagnetic wave reflector 8 may be a composite having a sandwich structure in which a soft magnetic material is sandwiched between nonmagnetic conductors.

  An electromagnetic wave absorber 1 is provided on the inner side surface 8 a of the electromagnetic wave reflector 8 in the shield chamber 2. The electromagnetic wave absorber 1 absorbs incident radiated electromagnetic waves and suppresses the generation of unnecessary reflected waves. For example, a cone 1a such as a cone or a pyramid made of polyurethane containing carbon or ferrite is placed at its center. The axis P is provided so as to be directed to the approximate center O of the shield chamber 2.

  Further, holding mechanisms 6 and 7 are disposed inside the shield chamber 2. Among these, the holding mechanism 6 is for holding, for example, the antenna under test 3 as a device under test at a substantially central portion O of the shield chamber 2, and from the outside toward the center in the vertical direction of the shield chamber 2. It is extended. The holding mechanism 6 has a structure in which a foamed electromagnetic wave absorber is accommodated in, for example, a resin cylinder, and the lower end portion thereof is rotatably held by the rotating means 11 so as to rotate in the vertical direction in FIG. The antenna under test 3 is rotated around to enable measurement of a two-dimensional electromagnetic wave intensity distribution in the circumferential direction. The signal generator 13 disposed outside the shield chamber 2 is connected to the antenna under test 3 by the signal wiring 12 so that the test signal can be supplied to the antenna under test 3. Note that an electromagnetic wave absorber made of the same material as that of the electromagnetic wave absorber 1 may be embedded in the lower part of the electromagnetic wave absorber made of the foam of the holding mechanism 6. Thereby, the electromagnetic waves in the central axis direction of the holding mechanism 6 can be efficiently absorbed, and generation of unnecessary reflected waves can be suppressed. An electromagnetic wave absorber made of the same material as the electromagnetic wave absorber 1 may be provided on the outer peripheral surface of the holding mechanism 6. Thereby, generation | occurrence | production of the unnecessary reflected wave of the electromagnetic wave in the holding mechanism 6 can be suppressed further.

  The holding mechanism 7 holds, for example, the measurement antenna 4 at the distal end, and extends from the outside of the shield chamber 2 toward the center. The holding mechanism 7 has the same configuration as the holding mechanism 6 and is supported by a positioner 14 whose rear end is integrally provided on the outer surface of the shield chamber 2, and is always directed to the antenna 3 to be tested. Thus, the measurement antenna 4 can be held. A slit (not shown) is formed in the side surface of the shield chamber 2 corresponding to the positioner 14 in the circumferential direction within the vertical plane including the antenna 3 to be tested, so that the holding mechanism 7 can move half a circle. Coupled with the rotation of the test antenna 3, the spherical electromagnetic wave intensity distribution can be measured. Here, flexible sheet-like electromagnetic wave absorbers are provided on both sides of the slit so as to cover the slit, thereby preventing unnecessary reflected waves from being generated in the slit portion and allowing the holding mechanism 7 to move freely. I have to. Note that the flexible electromagnetic wave absorber is not limited to the sheet-like material, and any electromagnetic wave absorber can be used as long as it can ensure free movement of the holding mechanism 7 along the slit and prevent unnecessary reflection of electromagnetic waves in the slit portion. There may be. Furthermore, the holding mechanism 7 is provided so as to be extendable and retractable so that the distance D between the antenna under test 3 and the measurement antenna 4 can be adjusted. The distance D may be adjusted manually, or may be automatically adjusted from the outside so that the expansion / contraction operation of the holding mechanism 7 can be automatically controlled. Then, the measurement antenna 4 and the analyzer 16 such as a spectrum analyzer or a network analyzer disposed outside the shield chamber 2 are connected by the signal wiring 15.

  The antennas 3 and 4 installed in the holding mechanisms 6 and 7 may be opposite to those described above. In this case, the analyzer 16 is connected to the holding mechanism 6 side, and the signal generator 13 is connected to the holding mechanism 7 side. Further, the positioner 14 may be provided not on the outer surface of the shield chamber 2 but on the inner surface.

Next, the operation of the electromagnetic wave measurement dark box according to the first embodiment configured as described above will be described with reference to FIGS.
First, among the moving rollers 10a and 10b of the shield chamber 2 shown in FIG. 2, for example, the moving roller 10b is fixed, and the moving roller 10a is set in a movable state.

  Next, the hemisphere 2 a is moved integrally with the moving roller 10 a to open the shield chamber 2, the antenna under test 3 is installed in the holding mechanism 6 held by the rotating means 11, and supported by the positioner 14. The measurement antenna 4 is installed in the holding mechanism 7. At this time, the holding mechanism 7 is simultaneously expanded and contracted to set the distance D between the antenna under test 3 and the measurement antenna 4 to a predetermined value manually or automatically.

  When the installation of the antennas 3 and 4 is completed, the hemisphere 2a is moved in the opposite direction to the above and the shield chamber 2 is closed. Then, as shown in FIG. 1, the signal generator 13 is connected to the holding mechanism 6 side, and the analyzer 16 is connected to the holding mechanism 7 side, and the preparation for measuring the electromagnetic wave intensity distribution of the antenna under test is completed.

  Next, the rotating means 11 is driven to rotate the antenna under test 3 about the vertical rotation axis in FIG. Then, a predetermined test signal is generated from the signal generator 13 and supplied to the antenna under test 3 through the signal line 12. At this time, when the measurement is performed with the holding mechanism 7 fixed in the horizontal position by the positioner 14, the horizontal radiation field intensity distribution of the antenna 3 to be tested is measured. In this case, since the electromagnetic wave absorber 1 is provided on the spherical inner surface of the shield chamber 2 so that the central axis P of each cone 1a is directed to the approximate center O of the shield chamber 2, as shown in FIG. The electromagnetic wave radiated from the antenna under test 3 installed at the center O substantially matches the direction of the central axis P of each cone 1a in any direction. As a result, the input impedance of the electromagnetic wave and the free space impedance are matched, and generation of unnecessary reflected waves is suppressed.

  4 and 5 show the electromagnetic wave intensity distribution of the dipole antenna measured by the electromagnetic wave measurement dark box according to the first embodiment. FIG. 4 shows a case where 2 GHz is applied as a test signal frequency, and FIG. 5 shows a case where 2.4 GHz is applied. Both of the dipole antennas to be tested and the measurement are arranged in a horizontal position, and the measurement results are obtained by changing the distance D between the antennas from 300 mm to 700 mm at equal intervals.

  As shown in FIGS. 4 and 5, according to the electromagnetic wave measurement dark box of the first embodiment, the disturbance of the electromagnetic wave intensity distribution and the antenna interval as in the measurement result of the conventional box type anechoic chamber 2 shown in FIG. The influence of unnecessary reflected waves, such as the dip position shift in the intensity distribution and the intensity distribution not being uniform, does not appear, and the measurement accuracy is improved by suppressing the unnecessary reflected waves.

  Next, the positioner 14 shown in FIG. 1 is driven to move the holding mechanism 7 half a cycle in a predetermined step, and the electromagnetic wave intensity distribution in each step is measured. As a result, the intensity distribution of the spherical radiation electromagnetic wave can be measured in combination with the rotation of the antenna 3 under test.

  Thus, according to the electromagnetic wave measurement dark box of the first embodiment, the inside of the shield chamber 2 is formed in a spherical shape, the electromagnetic wave absorber 1 is formed on the inner surface thereof, and the central axis P of the cone 1a is substantially the same as that of the shield chamber 2. By providing it so as to be directed to the center O, it is possible to suppress the occurrence of unnecessary reflected waves regardless of the distance D between the antenna under test 3 and the antenna 4 for measurement. Therefore, the electromagnetic wave intensity distribution in the shield room can be made uniform. Thereby, the measurement accuracy of the electromagnetic wave intensity distribution can be improved, and the shield chamber 2 can be downsized.

  Further, since the antennas 3 and 4 are held at the distal ends of the holding mechanisms 6 and 7 extending from the outside of the shield chamber 2 toward the center, generation of unnecessary reflected waves in the holding mechanisms 6 and 7 is generated. Can be suppressed, and electromagnetic wave measurement accuracy can be improved.

  Furthermore, the antenna under test 3 is installed in the central portion O of the shield chamber 2, and the measurement antenna 4 can be moved half a circle in a state where the antenna under test 3 is always directed to the positioner 14 provided on the outer surface of the shield chamber 2. With this configuration, the intensity distribution of the radiated electromagnetic wave can be measured in a spherical shape together with the rotation of the antenna under test 3.

  Still further, the shield chamber 2 is divided into hemispheres 2a and 2b by dividing the shield chamber 2 in the longitudinal direction, and the antennas 3 and 4 can be easily attached and replaced by opening and closing the hinges 9 respectively.

  Then, by providing the moving rollers 10a and 10b below the hemispheres 2a and 2b, the shield chamber 2 can be easily opened and closed.

Next, a second embodiment of the present invention will be described with reference to FIG. Here, the same elements as those in FIG. 1 are denoted by the same reference numerals, and different parts from the first embodiment will be described.
In the second embodiment of FIG. 6, the holding mechanism 6 extends horizontally from the outer surface of the shield chamber 2 toward the substantially central portion. The holding mechanism 6 includes a holding unit 16 that holds the antenna 3 to be tested at a front end portion thereof so as to be rotatable about a vertical direction (vertical direction in the figure), and a driving motor 17 at a rear end portion. The holding portion 16 and the driving motor 17 are connected by a belt 18 so that the rotational force of the driving motor 16 is transmitted to the holding portion 16.

  The electromagnetic wave measurement dark box of the second embodiment configured as described above has the same effect as that of the first embodiment.

  Note that the positioner 14 is not limited to one formed so as to make a semicircular inside of the spherical interior of the shield chamber 2 as shown in FIG. 6, and is orthogonal to the central axis of the holding mechanism 6 and includes the rotation axis of the antenna 3 to be tested. You may provide so that it may circulate in a surface. This also makes it possible to measure spherical electromagnetic wave characteristics.

  In any of the above-described embodiments, the antenna under test 3 is a transmission antenna and the measurement antenna 4 is a reception antenna.

  Furthermore, although the outer shape of the shield chamber 2 is spherical in this embodiment, the outer shape may be any shape as long as the inner shape is spherical.

  And in the electromagnetic wave measurement dark box of this invention, a to-be-tested object is not restricted to an antenna, What kind of thing may be used if it emits electromagnetic waves.

It is sectional drawing which shows 1st Embodiment of the electromagnetic wave measurement dark box by this invention. It is a front view which shows the state which opened the shield chamber of 1st Embodiment. It is explanatory drawing which shows the incident direction of the electromagnetic wave with respect to the cone of the electromagnetic wave absorber in 1st Embodiment. In 1st Embodiment, it is explanatory drawing which shows the measurement result of the electromagnetic wave intensity distribution of a dipole antenna with respect to the electromagnetic wave of frequency 2GHz. In 1st Embodiment, it is explanatory drawing which shows the measurement result of the electromagnetic wave intensity distribution of a dipole antenna with respect to the electromagnetic wave of frequency 2.4GHz. It is sectional drawing which shows 2nd Embodiment of the electromagnetic wave measurement dark box by this invention. It is sectional drawing which shows the structure of the conventional box-type anechoic chamber. It is explanatory drawing which shows the incident direction of the electromagnetic waves with respect to the cone of the electromagnetic wave absorber in the conventional box-type anechoic chamber. It is explanatory drawing which shows the measurement result of the electromagnetic wave intensity distribution of a dipole antenna with respect to the electromagnetic wave of frequency 2.4GHz in the conventional box-type anechoic chamber.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electromagnetic wave absorber 1a ... Cone 2 ... Shield room 2a, 2b ... Hemisphere 3 ... Antenna for test 4 ... Antenna for measurement 6, 7 ... Holding mechanism 8 ... Electromagnetic reflector 8a ... Inner side surface 10a, 10b ... Movement Roller for

Claims (11)

An electromagnetic wave measurement dark box for measuring a radiation characteristic or reception characteristic of an electromagnetic wave by installing a device under test and a measurement antenna in a shielded room,
An electromagnetic wave measurement dark box, wherein the inside of the shield chamber is formed in a spherical shape and an electromagnetic wave absorber is provided on the entire inner surface.   2. The electromagnetic wave measurement dark box according to claim 1, wherein the shield room space is covered with a radio wave reflector.   3. The electromagnetic wave measurement dark box according to claim 1, wherein the electromagnetic wave absorber includes a large number of cones, and is provided so that a central axis of each cone is directed to a substantially center of the shield chamber. .   The configuration according to claim 1, wherein either one of the device under test and the antenna for measurement can be installed at a substantially central portion of the shield chamber, and the other can be installed at a peripheral portion of the shield chamber. The electromagnetic wave measurement dark box according to any one of the above.   5. The electromagnetic wave measurement dark box according to claim 4, wherein a device under test or a measurement antenna installed at a substantially central portion of the shield chamber is configured to be rotatable about a vertical rotation axis.   6. The device according to claim 1, wherein the device under test and the antenna for measurement are each held by a tip of a holding mechanism extending from the outside of the shield chamber toward the center. The electromagnetic wave measurement dark box according to any one of the above.   7. A positioner configured to hold either one of the device under test and the antenna for measurement and to be movable in the circumferential direction of the shield chamber is provided integrally. The electromagnetic wave measurement dark box described in 1.   The electromagnetic wave measurement dark box according to any one of claims 1 to 7, wherein the shield chamber is configured by connecting a half body formed by dividing the shield chamber into two in a longitudinal direction so as to be openable and closable.   The electromagnetic wave measurement dark box according to claim 8, wherein a moving roller is provided at a lower portion of the half body.   The electromagnetic shielding dark box according to any one of claims 1 to 9, wherein the shield chamber is formed of an electromagnetic wave reflector itself.   10. The electromagnetic wave measurement dark box according to claim 1, wherein the shield chamber is formed of a resin material, and a metal is attached to the entire inner surface.

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