JP2979898B2 - Anechoic chamber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the measurement of characteristics of a receiving antenna and an antenna for mobile communication mounted on an automobile, an aircraft, etc., and the evaluation of unnecessary radio waves and noise generated from electronic equipment and the like. The present invention relates to an anechoic chamber used for measurement of EMI and EMS for testing the influence on electronic devices due to interfering radio waves from a computer.

[0002]

2. Description of the Related Art Conventionally, weather conditions, temperature and humidity conditions have been used as environments for measuring radio wave propagation characteristics of antennas and the like, evaluating and measuring noise generated from electronic devices, and testing the effects of external jamming radio waves on electronic devices. There is a demand for a stable and highly reliable room that can remove the influence of external noise. The anechoic chamber has a wall surface, a ceiling, and a floor surface covered with a radio wave absorber to provide such an indoor space, and its superiority is well known and widely applied.

As a characteristic of such an anechoic chamber, it is a major problem to realize a free space in a room without any obstacle in terms of radio waves, and the room is reflected from a side wall surface, a ceiling surface, and a floor surface in the room. It is desired to reduce unnecessary electromagnetic wave energy and to obtain excellent electric field uniformity in the receiving unit.

[0004] The radio wave propagation characteristics in free space means that when a transmitting antenna which is a radio wave generating source is modeled as a point wave source, the electric field of a radiated radio wave propagates concentrically and spreads. In other words, a so-called plane wave having the same magnitude and phase in the plane in a limited region far away is realized, thereby ensuring the uniformity of the electric field. However, at a sufficiently long distance, as the propagation distance increases, the electric field strength attenuates in inverse proportion to the distance.

[0005] The anechoic chamber has a general rectangular parallelepiped shape, a wall surface, a ceiling surface, and a floor surface in the middle area between the transmitting unit and the receiving unit which are widened to reduce reflection therefrom. A tapered anechoic chamber in which a transmitting section in a narrow space and a receiving section in a wide space are connected by a tapered waveguide section is used.

The tapered anechoic chamber is more economical than a rectangular parallelepiped anechoic chamber because it has a smaller volume when the same transmission / reception distance is taken. Also, because of the taper angle in the waveguide part, there is almost no influence of the reflection from the side wall part as in the radio wave radiation state in the horn antenna. Further, the path difference between the side wall reflected wave and the direct wave can be reduced in the transmission part, so that the phase difference is reduced. Since it is extremely small, the electric field uniformity in the receiving section is excellent.

FIG. 10 is a plan view schematically showing a conventional tapered anechoic chamber of this type, and FIG. 11 is a sectional view taken along line XI-XI of FIG.

As shown in these figures, the conventional tapered anechoic chamber has a tapered shape in both a plane shape and a cross-sectional shape, and all the wall surfaces, ie, the side wall surfaces 100,
The ceiling surface 101 and the floor surface 102 are covered with a pyramid-shaped or wedge-shaped radio wave absorber 103 made of a carbon-containing foam as a resistance loss material. A horn antenna type transmitting structure 105 having a waveguide is provided at an end of the transmitting section 104 in a narrow space. This transmitting unit 104
And the receiving section 106 in the wide space are the tapered waveguide section 10
7 are connected. The waveguide unit 107 is configured such that its side wall surface, ceiling surface, and floor surface are transmitted from the transmitting unit 104 to the receiving unit 10.
The taper shape is such that it gradually expands toward 6 and the cross-sectional area gradually increases.

[0009]

In a conventional tapered anechoic chamber, a radio wave absorber made of a resistance loss material is used. In order to obtain excellent radio wave absorption characteristics, the length of the radio wave absorber must be absorbed. It must be at least 波長 or more of the wavelength of the frequency. This is because if the frequency to be absorbed is, for example, 100 MHz, the length of the absorber becomes 1.5 m or more, and the size of the building constituting the anechoic chamber becomes extremely large, which is disadvantageous in terms of economy and also makes each wall The volume of the effective space sandwiched between the distal ends of the radio wave absorbers becomes extremely small.

When an antenna mounted on a ground moving body such as an automobile receives a radio wave in a mounted state, it receives a radio wave obtained by combining a reflected wave from the ground and a direct wave from a transmission source. However, in the conventional tapered anechoic chamber as described above, since the floor surface is also formed of the radio wave absorber, there is no reflected wave from the ground and only the direct wave is received. For this reason, the radio wave characteristics received in the anechoic chamber and the radio wave characteristics in a practical state are different from each other.

Further, in the conventional tapered anechoic chamber, the transmission frequency range is limited to the frequency range of the waveguide due to the transmission structure of the transmission unit. For this reason, in the case of performing wideband measurement with the recent expansion of radio wave use and widening of the frequency used, it is necessary to prepare a plurality of transmission units having different frequency bands and exchange them. This not only increases the economic burden, but also causes the inconvenience of requiring a great deal of time for replacement.

Instead of a radio wave absorber made of a resistance loss material, a part of the wall surface of the waveguide is covered with a ferrite radio wave absorber having a large magnetic loss and exhibiting excellent radio wave absorption performance with a small thickness. By doing so, it is possible to secure an economically inexpensive and effective space. However, with such a configuration, impedance mismatch occurs at the boundary between the radio wave absorber made of the resistance loss material and the ferrite radio wave absorber having a different radio wave absorption principle, and the radio wave is reflected.

Accordingly, the present invention is to solve the above-mentioned problems of the prior art, and it is an object of the present invention to provide a ferrite radio wave absorber provided in a waveguide portion and a radio wave generated by a resistance loss material which is disposed continuously from the ferrite radio wave absorber and constitutes a reception portion. It is an object of the present invention to provide an anechoic chamber that can reduce reflection at a coupling portion with an absorber and has better electric field uniformity.

[0014]

According to the present invention, the receiving portion is covered with a radio wave absorber made of a resistive loss material or a composite type loss material obtained by combining a ferrite tile and a resistive loss material. Are connected by a tapered waveguide, and at least a part of the ceiling and side walls of the waveguide is made of a ferrite electromagnetic absorber, and the ferrite electromagnetic absorber of the waveguide is Provide a conversion part consisting of a radio wave absorber changed so as to be electrically or physically smooth at the coupling part of the radio wave absorber of the receiving part,
An oblique incident radio wave absorber is provided at the boundary between the ferrite radio wave absorber of the waveguide portion and the radio wave absorber forming the above-described conversion portion to smoothly adjust the radio wave.

[0015] The floor of the waveguide and the receiving section is made flat with respect to the ground, and the floor of the receiving and the waveguide is constituted by a ground equivalent floor obtained by combining a ferrite tile and a conductive film. Is preferred.

It is also preferable that the coupling position between the waveguide section and the transmission section on the ceiling surface is different from the coupling position between the waveguide section and the transmission section on the side wall surface.

It is also an embodiment of the present invention to dispose an independent transmitting broadband antenna in the transmitting section.

[0018]

[Function] A receiving portion covered with a radio wave absorber made of a resistance loss material or a radio wave absorber made of a composite loss material obtained by combining a ferrite tile and a resistance loss material, and a waveguide portion covered with a ferrite radio wave absorber. By providing a conversion part consisting of a radio wave absorber changed so as to be electrically or physically smooth at the coupling part with, the reflection due to sudden impedance mismatch due to the completely different principle of radio wave absorption is suppressed . In addition, by providing an obliquely incident radio wave absorber at the boundary between the ferrite radio wave absorber of the waveguide and the radio wave absorber forming the above-mentioned converter, and smoothly adjusting the radio wave, the reflection due to impedance mismatch is achieved. Suppress.

Also, by making the coupling position between the waveguide and the transmitter on the ceiling surface different from the coupling position between the waveguide and the transmitter on the side wall, the boundary between the waveguide and the transmitter can be changed. The opening cross-sectional area at the part can be configured to change gradually, and in this regard, impedance mismatch can be improved,
Reflection can be suppressed.

Further, in order to form the same environment as a radio wave environment in a practical state in the field, the floors of the receiving section and the waveguide section are constituted by a ground equivalent floor having radio wave equivalent characteristics to the ground. Then, instead of a radio wave absorber made of a resistive loss material having a length equal to or longer than 波長 of the wavelength, a ferrite radio wave absorber is arranged on a part or all of the ceiling surface and the side wall surface of the waveguide. The ferrite electromagnetic wave absorber has a large magnetic loss, and has an excellent electromagnetic wave absorption performance at a thickness of 1/50 to 1/200 of the wavelength, so that a wider effective space is secured and an anechoic chamber is provided. Can be formed at low cost.

[0021]

Embodiments of the present invention will be described below in detail. FIG.
1 is a plan view schematically showing a configuration of an embodiment of an anechoic chamber according to the present invention, and FIG. 2 is a sectional view taken along line II-II in FIG.

As shown in these figures, the tapered anechoic chamber 10 has one end as a transmitting section 11 in a narrow space, and the other end as a receiving section 12 in a wide space.

The receiving unit 12 suppresses unnecessary reflected waves from the wall surface of the transmitted radio waves as much as possible in order to reproduce a situation in which the transmitted radio waves are infinite, so that only traveling wave components can be obtained in the receiving area. Designed for Receiver 12
The four wall surfaces excluding the floor surface, that is, the left and right side wall surfaces 12a and 12b, the ceiling surface 12c, and the back wall surface 12d are also radio wave absorbers 14 made of a resistance loss material, or a combination of a ferrite radio wave absorber and a resistance loss material. And is covered with a composite type radio wave absorber. The transmitting unit 11 is designed to transmit a single-mode radio wave as much as possible by minimizing unnecessary reflected waves from the wall surface.
The four wall surfaces except the floor surface of the transmitting unit 11, that is, the left and right side wall surfaces 11a and 11b, the ceiling surface 11c, and the back wall surface 11d are radio wave absorbers 13 made of a resistance loss material, or a ferrite radio wave absorber and a resistance loss material. Are covered with a composite type radio wave absorber 13 which is a combination of the above. These radio wave absorbers 1
Each of 3 and 14 has a pyramid shape, a wedge shape, or a plate shape in which the material constants are different in the thickness direction.

If a composite type radio wave absorber combining a ferrite radio wave absorber and a resistance loss material is used as the radio wave absorbers 13 and 14, excellent radio wave absorption characteristics from low frequencies can be obtained, and the radio wave absorbers 13 and 14 can be composed of only the resistance loss material. In comparison with the case where the length is less than or equal to the length, absorption characteristics equal to or greater than the length can be obtained. As a result, not only can the effective space in the anechoic chamber be widened, but also the building itself can be made smaller and the overall cost can be significantly reduced.

The transmission section 11 and the reception section 12 are connected by a tapered waveguide section 15. The waveguide section 15 minimizes reflection of a single-mode radio wave transmitted from the transmission section 11 due to local non-uniformity of the wall surface, and has a short transmission distance and is close to radio wave propagation characteristics in a distant region in free space. It is designed to obtain as high a radio wave attenuation effect as possible. Three wall surfaces of the waveguide unit 15 except the floor surface, that is, left and right side wall surfaces 15a and 15b, and a ceiling surface 1
All or a part of 5c is formed of a flat ferrite electromagnetic wave absorber 16. This ferrite wave absorber 16
Have a large magnetic loss and a large radio wave attenuation effect over a wide band, and have a wavelength of 1/50 to 1/20
Even with a thickness of 0, it has excellent radio wave absorption performance, so that it can be made extremely thin. As a result, uniform electric field characteristics can be obtained with a shorter propagation distance, a wide effective space can be secured, and an effective anechoic chamber can be realized in an economically small building.

Transmission section 11, reception section 12, and waveguide section 15
Of the floor surfaces 11e, 12e, and 15e have a flat structure parallel to the ground. This is in line with the fact that the ground is generally flat. Furthermore, these floor surfaces 11e, 12e, and 15e, except for a part thereof, are ground equivalent floors having radio-equivalent characteristics to the ground by combining a ferrite tile and a conductive film.

In the center of the transmitting section 11, an independent array type antenna 17 having a wide band characteristic is arranged.
The entire transmitting unit 11 is configured as a broadband transmitting device.
For this reason, it is not necessary to prepare a plurality of transmission units for each frequency band, and the trouble of exchanging these units can be omitted.

At the center of the receiving section 12, a turntable for mounting an object to be measured, for example, an automobile W is provided.

The radio wave absorber 14 and the waveguide 15 of the receiver 12
The radio wave absorber 20 is provided in the conversion unit 19 to which the radio wave absorber 16 is coupled so as to change smoothly electrically or physically. A radio wave absorber 22 is provided on the radio wave absorber 14 at a boundary portion 21 between the conversion unit 19 and the waveguide unit 15 so as to project obliquely in the direction of the waveguide unit 15. The structure is such that the body 14 and the radio wave absorber 16 of the waveguide portion 15 are smoothly coupled with each other in terms of radio waves, and impedance mismatch does not occur at this boundary portion 21.

FIGS. 3 and 4 show these radio wave absorbers 20.
FIGS. 3A and 3B are a plan view and a cross-sectional view illustrating a structure of a converter 19 and a boundary portion 21 of FIGS. FIGS. 5 and 6 illustrate another configuration example of the radio wave absorber 20 and the obliquely incident radio wave absorber 22, and correspond to the conversion unit 19 and the boundary part 21 of FIGS. 1 and 2. It is the top view and sectional drawing which each show a part in detail.

As shown in these figures, the side wall surfaces 19a and 19b and the ceiling surface 19c of the conversion section 19 are covered with the above-mentioned radio wave absorber 20. By arranging the radio wave absorber 20 so as to change smoothly electrically or physically, impedance change between the absorber 14 of the receiver 12 and the absorber 16 of the waveguide 15 is moderated. Thereby, the reflection at that portion is suppressed. Further, at the boundary portion 21, a pyramid-shaped or wedge-shaped radio wave absorber 22 made of a similar material is desirably placed on the radio wave absorber 20 located closest to the waveguide portion 15 among the radio wave absorbers 20. Are provided so as to project obliquely in the direction of the waveguide section 15, and the obliquely incident radio wave absorber 22 having such a double structure has an impedance between the absorber 20 of the conversion section 19 and the absorber 16 of the waveguide section 15. The structure is such that the change is made more gradual to suppress the reflection at that part.

As is clear from the difference between the distance D ₁ in FIG. ₁ and the distance D _{2 in} FIG.
5 and transmitting part 11 and waveguide part 1 on ceiling surface
5 and the transmission unit 11 are configured to be different from each other. Therefore, at the boundary between the waveguide unit 15 and the transmission unit 11, the opening cross-sectional area changes gradually. As a result, the impedance mismatch at the boundary can be improved, and the reflection can be suppressed.

FIGS. 7 and 8 show a conventional tapered anechoic chamber without the radio wave absorber 20 and the obliquely incident radio wave absorber 22 in the converter 19 and the radio wave absorber 20 and the obliquely incident radio wave absorber 22 in the converter 19. It shows the variation value characteristics of the electric field with respect to the frequency of the vertically polarized wave in the tapered anechoic chamber 10 of the above-described embodiment provided. This characteristic shows an electric field distribution in a circle having a height of 1.3 m and a diameter of 6 m.

As shown in these figures, in the conventional anechoic chamber, the maximum and minimum electric field fluctuation values fluctuate in the range of 1 to 4.2 dB, but in the tapered anechoic chamber of the present embodiment, the maximum and minimum electric field fluctuation values change. Has an electric field fluctuation value of about 2 to 3.4 dB,
Very stable.

Further, according to the present embodiment, in order to make the conditions the same as those of the outdoor radio wave propagation environment, a ground equivalent floor which is radio-equivalent to the ground is provided in the waveguide unit 15 and the receiving unit 12. The direct wave from the transmitter 11 and the floor 15e of the waveguide 15
The reflected wave from the signal is synthesized in the same manner as in the practical state, enters the receiving unit 12, and a receiving state close to radio wave propagation in the field is realized.

When the floor is a ground equivalent floor which is radio-equivalent to the ground, a direct wave from the transmitting unit 11 and a reflected wave from the ground equivalent floor interfere with each other and have a ripple having a large maximum value and a minimum value. A phenomenon may occur, and it is necessary to avoid electric field non-uniformity due to mutual interference. For this purpose, it is necessary to select the transmission / reception distance so that the difference between the phase of the reflected wave and the phase of the direct wave is at least 波長 wavelength or less.

As shown in FIG. 9, the height of the transmitting antenna 90 is h ₁ , the height of the receiving antenna 91 is h ₂ , the linear distance between the transmitting and receiving antennas is l ₀ , the reflection distance between the transmitting and receiving antennas is l ₁ , and Assuming that l ₂ and the wavelength are λ, this is represented by l ₁ + l ₂ −l ₀ = {l ₀ + (h ₁ + h ₂ )} − l ₀
≧ λ / 2. For example, the transmitting antenna 90
Height h ₁ and the sum of the height h ₂ of the receiving antenna 91 is h ₁
When + h ₂ = 3 m, the linear distance between the transmitting and receiving antennas is l
₀ is l ₀ ≧ 2.25 m when the frequency is 100 MHz.
Where l ₀ ≧ 8.75 when the frequency is 300 MHz.
m and the frequency is 600 MHz, l ₀ ≧ 17.
9m. When h ₁ + h ₂ = 4 m, l ₀ ≧ 4.58 m when the frequency is 100 MHz, l ₀ ≧ 15.75 m when the frequency is 300 MHz, and l ₀ ≧ 32 m when the frequency is 600 MHz. When setting is made so as to satisfy such a condition, a radio wave propagation environment in which the receiving antenna receives a radio wave from a practically distant transmission point is realized.

[0038]

As described above in detail, according to the present invention, a radio wave absorber made of a resistive loss material constituting a wall surface of a receiving portion or a composite type loss material obtained by combining a ferrite tile and a resistive loss material is used. At the joint between the radio wave absorber and the ferrite radio wave absorber that constitutes the wall of the waveguide,
Provide a converter made of a radio wave absorber changed so as to be electrically or physically smooth, and further at the boundary between the ferrite radio wave absorber of the waveguide and the radio wave absorber forming the above-mentioned converter. Since the boundary impedance is matched by providing an obliquely incident radio wave absorber and making smooth adjustments in radio waves, reflection at this part can be eliminated, and better electric field uniformity can be obtained. An anechoic chamber having characteristics similar to propagation can be provided.

Further, by making the floor surfaces of the waveguide section and the receiving section the ground equivalent floor, it is possible to obtain a characteristic almost similar to radio wave propagation in outdoor mounting. In addition, by constructing at least a part of the ceiling surface and side wall surface of the waveguide part with a ferrite radio wave absorber, effective radio wave attenuation can be obtained and excellent electric field uniformity can be obtained over a shorter distance, so that the performance of the anechoic chamber is improved. In addition to being excellent, it is possible to provide a radio wave anechoic chamber which can secure a wide space and is economically inexpensive because it can be constituted by an extremely short radio wave absorber. In addition, by arranging a wideband antenna in the transmission unit,
Since it is not necessary to prepare a plurality of transmission units for each frequency band, the cost is economically reduced, and the labor for replacing the transmission units can be omitted, so that significant labor saving and speeding up can be achieved.

[Brief description of the drawings]

FIG. 1 is a plan view schematically showing a configuration of an embodiment of an anechoic chamber of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a plan view showing a boundary portion of FIG. 1 in detail.

FIG. 4 is a sectional view showing a boundary portion of FIG. 2 in detail.

FIG. 5 is a plan view specifically showing a portion corresponding to a boundary portion in FIG. 1 in another embodiment of the present invention.

FIG. 6 is a sectional view showing in detail a portion corresponding to the boundary portion in FIG. 2 in another embodiment of the present invention.

FIG. 7 is a characteristic diagram showing electric field fluctuation values in the related art.

FIG. 8 is a characteristic diagram showing electric field fluctuation values in the embodiment of FIGS. 1 and 2.

FIG. 9 is a model diagram of radio wave propagation showing a relationship between a direct wave and a reflected wave of a radio wave.

FIG. 10 is a plan view schematically showing a conventional tapered anechoic chamber.

FIG. 11 is a sectional view taken along line XI-XI of FIG. 10;

[Explanation of symbols]

Reference Signs List 10 Tapered anechoic chamber 11 Transmitters 11a, 11b, 12a, 12b, 15a, 15b, 1
9a, 19b Side wall surface 11c, 12c, 15c, 19c Ceiling surface 11d, 12d, Back wall surface 11e, 12e, 15e Floor surface 12 Receiving unit 13, 14 Radio wave absorber 15 Waveguide unit 16 Ferrite radio wave absorber 17 Array antenna 18 Turntable 19 Converter 20 Radio wave absorber 21 Boundary part 22 Obliquely incident radio wave absorber

Continuing on the front page (72) Inventor Toshiaki Kobayashi TDC Corporation, 1-13-1 Nihonbashi, Chuo-ku, Tokyo (72) Inventor Shingo Seki Nippon Sheet Glass 3-5-11, Doshumachi, Chuo-ku, Osaka-shi, Osaka (72) Inventor Kazuhiko Ogawa 3-5-11, Doshu-cho, Chuo-ku, Osaka-shi, Japan Inside Nippon Sheet Glass Co., Ltd. (72) Inventor Harunori Murakami 3-5-1, Doshu-cho, Chuo-ku, Osaka-shi, Osaka Inside Nippon Sheet Glass Co., Ltd. (72) Keisuke Tanaka Inventor Nippon Sheet Glass Co., Ltd. 3-5-11, Doshu-cho, Chuo-ku, Osaka-shi, Osaka (56) References JP-A-6-104634 (JP, A) JP-A Heisei 6-104633 (JP, A) JP-A-2-174199 (JP, A) JP-A-62-45100 (JP, A) JP-A-2-12996 (JP, A) JP-A-57-102337 (JP, A) A) Japanese Utility Model Hei 5-77781 (JP, U) Japanese Utility Model Application Sho 56-38895 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05K 9/00

Claims (4)

(57) [Claims] 1. A wall of a receiving unit is covered with a radio wave absorber made of a resistive loss material or a radio wave absorber made of a composite loss material obtained by combining a ferrite tile and a resistance loss material, and the receiving unit is tapered. A taper-type anechoic chamber connected to a portion, wherein at least a part of a ceiling surface and a side wall portion of the waveguide portion is formed of a ferrite radio wave absorber, and the reception portion is formed from the ferrite radio wave absorber of the waveguide portion. As a method of coupling to the radio wave absorber, a conversion part comprising a radio wave absorber changed so as to be electrically or physically smooth is provided, and the ferrite radio wave absorber of the waveguide part and the conversion part are formed. An anechoic chamber characterized in that an oblique incidence radio wave absorber is provided at the boundary between the radio wave absorber and the radio wave for smooth adjustment. 2. A ground equivalent floor having a structure in which the floor surfaces of the waveguide unit and the reception unit are flat with respect to the ground, and the floor surfaces of the reception unit and the waveguide unit are a combination of a ferrite tile and a conductive film. 2. The anechoic chamber according to claim 1, wherein: 3. The coupling position between the waveguide section and the transmission section on a ceiling surface and the coupling position between the waveguide section and the transmission section on a side wall surface are different from each other.
Or the anechoic chamber described in 2. 4. The anechoic chamber according to claim 1, wherein an independent broadband antenna for transmission is arranged in the transmission unit.