JP3265646B2 - 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 a method for measuring characteristics of a receiving antenna mounted on an automobile or an aircraft, an antenna for mobile communication, and the like, as well as for evaluating unnecessary radio waves and noise generated from electronic equipment and for external use. 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 indoor space 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. This realizes a so-called plane wave having the same magnitude and phase in the plane in a limited region far away, 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. Recently, a tapered anechoic chamber has been developed in which a transmitting unit in a narrow space and a receiving unit in a wide space are connected by a tapered waveguide.

The tapered anechoic chamber is more economical than a rectangular parallelepiped anechoic chamber because it can be configured with a smaller volume when the same transmission and reception distance is used. In addition, the taper angle in the waveguide section hardly affects the reflection from the side wall section, and the path difference of the side wall reflected wave can be reduced in the transmission section, so that the phase difference becomes extremely small. Become excellent.

FIG. 7 is a plan view schematically showing a conventional tapered anechoic chamber of this type, and FIG. 8 is a sectional view taken along line VIII-VIII of FIG.

As shown in these figures, the conventional tapered anechoic chamber has a tapered shape in both a plane shape and a side sectional shape, and all the wall surfaces, that is, the side wall surfaces 70, are formed.
The ceiling surface 71 and the floor surface 72 are covered with a pyramid-shaped or wedge-shaped radio wave absorber 73 made of a carbon-containing foam as a resistance loss material. Transmitter 7 in a narrow space
A horn antenna type transmitting structure 75 having a waveguide is provided at the end of the fourth. The transmitting section 74 and the receiving section 76 in a wide space are connected by a tapered waveguide section 77. The waveguide portion 77 has a tapered shape such that the side wall surface, the ceiling surface, and the floor surface gradually expand from the transmitting portion 74 to the receiving portion 76 and the cross-sectional area gradually increases.

[0009]

SUMMARY OF THE INVENTION When an antenna mounted on a ground moving object such as an automobile receives a radio wave in a mounted state, it is necessary to receive a radio wave obtained by combining a reflected wave from the ground and a direct wave from a transmission source. Becomes 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.

In the 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 wavelength of the frequency at which the length of the radio wave absorber is to be absorbed is required. It must be at least 1/2 or more. This is because when 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 economically disadvantageous and from the wall surface. The volume of the effective space sandwiched between the tips of the radio wave absorbers becomes very small.

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.

Accordingly, the present invention solves the above-mentioned problems of the prior art, and provides an anechoic chamber which has excellent anechoic chamber performance, can secure a wide internal space, and can be formed at low cost. It is.

[0013]

According to the present invention, a wall of a transmitter and a receiver is covered with a radio wave absorber, and the transmitter and the receiver are connected by a tapered waveguide. In this case, an anechoic chamber is provided in which the floor of the waveguide is formed of a ground equivalent floor, and at least a part of the ceiling and side walls of the waveguide is formed of a ferrite radio wave absorber.

The floor of the transmitter, the waveguide, and the receiver has a flat structure with respect to the ground, and the floor of the receiver and the waveguide has a floor equivalent to a combination of a ferrite tile and a conductive film. It is preferable to configure

It is also preferable that the radio wave absorber disposed on the wall surfaces of the transmission section and the reception section be a composite radio wave absorber made of a combination of a ferrite tile and a resistance loss material.

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

[0017]

The transmission section and the reception section are connected by a tapered waveguide section to form the same environment as a radio wave environment in a practical use outdoors, so that the floor surface of the waveguide section is radio-equivalent to the ground. It consists of a ground equivalent floor with characteristics. 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. Ferrite radio wave absorbers have a large magnetic loss,
Since it has excellent radio wave absorption performance with a thickness of / 50 to 1/200, a wider effective space can be secured and an anechoic chamber can be formed at low cost.

[0018]

Embodiments of the present invention will be described below in detail.

FIG. 1 is a plan view schematically showing the configuration of an embodiment of an anechoic chamber according to the present invention, and FIG. 2 is a sectional view taken along the line II-II of 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 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 composed of a composite type radio wave absorber 1 formed by combining a ferrite radio wave absorber and a resistance loss material.
Covered with 3. The receiving unit 12 is designed so that the transmitted radio waves are suppressed as much as possible from unnecessary reflection waves from the wall surface in order to reproduce a situation where the infinite space continues, and only the traveling wave component is obtained in the receiving area. Have been. Four wall surfaces except the floor surface of the receiving unit 12, that is, left and right side wall surfaces 1
2a and 12b, the ceiling surface 12c, and the back wall surface 12d are also covered with the composite type radio wave absorber 14 formed by combining a ferrite radio wave absorber and a resistance loss material. These radio wave absorbers 13 and 14 are configured in a pyramid shape, a wedge shape, or a plate shape in which material constants are different in the thickness direction.

As described above, since the composite radio wave absorber combining the ferrite radio wave absorber and the 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 resistance can be improved. As compared with the case where the loss material is used alone, it is possible to obtain the same or better absorption characteristics with a length of 1/2 or less. 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 transmitting section 11 and the receiving 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 nonuniformity of a 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 excluding the floor surface of the waveguide unit 15, that is, left and right side wall surfaces 15a and 15b, and a ceiling surface 15
All or part of c is a flat ferrite electromagnetic wave absorber 1
6. 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 if the thickness is 0, it has excellent radio wave absorption performance, so that it can be made extremely thin. As a result, a uniform electric field characteristic 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 unit 11, reception unit 12, and waveguide unit 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. Further, these floor surfaces 11e, 12e, and 15e are ground equivalent floors having radio-equivalent characteristics to the ground by combining a ferrite tile and a conductive film.

At the center of the transmitting section 11, an independent array type antenna 17 having a wide band characteristic is installed.
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 18 for mounting an object to be measured, for example, an automobile W, is provided.

As described above, according to the present embodiment, in order to make the same conditions 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 section 15. The direct wave from 11 and the reflected wave from the floor 15e of the waveguide section 15 are combined in the same manner as in a practical state, enter the receiving section 12, and a reception 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 more.

As shown in FIG. 3, the height of the transmitting antenna 30 is h ₁ , the height of the receiving antenna 31 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 satisfies the relationship l ₁ + l ₂ −l ₀ = {l ₀ ² + (h ₁ + h ₂ ) ² } −l ₀ ≧ λ / 2. For example, the transmitting antenna 30
Height h ₁ and the sum of the height h ₂ of receive antennas 31 h ₁
When + h ₂ = 3 m, the linear distance l ₀ between the transmitting and receiving antennas
Is given by l ₀ ≧ 2.25 m when the frequency is 100 MHz, and l ₀ ≧ 8.75 m when the frequency is 300 MHz.
Where l ₀ ≧ 17.9 when the frequency is 600 MHz.
m. When h ₁ + h ₂ = 4 m, the frequency is set to 1
If 00 MHz, l ₀ ≧ 4.58 m, if the frequency is 300 MHz, l ₀ ≧ 15.75 m, and if the frequency is 600 MHz, l ₀ ≧ 32 m. When setting is made so as to satisfy such a condition, a radio wave propagation environment in which the receiving antenna receives radio waves from a practically distant transmission point is realized.

FIG. 3 and FIG. 4 show the fluctuation value characteristics of the electric field with respect to the frequency in the tapered anechoic chamber 10 of the above embodiment. This characteristic is 1.3m in height and 6m in diameter
3 shows the case of horizontal polarization, and FIG. 4 shows the case of vertical polarization.

In a conventional anechoic chamber, the maximum-minimum electric field fluctuation value may be 8 dB or more in some bands.
In the tapered anechoic chamber of the present embodiment, the maximum-minimum electric field fluctuation value is 4 dB or less, which is very stable.

FIG. 5 is a horizontal plane pattern characteristic diagram of the dipole antenna evaluated in the tapered anechoic chamber 10 of the above embodiment.

As can be seen from the figure, according to the tapered anechoic chamber 10 of the present embodiment, the point where the electric field is close to zero in the figure-eight characteristic unique to the dipole antenna, that is, the null point is in the free space Similarly to the above, it appears symmetrically at two places on both sides. This indicates that the tapered anechoic chamber 10 of the present embodiment can reproduce extremely excellent radio wave propagation characteristics close to free space with extremely little unnecessary reflection from the surroundings.

[0033]

As described above in detail, according to the present invention, by making at least the floor surface of the waveguide portion a ground equivalent floor, it is possible to obtain a characteristic substantially similar to radio wave propagation in a real outdoor field. 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 at a shorter distance. In addition to being excellent, it can be configured with an extremely short radio wave absorber, so that a large space can be secured and an economically inexpensive radio anechoic chamber can be provided. In addition, by disposing a wideband antenna in the transmitter, there is no need to prepare a plurality of transmitters for each frequency band, so that the cost is economically reduced and the labor for replacing the transmitter can be saved, so that significant labor saving and speeding up are achieved. 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 model diagram of radio wave propagation showing a relationship between a direct wave and a reflected wave of a radio wave.

FIG. 4 is a characteristic diagram showing the stability of electric field fluctuation values in the embodiment of FIGS. 1 and 2;

FIG. 5 is a characteristic diagram showing stability of an electric field fluctuation value in the embodiment of FIGS. 1 and 2;

FIG. 6 is a horizontal plane pattern characteristic diagram of the dipole antenna evaluated in the anechoic chamber of the embodiment of FIGS. 1 and 2;

FIG. 7 is a plan view schematically showing a conventional tapered anechoic chamber.

8 is a sectional view taken along line VIII-VIII in FIG.

[Explanation of symbols]

Reference Signs List 10 Tapered anechoic chamber 11 Transmitter 11a, 11b, 12a, 12b, 15a, 15b Side wall surface 11c, 12c, 15c Ceiling surface 11d, 12d Back wall surface 11e, 12e, 15e Floor surface 12 Receiving unit 13, 14 Composite electromagnetic wave absorption Body 15 Waveguide 16 Ferrite radio wave absorber 17 Array antenna 18 Turntable

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiaki Kobayashi 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK Corporation (72) Inventor Shingo Seki 3-5-1, Doshumachi, Chuo-ku, Osaka-shi, Osaka No. Nippon Sheet Glass Co., Ltd. (72) Kazuhiko Ogawa 3-5-1, Doshomachi, Chuo-ku, Osaka-shi, Osaka Prefecture No. 7 Nippon Sheet Glass Co., Ltd. (72) Harunori Murakami 3--5, Doshucho, Chuo-ku, Osaka, Osaka No. 11 Nippon Sheet Glass Co., Ltd. (72) Inventor Keisuke Tanaka 3-5-11 Doshomachi, Chuo-ku, Osaka City, Osaka Prefecture Nippon Sheet Glass Co., Ltd. (56) References JP-A-2-53337 (JP, A) JP-A-3-124099 (JP, A) JP-A-2-12996 (JP, A) JP-A-1-135139 (JP, A) JP-A-2-196500 (JP, A) JP-A-2-174199 (JP, A) JP-A-4-62900 (JP, A) JP-A-4-169866 (JP, A) JP-A-2-228097 (JP, A) JP-A-4-53198 (JP, A) JP-A-5-77782 (JP, A) JP-A-5-77781 (JP, A) JP-A-5-77783 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01Q 17 / 00 H05K 9/00

Claims (4)

(57) [Claims] 1. A tapered anechoic chamber in which a wall of a transmitting unit and a receiving unit is covered with a radio wave absorber, and the transmitting unit and the receiving unit are connected by a tapered waveguide. An electromagnetic wave anechoic chamber, wherein a surface is constituted by a ground equivalent floor, and at least a part of a ceiling surface and a side wall surface of the waveguide is constituted by a ferrite electromagnetic wave absorber. 2. The floor of the transmitter, the waveguide, and the receiver has a flat structure with respect to the ground, and the floor of the receiver and the waveguide is formed by combining a ferrite tile and a conductive film. 2. The anechoic chamber according to claim 1, wherein the anechoic chamber is constituted by a ground equivalent floor. 3. The radio wave absorber disposed on the wall surfaces of the transmission unit and the reception unit is a composite radio wave absorber made of a combination of a ferrite tile and a resistance loss material. The anechoic chamber described. 4. The anechoic chamber according to claim 1, wherein an independent broadband antenna for transmission is arranged in the transmission unit.