JPH0785517B2 - Anechoic chamber - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement of an anechoic chamber used for conducting characteristic tests of various electric devices indoors.

(Prior Art) Electromagnetic noise of electrical equipment is measured at an open site of a predetermined size without buildings that reflect radio waves in the surroundings, but in an urban area such an open site is secured. Is difficult. For this reason, in Japan, an anechoic chamber capable of obtaining a radio wave space similar to that of an open site in a factory or the like has become widespread.

The large anechoic chamber has a large pyramid-shaped absorber attached to the side wall and ceiling of the room so as to prevent reflection of electromagnetic waves from the wall surface. However, recently, small anechoic chambers with a limited frequency range are rapidly becoming popular.

Such a small anechoic chamber is, for example, as shown in Japanese Patent Laid-Open No. 64-16038, in which a tile-shaped ferrite absorber is attached as a radio wave absorber to the side wall, the ceiling and, in some cases, the floor surface. , The ferrite absorber is used only in the operating range (frequency range where the absorption rate is good). However, since the anechoic chamber has a box shape,
As shown in the figure, it is inevitable that the electromagnetic wave radiated from the transmission source (3) is primarily reflected on the wall surface or the ceiling surface and is incident on the reception antenna (4). Since the ferrite absorber has a characteristic that the absorption rate of electromagnetic waves that obliquely enter is extremely poor due to its operating principle, absorption of primary reflected waves can hardly be expected, and the correlation with open sites deteriorates and the ferrite absorption There is a problem that the function of the anechoic chamber is not exerted even in the operating range of the body.

(Problems to be Solved by the Invention) The present invention solves such conventional problems and provides an anechoic chamber capable of sufficiently absorbing a primary reflected wave using a ferrite absorber. It was completed for the purpose.

(Means for Solving the Problems) The present invention made to solve the above problems is to provide a receiving antenna from a transmitting source on at least one wall surface of a side wall or a ceiling of an anechoic chamber having a ferrite absorber attached to the inner surface. The structure is characterized in that an inclined surface inclined toward the transmission source is formed at a position where the primary reflection of the radio wave occurs, and the electric wave causing the primary reflection is vertically incident on the ferrite absorber on the surface of the inclined surface. It is one.

Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

(Embodiment) In the first embodiment shown in FIG. 1, (1) is an anechoic chamber, and a tile-shaped ferrite absorber is attached to the side wall (2) and the inner surface of the ceiling. (3) is a transmission source such as test equipment, and (4) is a receiving antenna. In the present invention, such a side wall (2) of the anechoic chamber (1).
And an inclined surface (5) inclined toward the transmission source (3) is provided at a position where primary reflection from the transmission source (3) to the reception antenna (4) occurs on one or both wall surfaces of the ceiling. . The ferrite absorber (6) is also attached to the surface of the inclined surface (5).

In the second embodiment shown in FIG. 2, the shape of the back surface of the inclined surface (5) is slightly different, and in the third embodiment shown in FIG. 3, the width of the back surface of the inclined surface (5) is continuous. It is formed in the narrow part. Further, such an inclined surface (5) may be movable in the longitudinal direction of the anechoic chamber.

In any of the examples, the primary reflected wave is vertically incident on the ferrite absorber (6) on the surface of the inclined surface (5), and the primary reflected wave is sufficiently absorbed and attenuated. Since the inclined surface (5) is for absorbing the primary reflected wave as described above, the inclined surface (5) is connected inside the maximum dimension line of the transmission source (3) and the maximum dimension line of the reception antenna (4). ) Need not be entered. This is to ensure that the direct wave from the transmission source (3) to the reception antenna (4) is transmitted to the reception antenna (4). As long as this condition is satisfied, the dimensions of the inclined surface (5) are the same as those of the transmission source (3).
It is desirable to set the projected size to approximately. This is to ensure that the primary reflected wave hits the inclined surface (5) regardless of the position of the noise source of the transmission source (3).

(Operation) In the anechoic chamber of the present invention thus configured, since the inclined surface (5) is provided at the position where the primary reflection from the transmission source (3) to the receiving antenna (4) occurs, the transmission source (3) The electric wave radiated in this direction is incident vertically on the ferrite absorber (6) of the inclined surface (5), and is reliably absorbed and attenuated. Therefore, according to the present invention, the influence of the primary reflected wave can be avoided and the correlation with the open site can be enhanced.

If the inclined surface (5) is movable as described above, the inclined surface (5) can be highly correlated with the open site even when the positions of the transmission source (3) and the receiving antenna (4) are changed. 5) can be adjusted, and the function as an anechoic chamber can be dramatically improved.

(Effects of the Invention) As is clear from the above description, the present invention can sufficiently absorb the primary reflected wave and enhance the correlation with the open site, even though it is an anechoic chamber using a ferrite absorber. The anechoic chamber eliminates the conventional problems and contributes greatly to the industrial development.

[Brief description of drawings]

1, 2, and 3 are horizontal sectional views showing an embodiment of the present invention, and FIG. 4 is a horizontal sectional view showing a conventional anechoic chamber. (2): side wall, (3): transmission source, (4): reception antenna, (5): inclined surface, (6): ferrite absorber.

Claims (2)

[Claims] 1. A position at which primary reflection of radio waves from a transmission source (3) to a reception antenna (4) occurs on at least one of the side wall (2) and the ceiling wall surface of an anechoic chamber having a ferrite absorber attached to its inner surface. The inclined surface (5) inclined toward the transmission source (3) is formed so that the radio wave causing the primary reflection is vertically incident on the ferrite absorber (6) on the surface of the inclined surface (5). A characteristic anechoic chamber. 2. The anechoic chamber according to claim 1, wherein the position of the inclined surface (5) is movable in the longitudinal direction of the anechoic chamber.