JPH0258799B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a radio anechoic chamber used for measuring radio waves emitted from a test object.

[Prior art]

Generally, when radio waves are measured in a normal room, there is a large error due to the influence of reflected radio waves from walls and floors.

For this reason, this type of experiment uses a so-called radio anechoic chamber in which the entire wall of the room is made of radio wave absorbers.

[Problems to be solved by this invention]

However, since conventional radio anechoic chambers are configured in a complete box shape, there are portions where the radio waves generated from the test specimen impinge obliquely rather than perpendicularly to the wall surface of the radio wave absorber.

Radio wave absorbers have extremely high radio wave absorption properties when radio waves strike vertically, but their absorption properties drop significantly when radio waves strike diagonally. Therefore, in a radio anechoic chamber in which a radio wave absorber is simply attached to the wall surface, it is impossible to completely absorb radio waves, and unnecessary reflected waves are generated, which adversely affects measurements.

Furthermore, installing radio wave absorbers on the entire wall surface of a radio anechoic chamber requires high construction costs because radio wave absorbers are expensive.

This invention was proposed in order to solve the above-mentioned conventional problems, and is a radio anechoic chamber that can completely absorb unnecessary radio waves generated from a test object when measuring radio waves and is inexpensive to construct. The purpose is to provide

[Means to solve the problem]

This invention uses a hemispherical anechoic chamber with an elliptical roof cross section.

The cross section of the roof is an elliptical hemisphere whose sum of distances from the two focal points on the floor follows a constant trajectory. An extension part protruding from the hemisphere is provided on one side of the extension line of the straight line connecting the two focal points. Place the radio wave test object on the focal point closest to the extension, and bury the radio wave absorber under the other focal point. Furthermore, a measurement antenna is installed within the extended portion, and a radio wave absorber is provided on the inner wall of the end portion of the expanded portion.

[Effect]

The radio waves emitted from the radio wave test object are reflected on the inner wall of the elliptical cross section and are absorbed by the other radio wave absorber under the focal point.

Radio waves that have entered the extension are measured by the antenna, and unnecessary radio waves are absorbed by the radio wave absorber on the back.

〔Example〕

Hereinafter, the present invention will be explained in detail based on an embodiment shown in the drawings.

In the figure, 1 is the roof of the anechoic chamber,
It is a hemisphere with an elliptical cross section in which the sum of the distances from the bifocal points F and F' on the floor 2 is constant. A copper-plated steel plate is laid on the floor 2, and this completely reflective surface allows radio waves to be accurately converged toward a focal point. As shown in FIG. 5, the roof part 1 is formed into a hemispherical shape by segments 3, 3 having an arcuate outer circumferential surface formed of fiber-reinforced plastic (FRP), and this outer circumference is made of copper foil. It is covered with 4. The segments 3, 3 are connected by reinforced plastic screws 5,
The copper foils 4, 4 on the outer periphery are connected by solder 6.

An extended portion 7 extending laterally from the roof portion 1 is formed on one side of the extension of the straight line connecting the bifocals F and F'. The roof portion 1' of the extension 7 extends radially around a focal point F close to the extension 7.

A radio wave absorber 8 is disposed in a spherical shape centered at F on the inner wall of the end portion of the extended portion 7 . The radio wave absorber 8 has a square pyramid shape.
There are multiple protruding pieces. As the radio wave absorber 8, a material such as carbon-impregnated urethane foam can be used. Furthermore, a measurement antenna 9 is installed within the extension section 7. A test specimen 10 for generating radio waves is placed on the focal point F, which is closer to the extension part 7, of the two focal points F and F'.

Under the other focal point F', a plurality of disc-shaped radio wave absorbers 11, in which the amount of carbon impregnated gradually increases toward the bottom, are stacked and buried in order to smoothly absorb radio waves. (“Radio wave penetration box”).

Next, the radio wave measurement work in the radio anechoic chamber as described above will be explained.

The radio waves emitted from the test object 10 hit the inner circumferential surface of the roof section 2, and due to the elliptical nature, they reverberate toward the other focal point F'. A radio wave absorber 11 is buried below the focal point F', which absorbs the radio waves and prevents them from reverberating any further.

The radio waves that have entered the extended portion 7 hit the measurement antenna 9 and are measured. Unnecessary radio waves that do not hit the measurement antenna 9 are absorbed by the radio wave absorber 8 on the back and do not echo.

〔Effect of the invention〕

The present invention has the above configuration and can obtain the following effects.

(b) Since the radio waves emitted from the test specimen hit the inner surface of the hemispherical roof with an elliptical cross section and reverberate toward the radio wave absorber, there is no need to install a radio wave absorber over the entire roof, reducing construction costs. It can be made cheap.

(b) The radio waves that have entered the extension section hit the measurement antenna without echoing, making accurate measurements possible.

[Brief explanation of drawings]

Figure 1 is a plan view of the radio anechoic chamber, Figures 2 and 3 are cross-sectional views taken along lines - and - in Figure 1, respectively.
FIG. 4 is a perspective view of the radio wave absorber, and FIG. 5 is a perspective view showing the structure of a part of the roof. 1... Roof, 2... Floor, 3... Segment,
7... Extension portion, 8... Radio wave absorber, 9... Measurement antenna, 10... Test object, 11... Radio wave absorber ("radio wave penetration chamber").

Claims (1)

[Claims] 1 A hemisphere in which the cross section of the roof forms an ellipse in which the sum of the distances from two focal points on the floor traces a constant trajectory, and an extension protruding from said hemisphere on one side on an extension of a straight line connecting these two focal points. a section, and place a radio wave test object on the focal point closer to the expansion section of the two focal points,
In addition to burying a radio wave absorber under the other focal point,
A radio anechoic chamber characterized in that a measurement antenna is installed inside the extension part, and a radio wave absorber is arranged on the inner wall at the end of the extension part.