JPH0640600B2 - Radio wave absorption structure - Google Patents

Description

TECHNICAL FIELD The present invention relates to a radio wave absorbing structure.

(Problems to be Solved by Related Art and Invention) As a conventional electromagnetic wave absorber, for example, a rubber sheet which is a mixture of ferrite and rubber is known. However, this rubber sheet has a drawback that it is heavy and due to this, it is unreliable when attached by an ordinary adhesive and it is difficult to carry out the work.

As a remedy for this shortcoming, the conductor surface has approximately λg / 4
Proposal of a wave absorber in which a foam having a thickness of (λg is the free space wavelength of the operating center frequency) is placed, and a carbon coating film with a characteristic impedance of approximately 377Ω, which is the characteristic impedance of free space, is provided on the surface of the foam. Has been done. However, there is a drawback that the characteristic impedance changes greatly with respect to the change in the thickness of the applied resistance film, and the manufacturing process must be strictly controlled.

In order to improve this drawback, the present applicant has previously filed a patent application
In 57-92964 (Japanese Patent Laid-Open No. 58-210696), it is an object to provide an electromagnetic wave absorber that is easy to manufacture, lightweight, excellent in workability, and excellent in impedance matching. We have proposed an electromagnetic wave absorber in which a resistive film arranged above is arranged parallel to the conductor surface at a distance of λg / 4 or less.

The applicant of the present invention has further developed the electromagnetic wave absorber described in Japanese Patent Application No. 57-92964, which is disclosed in Japanese Patent Application No. 58-90068 (Japanese Patent Application Laid-Open No. 59-215).
798) and Japanese Patent Application No. 58-228573.

In the electromagnetic wave absorber of Japanese Patent Application No. 58-90068, a conductive dielectric material or a resistance cloth body woven of conductive fibers and synthetic fibers is provided on the surface opposite to the foamed dielectric material having a conductor provided on one surface. In the radio wave absorber, the distance between the conductive fibers is λg / 4 (λ
g is equal to or less than the free space wavelength of the operation center frequency).

On the other hand, in the radio wave absorber of Japanese Patent Application No. 58-228573, a conductive cloth is provided on the surface opposite to the one surface of a dielectric material having a conductor provided on the one surface, and a resistance cloth body woven of conductive fibers and synthetic fibers is provided. In the electromagnetic wave absorber, the conductive fiber has a DC resistance of 30
It is characterized by being KΩ / m or more.

Japanese Patent Publication No. 55-35319 also discloses a radio wave absorber in which a sheet-shaped carbon fiber molding layer is provided on the front surface of a dielectric and a conductor is provided on the back surface.

However, each of the above-described radio wave absorbers has a soft resistor on the surface, and therefore has a problem that the surface is damaged when it is mounted on a building or the like, and the mounting work is difficult. Also, since the fibrous material layer has a single-layer structure,
If this is made thin, the mechanical strength cannot be maintained, and the thickness of the resistor is limited, making it difficult to match high frequency radio waves.

The present invention solves the above-mentioned problems of the prior art, and an object of the present invention is to provide a radio wave absorbing structure that is excellent in workability and can be matched well to radio waves of high frequency. .

(Means for Solving the Problems) According to the present invention, a radio wave absorption structure includes a dielectric, a rear plate provided on one surface of the dielectric and having reflectivity for electromagnetic waves, and the dielectric. Of the electromagnetic wave absorber, which is provided on the other surface of the electromagnetic wave absorber, and which is located on the front surface side and includes a reinforcing plate having a laminated structure including at least a non-conductive reinforcing plate and a resistance film, and the electromagnetic wave absorber as an attached body. F for mounting
It is composed of RP formwork.

(Operation) The electromagnetic wave incident on the radio wave absorption structure is reflected by the rear plate, and the standing wave formed by the reflected wave and the incident electromagnetic wave is the thermal energy in the resistance film included in the reinforcing plate. Is converted into a radio wave absorption effect. The electromagnetic wave arrival side surface of this electromagnetic wave absorbing structure is made up of a reinforcing plate having a laminated structure including at least a non-conductive reinforcing plate and a resistive film located on the surface side, so that not only the mounting work is facilitated but also the strength is improved. And, the directional resistance is improved. Moreover, since the reinforcing plate has a laminated structure including at least a non-conductive reinforcing plate and a resistance film, the thickness of the resistance film can be significantly reduced, which is excellent in matching well with high frequency radio waves. It is possible to obtain radio wave absorption characteristics.

Embodiment An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a perspective view showing a radio wave absorbing structure 1 of this embodiment. The radio wave absorbing structure 1 is composed of a radio wave absorbing body 2 and a FRP (glass fiber reinforced plastic) mold 3.
The radio wave absorber 2 includes a dielectric 4, a rear plate 5 and a reinforcing plate 6. A reinforcing plate 6 is provided on the surface of the dielectric 4 on the electromagnetic wave arrival side. The reinforcing plate 6 includes a resistance film 7. A rear plate 5 having a reflectivity for electromagnetic waves is provided on the surface opposite to the dielectric 4. The distance between the rear plate 5 and the resistance film 7 should be considered in consideration of the thickness of each of the reinforcing plate 5 and the rear plate 4, the wavelength being shortened by the dielectric constant E ′, and the partial reflection of electromagnetic waves. Then, it is preferably set within a range of ± 40% of λg / 4 (λg is a free space wavelength of the operation center frequency). In some cases, the side surfaces of the radio wave absorber 2 and the FRP frame 3 are caulked. In this example, the mold 3 has a crank-shaped cross section as shown in the drawing, but various shapes can be used according to the situation of the mounting location. In this example, since the electromagnetic wave absorber 2 is fixed without using an adhesive, the mold 3 has a structure in which the electromagnetic wave absorber 2 can be fixed so as to be clamped between the attached body. The material of the mold 3 is FRP in order to prevent reflection of electromagnetic waves.

As the dielectric 4, a material such as expanded polystyrene or expanded polyethylene is used to reduce the weight of the radio wave absorption structure 1.

The material and the form (foil shape, plate shape, etc.) of the rear plate 5 are not particularly limited as long as the rear plate 5 has a property of reflecting electromagnetic waves, but in order to further improve the strength of the electromagnetic wave absorbing structure 1, a reinforcing member is used. It is preferable that Examples of the reinforcing body include a metal plate such as aluminum and steel, a conductive FRP plate, a plate formed by laminating an FRP plate and a conductive plate, a conductive hard vinyl chloride sheet, and a hard vinyl chloride sheet. A plate in which a conductive plate and a conductive plate are laminated is used. In order to impart conductivity to the FRP plate or the hard vinyl chloride sheet, for example, a conductive material is kneaded.

As the reinforcing plate 6, for example, one in which a resistance film 7 is sandwiched between two FRP plates 8 and 9 and laminated as shown in the drawing is used. A hard vinyl chloride sheet may be used instead of the FRP plate. As the resistance film 7, a resistance cloth woven of conductive fibers or conductive fibers and synthetic fibers, a resistance cloth woven of silicon carbide fibers such as SiC or carbon fibers and synthetic fibers, a resistance film in which carbon is applied to the surface of plastic,
Alternatively, a non-woven fabric resistance film formed by impregnating or adhering a resistance paint such as carbon or silicon carbide on a short fiber material can be used. As the conductive fiber, for example, a conductive layer of copper sulfide (CuS) is adhered and formed on the surface of acrylic fiber by a dyeing technique, and copper sulfide (CuS) is formed on the surface of nylon fiber.
S) or other conductive layer adhered and formed,
Various ones can be used. As the weaving method, for example, each fiber may be woven in a lattice pattern at predetermined intervals, or other various weaving methods may be used. The resistance value of the resistance film 7 is preferably about 377Ω characteristic impedance in the free space in order to achieve impedance matching with the free space.
If the FRP plate 9 is too thick, reflection will increase and the characteristics of the structure will be deteriorated. Therefore, the thickness of the FRP plate 9 is preferably 6 mm or less.

To mount the electromagnetic wave absorbing structure 1 of this embodiment on a body to be mounted (not shown), for example, a hole or a screw hole 10 formed in the mold 3 is used by a well-known method such as screwing.
At this time, the electromagnetic wave arrival side portion 3 ′ of the mold 3 is placed in the electromagnetic wave absorber 2
Acts to push into the attached body, and the electromagnetic wave absorber 2 is fixed.

2 and 3 show the relationship between the thickness (d) and the reflection amount and the frequency and the reflection amount when the thickness (d) of the FRP plate 9 of the reinforcing plate 6 in the embodiment having the above-mentioned configuration is changed. It is a figure which shows a relationship. The distance between both plate-shaped parts was 16 mm. As is clear from these figures, the structure of this example has excellent electromagnetic wave absorption characteristics.

FIG. 4 is a perspective view showing another structural example of the present invention. In the figure, the same elements as those in FIG. 1 are designated by the same reference numerals. In this example, the rear plate 5 is extended and formed as shown in the drawing, and the mounting portion 11 is provided integrally with the rear plate 5. The radio wave absorbing structure 1'is attached to the attached body by using the attaching portion 11 by a well-known method such as screwing. The holes or screw holes 10 of the mold 3 are for fixing the dielectric 4 and the reinforcing plate 6 to the rear plate 5.

FIG. 5 is a perspective view showing still another configuration example of the present invention. In the figure, the same elements as those in FIG. 1 are designated by the same reference numerals. In this example, the C-shaped steel plate 12 is used to attach the electromagnetic wave absorbing structure 1 ″ to the attached body.
The mold 3 has a shape as shown in the drawing, and the FRP mold 3 is fixed to the C-shaped steel plate 12 by using a hole or screw hole 13 by a well-known method such as screwing. By this fixing, the radio wave absorber 2 is sandwiched and fixed between the surface of the C-shaped steel plate 12 on the radio wave arrival side and the front portion 3 ′ of the FRP frame 3.
The C-shaped steel plate 12 is attached to the attached body using the holes or the screw holes 14.

(Effects of the Invention) As described in detail above, according to the present invention, a reinforcing plate having a laminated structure including at least a non-conductive reinforcing plate located on the surface side and a resistance film is provided on one surface of a dielectric. Therefore, the incoming surface of the radio wave is protected by the strengthening plate, which not only facilitates the mounting work when mounting on a building or the like, but also improves the strength and directional resistance. Moreover, since the reinforcing plate has a laminated structure including at least a non-conductive reinforcing plate and a resistance film, the thickness of the resistance film can be significantly reduced, which is excellent in matching well with high frequency radio waves. It is possible to easily provide a radio wave absorption structure having radio wave absorption characteristics.

[Brief description of drawings]

FIG. 1 is a perspective view showing the construction of a radio wave absorbing structure of an embodiment of the present invention, and FIG. 2 is a view when the thickness of an electromagnetic wave arrival side FRP plate constituting a reinforcing plate in the above embodiment is changed. FIG. 3 is a diagram showing the relationship between the thickness and the reflection amount, FIG. 3 is a diagram showing the frequency dependence of the reflection amount of the embodiment, and FIG. 4 is a perspective view showing another configuration example of the radio wave absorbing structure according to the present invention. FIG. 5 is a perspective view showing still another configuration example of the radio wave absorbing structure according to the present invention. 1 ... Electromagnetic wave absorption structure, 2 ... Electromagnetic wave absorber 3 ... FRP frame, 4 ... Dielectric material 5 ... Rear plate, 6 ... Reinforcing plate 7 ... Resistive film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenichi Ichihara 1-13-1 Nihonbashi, Chuo-ku, Tokyo, TDK Corporation (56) References JP-A-58-84499 (JP, A) JP-B-56 -35319 (JP, B2)

Claims (11)

[Claims] 1. A dielectric material, a rear plate provided on one surface of the dielectric material and having reflectivity for electromagnetic waves, and a non-contact material provided on the other surface of the dielectric material and located on the front surface side. A radio wave absorber including a reinforcing plate having a laminated structure including at least a conductive reinforcing plate and a resistance film, and an FRP frame for attaching the radio wave absorber to a mounted body. Radio wave absorption structure. 2. The distance between the resistance film and the rear plate is 0.6 ×.
The electromagnetic wave absorbing structure according to claim 1, wherein λg / 4 to 1.4 × λg / 4 (λg is a free space wavelength of an operation center frequency). 3. The reinforcing plate is formed by laminating the resistive film between two FRP plates or a hard vinyl chloride sheet, thereby forming a laminated structure. The described electromagnetic wave absorption structure. 4. The resistance film is made of a conductive cloth or a resistance cloth made by weaving a conductive fiber and a synthetic fiber, and any one of claims 1 to 3 is claimed. The electromagnetic wave absorbing structure according to item 1. 5. The resistance film is composed of a resistance cloth formed by weaving silicon carbide fiber such as SiC or carbon fiber and synthetic fiber, and the resistance film is formed.
The electromagnetic wave absorbing structure according to any one of items. 6. The resistance film is formed by coating a resistance paint such as carbon or silicon carbide on the surface of a plastic, according to any one of claims 1 to 3. The electromagnetic wave absorbing structure according to item 1. 7. The non-woven fabric formed by impregnating or adhering a resistance coating material such as carbon or silicon carbide on a short fiber material as the resistance film. ~ The electromagnetic wave absorbing structure according to any one of the third item. 8. The electromagnetic wave absorbing structure according to claim 1, wherein the rear plate is composed of a reinforcing body. 9. The electromagnetic wave absorbing structure according to claim 8, wherein the reinforcing body is made of metal. 10. The electromagnetic wave absorbing structure according to claim 8, wherein the reinforcing body is a conductive FRP or hard vinyl chloride. 11. The electromagnetic wave absorbing structure according to claim 8, wherein the reinforcing body is formed by laminating a FRP plate or a hard vinyl chloride sheet and a conductive plate. .