Electromagnetic wave absorber

• US 7,804,439 B2
• Filed: 03/01/2004
• Issued: 09/28/2010
• Est. Priority Date: 03/01/2004
• Status: Expired due to Fees

• Current Assignee: Nitta Corporation
• Original Assignee: Nitta Corporation
• Inventors: Yoshida, Takahiko, Sato, Shinichi, Kiyohara, Yoshiharu, Go, Haruhide, Maenaka, Mamoru, Maezawa, Makoto
• Primary Examiner(s): Tarcza; Thomas H
• Assistant Examiner(s): GALT, CASSI J
• Application Number:
  US10/591,539
• Publication Number:
  US 20080084259A1
• Time in Patent Office: 2,402 Days
• Field of Search: 342/1, 342/4, 342/2, 342/3
• US Class Current: 342/4
• CPC Class Codes: H01Q 17/002 using short elongated elements as dissipative material, e.g. metallic threads or flake-like particles
• CPC Class Codes: H05K 9/0003 Shielded walls, floors, ceilings, e.g. wallpaper, wall panel, electro-conductive plaster, concrete, cement, mortar

Abstract

A thin, light and soft electromagnetic wave absorber is disclosed exhibiting an excellent workability. The first conductor element group of a first conductor element layer consists of aligned cross conductor elements and square conductor elements in regions surrounded by cross conductor elements. A radio wave incident from the first conductor element layer side is received by each element, internally subjected to multiple reflection and then absorbed by a first loss material layer. Since the first conductor element group is realized by the cross conductor elements and the square conductor elements, receiving effect is enhanced and the radio wave can be collected with a high collection efficiency.

Claims

1. An electromagnetic wave absorber, comprising:

an element receiving layer provided with a first type and a second type of conductor elements having resonant frequencies, to perform the same or different receiving operations, each of the element receiving layer conductor elements being disposed on a surface of the element receiving layer on a side from an incoming direction of electromagnetic waves, to be spaced away from each other; and

a loss material for causing energy loss to electromagnetic waves proximate to the element receiving layer,

wherein the first type of the conductor elements are cross conductor elements that are cross-shaped planes, and the second type of the conductor elements are quadrangular conductor elements that are quadrangle-shaped planes,

the cross conductor elements and the quadrangular conductor elements are arranged in a direction intersecting the incoming direction of electromagnetic waves,

the cross conductor elements are arranged in a regular manner,

the quadrangular conductor elements are arranged in areas surrounded by the cross conductor elements so as to fill in the areas,

each corner of the quadrangular conductor elements is arc shaped, the arc shape having a radius of curvature corresponding to the resonant frequencies, and

at least each concave corner of the cross conductor elements is arc shaped, the arc shape having a radius of curvature corresponding to the resonant frequencies.

2. The electromagnetic wave absorber of claim 1, wherein the conductor elements are arranged also in the incoming direction of electromagnetic waves, in addition to the direction intersecting the incoming direction of electromagnetic waves.

3. The electromagnetic wave absorber of claim 1, further comprising electromagnetic wave reflecting means for reflecting electromagnetic waves, disposed on a side opposite to a side from an incoming direction of electromagnetic waves with respect to the element receiving means.

4. The electromagnetic wave absorber of claim 1, wherein a conductivity of the conductor elements is at least 10,000 S/m.

5. The electromagnetic wave absorber of claim 1, wherein the conductor elements are made of metal.

6. The electromagnetic wave absorber of claim 1, wherein the electromagnetic wave absorber is formed in the shape of a sheet having a thickness of at least 0.1 mm and at most 4 mm.

7. The electromagnetic wave absorber of claim 1, wherein the electromagnetic wave absorber is formed in the shape of a sheet having a mass per unit area of at least 0.2 kg/m² and at most 5 kg/m².

8. The electromagnetic wave absorber of claim 1, wherein the cross conductor elements are arranged such that radially extending portions are faced with each other, and the quadrangular elements are formed in a shape corresponding to the areas surrounded by the cross conductor elements.

9. The electromagnetic wave absorber of claim 1, wherein a size of a spacing between the conductor elements is determined so as to lower the resonant frequencies of the conductor elements.

10. The electromagnetic wave absorber of claim 1, wherein a property value of the loss material is determined based on the resonant frequencies of the conductor elements so as to improve an absorption efficiency of electromagnetic waves with a same frequency as the resonant frequencies.

11. The electromagnetic wave absorber of claim 1, wherein the electromagnetic wave absorber is made flame resistant, quasi-incombustibile, or incombustibile.

12. The electromagnetic wave absorber of claim 2, further comprising electromagnetic wave reflecting means for reflecting electromagnetic waves, disposed on a side opposite to a side from an incoming direction of electromagnetic waves with respect to the element receiving means.

13. The electromagnetic wave absorber of claim 2, wherein a conductivity of the conductor elements is at least 10,000 S/m.

14. The electromagnetic wave absorber of claim 2, wherein a property value of the loss material is determined based on the resonant frequencies of the conductor elements so as to improve an absorption efficiency of electromagnetic waves with a same frequency as the resonant frequencies.

15. The electromagnetic wave absorber of claim 2, wherein the electromagnetic wave absorber is made flame resistant, quasi-incombustibile, or incombustibile.

18. The electromagnetic wave absorber of claim 1, the element receiving layer further comprising a third type of conductor element having a resonant frequency to perform the same or different receiving operation, spaced away from the first type and second type of conductor elements.

19. The electromagnetic wave absorber of claim 1, wherein all corners are arc-shaped, with a radius of curvature corresponding to the resonant frequencies.

16. A method of absorbing electromagnetic waves, the method comprising:

using an electromagnetic wave absorber to absorb electromagnetic waves, the electromagnetic wave absorber including,

an element receiving layer provided with a first type and a second type of conductor elements having resonant frequencies, to perform the same or different receiving operations, the element receiving layer conductor elements being disposed on a surface of the element receiving layer on a side from an incoming direction of electromagnetic waves, to be spaced away from each other, and

a loss material for causing energy loss to electromagnetic waves proximate to the element receiving layer,

wherein the first type of the conductor elements are cross conductor elements that are cross-shaped planes, and the second type of the conductor elements are quadrangular conductor elements that are quadrangle-shaped planes,

the cross conductor elements and the quadrangular conductor elements are arranged in a direction intersecting the incoming direction of electromagnetic waves,

the cross conductor elements are arranged in a regular manner,

the quadrangular conductor elements are arranged in areas surrounded by the cross conductor elements so as to fill in the areas,

each corner of the quadrangular conductor elements is arc shaped, the arc shape having a radius of curvature corresponding to the resonant frequencies, and

at least each concave corner of the cross conductor elements is arc shaped, the arc shape having a radius of curvature corresponding to the resonant frequencies.

17. The method of absorbing electromagnetic waves of claim 16, wherein the conductor elements are also arranged in the incoming direction of electromagnetic waves, in addition to the direction intersecting the incoming direction of electromagnetic waves.