Apparatus for shielding electromagnetic radiation

• US 5,045,638 A
• Filed: 05/18/1989
• Issued: 09/03/1991
• Est. Priority Date: 05/18/1988
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Mining & Cement Co. Ltd. (Mitsubishi Materials Corporation)
• Original Assignee: Mitsubishi Mining & Cement Co. Ltd. (Mitsubishi Materials Corporation)
• Inventors: Wada, Hideaki, Ono, Mikiya, Kitahara, Naoto, Koshimura, Masami
• Primary Examiner(s): Picard, Leo P.
• Assistant Examiner(s): Ledynh, Bot L.
• Application Number:
  US07/353,773
• Time in Patent Office: 838 Days
• Field of Search: 174/35 MS, 174/35 R, 174/36, 361/424, 264/104, 219/10.55 D, 219/10.55 R
• US Class Current: 174/377
• CPC Class Codes: G06F 1/182 with special features, e.g. for use in industrial environments; grounding or shielding against radio frequency interference [RFI] or electromagnetical interference [EMI]
• CPC Class Codes: H05K 9/0049 being metallic containers
• CPC Class Codes: H05K 9/0052 Shielding other than Faraday cages
• CPC Class Codes: H05K 9/0088 comprising a plurality of shielding layers; combining different shielding material structure

Abstract

This invention relates to an apparatus for shielding electromagnetic radiation which includes a casing made primarily of electromagnetic shielding material and an electromagnetic wave suppressor member having high permeability and/or permittivity. A method for using this apparatus also is described. The suppressor member has a high dielectric loss and/or high magnetic loss at a location close to the place in the casing where electromagnetic waves are less shielded, thereby reducing leakage of undesirable electromagnetic waves from the casing.

Claims

1. An apparatus for shielding electromagnetic radiation comprising:

a casing comprised of electromagnetic wave shielding material;

an electromagnetic wave suppressor member interior of the casing comprised of a material having at least one of high permeability and high permittivity at a high frequency and having electromagnetic loss; and

a circuit having said suppressor member positioned proximate thereto.

2. The apparatus of claim 1 wherein said suppressor member has both high permeability and high permittivity.

3. The apparatus of claim 1 wherein said suppressor member is positioned proximate a location at which electromagnetic waves are not sufficiently shielded by said casing.

4. The apparatus of claim 1 wherein said electromagnetic loss comprises at least one of magnetic loss and dielectric loss.

5. The apparatus of claim 1 wherein said suppressor member is comprised of particles of at least one of

ferrite, expressed by the chemical formula MOFe₂ O₃, where M comprises a metal, and

a dielectric material, which has a perovskite structure and is expressed by the chemical formula ABO₃, where A and B are metals.

6. An electronic device having a casing comprising:

electromagnetic wave shielding member;

an electromagnetic wave suppressor member interior the shielding member comprised of a material having at least one of high permeability and high permittivity at a high frequency and having electromagnetic loss; and

a circuit having said suppressor member positioned proximate thereto.

7. The device of claim 6 wherein said suppressor member has both high permeability and high permittivity.

8. The device of claim 6 wherein said suppressor member is positioned proximate a location at which electromagnetic waves are not sufficiently shielded by said casing.

9. The apparatus of claim 6 wherein said electromagnetic loss comprises at least one of magnetic loss and dielectric loss.

10. The device of claim 6 wherein said suppressor member is comprised of particles of at least one of

ferrite, expressed by the chemical formula MOFe₂ O₃, where M comprises a metal, and

a dielectric material, which has a perovskite structure and is expressed by the chemical formula ABO₃, where A and B are metals.