Method and apparatus for controlling electromagnetic radiation emissions from electronic device enclosures

• US 20030221849A1
• Filed: 05/06/2003
• Published: 12/04/2003
• Est. Priority Date: 06/15/2001
• Status: Active Grant

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: David Dickey, David Pommerenke, James J. Deblanc, Victoria Tsang
• Inventors: Pommerenke, David, Dickey, David, DeBlanc, James J., Tsang, Victoria
• Granted Patent: US 6,825,411 B2
• Time in Patent Office: Days
• US Class Current: 174/35GC
• CPC Class Codes: H05K 9/0015 Gaskets or seals

Abstract

A method and apparatus is provided for reducing electromagnetic radiation emissions. The method and apparatus of the present invention also reduce or prevent electromagnetic radiation generated by sources outside of a system assembly from interfering with and adversely affecting electrical circuits in the assembly. An electromagnetic compatibility (EMC) solution uses a lossy element, and/or an element comprised of a combination of lossy and conductive material.

Claims

1. An assembly, comprising:

an enclosure having opposing side walls, a top, and a bottom;

a module configured to integrate with the enclosure, the module having opposing side walls, a top, and a bottom, that substantially surround electrical circuitry, wherein the module is partially surrounded by the enclosure such that a gap is formed between an outer surface of the module and an inner surface of the enclosure along an opening of the enclosure formed by adjacent edges of the opposing side walls, the top, and the bottom of the enclosure;

a low-impedance contact disposed between an outer surface of the module and an inner surface of the enclosure, wherein the low-impedance contact electrically couples the module to the enclosure; and

a lossy element disposed in the gap.

2. The assembly of claim 1, wherein a portion of the module and the enclosure that substantially overlap the low-impedance contact are manufactured with materials selected from the group consisting of metal, conductive plastic, or plastic with a thin metalization layer.

3. The assembly of claim 1, wherein the low-impedance contact has a length that is at least one-fourth the wavelength of a transition frequency, wherein electromagnetic energy of frequencies approximately below the transition frequency are prevented from traversing the gap via conventional electrical conduction.

4. The assembly of claim 1, wherein the lossy element is fixed to an outer surface of the module.

5. The assembly of claim 1, wherein the lossy element is fixed to an inner surface of the enclosure.

6. The assembly of claim 1, wherein the lossy element has a depth that approximates the length of the low-impedance contact.

7. The assembly of claim 1, wherein the lossy element comprises a material that both absorbs and reflects high-frequency electromagnetic energy.

8. The assembly of claim 1, wherein the lossy element comprises a sheet manufactured from a dielectrically-lossy polyethylene.

9. The assembly of claim 1, wherein the lossy element comprises a pad manufactured from a dielectrically-lossy polyethylene.

10. The assembly of claim 1, wherein the enclosure further comprises a transverse internal wall configured with at least one opening.

11. The assembly of claim 1, wherein the lossy material comprises a dielectrically-lossy polyethylene.

12. The assembly of claim 2, wherein the low-impedance contact has a length that is at least one-fourth the wavelength of a transition frequency, wherein electromagnetic energy of frequencies approximately above the transition frequency are prevented from traversing the gap by being reflected and attenuated by the lossy material.

13. The assembly of claim 7, wherein the lossy element comprises a material that is electrically conductive.

14. The assembly of claim 10, wherein the transverse internal wall comprises a layer of lossy material on the surface adjacent to the module.

15. The assembly of claim 11, wherein the lossy material comprises a material selected from the group consisting of conductive polyethylene, conductive rubber and magnetically-filled silicon rubber.

16. The assembly of claim 13, wherein the lossy element comprises a gasket.

17. An assembly, comprising:

means for preventing electromagnetic energy of a frequency approximately below a transition frequency from traversing a gap formed by the outer surface of a module and the inner surface of an enclosure; and

means for preventing electromagnetic energy of a frequency approximately above a transition frequency from traversing the gap.

18. The assembly of claim 17, wherein the means for preventing electromagnetic energy of a frequency approximately below the transition frequency from traversing the gap comprises an electrically conductive path from the module to the enclosure.

19. The assembly of claim 18, wherein the means for preventing electromagnetic energy of a frequency approximately above the transition frequency from traversing the gap comprises disposing at least one lossy element in the gap.

20. The assembly of claim 17, wherein the electrically conductive path from the module to the enclosure comprises a low-impedance contact that substantially overlaps an electrically conductive portion of both the module and the enclosure.

21. The assembly of claim 19, wherein the lossy element comprises a material selected from the group consisting of conductive polyethylene, conductive rubber and magnetically-filled silicon rubber.

22. The assembly of claim 20, wherein the low-impedance contact has a length that is at least one-fourth the wavelength of the transition frequency.

23. A method for controlling electromagnetic interference, comprising the steps of:

providing a low-impedance contact to electrically couple an electrically conductive assembly enclosure to an electrically conductive module, the enclosure partially surrounding the module, wherein the module substantially surrounds electromagnetic emitting circuits; and

introducing at least one lossy element in a channel formed by the inner surfaces of the assembly enclosure, the outer surfaces of the module, and the low-impedance contact.

24. The method of claim 23, wherein the low-impedance contact has a length that is at least one-fourth the wavelength of a transition frequency, wherein electromagnetic energy of frequencies approximately below the transition frequency are prevented from traversing the channel via conventional electrical conduction.

25. The method of claim 23, wherein the low-impedance contact has a length that is at least one-fourth the wavelength of a transition frequency, wherein electromagnetic energy of frequencies approximately above the transition frequency are prevented from traversing the channel by being reflected and attenuated by the lossy material.

26. An assembly, comprising:

an enclosure having opposing side walls, a top, and a bottom that substantially surround electrical circuitry, wherein the enclosure comprises an opening formed by adjacent edges of the enclosure; and

a composite material that is dielectrically-lossy and electrically conductive disposed in the opening.

27. The assembly of claim 26, wherein a portion of the enclosure that substantially overlaps the composite material is manufactured with materials selected from the group consisting of metal, conductive plastic, or plastic with a thin metalization layer.

28. The assembly of claim 26, wherein the lossy element comprises a material that both absorbs and reflects high-frequency electromagnetic energy.

29. The assembly of claim 28, wherein the lossy material is selected from the group consisting of conductive polyethylene, conductive rubber and magnetically-filled silicon rubber.

30. The assembly of claim 28, wherein the lossy element comprises a gasket.