Lossy coating for reducing electromagnetic emissions

• US 20040173368A1
• Filed: 03/07/2003
• Published: 09/09/2004
• Est. Priority Date: 03/07/2003
• Status: Active Grant

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Dickson, Andrew H.
• Granted Patent: US 6,982,378 B2
• Time in Patent Office: Days
• US Class Current: 174/35C
• CPC Class Codes: H01B 11/1083 the coating containing magnetic material
• CPC Class Codes: H01B 9/027 composed of semi-conducting layers

Abstract

An EMI reduction system comprises a conductor and a lossy coating encasing the conductor and comprising one or more lossy layers. The one or more lossy layers further comprise a binder and a lossy material mixed into the binder. The lossy material is selected to attenuate electromagnetic interference frequencies in a narrow or moderate band.

Claims

1. An apparatus comprising:

a conductor; and

a lossy coating encasing the conductor and comprising one or more lossy layers,

the one or more lossy layers further comprising;

a binder; and

a lossy material mixed into the binder, the lossy material being selected to attenuate electromagnetic interference frequencies in a narrow or moderate band.

2. An apparatus according to claim 1 further comprising:

a lossy material mixed into the binder that is controlled in composition and in concentration within the binder to attenuate frequency within a predetermined frequency band.

3. An apparatus according to claim 1 further comprising:

a plurality of lossy layers in the lossy coating, individual lossy layers of the plurality of lossy layers having different compositions selected to attenuate frequencies in multiple frequency bands.

4. An apparatus according to claim 1 further comprising:

a plurality of lossy layers in the lossy coating, individual lossy layers of the plurality of lossy layers having different lossy materials or different combinations of lossy materials, and different concentrations of lossy materials within the elastomeric binder matrix to control attenuation of frequencies in multiple frequency bands.

5. An apparatus according to claim 1 further comprising:

a braid shield encasing the conductor and forming a shield layer.

6. An apparatus according to claim 1 wherein:

the conductor is a wire or cable and the one or more lossy layers encase an outer circumferential surface of the wire or cable.

7. An apparatus according to claim 1 further comprising:

a braid shield coupled on an outer surface of the conductor wherein;

the conductor is a wire or cable and the braid shield encases an outer circumferential surface of the wire or cable, the one or more lossy layers encasing an outer circumferential surface of the braid shield.

8. An apparatus according to claim 1 wherein:

the lossy material mixed into the binder in the one or more lossy layers is selected from among a group of materials including nickel-zinc (NiZn) ferrites, manganese-zinc (MnZn) ferrites, flakes of magnetic amorphous alloy, other ferrites, high permeability iron-based (ferrous) alloy, high permeability iron-based alloy such as 4-79 Permalloy, MUMETAL®

, Hymu 80, 45 Permalloy, and 50% nickel iron, ferromagnetics, nickel, iron, nickel-iron alloys, silicon-iron alloys, cobalt-iron alloys, steel, mumetal, permalloy, supermalloy, supermumetal, nilomag, sanbold.

9. An apparatus according to claim 1 wherein:

the lossy material mixed into the binder in the one or more lossy layers is selected from among a group of materials including metal-coated lossy particles fabricated using electrodeposition and vacuum deposition such as ferrites, magnetites or a blend of ferrites and magnetites and other soft-magnetic, homogeneous ceramic materials composed of iron oxide (Fe₂O₃) with carbonates or oxides of one or more bivalent metals such as manganese, zinc, nickel, or magnesium.

10. An apparatus according to claim 1 wherein:

the lossy material mixed into the binder in the one or more lossy layers is selected from among a group of materials including ferromagnetic particles mixed with other metal particles including one or more of copper, silver, silver-coated copper, nickel, manganese, zinc, and others into a polymer matrix.

11. An apparatus according to claim 1 wherein:

the lossy material mixed into the binder in the one or more lossy layers is selected from among a group of materials including metal-coated particles in combination with metal particles, core materials for the metal-coated particles including vitreous mineral such as glass, silicates of aluminum, magnesium, calcium, kevlar, graphite, carbon powders, carbon particles, mica, and composites.

12. An apparatus according to claim 1 wherein:

the binder in the one or more lossy layers is selected from among a group of materials including elastomers, thermoplastics, poly-vinyl-chloride (PVC), polyethylene (PE), polypropylene (PP), specially formulated plastics, thermoplastic resins such as polycarbonates, polyesters, polyetheresters, polyestercarbonates, polyamides, polyamideimides, polystyrenes, polyethers, polyetherimides, polyaryleneethers, acrylonitrile-butadiene-styrene copolymers, and combinations of two or more thermoplastic resins.

13. An apparatus according to claim 1 wherein:

the conductor is an electronic device in an anechoic chamber within a housing and the one or more lossy layers encase a housing surface.

14. An electromagnetic interference-protected cable comprising:

one or more interior conductor cables;

a shield coupled to and encasing the one or more interior conductor cables; and

a plurality of lossy layers coupled to and encasing the shield and the one or more interior conductor cables, individual lossy layers of the plurality of lossy layers having different compositions selected to attenuate frequencies in multiple frequency bands.

15. A cable according to claim 14 wherein:

lossy layers of the plurality of lossy layers further comprise;

a thermoplastic base material; and

a lossy material mixed into the thermoplastic base material, the lossy material being selected to attenuate electromagnetic interference frequencies in a narrow or moderate band.

16. A cable according to claim 14 wherein:

the electromagnetic interference attenuation of the plurality of lossy layers in combination exceeds attenuation of a single broad band lossy material.

17. A cable according to claim 14 wherein:

lossy layers of the plurality of lossy layers further comprise;

a thermoplastic base material; and

a lossy material mixed into the thermoplastic base material, individual lossy layers of the plurality of lossy layers having different lossy materials or different combinations of lossy materials, and different concentrations of lossy materials within the thermoplastic base material to control attenuation of frequencies in multiple frequency bands.

18. A method for protecting against electromagnetic interference and electromagnetic pulse signals comprising:

determining an interference frequency band within which electromagnetic interference is to be attenuated;

mixing a lossy material into a binder in a composition and concentration that attenuates electromagnetic interference in the determined frequency band; and

forming the mixed lossy material and binder over a conductor.

19. A method according to claim 18 further comprising:

mixing lossy materials into binders in a plurality of compositions and concentrations into a respective plurality of lossy layers for attenuating electromagnetic interference in a plurality of frequency bands.

20. A method according to claim 18 further comprising:

extruding a plurality of layers of lossy material and binder in a plurality of compositions and concentrations to attenuate electromagnetic interference in a plurality of frequency bands that function in combination to increase the overall attenuation over the attenuation of a single broadband layer.

21. An apparatus comprising:

means for conducting electrical signals;

means for encasing the conducting means, the encasing comprising;

means for attenuating electromagnetic interference frequencies in a narrow or moderate band; and

means for binding the attenuating means.