Abstract:
A system includes a chassis having at least one wall, the chassis housing electrical components and a layer of flexible electromagnetic interference (EMI) emission absorption material covering an interior surface of the wall. A system also includes a chassis containing slots, the chassis housing electrical components and a layer of flexible electromagnetic interference (EMI) emission absorption material covering at least one of the slots.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to reducing EMI emissions.  
         BACKGROUND  
         [0002]    During the operation of computers, or other similar electronic components, electromagnetic interference (EMI) emissions, or radiation, are generated by motors, drives, processors, chips and circuits. One way to contain these emissions is to surround the circuit in a metal panel. Further, in some situations, these emissions must be contained in order to comply with certain regulations. 
       
    
    
     DESCRIPTION OF DRAWINGS  
       [0003]    [0003]FIG. 1 is a block diagram.  
         [0004]    [0004]FIG. 2 is a block diagram.  
         [0005]    [0005]FIG. 3 is a block diagram. 
     
    
     DETAILED DESCRIPTION  
       [0006]    Referring to FIG. 1, a computer  10  includes a metal or plastic chassis  12  in which a motherboard  14  is mounted. A chassis is the physical frame or structure of a computer that houses the main electronic components, including the motherboard  14  with places (not shown) to insert or replace microchips for the main and possibly specialized processors and random access memory (RAM) and places for adding optional adapters like audio or video capabilities, for example. Typically, room is also provided for a hard-disk drive and a CD-ROM drive. A processor  16  is connected to the motherboard  14 . A number of memory devices or modules  18  and two input/output (I/O) devices  20  are also mounted to the motherboard  14 . Two buses  16   a  and  16   b  are also provided on the motherboard  14  and connect the processor  16  to the memory modules  18  and to the input/output devices  20 , respectively. A power supply  22  is connected to the motherboard  14  and a pair of cable assemblies  24   a  and  24   b  connect the motherboard  14  to a hard drive unit  26  and a disk drive  28 . Other components (not shown), electrical traces, electrical circuits and related devices may also be provided in the chassis  12 .  
         [0007]    At least part of the interior walls of the chassis  12  is covered with a layer  30  of electromagnetic interference (EMI) emission absorption material. The layer  30  is affixed to the interior walls of chassis  12  and absorbs electromagnetic emissions. For example, in a personal computer where the chassis  12  may be expected to provide 6 dB attenuation of EMI emission, the layer  30  can absorb 6 dB of the EMI emission. In another example, the layer  30  can protect sensitive components in a wireless device from emissions from circuitry or transmitting antenna. Rather than containing EMI emissions, the layer  30  absorbs the EMI emissions. One or more layers of EMI emission absorption materials can easily be applied to all computer-type systems, such as work stations, desktop computers, servers, as well as any electronic device, such as personal data assistants (PDAs), wireless devices, internet tables, game consoles and peripherals.  
         [0008]    Referring to FIG. 2, the layer  30  is shown attached to an interior of a side panel  32  of the chassis  12 . An adhesive is used to bond the layer  30  to the side panel  32  during manufacturing and assembly of the chassis  12  and sized to the dimensions of the interior portion of the side panel  32  of the chassis  12 . No electrical grounding is required. The layer  30  may be fabricated in a variety of thicknesses to cover a wide range of EMI emission ranges. For example, the layer  30  may be constructed as a lightweight, flexible, low density, and high-loss foam. Thickness may range, for example, from 0.01″ to 1.0″, and densities may range, for example, from 0.05 to 5.0 pounds per cubic foot, however the thickness and densities are not limited to these values. The layer  30  may be single layer, multilayer, weatherproof, reticulated and or rigid. Suitable EMI emission absorber material is supplied, for example, by R+F Products of San Marcos, Calif. and ARC Technologies of Amesbury, Mass.  
         [0009]    Referring to FIG. 3, in another approach, the chassis  12  may be fitted with a molded, i.e., rigid, EMI emission absorption panel  34  that replaces a metal or plastic panel of FIG. 1. The panel  34  is, for example, a reticulated foam with a continuously graded lossy coating produced using a two part closed cell polyurethane filler to provide structural integrity. Thus, rather than bonding a layer  30  to the interior walls of the chassis  12 , the front panel  34  replaces the front wall of the chassis with a rigid material capable of EMI emission absorption.  
         [0010]    In other examples, one or more of the interior and/or exterior metal or plastic walls of the chassis  12  are replaced with solid molded EMI emission absorption panels. Use of the molded EMI emission absorption panels also provides thermal venting since it is porous and not impermeable. Further, combining a different EMI emission absorption material in a single panel or layer covers a very wide frequency band.  
         [0011]    In still other examples, layers of EMI emission absorption materials are used to line internal bays within the chassis, like, for example, a bay in which the power supply  22  resides.  
         [0012]    In another example, where slots are common in computer peripherals for assembly and thermal reasons, radiation from these slots may cause EMI problems. Layers of EMI emission absorption materials are used to suppress EMI around slots in computer peripherals, such as CD-ROMs, DVDs, CD-RWs and floppy/disk drives.  
         [0013]    Other embodiments are within the following claims.