Ventilation port and EMI wave-guide for electronic equipment

Details Ventilation port and EMI wave-guide for electronic equipment Ventilation port and EMI wave-guide for electronic equipment

2000-06-01

2002-05-07

Reichard, Dean A. (Department: 2831)

Electricity: conductors and insulators

Anti-inductive structures

Conductor transposition

C454S184000, C361S602000

Reexamination Certificate

active

06384325

ABSTRACT:

TECHNICAL FIELD
The present invention is generally related to a ventilation port and wave-guide for suppressing electromagnetic radiation generated by an electronic component and, more particularly, is related to a system for air cooling of electronic components within an enclosure via ports. The ports are constructed to provide for attenuation of high frequency EMI radiation through the ports.
BACKGROUND OF THE INVENTION
In electronic equipment it is typically necessary to provide for cooling/ventilation of the electronic components during operation. Typical ventilation techniques incorporate air holes (ventilation ports) in the case or housing of the piece of electronic equipment to allow air flow to circulate through the case to cool the electronic components. An example of a typical configuration for cooling electronic components of a piece of electronic equipment
3
is shown in FIG.
1
.
FIG. 1
shows a case
5
, having a fan
6
for inducing airflow “A” through a series of holes
10
, punched through the cabinet
5
to provide for cooling of components in the case
5
.
In electronic equipment which incorporate electronic devices having high operating frequencies, electromagnetic interference (EMI) is often generated by the high frequency electronic devices. This EMI can escape from the housing containing the electronic devices via typical ventilation ports
10
(FIG.
1
). At high frequencies of operation, it is difficult to simultaneously provide for both cooling and EMI/ESD (electrostatic discharge) attenuation in an electronic equipment by simply providing for air holes (ventilation ports) in, for example, a cabinet
5
of the electronic equipment as is shown in FIG.
1
. Further, electrostatic discharge generated from external sources can radiate via the ventilation ports
10
into the case
5
. In short, while punching air holes in the sheet metal cabinet might provide for sufficient airflow A to properly cool an electronic device, such air holes typically are insufficient to provide for an appropriate level of attenuation of EMI and ESD radiation.
Certain properties of electromagnetic wave propagation allow for a “hole” in a sheet metal cabinet to provide for sufficient attenuation of electromagnetic wave propagation where the hole has sufficient depth. More particularly, where the depth of the hole is at least 50% or more of the maximum cross section length (diagonal), the “hole” will provide substantially greater attenuation of electromagnetic wave radiation than would be provided based simply upon the size of the hole alone. Wave-guide EMI filters have been developed in accordance with these properties. However, these wave-guide filters have typically required multiple parts and processing steps, including soldering of wave-guide components in order to obtain electrical conductivity. Thus, the cost of production of such a wave-guide is significant. These costs make the use of these types of wave-guides cost effective only for more expensive equipment or computer systems, such as mainframe computers. For smaller, less expensive electronic equipment assemblies such as individual input/output (I/O) modules including industry standard VersaModule Eurocard (VME), Compact Peripheral Component Interconnect (CPCI), and Peripheral Component Interconnect (PCI) modules, the cost of these types of wave-guides make them unfeasible. As the operational frequencies of electronic equipment, such as I/O modules, is increasing with frequencies of 2.5 GHz-10.0 GHz becoming common, a cost-effective wave-guide solution will be needed.
In order to attenuate the level of EMI radiated from a piece of electronic equipment, it has been common to provide for metal wave-guide structures to be used in place of typical ventilation ports or filtration screens. One example of a wave-guide structure of this type is illustrated in FIG.
2
.
FIG. 2
illustrates an electronic component
3
having a case
5
that incorporates a typical wave-guide filter structure
20
(filter structure
20
). This filter structure
20
is further illustrated in FIG.
3
A and FIG.
3
B.
With reference to FIG.
3
A and
FIG. 3B
, it can be seen that filter structure
20
is constructed of multiple individual hexagonal wave-guide tubes (ducts)
21
which are attached to each other via, for example, a solder joint or weld. The hexagonal wave tubes
21
are then attached to front and back plates
22
a
and
22
b
, respectively, to form the filter structure
20
. Filter structure
20
is used as an air inlet port for a case
5
as illustrated in FIG.
2
.
With reference to
FIG. 3B
, if the individual hexagonal wave-guide tubes
21
are constructed for a depth T which is at least 50% or more of the maximum cross-section length D of the wave-guide tube
21
, then the wave-guide tube
21
will also function as an EMI filter and thus function to attenuate the radiation of any EMI radiation via the wave-guide tubes
21
. The filter structure
20
is a labor intensive structure to construct and is, thus, expensive and not suitable for less costly equipment applications in which profit margins are narrow.
Thus, a heretofore unaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies.
SUMMARY OF THE INVENTION
The present invention provides a system for ventilating electronic equipment and suppressing the radiation of electromagnetic interference (EMI) from the electronic equipment. More particularly, the present invention relates to a ventilation port and EMI wave-guide. Briefly described, in architecture, the system can be implemented as follows. A corrugated spring member is inserted (under tension) between a first plate and a second plate so as to establish electrical contact, as well as define a plurality of ducts, each having a depth and a cross-sectional width.
Other systems, methods, features, and advantages of the present invention will be or become apparent to one with skill in the art upon examination of the following drawings and detailed descriptions. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present invention, and be protected by the accompanying claims.


REFERENCES:
patent: 6211458 (2001-04-01), Mitchell et al.

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