Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1998-04-14
2001-07-31
Picard, Leo P. (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S754000, C361S741000, C439S945000
Reexamination Certificate
active
06268999
ABSTRACT:
TECHNICAL FIELD
This invention pertains to computer peripheral devices. More specifically, the present invention pertains to an apparatus and method for dissipating ground signals in order to control the level of electromagnetic interference emissions generated by computer communications I/O devices, such as PC (personal computer) cards and compact flash cards.
BACKGROUND ART
Computer peripheral devices, such as Local Area Network (LAN) or modem Personal Computer (PC) Cards perform input/output (I/O) communications functions in portable computers. These computer peripheral devices, generate some level of electromagnetic interference (EMI) emissions during data transmission. The permissible level of EMI is strictly regulated by national or regional regulatory bodies. For instance, in the U.S., any portable computer or handheld computer used in a home environment may only use a PC card which meets FCC Class B standards for EMI. In Europe, the corresponding requirement is the CE standard.
The ability of a LAN or modem I/O card to meet the proscribed EMI levels is directly related to effectiveness with which ground signals are dissipated from the I/O card during active LAN or modem data transmissions. In PC cards, the PCMCIA (personal computer memory card international association) industry standard allocates and designates 4 pins out of a total of 68 interface pins as ground signal pins.
In one prior art approach, even 4 pins prove inadequate to sufficiently dissipate the ground signals, thereby requiring manufacturers to add a bulky ferrite core externally to the I/O cable used in conjunction with the PC Card, to limit EMI to the required levels. This method adds cost and bulk to the PC Card, and is aesthetically displeasing to the end-user.
In another prior art approach, in addition to using the 4 pins available for ground signals, some manufacturers use a complicated arrangement of individual and separate ground clips, which are then assembled onto the card frame to provide additional grounding paths from the I/O card through the host computer. Assembly of these clips onto the card frame requires time-consuming, multi-step manual operations. Such extensive manual labor results in a more costly finished product. The manual assembly process is also prone to wide variation in skill level among individual manual assemblers, and results in inconsistent quality of finished product, as regards effectiveness in meeting regulatory EMI limits.
In yet another attempt to control the EMI levels generated in PC Cards, other manufacturers, in addition to using the 4 pins designated, use metal tabs on the top surface of the 15 pin I/O connector at the I/O end of the card. This arrangement is intended to provide an additional grounding path from the card circuitry, through the metal tabs being in direct contact with the metal covers of the card, which in turn are electrically connected to a grounding signal path on the host computer. However, the location of such metal tabs at that I/O end of the card results in the tabs being continually subjected to compressive forces during user insertion and removal of the card into the host computer PC Card slot. These repeated cycles of compressive forces result in the metal tabs being permanently deformed after only a few hundred cycles of usage, so that they are no longer in contact with the metal cover of the card, and this feature ceases to function as a grounding path. Thus, a PC card which might meet EMI regulatory requirements upon shipment of the product to a customer, gets progressively worse when used as intended.
As handheld computers, which are even smaller than portable computers, become more widespread, users will increasingly have a need for correspondingly smaller I/O cards to handle LAN and modem communications functions. Currently, the Compact Flash Card is a relatively newer form factor which is about one-third the overall size of a PC card. The Compact Flash Association has allocated and designated 2 pins out of a total of 50 interface pins as ground signal pins. For LAN or modem I/O cards having a Compact Flash form factor, it will be practically impossible, or extremely difficult at least to meet FCC Class B and CE regulatory requirements during active data transmission, when only the allocated 2 pins are available as ground signal pins.
Therefore, a need exists for a computer communications I/O device structure that will effectively dissipate ground signals while not requiring more than two interface pins dedicated to ground signals. A further need exists for a computer communications I/O device structure which effectively dissipates ground signals wherein the device does not require costly, labor intensive, manual operations which are likely to result in widely varying finished product quality, in terms of EMI effectiveness. Still another need exists for a computer communications I/O device structure which effectively dissipates ground signals, and in which the effectiveness of any ground signal paths used does not degrade relatively rapidly with time, and wherein the device does not violate EMI regulatory requirements when used as intended.
DISCLOSURE OF THE INVENTION
The present invention provides a computer communications I/O device structure to effectively dissipate ground signals that does not require more than 2 interface pins dedicated to ground signals. The present invention further provides a computer communications I/O device structure to effectively dissipate ground signals that does not require costly, labor intensive manual operations that are likely to result in widely varying finished product quality, in terms of EMI effectiveness. Additionally, the present invention provides a computer communications I/O device structure which effectively dissipates ground signals, and in which the effectiveness of any ground signal paths used does not degrade relatively rapidly with time, and wherein the device does not violate EMI regulatory requirements when the device is used as intended. The present invention achieves the above accomplishments with a computer peripheral device with an integral ground clip.
Specifically, in one embodiment, the present invention includes a substrate. The substrate has a ground signal receptacle location coupled thereto. The present embodiment further includes an enclosure which adapted to be coupled to the substrate. In this embodiment, the enclosure has a conductive region coupled thereto. The enclosure further includes a grounding member which is integral therewith. The grounding member is disposed such that the grounding member is electrically coupled to the ground signal receptacle location when the enclosure is assembled to the substrate. In so doing, the present invention provides a computer peripheral device which, among other benefits, effectively dissipates ground signals.
In another embodiment, the present invention includes the features of the above-described embodiment and further recites a plurality of ground receptacle locations and a plurality of grounding members wherein the plurality of grounding members are integral with the enclosure. The plurality of grounding members are disposed such that each of the plurality of the grounding members is electrically coupled to a respective one of the plurality of the ground signal receptacle locations when the enclosure is assembled to the substrate.
In yet another embodiment, the present invention includes the features of the first above described embodiment and further includes a second enclosure. In such an embodiment, the second enclosure is adapted to be coupled to the substrate. The second enclosure has at least a second conductive region coupled thereto. The second enclosure further comprises a second grounding member integral with the second enclosure. The second grounding member is disposed such that the second grounding member is electrically coupled to the ground signal receptacle location when the second enclosure is assembled to the substrate.
These and other advantages of the present invention will no doubt become obvious to
3Com Corporation
Duong Hung Van
Picard Leo P.
Wagner , Murabito & Hao LLP
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