Browse Prior Art Database

Electro-Magnetic Interference-Clip High Speed Interconnect

IP.com Disclosure Number: IPCOM000117325D
Original Publication Date: 1996-Feb-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 6 page(s) / 230K

Publishing Venue

IBM

Related People

Weekly, RD: AUTHOR

Abstract

Disclosed is a method which minimizes Electro-Magnetic Interference (EMI) radiation in a low cost manner without jeopardizing the ability to install and change feature modules in a simple manner. No hard attachments, such as screws, between the pluggable modules and the faceplate are need (Fig. 1). Application is pluggable modules mounted through a faceplate (part of the system chassis electrical EMI containment enclosure) on a tight pitch and residing on opposite sides of a carrier PC board. Copper cables shown as twinax plug in to exposed ends of the pluggable module to form links with other boxes.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 36% of the total text.

Electro-Magnetic Interference-Clip High Speed Interconnect

      Disclosed is a method which minimizes Electro-Magnetic
Interference (EMI) radiation in a low cost manner without
jeopardizing the ability to install and change feature modules in a
simple manner.  No hard attachments, such as screws, between the
pluggable modules and the faceplate are need (Fig. 1).  Application
is pluggable modules mounted through a faceplate (part of the system
chassis electrical EMI containment enclosure) on a tight pitch and
residing on opposite sides of a carrier PC board.  Copper cables
shown as twinax plug in to exposed ends of the pluggable module to
form links with other boxes.

      The Figures depict a cross section through a mounted pluggable
module with an electrical shielded twisted pair cable plugged into
the module on the bottom.  The pluggable module has a conductive
flange to electrically connect to the Cable Shield (reference a
D-Subminiature Connector) and signal pins to connect the electronics
in the pluggable modules to the cable signal wires.  The pluggable
modules protrude through holes in the Chassis Electrical Enclosure
(providing EMI containment) to provide access of the external cables
to the pluggable module link side connector.  The pluggable module is
not screwed or mounted in any permanent fashion to the Faceplate, so
that the position between faceplate and module is very forgiving.
Not shown is the electrical and mechanical connection between
pluggable modules and the PC board, which in the application
described could dictate the positional tolerance of the pluggable
module.  Also not shown on Fig. 2 is the mounting methodology between
the Faceplate and the PC board, which may be imprecise, yet rigid.

      Figs. 3 and 4 highlight the module depicted with a cable
plugged in.  Two elements have been added to the illustration: A
conduction path is shown on both sides of the module from the chassis
to the connector shield contact, and dashed arrows depicting net
common mode current flow through the signal wires, returning through
the cable shield back to the chassis.  This is the desired situation
to minimize far field EMI emissions, as the net spacial common mode
return current is always equal and opposite in direction to that on
the signal wires.  Thus, no net radiating current loops exist
anywhere along the path.

      Fig. 4 illustrates the condition where one of the conduction
paths to the pluggable module's connector shield contact does not
exist.  In this case, the net common mode return current near the
plug end of the cable must pass to the chassis only on the side where
electrical contact is assured.  The result is that a small net
current loop results where the net spacial common mode return current
does not always spatially coincide with the common mode current on
the signal wires.  Thus, a small yet significant net radiating
current loop exists near the plug end of the cable.

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