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Browse Prior Art Database

Apparatus for Containing Radiated Electrical Noise

IP.com Disclosure Number: IPCOM000107703D
Original Publication Date: 1992-Mar-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 2 page(s) / 69K

Publishing Venue

IBM

Related People

Kaiser, EJ: AUTHOR [+2]

Abstract

This article describes a design solution to prevent radiated noise inside a metal EMC/EMI enclosure from following along a flex-circuit cable which exits the enclosure and radiating outside the enclosure. This solution facilitates meeting FCC and VCCI requirements for emitted electrical noise.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 69% of the total text.

Apparatus for Containing Radiated Electrical Noise

       This article describes a design solution to prevent
radiated noise inside a metal EMC/EMI enclosure from following along
a flex-circuit cable which exits the enclosure and radiating outside
the enclosure.  This solution facilitates meeting FCC and VCCI
requirements for emitted electrical noise.

      The figure depicts a chassis for an electronic device, shown
with the chassis lid removed.  Inside is a typical planar board which
is a source of electrical noise which needs to be contained.
Seven-segment LEDs (light emitting diodes) are attached to a flex
circuit assembly for visibility outside of the chassis enclosure.
However, when the flex cable assembly is plugged into the planar
board, it becomes a conduit for noise on the planar board to exit
through the chassis wall.

      The design solution is to orient the flex cable so that its
insulation-coated, signal-plane side faces toward the floor of the
chassis, and its ground-plane side faces up and has an uncoated
(conductive) zone, as shown.  The relatively large conductive contact
area on ground-side land of the flex cable provides extra capacitive
coupling to ground, not just electrical continuity.

      A conductive spring-clip is then installed where the flex cable
assembly passes through a porthole that is part of the conductive
chassis.  The spring-clip clamps the flex cable assembly so that its
signal-plane circuits are held in close...