Browse Prior Art Database

Electromagnetic Interference I/O Filter

IP.com Disclosure Number: IPCOM000104074D
Original Publication Date: 1993-Mar-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Siverling, MM: AUTHOR

Abstract

The first piece of this solution is to put the I/O cable connector on an isolated "island" on the printed circuit board - detached from the rest of the circuitry. Thus, if the lines are filtered going to the island, the cable is relatively free of electromagnetic interference (EMI) noise as it exits the printed circuit board.

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This is the abbreviated version, containing approximately 68% of the total text.

Electromagnetic Interference I/O Filter

      The first piece of this solution is to put the I/O cable
connector on an isolated "island" on the printed circuit board -
detached from the rest of the circuitry.  Thus, if the lines are
filtered going to the island, the cable is relatively free of
electromagnetic interference (EMI) noise as it exits the printed
circuit board.

      The second piece to the solution is to recognize that: 1) The
need is to reduce common mode EMI noise signals.  2) The useful
signals in the cables are largely differential - either because they
return to the source device through an included ground or, in the
case of a power cable, the net current sum for all the power and
ground lines attached to the common subassembly is close to zero when
compared to the current that may be in any of the individual power
lines.

      The above information allows making a "surface mount on printed
circuit" device similar to Fig. 2.  Fig. 2 is a modular device having
enough separate lines passing through the same filter that common
mode filtering of an entire cable can be done prior to exiting as a
small computer system interface (SCSI) cable, or "total power" cable,
for example.

      Organizing the cable constituents so that they are more like
Fig. 4 or even coaxial allows a smaller ferrite core to be used when
compared to the windings in Fig. 3.  While the current in either lead
'a' or 'b' might individually saturate areas 'u,v,w,x' in Fig...