Browse Prior Art Database

Circuit for Suppressing Common-Mode Energy on Unshielded Twisted-Pair Media

IP.com Disclosure Number: IPCOM000104524D
Original Publication Date: 1993-Apr-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 1 page(s) / 46K

Publishing Venue

IBM

Related People

Bevill Jr, B: AUTHOR [+3]

Abstract

The disclosed circuit provides the means by which the common mode energy incident on a 4-wire communications link may be suppressed in order to meet the Electro-Magnetic (EM) emission requirements specified by various licensing agencies. The topology, a 2-wire coupled inductor for each wire pair followed by a 4-wire coupled inductor for both wire pairs, is superior in performance to a filter fabricated from only 2-wire devices or 4-wire devices.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 85% of the total text.

Circuit for Suppressing Common-Mode Energy on Unshielded Twisted-Pair Media

      The disclosed circuit provides the means by which the common
mode energy incident on a 4-wire communications link may be
suppressed in order to meet the Electro-Magnetic (EM) emission
requirements specified by various licensing agencies.  The topology,
a 2-wire coupled inductor for each wire pair followed by a 4-wire
coupled inductor for both wire pairs, is superior in performance to a
filter fabricated from only 2-wire devices or 4-wire devices.

      In 4-wire systems where transmission and reception each have
dedicated wire pairs, three distinct common mode energy components
may exist that are exclusive of each other.  They are as follows:

o   Energy common to the transmit wire pair
o   Energy common to the receive wire pair
o   Energy common to both wire pairs

      To insure the overall effectiveness of the filter in EM
emission suppression, each of these sources must be considered
independent of the others.  To this end, this circuit as illustrated
in the figure, contains a 4-wire common mode inductance designed to
present a high impedance to currents whose phase is equal on both
wires of the transmit pair, and a 2-wire common mode inductance
designed to present a high impedance to currents whose phase is equal
on both wires of the receive pair.

      Each of the coupled inductors must be constructed to minimize
differential-to-common mode conversion of signal...