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1. (WO2018022381) COMMUNICATIONS SYSTEM USING HYBRID COMMON MODE CHOKE AND KELVIN SENSING OF VOLTAGE

Pub. No.:    WO/2018/022381    International Application No.:    PCT/US2017/042893
Publication Date: Fri Feb 02 00:59:59 CET 2018 International Filing Date: Thu Jul 20 01:59:59 CEST 2017
IPC: H04L 12/10
H04L 12/40
H04L 25/02
H04B 3/54
Applicants: LINEAR TECHNOLOGY CORPORATION
Inventors: GARDNER, Andrew J.
Title: COMMUNICATIONS SYSTEM USING HYBRID COMMON MODE CHOKE AND KELVIN SENSING OF VOLTAGE
Abstract:
In a communications system that conducts differential data via a pair of wires (12), AC common mode noise is undesirably coupled to the wires (12) in a noisy environment. A hybrid common mode choke, HCMC (16), attenuates the AC common mode noise while passing the differential data to a PHY (150). The HCMC (16) includes a CMC (20) (windings with the same polarity) and a differential mode choke (24) (windings with opposite polarities). The CMC (20) attenuates the AC common mode noise, and the DMC (24) passes the attenuated AC common mode noise to termination circuity (26) to eliminate it. Also disclosed is a technique for Kelvin sensing the DC voltage at the pair of wires (12), in a PoDL system, by detecting the voltage on wires (12) that do not carry DC current, so as to provide a more accurate measurement.