{"id":4896,"date":"2025-09-26T11:12:00","date_gmt":"2025-09-26T11:12:00","guid":{"rendered":"https:\/\/lp.szlogic.cn\/uncategorized\/common-mode-noise-in-ethernet-systems\/"},"modified":"2026-06-22T09:04:14","modified_gmt":"2026-06-22T09:04:14","slug":"common-mode-noise-in-ethernet-systems","status":"publish","type":"post","link":"https:\/\/resources.l-p.com\/ru\/products\/common-mode-noise-in-ethernet-systems","title":{"rendered":"Common-Mode Noise: Definition, Causes & Mitigation in Ethernet Systems"},"content":{"rendered":"
\"Common-Mode<\/figure>\n\n\n\n

🔄 <\/strong>Introduction<\/h2>\n\n\n\n

Common-mode noise<\/strong> is a common challenge in Ethernet and other high-speed digital systems. It occurs when identical noise voltages or currents appear on both conductors of a pair relative to ground. Left unmitigated, it can lead to electromagnetic interference (EMI)<\/strong><\/a>, compliance failures, and degraded signal integrity. This article explains the concept, causes, measurement methods, and suppression techniques of common-mode noise \u2014 with a focus on Ethernet design and LINK-PP LAN transformers<\/a>.<\/p>\n\n\n\n

🔄 What Is Common-Mode Noise?<\/h2>\n\n\n\n

Common-mode noise refers to unwanted signals that appear in the same phase<\/strong> on two conductors relative to ground.<\/p>\n\n\n\n

Formula:<\/p>\n\n\n\n

\"Common-Mode<\/figure>\n\n\n\n

In contrast, the useful differential-mode<\/strong> signal is:<\/p>\n\n\n\n

\"differential-mode<\/figure>\n\n\n\n

While differential-mode signals carry data, common-mode noise represents interference that may radiate as EMI or couple into sensitive circuitry.<\/p>\n\n\n\n

🔄 Differential Mode vs Common Mode<\/h2>\n\n\n\n
\n\n<\/colgroup>

Aspect<\/p><\/th>

Differential Mode<\/p><\/th>

Common Mode<\/p><\/th><\/tr>

Signal<\/p><\/td>

Opposite polarity on conductors<\/p><\/td>

Same polarity on both conductors<\/p><\/td><\/tr>

Purpose<\/p><\/td>

Carries data<\/p><\/td>

Unwanted interference<\/p><\/td><\/tr>

Radiation<\/p><\/td>

Relatively low<\/p><\/td>

High, cables act as antennas<\/p><\/td><\/tr>

Reference<\/p><\/td>

Between lines<\/p><\/td>

Relative to ground<\/p><\/td><\/tr>

Mitigation<\/p><\/td>

Pair symmetry, impedance control<\/p><\/td>

Common-mode chokes<\/a>, isolation<\/p><\/td><\/tr><\/tbody>\n<\/table>\n<\/figure>\n\n\n\n

🔄 Causes of Common-Mode Noise<\/h2>\n\n\n\n