One important EMC compliance test is to determine whether external low frequency radiated RF fields can couple into your product via I/O or power cables. This test is often referred to as conducted immunity or conducted susceptibility and is defined by IEC 61000-4-6 for commercial products. The test is usually performed from 150 kHz to 230 MHz at voltage levels of 1, 3, or 10 volts root mean square (RMS), depending on the product environment or application. Some military, vehicular, or aerospace applications require testing at more rigorous levels. The RF signal is generally modulated by a 1,000 Hz AM modulation set to 80% for commercial testing and a 1 kHz square wave pulsed modulation is used for military and aerospace testing. The modulation is designed to test for audio rectification issues. For example, if the modulation is rectified (in audio or other analog circuitry), it could cause bias upsets or otherwise disrupt sensitive analog circuitry. Because it is difficult to reproduce a uniform field at these frequencies in a shielded chamber, the RF is coupled directly to the product I/O or power cables through various means. For commercial products, the test is performed only on I/O cables that are typically longer than 3 meters (e.g., Ethernet) or power cables.

Chapter Contents:

• 7.1 Introduction to Conducted Susceptibility
• 7.2 Conducted Susceptibility Check List
• 7.3 Typical Failure Modes
• 7.4 Troubleshooting at the Test Lab
• 7.5 Troubleshooting at Your Facility
• 7.6 Special Cases and Issues
• 7.7 DIY Tricks and Low-Cost Tools
• 7.8 Typical Fixes

Inspec keywords: amplitude modulation; immunity testing; radiowave propagation; IEC standards; least mean squares methods; pulse modulation; electromagnetic shielding; electromagnetic compatibility; power cables

Other keywords: shielded chamber; aerospace testing; AM modulation; I/O cables; vehicular application; RMS; RF signal modulation; aerospace application; IEC 61000-4-6; conducted susceptibility; EMC compliance test; low frequency radiated RF field; square wave pulsed modulation; audio rectification; military applications; frequency 150 kHz to 230 MHz; conducted immunity; commercial testing; root mean square; power cable; military testing; analog circuitry; frequency 1000 Hz; commercial product

Subjects: Electromagnetic compatibility and interference; Radiowave propagation; Signal processing and detection; Interpolation and function approximation (numerical analysis); Modulation and coding methods