When faced with excessive conducted emissions from switching power supplies, one of the first things to investigate and to determine the adequacy of is the power line filter. Line-powered switching supplies generally have both common mode and differential mode sections of the filter as shown in the generalized schematic in Figure 1. When using a line impedance … [Read more...]
ESD Effects of Digital ICs
One issue I see fairly often with unshielded consumer or commercial products is CPU resets during periods of immunity testing, such as during electrostatic discharge (ESD) testing. Untreated, this can lead to field failures and associated customer satisfaction issues. The remedy is usually quite simple and IC manufacturers even mention the solution, but it’s usually buried … [Read more...]
Narrowband Versus Broadband Harmonic Signals
Radiated and conducted emissions measurements are often comprised of both narrowband and broadband sources. So what differentiates “narrowband” and “broadband” signals? Narrowband Versus Broadband Signals The definition of whether a signal is narrowband or broadband as measured using a spectrum analyzer, depends entirely on the receiver bandwidth (resolution bandwidth, or … [Read more...]
Assembling A Low Cost EMI Troubleshooting Kit – Part 2 (Immunity)
This article concludes the two-part series, Assembling Your Own EMI Troubleshooting Kit – Part 1, which included a listing of the major components of a complete EMI trouble shooting kit that can be easily transported where needed. Most of the probes and tools listed in Part 1 were useful for troubleshooting radiated emissions. In Part 2, we’ll discuss several other useful … [Read more...]
Gaps In Return Planes – Bad News for EMI
Currently, there is an ongoing discussion among SI and EMC engineers on the fine points of PC board design for best signal integrity and EMI performance. Among the topics it seems designing in gaps or slits in ground return planes always comes up. Gaps can also occur mistakenly due to the addition of some connectors or other object that creates gaps in the copper. In fact, … [Read more...]
Interference Technology’s Top Ten Articles From 2005 to 2016
Each year, I like to capture the top “clicked on” articles. Knowing this will help me determine what topics readers feel are most engaging. The data will help me as technical editor round up articles for 2017 that will be equally compelling. Some of these topics include EMC basics, product design for compliance, EMC standards updates, medical EMC, vehicular EMC, and military … [Read more...]
Book Review – Grounds For Grounding: A Circuit To System Handbook
Proper grounding for the best EMC design is still one of the most hotly debated topics of all time within the EMC and product design communities. The problem is that what worked for a past product or system may not work for another using more recent technology or clock speeds. Likewise, a list of “Rules of thumb” aren’t applicable for all cases and, by their very essence, … [Read more...]
Autonomous Vehicles – Ethics and Liability?
By Kenneth Wyatt Sr. Technical Editor, Interference Technology kwyatt@interferencetechnology.com One of the most exciting technologies today is the current development of semi-autonomous (driver assisted) and fully-autonomous vehicles. Dozens of manufacturers are rapidly developing autonomous, or self-driving, vehicles and related intra-vehicle and vehicle-to-vehicle … [Read more...]
Measuring Cable Resonance with a Comb Generator
by Kenneth Wyatt Cables are one of the key metallic structures on a product that can act as an antenna and couple energy, causing radiated emissions and possible compliance test failures. This has been discussed extensively in the literature on product design for EMI compliance. In many cases, they can resonate at their half-wave frequency and actually amplify any harmonic … [Read more...]
Budget SDR-Based Spectrum Analyzer
While there are a number of affordable spectrum analyzers available to the product designer or EMC engineer, such as the Rigol DSA800-series or Siglent SSA3000X-series, I discovered an extremely low cost analyzer useable for general-purpose EMI troubleshooting. This tiny module (Figure 1) is actually a high quality software defined radio (SDR) that can tune from 24 … [Read more...]
