How do you decide on the size of a bypass capacitor (or capacitors) for your project? Do you need multiple capacitors to bypass a specific chip? Are multiple value capacitors important for a given use? Do you subscribe to the old Wife’s Tail about having a couple capacitors a couple orders of magnitude different in value in parallel? Here is one take on the subject for you … [Read more...]
Emissions Test Facility – OATS vs SAC?
You’ve been tasked by management to build a new, from scratch, EMC test facility. Among other items, you need to decide between an Open Area Test Site (OATS) or an RF Semi-Anechoic Chamber (SAC). How do you decide? To someone who has been there, done that, the choice is clear, but what are some factors that might sway the decision one way or the other? Design of an … [Read more...]
Classical Shielding Theory vs. Near-Field Measurements
This article addresses the fundamental concepts underlying the classical shielding theory based on Schelkunoff’s equations [1]. In order to assess the applicability of these equations, an understanding of their origin, assumptions made in their derivations, and their limitations, are needed. This tutorial article addresses each of these points. The goal is not to show the … [Read more...]
Review of MIL-STD-461 CS114– Conducted Susceptibility, Bulk Cable Injection
Introduction This article discusses CS114, including the updates contained in MIL-STD-461 revision “G”, the current revision and the associated nuances that lead to test errors. The fundamental idea behind CS114 testing is to simulate currents induced into cabling from electromagnetic (EM) fields from high level emissions, intentional or unintentional. This test allows an … [Read more...]
What You See With Near Field Probes
In EMI/EMC troubleshooting, near field probes (NFPs) are great tools. Let's review how to understand what you really see at the screen of your instrument with a magnetic near field probe. EMI/EMC problems (radiated and conducted emissions) are usually related with current in your circuits: high frequency currents (i.e. high di/dt currents) are responsible of radiation from … [Read more...]
What is the Number One Item That Causes EMC Problems at the Board Level?
There are many “rules” for laying out a printed wiring board (PWB) to minimize generation of EMI from a board. These cover a wide range of issues that are important. Some more than others, but all can be important. But, if you were to ask what the number one item on the hit parade would be, what would you say? What are the important factors to consider when laying out a … [Read more...]
Tips for Writing Technical Articles for Magazines
Why write? Pride – To see your work in print is a just reward for a creative person. We all have a built-in desire to be creative and to be recognized for that creativity. Contribution – Well-written technical articles contribute to the total body of knowledge for the engineering community and will potentially help many engineers. Articles do not need to be detailed … [Read more...]
Introduction to DoD Policy, Guidance & the Acquisition Process
Introduction This article provides an introduction to DoD policy, guidance and the acquisition process. E3 is defined as the impact of the Electromagnetic Environment (EME) upon the operational capability of military forces, equipment, systems, and platforms. E3 encompasses all electromagnetic disciplines, including Electromagnetic Interference and Electromagnetic … [Read more...]
EMI Troubleshooting with Real-Time Spectrum Analyzers
The latest tool for serious EMI troubleshooting or debugging has become the real-time (RT) spectrum analyzer. Because manufacturing costs have been decreasing, some RT analyzers are becoming more affordable than ever. In this article, I’ll show you the advantages in using RT analysis for observing and troubleshooting unusual EMI. INTRODUCTION First, let’s review the … [Read more...]
Review of MIL-STD-461 RS101– Radiated Susceptibility, Magnetic Field and RS103 Radiated Susceptibility, Electric Field
Introduction This article discusses RS101 and RS103, including the updates contained in MIL-STD-461 revision “G”, the current revision. These tests quantify the ability of a device to tolerate undesired signals present as a field at the device and associated cables. The field has the potential of coupling the interference into the device circuitry and cause performance … [Read more...]
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