EMI emission test failures are a major cause of product development delays. The fact is most products fail in their first trip to the lab. Radiated Emissions is the most common problem and one that is difficult to fix. This is true for both military and commercial products.
EMI Emission Design Issues
Application of ferrites and shielding at the lab is often a desperate battle with diminishing returns. The best strategy is to identify major sources of emissions early in the design and mitigate at the source. A well-designed Printed Circuit Board (PCB) can alleviate many problems but it is important to remember that every interconnecting cable is an antenna that can provide a path for radiated emissions.
Unwanted radiated emissions can be mitigated utilizing a number of strategies in the design stage but, each product has its area of special concern. A product that controls stepper motors will have very different mitigation issues than a Bluetooth communication device.
Switching power supplies are a common area of concern for all products. This includes main power sources and Point of Load (POL) circuits. Care must be taken to ensure the selection of components (e.g. low ESR capacitors) and their proper placement and interconnection.
Preparation for Emissions Testing
A great design can still fail if poorly constructed. Pre-production or early production samples of products often will have paint and coatings in unwanted areas resulting in ungrounded cables and chassis parts. Cables utilized for testing will often not be representative due to size constraints of the lab. These cables often are not constructed to the same standards and may not have adequate shielding. Off-chamber simulation and monitoring equipment requires special attention. This equipment can often contribute emissions that will cause a “false” EMI emissions test failure.
Our experts at CVG Strategy have extensive experience in EMI/EMC. We can provide pretest analysis to help reduce EMI emission test failures and their resultant delays. We also have expertise in Environmental testing and evaluation in a number of industries and products, both military and commercial. CVG Strategy specializes in Independent Developmental Testing and Evaluation including: Development of Life Cycle Environmental Profiles, Test Plans, Test Witnessing and Troubleshooting.
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