Consider EMC throughout a product’s lifecycle

Aug. 11, 2017

National Harbor, MD. EMC aspects must be considered throughout a product’s life cycle—a point emphasized by Colin E. Brench of Amphenol during a presentation this morning at the EMC+SIPI Symposium. He strongly advised against a “build it and see what happens” approach. That’s not EMI design, he said—that’s crisis management.

He described by way of example a 15- to 20-year-old project that nevertheless remains relevant and for which he had input for all aspects—the silicon, printed-circuit board, packaging, and system. In a typical design, the engineer will lack control of one or more of these aspects, especially the silicon, which may not even be available for months into a project.

Before describing his project, he summarized the responsibilities of EMC engineers: regulatory and spectrum management, compliance testing, ongoing quality testing as parts are replaced or upgraded in the field, early simulation when silicon is not available, platform integration, and—as frequencies increase—materials research.

Non-EM skills are important too, Brench said, such as knowledge of the silicon. “If you know how the silicon works, it gives you an edge,” he said. Other non-EM issues include thermal and cooling effects plus acoustics. “We can cool it,” he said, “but if it sounds like a jet engine no one will use it.” Other issues to consider include mechanical assembly and vibration and corrosion effects. Software will have an impact as well, he said. Automatic fault correction can temporarily hide EMC issues, and software can put a product into an electromagnetically noisy idle mode.

EMC design will depend on the scope of a product. Selling consumer products such as PCs is like selling strawberries, he said. They have a short lifetime. Some systems, however, will be upgraded one or more times in the field, and some foresight at the design stage can be helpful down the road. Upgrading with newer, faster parts can open a whole new spectrum of trouble, he noted.

Brench then described his project from years ago—a server based on a Digital Equipment Corp. Alpha processor that ran at 440 MHz—blazingly fast for the time. He and his team were able to optimize the processor circuitry to minimize switching currents. They also designed the VLSI packaging to minimize antenna affects and the PCB layout to minimize emissions. In addition, they designed the system enclosure to contain the RF energy and ensured that the external interfaces had adequate filtering and shielding.

Brench emphasized that “old skills only help show the way” and should not be considered a blueprint for the future. The key lesson, he said, “…is that to produce a cost effective, compliant product the EMC design engineer must be conversant with a number of disciplines in addition to electromagnetics.” The future, he said, will present challenges related to the IoT and personal-area networks and the resulting incredible density of wirelessly connected electronic devices, with decreasing size and power adding more immunity concerns.

Brench concluded by saying a successful EMC full system design requires you to think outside the box, think about the box, and think inside the box.

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