EMC: misconceptions and challenges

As products become more sophisticated, the probability they will experience electromagnetic compatibility (EMC) issues also increases; both as potential emitters of electrical interference and as victims of interference. Below are some insights, from EMC expert Martin O’Hara*, on misconceptions and challenges regarding EMC.

Why is EMC a compelling subject for engineers and designers?

It is a legal requirement to produce equipment that does not pollute the atmosphere with electrical noise which may cause products to interfere with each other; in some cases this may cause an issue with a safety-critical or life-critical product malfunctioning.

Some of the EMC problems may be caused by subsuppliers changing their process making, switching speeds faster in microprocessors for example. If the EMC implications have not been considered, the generated noise can be increased, without the knowledge of the product designer, even if the driving clock stays the same frequency.

What might be the biggest challenges facing engineers as they strive to achieve compliance?

Engineers need to acknowledge that EMC compliance should be considered at the beginning of the design cycle and embedded into the design itself - that it is not just ‘another test’ to be passed after the product has been produced. For example, being aware of where to place components, physically as opposed to schematically, to give best EMC performance is a critical but often overlooked aspect and usually very simple to implement.

Most test standards stop at 2 GHz frequency, but we are surrounded today with higher frequency radio noise; Wi-Fi and Bluetooth are two common areas that exceed 2 GHz and we all have to work with these signals. Hence, sometimes EMC design may be functionally necessary even if the current standard doesn’t cover areas of interference. The test standards themselves will eventually catch up and cover these higher frequencies and therefore testing and compliance will become more challenging.

There are many products which traditionally have very few issues with compliance, and learning how to become competent in preventing test failure, when for instance monitoring systems are introduced, is a new challenge for designers that might today think they don’t need to worry about this issue.

What are the most common misconceptions surrounding this subject?

EMC compliance is truly about design and not just about testing; it is much cheaper to design for compliance than fix after a test failure. Designing for compliance can not only reduce development and test costs, but it can also reduce production and manufacturing costs. If the PCB is designed to maximise its EMC performance for example, shielding may be avoidable and products may be able to use plastic rather than metal casing.

*Martin O’Hara is a leading figure in the EMC arena and in addition to his widely acclaimed EMC textbook he has written numerous technical papers on automotive electronics, circuit stimulation as well as EMC. He is currently head of product development at Chargemaster (UK).

O’Hara will be in Australia presenting his one-day EMC workshop at the SMCBA conference and ElectroneX expo on 12 September. He will demonstrate how, with the use of available PCB technology, layout and component selection, you can improve all aspects of EMC performance and achieve compliance early in the design process. The techniques are presented in an easy-to-understand and -use format, without resorting to complex mathematics or an in‐depth knowledge of electromagnetics. His no‐cost methods have led him to achieve almost 100% first‐time compliance in every design he has been involved with.