EMI suggested reading

Electromagnetic interference (EMI) can wreak havoc on the performance of a device. So selecting the right shielding to protect it is important, but that can also be a bit daunting. A glance through the products we’ve covered in our EMI/RFI section shows that there are a lot of solutions out there to choose from. But how do you know that you’re using the proper solutions for your particular device or application? There are various shielding and ferrite solutions, including types of packing and coatings.

While I was searching for more in-depth information on EMI suppression, I came across the following white paper from Laird Technology (www.lairdtech.com). The paper, “Automotive EMI Shielding Controlling Automotive Electronic Emissions and Susceptibility with Proper EMI Suppression Methods,” by John Noto, Gary Fenical, and Colin Tong, offers a clear explanation of what EMI is, and how crucial it is to contain or suppress it. The paper’s introduction states, “Placing a large amount of electrical and electronic systems into a very confined space poses the problem of keeping the Electromagnetic Interference (EMI) of these systems from interfering with each other through radiated and conducted emissions, sometimes referred to as crosstalk. If not properly controlled, the interference can cause each system to malfunction, and even fail. With most systems now fully electronic, the need to contain EMI is more vital than ever.”

The paper goes on to discuss, in detail, how automobiles today require numerous electrical and electronic systems to be contained in a small space, which makes the issue of containing their EMI emissions even trickier. The paper also describes how susceptible these systems are to both internal and external EMI. Without the proper control, the interference could cause system malfunction or failure.

Any vehicle device used internally or externally (such as ignition systems, CAN Bus, garage door opener, MP3 player with Wi-Fi) must be used according to electromagnetic compliance (EMC) design. “EMC can be achieved from different design levels, such as from chip level integrated design, PCB, module or enclosure, and interconnect to software control. Different design techniques have been developed for various EMI problems, depending on the particular system, its electronic design, and the type of interference source.” If a device does not meet these requirements, then generally the applicable solution is shielding. The paper offers equations for analyzing emission levels and susceptibility.

Of course, it must be taken into account that this paper is application specific. However, the information presented can be applied to any number of applications with several components in a compact space. Following the paper’s format, it would be interesting to catalog how EMI affects other applications, say, medical or consumer electronics. The paper in its entirety can be found here: http://bit.ly/jcT16X. After you’ve read through, let me know what you think. Or, give me your product/solutions suggestions for EMI. For either, e-mail me at
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