3 Dealing with EMC Phenomena

For most engineers, EMC design is a relatively new subject. Before Europe introduced the EMC directive, it was possible for a company to build and sell their products without paying too much attention to the problem. As long as the products worked as intended and did not interfere with broadcast stations, everything was basically fine.

The three-year transition period from the time the directive was effective in 1992 until it was a requirement in 1995 did not do much to change this. In many companies, the real work did not start until there was no longer a choice. And then, the only option was the hard, expensive way: take an existing product, which perhaps was designed without any thoughts of EMC at all, and try to add the necessary filter, protectors, shielding, and whatever to make it EMC compliant. This is the worst possible approach; the cost is high and the results are usually poor.

When designing a new product, it is very important to start thinking EMC from the beginning. This is when all the low-cost solutions are available. A good PCB layout does not cost more in production than a bad one, but the cost of fixing a bad one can be high. One of the most expensive mistakes a designer can make is to believe that EMC is something that can be dealt with after everything else is finished.

What approach to use depends, as always, on estimated system cost and production volume. For a low-volume system, the best way out may be to use expensive components and system solutions to reduce design time. For a high-volume, low-cost application, it may be better to spend more time and resources on the design to reduce the overall cost of the final product.