Designing for EMC -- requires a continual focus on many levels throughout the entire product development cycle. The things that are done to insure acceptable EMC performance are usually things that should be done simply as a matter of good sound design practice.

People often loose focus regarding the sources of emissions and the vulnerabilities to interference. It seems EMC is one of the first issues to get lost when the pressures of showing progress start to take control of time allocation. It's only natural....nobody can see EMC performance. When it comes time to show off the first prototype people want to see lights flash or whatever else the product is supposed to do.

I can't remember the last time I was in a conference room to demonstrate the first operational model of a new product to the executive staff or even the engineering staff and heard someone ask "Ok it's farther along than we had expected but, how do we stand on emissions and immunity? It just isn't something that's all that visible and most people don't know it is an issue to begin with. That's why the design engineers are there anyway; to stay on top of all the details.

The Scenario goes like this....
The schedule says the board layout is to be complete on the 12th so "first copper" boards can be in the manufacturing plant for a pilot run on the 19th (the next opportunity to slip your board in the production flow won't come around again for three weeks) and the engineer missed three critical days for jury duty. The next thing you know the remaining components are being put on the board "wherever" and they are being hooked up "however" so the fabrication files can be released to the board house on the 12th. What the heck - this is only the first copper and you'll take time to improve the layout on the next pass (like that'll ever happen).

This is just one of the many ways we end up at the test lab wondering how our 12MHz Gizmo is producing all that energy in the 900MHz band where the spectrum analyzer shows a display that looks like comb with teeth 24MHz apart. The product is exceeding emissions limits.

The truth is that keeping EMC in mind during the entire process isn't all that much of a distraction; it just requires a bit of discipline. The things that are done to insure acceptable EMC performance are usually things that should be done simply as a matter of good sound design practice.