-- 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.
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.
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