Walk-in EMC testing a Bluetooth speaker

You can make single board products with fast electronics pass CE/FCC in plastic or no housing.

It is easier if you:

• keep all cables attached in one end only
• use fewer cables
• specify a specific simple application for the FCC/CE test
• don't have things that stick off the board (display, large connectors etc.)
• make a very low impedance power distribution network (PDN)
• have good filtering on the interfaces off the board

It is very difficult if you have multiple boards (plug-in, stacked, cable connected etc.). Actually I would specify a Faraday cage type box if you have multiple boards.

If you absolutely must include a display - try to get one with LVDS interface.

If you have a radio as part of your design, some of this becomes a bit more complex.

I suspect many go fairly light on the CE/FCC thing and self-certify with limited time spent on measurements. It is highly unlikely anyone will ever sue you for an eval board that is out of FCC/CE spec and most of these boards runs in fairly limited volumes.

Also: I have seen some outfits in China offer to do very cheap CE/FCC marking for you. You get the paperwork - they get some money. Win-win. :-)

In my experience, the WiFi module supplier will have programmed test modes into the module that support the testing that is required for product certification. Hopefully your supplier has done so as well.

The problem I've seen is that the documentation for these modes is not publicly available, so we have to call and establish an engineering relationship to get it. Often times it is not as stable as we'd like (meaning: we've seen "undocumented features" in test modes).

My group had to hound a very large and well known silicon manufacturer to get their certification documentation (which we found was incomplete and nudged them to get it up to date) and information on how the test API worked. Once we got it, we wrote custom test software packages to set up the proper transmission for the proper test.

We included a user interface since fiddling with software configurations at a test lab is the wrong place to be doing that - better to make it quick, easy and foolproof.

When we started with WiFi modules, we thought that it was super easy - simply put the module into the product and use it in the way that it was certified by the manufacturer, put their FCC ID on the sticker and done. Not so. WiFi module manufacturers may not certify to all product applications - or in fact only a few generic ones - and so you may find yourself having to go to the lab for a wireless cert because you put it in a product whose application didn't conform to the FCC cert the module manufacturer did.