USB 2.0 and FCC/CE EMC compliance

Regarding cables etc. ask the range engineer how this is typically done. I have not done FCC for USB but for other devices. How bad are you failing? When you quasi-peaked were you still over? Is your device shielded? In addition to the things you listed above, it could actually be your device which is failing FCC Class B...when you were connected to a usb 1.1 port the 480MHz clock on your device was probably not operating. When you connected to the two different PCs it was operating...just pointing this out.

If your device is not shielded go to the grocery store and buy some disposable baking pans cut out appropriate holes for USB, power, etc. At the range with the baking pan in place, does your emissions go down? If your emissions goes down it is probably an issue with your design. You will need to look at PCB layout etc.

regards, Kadir "Solid Gold" Suleyman

Thanks. My device is enclosed in a partially metallic(steel) enclosure. An older design had a fully metallic enclosure, and the spikes were slightly less but still there. The layout/design for the older design is different though, so it's not an apples to apples comparison. I thought about wrapping the device up with aluminum foil as well, but seeing that the older design was already fully shielded, would that help?

Unfortunately for us, the testing engineer isn't very interested in helping us pass. He's just doing his tests and telling us that we're failing without providing us with much help, and this is the first time I'm doing FCC/CE testing, so I'm kinda lost as to what I should be doing as well. I'm hoping it's a simple cable issue, but I'm just not sure.

Hmm.. Partially metalized is pretty good for a consumer device. You never mentioned how bad you are failing with the spikes. It's impossible to say without looking at your layout, and having someone who is knowledgeable of USB testing advise you of the correct procedure. But...

Do you have an EMC analyzer? If you can at least rent one, and a close-field probe (or make one using coax and an improvised antenna), you should be able to probe around and take relative readings and isolate out where the radiation is coming out. Check the data sheet and make sure you don't have any unnecessary clocks turned on. Try both shielded and unshielded cables.

Eliott labs (Silicon Valley area) is an excellent EMC lab and you can ask their EMC engineers questions. First thing I would do, tho is check your layout.

The spikes are pretty bad. For FCC, here's how much it's failing by

For CE, here's how much it's failing by

Theses are over a few different PCs.

I might have access to a spectrum analyzer, but I'm not sure if I have antennas or near field probes available. I'll check though. I'm not in the USA so I don't think I'll be able to use their services.