Preparing Your Product For The FCC

At some point you’ve decided that you’re going to sell your wireless product (or any product with a clock that operates above 8kHz) in the United States. Good luck! You’re going to have to go through the FCC to get listed on the FCC OET EAS (Office of Engineering and Technology, Equipment Authorization System). Well… maybe.

As with everything FCC related, it’s very complicated, there are TLAs and confusing terms everywhere, and it will take you a lot longer than you’d like to figure out what it means for you. Whether you suffer through this, breeze by without a hitch, or never plan to subject yourself to this process, the FCC dance is an entertaining story so let’s dive in!

There are two kinds of things that are getting tested; intentional radiators and unintentional radiators. Intentional means they are purposely putting out RF signals, like WiFi, Bluetooth, or any other transmitting radio. These must be tested and filed with the FCC before you can start selling or even marketing your product. Here you are looking at CFR 47 Part 15, Section 247 most likely.

Then there are unintentional radiators. This could be switching noise from a power supply, accidental antennas from poor ground pours, or long clock traces. You need to have your product tested for unintentional radiation (if you are an intentional transmitter you still have to have unintentional radiation testing as well), but you don’t necessarily need to have the reports sent to the FCC. Depending on the type of product, you will either need to do Verification (you don’t need an official testing lab and you keep the reports yourself in case you get asked), Declaration of Conformity (you need an official testing lab, but you keep the reports yourself in case you get asked), and Certification (in which you use an accredited testing lab and the FCC reviews the filed documents). The relevant part of the FCC guidelines is CFR 47, Part 15, Section 109.

There’s another thing to consider, and that’s FCC Modular Approval. If you want to avoid all the hassle and expense of intentional emission testing, you can use a wireless module that has modular approval. There are lots of companies that make these modules for BLE, WiFi, Zigbee, GSM, and pretty much any wireless tech. They go through the painful FCC process for you and sell you their module, which has the chip, balun, antenna, crystal, and shield, all in a pretty package that you can solder onto your PCB. This will avoid the intentional emissions testing and give you an optimized transmitter. You’re still responsible for unintentional radiation on your full board, but this is much cheaper and easier and may not even need to be filed.

For low volumes of products, modules are a great way to jumpstart product development and start scaling up, and when you have proven the market and the economics make sense to switch (usually in the tens of thousands in volume), then you can go to your own design.

Let’s pretend you’re selling a WiFi toothbrush that records how long you’ve been brushing and uploads it to the cloud so that parents can hover over their children in yet another way. You’ll have to get your product tested for both Sections 109 and 247. The FCC doesn’t have their own testing facilities to do this; they accredit other testing facilities, and they’re located around the world. They even have a tool to help you find them.

Request quotes from a few test facilities as well as timelines for when they can get your product into their facility for testing. They will generally handle the filing after you fill out a few forms. Quotes for an intentional transmitter may contain sections for the following (rough ballpark numbers. your results may vary):

What’s the IC? That’s Industry Canada, and if you want to sell in Canada, you have to jump through a couple extra hoops, but it’s better to do it at the same time than later and have to rerun the tests. Your test facility will help you navigate all the accounts you need to create and documents to file.

Once you’ve picked your facility, you need to prepare your Equipment Under Test (EUTs) and LOTS of documentation. The documentation can take a month or more to prepare and get settled. They want to know everything, including what the label is going to look like and how it will be affixed to the product permanently.

This prep work doesn’t end with the photos, user manual, Description of Operation, schematics, and block diagrams (the documents you see on the FCC EAS web site are a subset of the total number of documents prepared). You also have to prepare a test procedure document and make sure that your firmware is ready to handle all the strange modes you will have to put it in, and the other hardware you send (like any computers you install software on to control or reprogram the EUTs) is ready and easy to use. Time in the chamber is extremely expensive, and you want your testers to have as easy a time as possible and not need to contact you with a simple problem caused by an oversight.

With the EUTs, they’re going to want to test in all possible configurations, so you’ll need to test your WiFi toothbrush when it’s running on battery, but also when it’s plugged in to the wall to charge. If you are including a charger, you’ll have to include the charger in the tests, even if it says it’s already FCC certified, because it’s the combination that you are selling which must meet the standards.

You’ll test it in normal operating mode, but also in continuously transmitting mode on every channel possible, so you’ll need to include firmware (or some way to control) which channel it is on and to put it in a special mode that allows for continuous transmission. Sometimes, manufacturers have made this a bit easier for you. For instance, if you are using a TI chip there is SmartRF Studio, which makes this really easy.

The FCC guidelines allow for certain powers at specific frequency ranges, so it’s possible that your device might be ever so slightly outside the range at the highest or lowest channel. You’ll either have to change the PCB, or you may be able to get away with writing firmware that limits the power at those extremes (you’ll have to have this tested), or write firmware that prevents the device from using those channels.

The testing facility will also want to measure output power directly, which means hooking up an SMA connector to the antenna. Lots of times your product won’t HAVE an SMA connector and will just pipe straight to a trace or chip antenna. This is where you get creative and cut the trace and airwire a short wire to an SMA connector that’s firmly glued to the PCB. It’s a hack, but it’s as close as you can get to being a good measure of the output power.

It’s not uncommon for a design to fail the first time. This sucks, but it’s not the end of the world. The testing facility may suspend tests, tell you what they think might be wrong, and let you fix it before continuing. You’ll often see space for extra passive components in the path between the transmitter and the antenna. These are for making whatever fine adjustments are necessary to get the PCB to be in compliance.

A note from personal experience; stay engaged with your testing facility. I was unfortunate in that mine needed constant prodding, for a few months it wasn’t responding to email or phone calls, and from signing the contract to filing with the FCC was a whopping ten months. Usually you can expect it to take one or two, but as a little guy you may have to fight a little harder.

FCC testing can be intimidating, especially if it’s your first time. Testing facilities are accustomed to FCC virgins and will do some hand-holding, but a lot of the preparations are time consuming and need to be done by you. However, this certification is crucial in unlocking a huge market for your product. As with choosing the right components, case design, manufacturing process, and packagaing, FCC testing needs to be considered when planning product development timelines and throughout the design process.

[FCC testing image source: Some Hardware Guy]