Testing and Approval of Radio Modules in North America

Hello! Who are you, and why are you reading this article?

That’s actually part of the problem with this topic. Many of the people who need this information are unaware that the topic actually applies to them. I meet people all the time who tell me “I don’t need to know about radio module compliance or the Radio Equipment Directive (RED) because I just make this cool new IT gadget (for the home, car, clothing, etc.). It uses CE-marked modules to connect to a phone and uses GPS to know the location.”

Of course, they really do need to know, because they are now a manufacturer of radio equipment.

Or, I hear “I don’t need to know about the FCC rules for radio testing because I bought a pre‑certified radio module.” Again, that is another misconception.

In this article I’ll provide an overview of the basic requirements for North America (the FCC for the U.S. and ISED for Canada). In a future installment of this article, we’ll cover radio module requirements for the European Union (EU) (the Radio Equipment Directive (RED) and the EMC Directive (EMCD)).

A Brief Word About “Testing” Versus “Approvals”

Before we go any further, I want to say something critical to understanding this topic and regulatory compliance in general. Anyone involved in getting equipment approved for use by meeting the regulatory requirements needs to separate the process of “testing” from that of “approval.”

“Testing” (or other forms of technical assessment) is an engineering assessment or set of measurements, typically with the purpose of identifying whether or not a product passes some technical limits. Often, testing is performed by a test lab and it could be used to determine if the hardware can pass or fail the test standard. “Approval,” on the other hand, is the administrative and legal process for getting the product authorized for sale, marketing, placing on the market, etc.

Please keep that difference clear in your head at all times and remember that “testing” and “approval” are not the same thing.

A device may pass the tests in the standard, but it may not be authorized for use until the correct legal procedures have been followed. Or, a product may appear to be legally authorized but may not pass the tests when taken to a measurement site or test lab. Sometimes, a change to a product requires re‑testing but not re‑approval. Sometimes, a change to a product requires re‑approval but not re‑testing.

I hope you get the idea.

Compliance Requirements for Radio Module Manufacturers

To really understand this topic of radio-enabled equipment using radio modules, we need to begin by looking at the radio module itself and the compliance requirements for the radio module. This is looking at the industry from the view of the radio module manufacturer. You may already be gazing out of the window in boredom if you do not actually make the radio module, but it is important for the installer to know the legal and technical status of the module they purchased. After that, we will look at the topic from the point of view of the installer.

So grab yourself an Americano coffee and maybe a snack as we begin with North America because the requirements and the situation are most simple there. We will move on to the requirements for the EU in the second installment of this article.

In North America, the FCC and ISED Canada both require “certification” for radio transmitters. Certification does not just mean that a device passed some tests. Rather, certification is a formal procedure that involves registering a product with the relevant national authority and providing them with the technical details of that product. For the FCC for example, the manufacturer would test their transmitter and then get it certified by a telecommunications certification body (TCB), submitting to the FCC the test results as part a technical file for the device. The same applies with ISED Canada. The FCC ID or ISED certification number on a radio transmitter reflects the certification filing for that product as submitted to the FCC or ISED.

The “Modular Approval” Route

Certification applies to most transmitters, but it is possible to get a special type of certification which is specific to radio modules intended to be installed into other equipment. This special certification type is known as “modular approval.” However, in the U.S. and Canada, it is not mandatory for the module manufacturer to get their device certified; therefore, modules can be sold to installers with or without certification.

It is also possible to certify a radio module as a standard radio transmitter, bypassing the modular approval route. But then, the device would only be certified for use as a standalone radio, which is not the intention of most module manufacturers.

So, the FCC and ISED have an established and mature modular approvals process. It is a special type of certification that allows the certification of the radio transmitter module to remain valid, even after the module is installed into a host. In most cases, a transmitter certified without this modular approval process cannot keep its certification when installed inside a host device.

In compliance terms, applying the modular approval process can give the transmitter “super-powers.” But achieving modular approval involves meeting additional requirements. The radio module must pass all the tests associated with the particular type of radio transmitter (for example, if it is a Bluetooth module, it must pass the Bluetooth tests). But additional requirements exist, including the following:

• A shield over the module’s transmitter section, to help reduce coupling of signals between the module and host;
• A form of voltage regulation, such that the final transmitter section of the module will see the same voltage, regardless of the supply from the host;
• Testing in stand-alone mode, ideally on the end of a length of cable (a test jig can be used if the module manufacturer can ensure the jig does not affect the testing);
• Control over the antenna used with the module;
• Labelling with its own unique FCC ID or ISED certification number.

Of course, meeting these additional requirements does not guarantee that the radio module transmitter will continue to pass all the tests when installed in the host product. You might reasonably ask why that might be the case. Well, as an engineer, I could argue that the use of a shield, voltage regulator and fixed antenna provide a good level of confidence that interference between the module and the host product are minimized. But there are never any guarantees. And, from a legal point of view, it’s in the rules.

So the radio module manufacturer tests their module in a stand-alone configuration and then certifies it as both a radio transmitter and a radio module, with “modular approval” written on the FCC Grant or ISED certificate. The module can then be used in any host and under most conditions (the exceptions being certain parameters associated with RF exposure compliance).

If the radio module does not meet all of the applicable regulatory requirements for modular approval, then it’s possible to obtain a “limited modular approval” (LMA) certification, in which the module is specifically tested and certified for use with the intended host product or device. This approach allows the LMA module certification to remain valid when used within that host device, or within other host devices sharing the same conditions.

A Word About Documentation

There is something which often confuses people about modular approvals, and that is the text on the FCC Grant. Most FCC Grants include a rather confusing statement which says “Must not be co-located with any other transmitter” or “Must not be used within 20 cm of a person.” What this really means is that the radio module manufacturer did not perform an assessment of what could happen when the module is installed next to another transmitter or used in close proximity to a body. Generally, this is not a failing by the module manufacturer. More likely, the module manufacturer simply did not conduct a co-location assessment since they didn’t know where their module would be installed, or what other transmitters might exist in the final product.

Actually, that note on the FCC Grant does not mean “cannot” or “must not,” and those terms are very misleading. The text on the FCC Grant basically means that, if you want to co-locate the module close to another transmitter that is active at the same time, or use the module close to a person, you’ll need to check that out. In effect, the term “cannot” actually means “cannot do it without some additional effort.” A more accurate Grant note would be something like “Co-location of this transmitter with another transmitter requires the use of the FCC’s multi-transmitter product procedure.”

I also want to point out that one of the most important documents for certification of a radio module is actually not the module’s test report. Of course, the test report is important and will be carefully reviewed by the TCB. But perhaps even more important are the installation instructions that accompany the module. This is clearly the case regarding the antenna, and module installation instructions must make clear which antenna(s) can be used. In cases in which a module only provides an RF pin or solder pad for an antenna path built into the host’s board, the installation instructions must clearly detail the precise design of the antenna path, including copper track widths, track corner angles, layout, etc. It’s a lot more complex than simply saying “use an antenna with x dBi gain.”

This is perhaps a good time to point out that FCC and ISED approvals essentially deal exclusively with the output or emissions of devices. Testing for the U.S. and Canada consists of transmitter output performance, EMC spurious emissions and the risks of RF exposure from the transmitter. With a few rare exceptions, such as the dynamic frequency selection (DFS) testing of 5 GHz WiFi, all tests are based on outputs from the transmitter and digital circuitry.

Compliance Requirements for Radio Module Integrators

Now let’s look at the world from the point of view of the company installing that radio module into their host product, and selling that host product in North America. Arguably, it is the more difficult role.

Many installers think that all the work has already been done for them and they can just install the module and relax. It’s generally true that the installer typically has less testing to do and can often avoid the legal aspect of module certification by using a certified radio module. However, the installer still inherits some responsibility for the overall technical compliance and has some important decisions to make. (Remember that there is a difference between testing and approval!)

Let’s start by looking at the legal equipment authorization requirements. The radio module is a transmitter and must be certified, such that the details of the transmitter are reviewed by a TCB and then uploaded to the FCC and ISED. Well, the good news here is that the radio module manufacturer already did all of that work! So the installer will probably not need to certify the transmitter part of the final radio product, since the modular approval process reduces or eliminates that part of the process.

If the radio module’s label is not visible on the final radio product, the installer must mark their product to indicate that a certified radio module has been installed. Suitable marking would include putting the text “Contains FCC ID: XXXXX” and “Contains IC: YYYY-YYY” on the product label, where XXXX is the FCC ID of the radio module and YYYY-YYY is the ISED certification number of the radio module.

Remember that only the radio module has been certified at this point and the final radio product remains uncertified. However, depending on what else exists within the final radio product, further certification may not be required. If further certification is required, the final radio product would need to be marked with its own FCC ID or ISED Certification number, along with variations of the “Contains” statements noted previously.

Technical Testing

We’ve now taken care of the regulatory approval of the transmitter, but what about the technical testing? The installer or manufacturer of the final radio product is responsible for ensuring that the final radio product meets all the technical requirements for that type of product. Simply put, modular approval exempts the installer from having to certify the radio transmitter, but not the need to test radio transmitter performance and transmitter emissions of the final radio product.

First, the inclusion of the radio module may have affected the testing of the digital device or general electronics of the host product. Let’s say you have a host with a clock frequency of 30 MHz, which means you have historically been performing your emissions testing up to 1 GHz for your Supplier’s Declaration of Conformity (SDoC). Now you install a Bluetooth or 2.4 GHz WiFi module into your device, so now you have a signal at 2.4 GHz in your device, which means you now must perform your §15.109 emissions testing up to 12.5 GHz for your Part 15 subpart B sDoC. The host product may still require its own authorisation, such as sDoC.

Second, you need to understand how the integration of a radio module might have affected the transmitter performance of your final radio product. We know that the radio module passed the tests when it was in standalone mode or on a test jig. But those results do not represent the compliance of the final radio product, and we have no way to predict if the combination of module and host will pass or fail the tests.

You may be surprised to learn that a very high number of installations actually fail the tests at first, until the installer fixes them. Installers may need to re‑work how they install their module until the final radio product is passing the required transmitter tests. Therefore, the installer is responsible for checking the transmitter tests on their final radio product.

I am not saying you must fully perform every radio transmitter test. I would say that some test cases, such as those for signal bandwidth, duty cycle or hopping requirements, are unlikely to change if the module has been installed correctly without modification. However, the output power or equivalent isotropically radiated power (EIRP) and spurious emissions are really unknown until the manufacturer of the final radio product performs their own measurements.

There’s often someone who will optimistically say that the enclosure of the host product should provide shielding to any radio signals from the module and that, if the module passed the output power and emissions tests while on a jig or stand-alone, then the emissions and output power would only be lower when installed in the host. However, attending a simple radio class or spending any time in a test lab will teach you that the host could: a) shield the signals from the module; or b) direct and re‑radiate the signals from the module; or c) signals could couple from the module such that they become signals from the host or create new signals by mixing with signals already in the host; or d) some other thing that no one quite expected.

(If I could accurately predict EMC test results without making any measurements, I would be writing my memoirs from a warm beach, not writing this technical article from my office.)

Therefore, you must take steps to assure that the final radio product passes the necessary tests, and that most likely means taking some measurements at a test lab. If you have installed multiple radio modules, or the final radio product contains multiple radio transmitters that could transmit simultaneously, then you must test it in that way. This is not a formalised test routine, with clear instructions about how many modes and channels you must test. Rather, it is the installer’s responsibility to test until they have established that the final radio product meets the technical requirements.

Some Testing Exceptions and Deviations

If it sounds like I have over-simplified things so that you have a hope of finishing this article before you retire, you would be correct. However, there are some cases with exceptions or deviations to what I have presented so far. Let me give you some examples: 

If the radio module is co-located with another transmitter and both can transmit at the same time in the same band, you need to check if the combined output powers exceed the total limit for that band, and whether the combined emissions pass the tests. If the radio module was certified for use at >20 cm from a person (known as ‘mobile’) and you want to install it into a device used near the body (known as ‘portable’), the radio module manufacturer will need to update their module certification for you.

If you use an antenna that’s different from the one that was certified with the radio module, the radio module manufacturer will need to update their module certification for you.

If the module is a solder-down type with an RF pin or pad, and if you’re not sure if your antenna path trace is identical to the one used on the test jig by the module manufacturer, then you need to check with the radio module manufacturer. If they tell you that your trace layout is not within their parameters, the radio module manufacturer will need to update their module certification for you.

…and these are just a few of the more obvious examples.

When I talk about changes to the module certification, I’m talking about a thing called a “Permissive Change,” which is a change to a certification permitted within the rules of the FCC and ISED. The radio module certification is in the name of the radio module manufacturer, so it is their certification to change.

Alternatively, instead of the radio module manufacturer updating their own module certification for you, they could give you permission to put your own FCC ID or ISED certification number onto their module through a process known as a “Change in ID” (FCC) and “Multiple Listing” (ISED). This allows the installer to take legal control of the module and make their own Permissive Change. The certification would still apply to the module only, not to the final radio product, but the module certification and legal responsibility would be in the name of the installer.

If the radio module is installed into a small wearable device which is used or held within 20cm of the person (known as ‘portable’) and requires specific absorption rate (SAR) testing (a type of RF exposure test); the modular approval route cannot be used
and the whole final radio product needs to be tested and certified.

Other Considerations

While we’re on the subject of legal control and responsibility, everyone always wants to know who is in trouble if market surveillance finds a non-compliant device. (Not that you would ever consider marketing a risky product, of course!)

As you can imagine, if market surveillance officials find a radio module on the market and test it, and find it is non-compliant, the module manufacturer is in trouble.

But let’s say that market surveillance officials assess a final radio product, for which the manufacturer has an electronic product with “Contains FCC ID: XXXXX” on the label, and the tests show that the combined product fails the FCC’s tests. Who is in trouble then? 

Well, to start with, the eyes of the FCC’s enforcement officers will likely be on both the module manufacturer and the manufacturer of the final radio product. If the radio module is removed from the host and the module is found to pass on its own but the final system fails, then the radio module manufacturer is no longer on the hook, and it’s the installer (i.e., the manufacturer of the final radio product) that’s in trouble.

On the other hand, if the radio module is removed from the host and it turns out that the module fails when tested alone (perhaps because of problems in manufacturing by the module manufacturer), and also it causes the final radio product to fail, then both companies are in trouble. That’s because the module manufacturer is selling a non-compliant module and the installer should have noticed that the final radio product did not comply before marketing their final product.

The most common mistakes people make with this topic are at the two extremes. Some people say “We installed two radio modules and the Grant says we cannot co-locate it; therefore we must fully test and certify our device.” Others might say “We installed a radio module and it is certified, so we do not need to do anything.” As you (hopefully!) know by now, neither position is correct. The answer lies between those two positions.

Conclusion

Radio modules are a very popular solution to the problem of product manufacturers wanting a quick radio connectivity solution because their boss told them that IoT is important, without the headache of employing a radio design team. In my experience, radio modules allow manufacturers of typically non-radio products to have access to the latest expertise in radio communication. The FCC ID and ISED certification number are signs of compliance and they indicate a level of quality that installers desire.

It is important for installers to know that you have bought into a great solution for connected business in the 2020s! However, it may not be quite the ‘plug it in and forget about it’ approach you had assumed or hoped for.

Part 2 of this article will appear in the May issue of In Compliance Magazine.