A manufacturer can use radio modules to enable connectivity of electronic and consumer products, for wireless communication and the IoT. That means that you are now a radio equipment manufacturer. Even if your product’s purpose was something totally different. When integrating an RF module (even if its a pre-certified module) into your product then you must know the module integration rules for your country approval.
FCC & ISED
In North America, the FCC and ISED both require certification for radio transmitters. That is a formal procedure to register a product with the relevant national authorities and provide them with the technical files of that product. So its not just passing some compliance tests. The FCC ID and IC ID on a radio transmitter relates directly to the certification filing for that product, held by the FCC and ISED.
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.” Please note that in the US 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.
There is also a possibility 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 a modular approvals process. It allows the certification of the radio transmitter module to remain valid, even after the module is installed into a host. This is very handy, because a transmitter certified without this modular approval process can not keep its certification when installed inside a host device.
There are additional requirements for modular approval. Not only does the radio module need to pass all the tests associated with the technology it supports in terms of radio transmitter (for example, if it is a Bluetooth module, it must pass the Bluetooth tests). But there are other requirements specific only to the modular approval that it needs to pass. For the US requirements, you should check FCC §15.212 and for Canada requirements ISED RSP-100 issue 12 section 8 for the details. 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 will pass all the tests when installed in the host product.
But this how it starts with RF modules, 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 or ISED certificate. The module can then be used in any host and under most conditions.
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. 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.
Documentation related to RF modules
With modular approval comes also the need to document it well in your filing. For example the text on the FCC grant, which mostly includes statements like: “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. This is because 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.
Its important to understand that the note on the FCC grant does not mean “cannot” or “must not” but it 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.
Besides the module’s test report, there is another document, which is very important for certification of the radio module. Perhaps even more important are the installation instructions that accompany the module. This is clearly the case regarding the antenna, and module installation instructions, which should 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.”
Also note that FCC and ISED approvals essentially deal exclusively with the output or emissions of devices, so that 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
So now that we looked at module approvals from the module manufacturer side, we can switch to the side of module installers. They buy a module and install it in their host device and they want to sell that host product in North America. Many module installers think that all the work has already been done for them, because the module is certified and they can just install the module and relax. But that’s not how it works. 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 has responsibility for the overall technical compliance and has some important decisions to make. (Remember that there is a difference between testing and approval!)
The legal requirements for the radio module, as it is a transmitter and must be certified, should already have been fulfilled if the module manufacturer has certified the module. So looking at the labeling requirements of your host product, you have to make sure the integrated module’s FCC ID or IC ID has been marked on the host product. This way you have correctly indicated that a certified radio module has been installed in your product. Suitable marking would include putting the text “Contains FCC ID: XXXXX” and “Contains IC: YYYY-YYY” on the product label.
At this point only the module is certified and your host product still remains uncertified. 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 IC ID, along with variations of the “Contains” statements noted previously.
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. For example if you have a host with a clock frequency of 30 MHz, which means you have always 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.
Also, 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.
The installer is responsible for checking the transmitter tests on their final radio product. This is because a high number of installations actually fail the tests at first, until the installer fixes them. Installers may need to redo some work on how they install their module until the final radio product is passing the required transmitter tests.
Its also not the case that you have to fully perform every radio transmitter test. But some tests, 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 isotopically radiated power (EIRP) and spurious emissions are really unknown until the manufacturer of the final radio product performs their own measurements.
You might think 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 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.
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 formalized 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.
Testing exceptions and deviations
There are some cases with exceptions. To take 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.
What is meant with changes to the module certification, is 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 IC ID 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 now.
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.
Radio modules for the EU (CE marking and RED)
For the EU, we work with CE marking and in this case we have to look at the Radio Equipment Directive (RED). After much searching, we realize there is no section on radio modules in the RED and there is no section for modular approvals. In fact, we realize there is no certification either! Everything is Declaration of Conformity (DoC) for the RED. The DoC applies to the final radio equipment, and the DoC is created (and signed) by the manufacturer of the final radio equipment, to cover everything within their product. The RED includes assessments of radio performance, EMC performance and product safety (including RF exposure) on any equipment that includes a radio function, transmitter or receiver.
There is nothing in the RED specific for radio modules, or radios intended for installation into other equipment; and therefore, a radio module is just like any other piece of radio equipment in the EU. In this case, the radio module manufacturer has defined their module as radio equipment within scope of the RED, they must CE Mark it for the RED. They do not have the choice to provide it without authorization, that we saw in North America. They are placing radio equipment on the market in the EU and it must be CE Marked, even if its marketed exclusively for business-to-business.
How the module is marketed into the market is as follows; The RF module has to be assessed by the module manufacturer, which most likely would include testing. After that the module manufacturer creates his DoC, and CE Mark the module to the RED. You may know that there is a Notified Body role and that the Notified Body can issue a certificate called an EU Type Examination Certificate.
The difference between the EU and North America in how they handle module approval, is that in the case of North America, they focus on transmitter performance and EMC emissions only, with RF exposure as the safety requirement. In the EU however, we have radio transmitter performance, radio receiver performance, EMC emissions, EMC immunity, product safety and RF exposure. The radio module must be assessed to all of these requirements by the module manufacturer, in just the same way that any other radio equipment would be assessed. They cannot leave part of the assessment of their device to the installer.
For the EU, there are no special assessment procedures for radio modules, there is no ‘EU modular approval’. There are no requirements that a module must have a dedicated antenna or voltage regulation, etc.
But what the RED states, is that radio equipment shall be assessed for its intended use and intended environment, which is quite simple for most products, but for radio equipment which is expected to be installed into other products, where the module manufacturer generally does not know which other products it will be installed into, or how it will be installed. For that reason, the most common solution by radio module manufacturers is that the radio module is assessed on a test jig or at the end of a length of cable, and then it is CE Marked as radio equipment, for use on that test jig or cable.
CE Marking of the radio module is a declaration by the module manufacturer that the radio module complies with the RED, and the installation instructions and DoC document of the radio module should state the conditions in which it is compliant. The installer should be able to confirm which antenna, test jig, temperature range, voltage range, software version, etc., was used by the module manufacturer. And if the radio module has a Type Examination Certificate from a Notified Body, then this information could also be found on the certificate. But if there is one place where it should not be missing, then its the installation manual.
But please note one thing. The CE mark on the radio module does not guarantee that the final radio product will also comply with the essential requirements when the module is installed into a host (CE + CE ≠ CE). What the CE mark on the module says is that at least the module is capable of passing all the tests, in at least one condition.
Module installers in the EU
The manufacturer of the final product will install the radio module into their device (the host) and therefore create a new final radio product. Until this point, their host was perhaps not even a radio product at all and maybe they had previously only applied the EMCD and LVD. Now, with the inclusion of the radio module, the final radio product comes within scope of the RED; which means that the EMCD and LVD no longer apply to the equipment because EMC and Safety assessments are covered within the RED. The manufacturer of the final radio product takes full responsibility for the new radio equipment. They create their own DoC to the RED for their product, and put the CE mark on their product.
Safety, EMC and Radio performance testing must be assessed at the final radio product; but the installer may decide that some of those radio tests do not need to be fully repeated (compared with the results from the module it self). The installation into the final product could make the radiated radio and EMC performance better, worse, keep it the same or completely different.
Most likely, tests like duty cycle, frequency hopping, etc., would be unlikely to change if the module is installed correctly without any modification. However, the test cases where the change of enclosure could affect it, such as e.i.r.p., spurious emissions, receiver performance, etc., should be investigated; especially if the radio’s antenna is inside the host equipment. The addition of a new type of antenna could also affect the radio performance.
Conclusion
Radio modules are a very popular solution to the problem of product manufacturers wanting a quick radio connectivity solution, without the headache of designing their own radio. Many times these are manufacturers involved with the IoT, which design typically non-radio products, but could use radio modules to allow them to have access to the latest expertise in radio communication in a quick way. The FCC ID, IC ID and CE mark are signs of compliance and they indicate a level of quality that installers desire.
