Incorporating modules that have already been FCC certified can be a good way to introduce wireless functionality into a product line. While the use of pre-certified modules simplifies the compliance testing process, several factors must be considered.

Certified modules have grant conditions associated with them. The grant conditions for a device are supposed to be documented in the device user manual, but they can also be found by looking up the device FCCID Form 731 on the FCC website. Grants usually include restrictions on antennas, operational duty cycle, and the intended usage model of the device, including collocation of the device with other transmitters and end user exposure to rf signals.

At minimum, an end product incorporating a wireless module still requires emissions testing, an emissions report, and appropriate FCC labeling prior shipping in US. If the module is used in a manner consistent with the module’s grant conditions, FCC part 15 subpart B unintentional radiator testing and documentation is required. FCC regulation 15.212 describes how labels must identify certified modules used internal to the end product.

If the module is collocated with another transmitter closer than either transmitter grant allows, or if the module is used in a manner inconsistent with its grant (i.e a mobile device grant used in a user extremity exposure configuration), additional testing and documentation must be provided to prove that EMC and end user rf exposure limits are not exceeded. EMC testing would include scanning for intermodulation noise products, and at minimum SAR exclusion thresholds for the collocated transmitters must be calculated. See KDB 447498 D01 for information about SAR testing and exclusion requirements.

If testing and calculations prove that transmitter performance is not degraded, the testing described above would be consistent with a Class 1 Permissive Change, which does not require filing with the FCC. Documentation for Class 1 configuration changes should be forwarded to the module manufacturers.   See FCC regulation 2.1043 and KDB 178919 for more information regarding Permissive Changes.

If a module is modified in a manner that increases its output power, a new FCCID is required for the device. This can be filed by either the end product manufacturer or the module manufacturer. A full suite of transmit performance tests are required specific to the operating frequency and mode of the module.

If a module is used in a manner that is inconsistent with the grant and degrades the performance of the module, including changes to the antenna or operational parameters, then a class 2 permissive change may be necessary for the module.

Class 2 permissive changes are required to be filed by the certified module manufacturer. If the module manufacturer does not wish to file the change, the end product manufacturer can request a cover letter from the module manufacturer granting permission to file the change. If the module manufacturer is not willing to give the end product manufacturer permission to file the change, then the end product manufacturer must obtain a new FCC ID. For more information regarding transmitter module equipment authorization, see the FCC KDB 996369 document.

In conclusion, while use of certified transmit modules in end user products can simplify the compliance process, care must be taken with regard to grant restrictions associated with the module. Factors such as antenna usage, operational duty cycle, intended usage model of the device, and collocation of the device with other transmitters all affect what testing and documentation is required before marketing a device in the US.

The contributions towards this discussion from Jeff Woods CB Manager at ACS test labs and Gordon Helm at AHD test lab are greatly appreciated. Feel free to comment on this and other upcoming blogs. The interpretation of rules and regulations with regard to EMC compliance test rules are often conflicting and confusing, and certainly warrant discussion.