FCC Part 15 Requirements — EMC Compliance Guide
Complete guide to FCC Part 15 requirements for intentional and unintentional radiators, covering Class A and Class B limits, testing procedures, and the path to compliance for the US market.
What Is FCC Part 15?
FCC Part 15 is a section of Title 47 of the United States Code of Federal Regulations (47 CFR Part 15) that governs the emission of radio frequency (RF) energy from electronic devices. Administered by the Federal Communications Commission (FCC), Part 15 establishes the technical requirements and operating conditions under which electronic devices may be marketed and operated in the United States without an individual radio station license.
Virtually every electronic device sold in the US market must comply with FCC Part 15, making it one of the most widely applicable EMC regulations in the world. Unlike the European ECE R10 framework, which is specific to automotive applications, FCC Part 15 covers a broad range of consumer, commercial, and industrial electronic products including computers, monitors, LED lighting, power supplies, wireless devices, digital cameras, and automotive electronics destined for the US aftermarket.
Device Categories Under Part 15
Unintentional Radiators
An unintentional radiator is a device that generates RF energy as a byproduct of its operation but is not designed to emit RF energy intentionally. Examples include computers, switching power supplies, LED drivers, motor controllers, and digital circuit boards. These devices must meet the conducted and radiated emission limits specified in Part 15 Subpart B.
Intentional Radiators
An intentional radiator is a device that deliberately generates and emits RF energy by radiation or induction. Examples include Wi-Fi routers, Bluetooth devices, wireless sensors, RF remote controls, and short-range communication modules. Intentional radiators must comply with the requirements in Part 15 Subpart C (or other applicable subparts) and are subject to stricter authorization procedures.
Incidental Radiators
An incidental radiator is a device that is not designed to generate RF energy at all, such as a DC motor or a mechanical thermostat. These devices are subject to the general operating requirements of Part 15 but are not required to meet specific emission limits or obtain FCC authorization.
Class A vs. Class B Limits
FCC Part 15 Subpart B defines two classes of emission limits for digital devices:
Class A — Commercial, Industrial, and Business Environment
Class A limits apply to digital devices marketed for use in commercial, industrial, or business environments. These limits are less stringent than Class B because the electromagnetic environment in commercial settings is generally less sensitive.
Class B — Residential Environment
Class B limits apply to digital devices marketed for use in residential environments or devices that may reasonably be expected to be used in a residential setting. Class B limits are approximately 6-10 dB more stringent than Class A because residential environments contain sensitive consumer electronics such as televisions, radios, and communication equipment.
Emission Limits Comparison
Radiated Emission Limits (measured at specified distance):
| Frequency Range | Class A Limit (10 m) | Class B Limit (3 m) |
|---|---|---|
| 30 - 88 MHz | 90 uV/m (39 dBuV/m) | 100 uV/m (40 dBuV/m) |
| 88 - 216 MHz | 150 uV/m (43.5 dBuV/m) | 150 uV/m (43.5 dBuV/m) |
| 216 - 960 MHz | 210 uV/m (46.4 dBuV/m) | 200 uV/m (46 dBuV/m) |
| Above 960 MHz | 300 uV/m (49.5 dBuV/m) | 500 uV/m (54 dBuV/m) |
Note: Class A limits are measured at 10 meters, while Class B limits are measured at 3 meters. When normalized to the same distance, Class B limits are significantly more stringent.
Conducted Emission Limits:
| Frequency Range | Class A Limit (QP) | Class A Limit (Avg) | Class B Limit (QP) | Class B Limit (Avg) |
|---|---|---|---|---|
| 150 kHz - 500 kHz | 79 dBuV | 66 dBuV | 66-56 dBuV* | 56-46 dBuV* |
| 500 kHz - 5 MHz | 73 dBuV | 60 dBuV | 56 dBuV | 46 dBuV |
| 5 MHz - 30 MHz | 73 dBuV | 60 dBuV | 60 dBuV | 50 dBuV |
*Class B limits decrease linearly with the logarithm of frequency in this range.
Testing Requirements
Conducted Emissions (150 kHz - 30 MHz)
Conducted emission testing measures the RF noise that the device injects back onto its AC power cord (or other external cables). The measurement uses a Line Impedance Stabilization Network (LISN) that provides a defined 50-ohm impedance at the measurement port. Testing is performed using both quasi-peak and average detectors.
Radiated Emissions (30 MHz - 40 GHz)
Radiated emission testing measures the electromagnetic fields emitted by the device and its associated cabling. Testing is performed on an Open Area Test Site (OATS), in a semi-anechoic chamber, or in a fully anechoic room. The device is operated in its highest emission configuration, and measurements are taken at the specified distance while the device is rotated and the antenna height is varied to find the maximum emission level.
For devices operating above 1 GHz, additional radiated emission measurements may be required up to the fifth harmonic of the highest intentional frequency or 40 GHz, whichever is lower.
Additional Tests for Intentional Radiators
Intentional radiators must also demonstrate compliance with:
- Spurious emission limits: Emissions outside the authorized operating band.
- Occupied bandwidth: The bandwidth containing the intentional transmission.
- Antenna requirements: Fixed antenna requirements for certain device categories.
- Power spectral density: Maximum power per unit bandwidth.
Compliance Pathways
FCC Part 15 defines three levels of authorization depending on the device type:
| Authorization Type | Applicable Devices | Process |
|---|---|---|
| Certification | Intentional radiators, devices operating in specific bands | Testing by accredited lab, application submitted to FCC or TCB |
| Supplier’s Declaration of Conformity (SDoC) | Unintentional radiators (Class A and Class B digital devices) | Testing by qualified lab, manufacturer self-declares compliance |
| No authorization required | Incidental radiators | General compliance with Part 15 operating conditions |
Certification
Devices requiring certification must be tested by an FCC-accredited laboratory. The test results, along with technical documentation, are submitted to the FCC directly or through a Telecommunication Certification Body (TCB). Upon approval, the device receives an FCC ID that must be displayed on the product label.
Supplier’s Declaration of Conformity (SDoC)
For unintentional radiators, manufacturers may self-declare compliance based on testing performed at a qualified laboratory. The manufacturer maintains a Declaration of Conformity on file and applies the FCC compliance marking to the product. No FCC ID is required, but the product must display the appropriate FCC compliance statement.
FCC Part 15 and Automotive Products
While vehicles sold in the United States are not subject to FCC Part 15 for their primary EMC requirements (vehicle-level EMC is addressed by manufacturer standards and FMVSS regulations), aftermarket automotive electronic accessories and modules that are sold separately do fall under FCC Part 15 jurisdiction. Products such as aftermarket head units, dashcams, GPS devices, and OBD-II diagnostic tools must comply with FCC Part 15 before they can be legally marketed in the US.
How TESTUPS Can Help
TESTUPS provides FCC Part 15 pre-compliance and compliance testing for both intentional and unintentional radiators. Our testing facilities include semi-anechoic chambers, LISN networks, and calibrated measurement systems covering the full FCC Part 15 frequency range. We can assist with product classification, test plan development, and preparation of the documentation required for FCC certification or SDoC. For automotive electronics entering the US market, our team understands the intersection of FCC requirements and automotive EMC standards.
Contact TESTUPS to discuss your FCC Part 15 compliance testing needs.
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