PART 15—RADIO FREQUENCY DEVICES
Active Regulation FCC47 CFR Part 15 regulates unlicensed devices, such as Wi-Fi routers and Bluetooth transmitters, to prevent interference with licensed services. It includes technical standards for intentional and unintentional radiators, with power limits for devices in bands like 2.4 GHz and 5 GHz. For Wi-Fi, output power is limited to 1 watt in certain U-NII bands (47 CFR § 15.407). Devices must undergo testing and meet specific emission thresholds to ensure compliance (47 CFR § 15.209).
Part 15 governs the operation of unlicensed RF devices in the U.S., including Wi-Fi, and other consumer electronics. It specifies technical standards, power limits, and interference rules to ensure that these devices do not disrupt licensed services. Devices operating under Part 15 must not cause harmful interference and must accept any interference received (47 CFR § 15.5). Compliance includes emission limits, certification, and labeling requirements (§§ 15.201, 209).
Summary of Technical Regulations
| Freq. Range (GHz) | Bandwidth (MHz) | Max Power (mW) | Max EIRP (mW) | Notes & Citations |
|---|---|---|---|---|
| 0.902-0.928 | 26 | 1,000 | ISM applications, including RFID. See 47 CFR § 15.247 | |
| 2.400 –2.4835 | 83.5 | 1,000 | 4,000 | Wi-Fi, Bluetooth. See 47 CFR § 15.247 |
| 5.150 –5.250 | 100 | 50 | 200 | U-NII-1. See 47 CFR § 15.407(a)(1)(i) |
| 5.250 –5.350 | 100 | 250 | 1,000 (+DFS*) | U-NII-2A. See 47 CFR § 15.407(a)(2) |
| 5.350 –5.470 | 120 | — | — | U-NII-2B (not currently authorized for unlicensed use) |
| 5.470 –5.725 | 255 | 250 | 1,000 (+DFS*) | U-NII 2C. See 47 CFR § 15.407(a)(2) |
| 5.725 –5.850 | 125 | 1,000 | 4,000 | U-NII-3. See 47 CFR § 15.407(a)(2) |
| 5.850 –5.895 | 45 | 1,000 | 4,000 | U-NII-4. See 47 CFR § 15.407(a)(3) |
| 5.895 –5.925 | 30 | — | — | U-NII-4 (DSRC/ITS/C-V2X**). See See 47 CFR § 15.407(a)(4) |
| 24.0 –24.25 | 250 | 100 | — | Used for short-range radar. See 47 CFR § 15.249 |
*DFS (Dynamic Frequency Selection) is required by the FCC for U-NII 2A and 2C wireless communication devices to avoid interference with radar systems that operate in the same frequency bands (to protect incumbent users). DFS allows devices to detect radar signals and automatically switch to a different channel if radar activity is detected. See 47 CFR § 15.407(h)(2).
**DSRC (Dedicated Short-Range Communications) or Celullar Vehicle-to-Everything (C-V2X) systems include road side units (RSUs) that require individual licenses under Part 90, Subpart M and on-bouard units (OBUs) (in-vehicle units) that are licensed-by rule under Part 95 (See 47 CFR Part 95 Subpart L).
47 CFR Part 15 provides the technical framework for unlicensed RF devices, ensuring safe and interference-free operation across various applications. Engineers and technicians implementing such systems should be aware of the following key details:
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Operation in Specific Frequency Bands (47 CFR § 15.247, § 15.401 - § 15.407):
Devices under Part 15 can operate in unlicensed frequency bands, such as the 2.4 GHz ISM band and U-NII bands in the 5 GHz range. The 6 GHz U-NII band (5.925-7.125 GHz) is now also available for Wi-Fi 6E devices. These bands support technologies like Wi-Fi and Bluetooth, with specific rules regarding power levels, spectrum sharing, and channel bandwidths. -
Power Limits and Antenna Requirements (47 CFR § 15.209, § 15.247, § 15.407):
Part 15 specifies power limits for different frequency bands. For example, in the 5 GHz U-NII bands, the maximum conducted power is 1 watt (30 dBm), and the effective isotropic radiated power (EIRP) can reach up to 4 watts (36 dBm) if the antenna gain exceeds 6 dBi. Engineers must consider these limits when designing systems to ensure compliance and avoid interference. -
Interference Mitigation and Frequency Sharing (47 CFR § 15.5):
Part 15 requires that devices do not cause harmful interference to licensed services and must accept interference from such services. Frequency coordination is not typically required for Part 15 devices, but spectrum sharing techniques like dynamic frequency selection (DFS) are mandatory in certain U-NII bands to avoid conflicts with radar systems. -
Emission Limits for Intentional and Unintentional Radiators (47 CFR § 15.209, § 15.109):
Devices must adhere to stringent radiated emission limits to minimize interference. Intentional radiators (e.g., Wi-Fi transmitters) have specific output restrictions, while unintentional radiators (e.g., computers) must limit spurious emissions. These limits ensure that devices operate within acceptable RF noise levels, particularly in environments with sensitive equipment. -
Testing and Equipment Authorization (47 CFR § 15.201, § 15.31):
Devices must undergo testing for compliance with Part 15 standards, including radiated emissions, power levels, and frequency stability. The type of authorization (certification, verification, or declaration of conformity) depends on the device’s characteristics, such as whether it is an intentional or unintentional radiator. Proper labeling with FCC IDs ensures compliance and aids in field verification. -
Considerations for UWB Devices (47 CFR § 15.503 - § 15.525):
UWB devices, used for short-range communication and radar, must meet additional technical requirements due to their wide frequency range and low power levels. Engineers designing UWB systems should carefully review the applicable rules to ensure that emissions are kept within the permitted levels. -
Antenna Structure Compliance (Part 17):
For outdoor installations involving antennas, compliance with Part 17 may be necessary to ensure that the structures are registered if they exceed certain height thresholds or are near airports. Proper coordination helps avoid conflicts with aviation safety regulations.
We provide assistance on FCC Part 15 engineering compliance, advice on unlicensed device power limits, and more.