WIRELESS CHARGING & RF EXPOSURE

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Introduction

The FCC (Federal Communications Commission) has developed technical standards for RF equipment, and components or parts of RF equipment, in order to promote efficient use of the radio spectrum, and to carry out responsibilities under the Communications Act. The technical standards applicable to specific types of equipment are found in the part of the rules that govern the service were the equipment is to be operated. Beyond the technical standards provided, the rules governing the service may require that such equipment receive a Grant of Certification from a Telecommunication Certification Body, or be authorized under a Supplier’s Declaration of Conformity (SDoC). Here we discuss the SDoC authorization process.

FCC Authorization

Relevant Rule Parts:

  • [1] Part 15 ‐ If charger uses radio energy for communication with device (may not transmit in the 90‐110 kHz band, restricted under 15.205)
  • [2] Part 18 ‐ If charger uses RF only to perform work (i.e. charge). Load impedance detection with limited communication for load management ok. (i.e. backscatter load modulation)
  • [3] Devices that use a secondary frequency for load management, control and data functions must be authorized according to both Part 15 and Part 18 requirements, as appropriate.

Exclusions; RF Exposure:

Inductive wireless power transfer applications that meet all of the following requirements are excluded from submitting an RF exposure evaluation.

  • [1] Power transfer frequency is less than 1 MHz
  • [2] Output power from each primary coil is less than or equal to 15 watts
  • [3] The transfer system includes only single primary and secondary coils. This includes charging systems that may have multiple primary coils and clients that are able to detect and allow coupling only between individual pairs of coils.
  • [4] Client device is inserted in or placed directly in contact with the transmitter.
  • [5] Mobile exposure conditions only (portable exposure conditions are not covered by this exclusion).
  • [6] Aggregate leakage fields at 15 cm surrounding the device and 20 cm above the top surface from all simultaneous transmitting coils are demonstrated to be less than 50% of the MPE limit.

In all other cases, unless excluded above, an RF exposure evaluation report must be reviewed and accepted through a KDB inquiry to enable authorization of the equipment. When evaluation is required to show compliance; for example, using field strength, power density, SAR measurements or computational modeling etc., the specific authorization requirements will be determined based on the results of the RF exposure evaluation.

If not excluded by the above, devices specifically intended to use for wireless power transfer or inductive charging require FCC guidance for frequency exposure review. This includes Part 18 devices. The responsible party or manufacturer must seek guidance from the FCC by submitting a wireless charging application inquiry through the FCC’s website.