To determine whether your product needs Specific Absorption Rate (SAR) testing, there are a few items to consider.
First, is the device operated within 20cm (7.87”) of the head or body? If no, then SAR does not apply. If yes, then SAR does apply, but testing may be excluded based on the device’s output power.
The maximum conducted output power is the average conducted power at the antenna port plus any production tolerance. When calculating output power, keep in mind the device’s duty-cycle. For SAR, the on and off time-averaged power is to be considered. So if not already accounted for, the duty cycle factor may be applied directly to the output power.
To determine whether the output power is below the threshold for testing, it depends on where the device is being certified for. Here are some common jurisdictions:
The Federal Communications Commission (FCC) utilizes a formula to determine SAR test exclusion in KDB 447498 D01v05 Section 4.3. For separation distances of <50mm if the following equation results in <3.0 then test exclusion for 1g SAR applies: (Output power, mW) / (separation distance, mm) x (sqrt(freq), GHz). Use 5mm for separation distances <5mm.
Industry Canada stipulates the exclusion threshold in RSS-102. For 3kHz – 1GHz it is 200mW, for 1GHz – 2.2GHz it is 100mW, for 2.2GHz – 3GHz it is 20mW and for 3GHz – 6GHz it is 10mW. Note that per Industry Canada, output power is always the higher of conducted or equivalent isotropically radiated power (EIRP).
In the EU, the threshold is given in IEC/EN 62479:2010. A simple formula is used: Pmax = SARmax * m.
For each jurisdiction, if the devices output power is less than the threshold, SAR testing is not required. However, in most cases, a statement showing why it is excluded and how it still meets the requirements must be submitted.
Sign up for one of our upcoming complimentary wireless product testing seminars in Silicon Valley, California:
At the recent Telecommunication Certification Body Council Workshop in Baltimore, Kwok Chan and Mark Neumann of the Federal Communications Commission (FCC) Office of Engineering and Technology outlined testing and certification requirements for Consumer Wireless Charging Devices.
Wireless charging devices are generally used to charge batteries in portable electronic devices via magnetic induction. Chargers can deliver up to 5W of power, enough to charge most wireless handsets, and work at distances up to 10mm.
These products have been around since the 1990s, but only have become practical in recent years, so FCC thought it was worthwhile to cover how these devices fall into the existing regulatory compliance framework. Following are main points from the presentation.
Chargers and clients are generally approved separately; however, they should satisfy compliance in both standalone mode and as a system.
Wireless charging devices can be approved under Part 15 or Part 18 or both rule parts.
Part 15 authorization required if:
- Primary charging frequency includes information not related to power management
- A secondary frequency is used for communications
Part 18 authorization for the charger and clients:
- Load and power management must be integral to wireless charging operation and frequency
- May not communicate any information not related to power management and control
- Proximity of the charger and client device(s) must satisfy Part 18 requirement that the RF energy is locally generated and used
- Other communications are authorized separately under Part 15
Electromagnetic Compatibility (EMC) considerations:
- Charger must be evaluated with appropriate client(s) in place
- The worst case transmitting conditions for the system as a whole must be evaluated for each applicable configuration: Bluetooth, WWan, WLan, etc.
Radio Frequency Exposure
Single client low power devices generally do not present exposure concerns for nearby users, but multi-client devices or short-distance power transfer can result in widely varied fields and potential exposure concerns.
For most small consumer chargers, exposure conditions identified in §2.1091(d)(4) may apply.
Specific Absorption Rate (SAR) and Maximum Permissible Exposure (MPE) limits do not cover wireless chargers operating below 100 kHz and 300 kHz, respectively.
The presentation concluded with two points:
- A KDB Inquiry should be submitted for guidance for wireless charger applications
- Wireless Chargers remain on the Permit But Ask (PBA) list
Sign up for a Wireless Testing & Certification Seminar in Austin, Texas in December.
In June, the Federal Communications Commission (FCC) announced it would review its rules on radiation exposure from cell phones. The FCC’s current Specific Absorption Rate (SAR) limits were set fifteen years ago, in 1996.
Any day now, the FCC is expected to publish a Notice of Inquiry, which will be open to public comment for a couple months. After that, the commission may issue some proposed rules. After another comment period, the FCC could issue a final rule.
It is unlikely there will be a change to the SAR regulations. The last time the FCC proposed a change to its RF rules was in 2003, and these minor-change amendments are still pending.
The FCC’s current SAR limits are already the tightest in the world. SAR is the rate at which your body absorbs energy from a radio-frequency magnetic field. It’s measured in watts per kilogram or W/kg. To be considered safe, every cell phone model sold in the U.S. must adhere to a SAR that’s less than 1.6 watts per kilogram taken over a volume containing a mass of 1 gram of tissue, even under the worst conditions.
The likely reason for the review of the cell phone radiation exposure rules now? The Government Accountability Office (GAO) has been looking into the adequacy of the cell phone standard, and the FCC wants to be seen as proactive in this area.
Read about MET’s SAR Testing capabilities.
The U.S. Federal Communications Commission (FCC) has issued draft revisions to six Knowledge Database (KDB) publications for RF exposure and SAR compliance.
KDB Publication 447498 – General RF Exposure Policies for Equipment Authorization
KDB Publication 941225 – SAR Evaluation Considerations for LTE Devices
KDB Publication 865664 – SAR Measurement Requirements, Compliance Reporting and Documentation for 100 MHz – 6 GHz
KDB Publication 616217 – SAR Evaluation Considerations for Laptop, Notebook, Netbook and Tablet Computers
KDB Publication 648474 – SAR Evaluation Considerations for Handsets with Multiple Transmitters and Antennas
KDB Publication 643646 – RF Exposure Evaluation Considerations for Occupational Push-to-Talk Two-Way Radios
The public may post a comment on these proposed revisions through June 1, 2012.
Other RF Exposure KDBs
Remaining RF exposure KDB publications that do not have draft revisions are:
- KDB Publication 248227 – Additional SAR Measurement Procedures that Specifically Address 802.11 a/b/g Devices
- KDB Publication 615223 – SAR Requirements and Procedures for 802.16e/WiMax Devices
- KDB Publication 450824 – SAR Probe Calibration and System Verification Considerations for Measurements from 150 MHz to 3 GHz
- KDB Publication 680106 – Rules Regulating Short Distance Wireless Inductive Coupled Charging Pads or Charging Devices
Questions about SAR compliance? A SAR testing expert will be available next week at 2012 International CTIA Wireless at the MET Labs exhibit.
Following are recent and near future changes to electrical product regulatory requirements in South Korea.
Effective January 1, 2012, the Korean Communications Commission (KCC) requires radiated emission measurements at the limit, above 1GHz, by the highest internal source of the device and also conducted disturbance testing for devices with telecommunication ports. The limit is the same as CISPR 22:2006.
Effective July 1, 2012, the Ministry of Knowledge Economy (MKE) will assume responsibility for regulating safety of electrical products sold in Korea, a role currently carried out by KCC. After July 1, KCC will only regulate IT/RF/Telecom products.
Effective January 1, 2013, KCC plans to expand its existing SAR requirements for mobile phones to include all radio equipment that is used within 20 cm of the human body. This harmonizes the Korean SAR requirements with FCC and other international standard requirements. Low powered radio devices (below 20mW) are exempt from this new requirement.
Learn how to gain certification for the Korean market using a Conformity Assessment Body (CAB) under Phase I of the Asia Pacific Economic Cooperation Mutual Recognition Agreement for Conformity Assessment of Telecommunications Equipment (APEC Tel MRA).
Participate in a free International EMC Homologation webinar on April 10, 2012.
Starting this month in San Francisco, retailers are required to list the Specific Absorption Rate of all mobile phones they sell. The city is the first locality in the United States to have such a requirement.
Here are the key points of the new ordinance that was signed into law last July:
- The Specific Absorption Rate or SAR must be listed on a 1.00” x 1.62” minimum label, with the SAR value in Arial 11-point type or larger
- Optionally, retailers can post an 8.50” x 11.00” or larger sign that lists SAR values for the phones they carry
- Effective date is February 1, 2011
- Fines for non-compliance start at $300USD
A cell phone’s SAR is a measure of the amount of radio frequency (RF) energy absorbed by the body when using the handset. The SAR value is determined by Specific Absorption Rate testing, as conducted by MET Labs and other test labs.
The Federal Communications Commission (FCC) mandates that all cell phones sold in the U.S. must not exceed a SAR level of 1.6 W/kg¹ for 1-g volume-averaged. Canada and Australia have the same limit, while Europe is more liberal, with a cap of 2 W/kg¹ for 10-g volume-averaged.
Some studies have shown that RF even at these levels increases the risk of brain cancer, but the evidence is far from conclusive.
Since the San Francisco legislation, and subsequent CTIA lawsuit to reverse it, industry observers have wondered whether the leftist city has started a trend, or is an anomaly. Then came word this week that an Oregon senator introduced a bill on Monday that would require warning labels on cell phones and wireless device packaging in that state.
Time will tell whether it will die like other initiatives in Maine, other California cities, and on the federal level, but one thing is for sure: The CTIA Wireless 2011 tradeshow won’t be held in San Francisco this year. The wireless industry group has vowed to boycott the city for major events until the cell phone labeling law is reversed.