What is SAR testing?
Specific absorption rate (SAR) test is a radio frequency (RF) dosimetry method to quantify the size and distribution of electromagnetic energy absorbed by biological objects exposed to RF field. Excessive exposure to RF energy will damage human tissues. In order to prevent this situation, many countries in the world have introduced standards to limit the amount of RF radiation allowed by all types of transmitters.
RF exposure is assessed using a "phantom" that simulates the electrical characteristics of the human head or body. The RF energy passing through the phantom is monitored by a precisely positioned probe that measures SAR in watts per kilogram of tissue. The Federal Communications Commission has specified SAR in accordance with 47 CFR Part 2, section 2.1093, General purpose products must reach the SAR limit of 1.6 MW / g for 1g tissue of head or body, and 4 MW / g for 10G tissue of hand, wrist, foot and ankle.
In the European Union, the Council recommended 1999 / 519 / EC to establish RF exposure limits. The harmonized standards cover the most common products, such as mobile phones and RFID devices. The limits and methods of RF exposure assessment in the European Union are similar to but not identical to those in the United States.
These levels are expressed in watts per kilogram (w / kg), and most portable and mobile wireless technologies are required to be evaluated by international regulators.
The parameters that can affect SAR include:
1. Types of radio services (cellular, PCs, LMR, WLAN, etc.).
2. Modulation type (CDMA, GMSK, TDMA, amps, etc.).
3. Body orientation (keep ears, face, belt clip, knee, etc.).
4. RF power level (watts or milliwatts).
5. Change of transmitter, antenna (extraction / retraction) or accessories (clip, battery, etc.).
Maximum permissible exposure (MPE)
When the user is usually located away from the radio transmitter, usually more than 20cm, the RF exposure evaluation method is called maximum allowable exposure (MPE). In many cases, MPE can be calculated according to the output power of the transmitter and the type of antenna. In some cases, MPE must be measured directly according to the electric or magnetic field strength or power density, depending on the operating frequency of the transmitter.
SAR damage:
Mobile And Cellular Phone Standards SAR Limit 。
* IEEE standard for general public whole body SAR (1/6 of an hour). 200
mW/kg 。
* FCC (IEEE) SAR limit for 1 gram (.032 ounces) of head tissue (phone held
to ear). 1,600 mW/kg 。
*You can query the SAR value of most mobile phones on the FCC website www.fcc.gov/oet/rfsafety
