SAR Testing for Cellular PhonesCalling the Asia Pacific Market with Specific Absorption (SAR) Testing Technology drives the way people live and work today. For example, mobile phones have become essential tools, allowing business and pleasure to continue from wherever, whenever. But this technology can pose some risks. Radio equipment, including mobile phones, walkie-talkies and cordless phones, emits energy which is absorbed by the human body during use. This is why the ANSI/IEEE C95.1-1991 standard was revised in 1997 to include Specific Absorption Rate (SAR) testing - the measurement of RF energy absorbed by human tissue from handheld cellular phones and other radio devices. According to this standard, the Federal Communications Commission (FCC), based in the U.S., and Industry Canada (IC), based in Canada, allow an SAR not greater than 1.6 W/kg averaged over one gram of tissue in any part of the body, and 4 W/kg averaged over 10 grams for hands, wrists, feet and ankles. ETL SEMKO became one of the first testing organizations to provide the facilities and capabilities for SAR testing, and is now one of the first to expand its SAR testing capabilities into the Asia-Pacific market, with its recent addition of a dedicated testing facility to its Taiwan lab. The state-of-the-art facility has the ability to test several types of radio products to SAR requirements named in ANSI/IEEE C95.1-1997. "Adding this new facility to the ETL SEMKO network helps us better serve our customers worldwide who do not want to ship their equipment thousands of miles away for testing," said Michael Chen, general manager, ETL SEMKO Taiwan. "Providing this local service not only helps customers save costs in shipping, but it also helps them decrease their time-to-market - an imperative for such an innovative industry." To remain competitive, manufacturers must keep up with advancing radio technology, the standards that apply to it, and all testing procedures that make these products safer to use. ETL SEMKO focuses on educating customers in the latest standards and services, as well as providing state-of-the-art facilities to conduct accurate testing. This commitment expands beyond mobile phones to other types of radio equipment as well. Expert comments on radiation from mobile phones Gert Anger is a physicist who works with electromagnetic fields at the National Institute of Radiation Protection in Sweden. His work includes the study of the radiation characteristics of mobile phones and he measures the SAR values of different types of phones. "The same telephone can record different SAR values depending on how you hold the phone to your head. A greater distance between the mobile phone and your head will reduce exposure, and it is not just the antenna that should be angled away, because the telephone itself often works as a part of the antenna. "Many factors affect the radiation characteristics of the telephone, including how you hold the phone. Your hand absorbs part of the radiation and reflects part of it. If you grasp the phone, it becomes shielded and is forced to transmit at a greater power, which can increase exposure. Measurements are taken when the phone transmits at full power. When using a phone, it often transmits with lower power, which also reduces your head's exposure to radio waves." Taking measurements In order to determine the SAR value, the mobile phone is placed in a nonmetallic holder in a well-defined position by a test dummy, which represents the head and upper body of a person. The test dummy is made of 2 mm thick glass fiber and is filled with a liquid that resembles the body's liquids. The mobile phone is placed beside the test dummy and is operated so that it transmits with maximum power with a middle frequency on the 900 MHz and 1800 MHz bands. A sensor is placed in the test dummy and a general preliminary scan is carried out using a robot to find the area with the highest SAR value. Fine scanning is then carried out in this area. Gert Anger is a physicist and works with electromagnetic fields at the National Institute of Radiation Protection in Sweden. |
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