Wireless terminals, such as 5G, LTE, GSM & GPRS, CDMA, WLAN, Bluetooth, and WCDMA, including cell phones and other mobile devices, emit radio frequency energy. Strong electrical and magnetic radiation has been proven to be harmful to human health. As a result, many countries have introduced SAR levels that must be met in order to sell your product in their market.
The Specific Absorption Rate (SAR) is a measure used to evaluate the rate at which RF (radio frequency) energy is absorbed by the body or head due to human exposure to radio frequency fields. It plays a crucial role in ensuring the safety of radio devices by measuring their RF exposure characteristics and keeping them within certain safety limits. SAR testing involves the use of standardized liquid-filled models of the human head and body, which simulate the RF absorption characteristics of different human tissues.
The primary focus of SAR measurements is on portable devices with wireless functions that are used in close proximity to the human head or body, typically within 20 cm. This is because the distance between the device and the body impacts the RF exposure levels significantly. For devices used at greater distances, Maximum Permissible Exposure (MPE) measurements or calculations are more appropriate.
Different regions and countries have established specific regulations and standards for SAR and MPE measurements. In the European Union (EU), the SAR limits are defined by EN 50360 for head exposure and EN 50566 for body exposure, for example; MPE measurements are governed by EN 62311. In the United States, the Federal Communications Commission (FCC) sets the SAR limits under 47 CFR § 2.1093, while MPE measurements are regulated by 47 CFR § 2.1091. In Canada, the relevant standard for SAR measurements is RSS-102.
The SAR limits (or recommended SAR limits) set by regulatory bodies vary slightly across different regions. Countries that follow the United States FCC limit (for example, Canada and Korea) impose a SAR limit of 1.6 watts per kilogram over a volume containing a mass of 1 gram of tissue. On the other hand, countries adhering to the Council of the European Union limit (for example, Australia, Japan, and China) have a SAR limit of 2.0 watts per kilogram, averaged over 10 grams of tissue. These limits ensure that the RF exposure from radio devices remains within safe levels to prevent any potential adverse health effects.
The use of standardized liquid-filled models in SAR testing allows for an accurate simulation of RF absorption in different human tissues. These models replicate the dielectric properties of various tissues, such as the brain, muscle, and bone. By measuring the RF absorption characteristics of these models, the SAR of a device can be determined and compared against the established safety limits.
SAR testing is an essential part of the regulatory process for radio devices, as it ensures that these devices comply with safety guidelines and do not pose a risk to human health. Manufacturers are required to conduct SAR testing and to provide documentation to demonstrate compliance with the applicable SAR limits before their products can be legally sold in the market.
Summary
In summary, the Specific Absorption Rate (SAR) is a measure of the RF energy absorbed by the body or head due to human exposure to radio frequency fields. SAR testing using standardized liquid-filled models is crucial in determining the RF exposure characteristics of radio devices and ensuring that they comply with safety limits. Different regions and countries have specific regulations and standards for SAR and MPE measurements, with slight variations in the SAR limits. Compliance with SAR limits is vital to protecting individuals from the potential health risks associated with excessive RF exposure. Our SGS laboratories provide SAR testing for all kinds of wireless equipment.
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