TC34_SC1 - SAR evaluation - measurement techniques

Mark Douglas

This Guide provides a methodology for classifying IoT devices based on RF exposure characteristics. Classification is based on frequency, bandwidth, radiated power, device shape, and typical installation configuration. Links between device class and available measurement/computational standards are provided. A framework criteria for exclusion classes for exposure assessment and criteria for addressing situations where exposure assessment is unavailable are included.

This International Standard specifies protocols and test procedures for the reproducible and conservative measurement of the peak spatial-average SAR (psSAR) induced inside a simplified model of the head or the body by radio-frequency (RF) transmitting devices, with a defined measurement uncertainty. The protocols and procedures apply to a significant majority of the population including children during the use of hand-held and body-worn wireless communication devices. These devices may include single or multiple transmitters or antennas, and may be operated with their radiating structure(s) at distances up to 200 mm from a human head or body. This standard can be employed to evaluate SAR compliance of different types of wireless communication devices used next to the ear, in front of the face, mounted on the body, operating in conjunction with other RF-transmitting, non-transmitting devices or accessories (e.g. belt-clip), or embedded in garments. The applicable frequency range is from 4 MHz to 10 GHz. Devices operating in the applicable frequency range can be tested using the phantoms and other requirements defined in this standard. The device categories covered include but are not limited to mobile telephones, cordless microphones, and radio transmitters in personal, desktop and laptop computers for multi-band operations using single or multiple antenna, including push-to-talk devices. Wireless power transfer devices operating above 4 MHz may also apply this International Standard. This standard is not intended to apply to implanted medical devices.

Protocols and test procedures are specified for the measurement of the peak spatial-average SAR induced inside a simplified model of the head of users of certain handheld radio transceivers. These transceivers are intended to be used for personal wireless communications services, operate in the 300 MHz to 6 GHz frequency range, and are intended to be operated while held against the ear. The results obtained by following the protocols specified in this recommended practice represent a conservative estimate of the peak spatial-average SAR induced in the head of a significant majority of persons, subject to measurement and other uncertainties that are defined in this recommended practice. The results are representative of those expected during conditions of intended use of a handheld wireless device. It is not the intent of this recommended practice to provide a result representative of the absolute maximum SAR value possible under every conceivable combination of head size, head shape, handset orientation, and spacing relative to the head. The measurement of SAR induced in the external tissues of the head, e.g., the external ear (pinna), is not addressed in this document. This recommended practice also does not address the body SAR measurements typically required for wireless handsets. The following items are described in detail: measurement concepts, measurement techniques, instruments, calibration techniques, simulated-tissue (phantom) models, including homogeneous anatomically equivalent models of the human head and simple phantoms for validation of the SAR measurement system, and the limitations of these systems when used for measuring the spatial-peak mass-averaged SAR. Procedures for calibrating electric field (E-field) probes used for SAR measurements and assessing the SAR measurement and system uncertainties are provided in the annexes. This recommended practice is intended primarily for use by engineers and other specialists who are familiar with electromagnetic (EM) theory and SAR measurement techniques; it does not recommend specific SAR limit values since these are found in other documents. The benefits to the users include standardized and accepted protocols, validation techniques, and means for estimating the overall measurement uncertainty in order to produce valid and repeatable data.