2-7 Calibration of SAR Probe

Specific Absorption Rate (SAR) is one index for assessing electromagnetic field exposure from devices and equipment that emit electromagnetic waves such as mobile wireless devices and base stations. In Japan and overseas, SAR limitation values are established based on radio-radiation protection guidelines [1]−[6], and are mainly applied to wireless communication devices used near the human body, such as mobile phones. Therefore, for wireless communication devices such as mobile phones, compliance evaluation to radio-radiation guidelines are legislated under the standards and regulations in Japan and overseas [7]− [10]. Measurement equipment used in tests of wireless communication devices must be calibrated periodically, based on regulations. In tests to assess compliance with SAR limit, a SAR probe is used to measure SAR, and the SAR probe must be calibrated. NICT is the only institution performing SAR probe calibration service in Japan. This paper describes SAR probe calibration at NICT. Several SAR probe calibration methods have been standardized in Japan and overseas. Explained here are the principles of three major methods, including detailed steps and examples for measurement and uncertainty evaluation for the waveguide calibration method used in the calibration work of NICT.