New IEEE Standards on Measurement of Potentially Hazardous Radiofrequency/Microwave Electromagnetic Fields
In September 1991, the Institute of Electrical and Electronics Engineers (IEEE) Standards Board approved two important standards that pertain to radiofrequency (RF)/microwave safety: IEEE Standard for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz, C95.1–1991,1 and IEEE Recommended Practice for the Measurement of Potentially Hazardous Electromagnetic Fields — RF and Microwave, IEEE C95.3–1991.2 The first standard is primarily a safety standard specifying maximum permissible exposure (MPE) values expressed in terms of field parameters (electric field strength, magnetic field strength and power density) and, for frequencies below 100 MHz, induced current (body and contact). Exclusions expressed in terms of maximum whole-body-averaged and peak specific absorption rates (SAR) are also included. The second standard recommends measurement techniques and procedures that should be followed to ensure compliance with the safety standard.
Just as the 1991 safety standard is considerably more complex than its predecessors, so to is the measurement standard. Instruments and techniques for measuring electric and magnetic fields in both near and far field situations, and for measuring induced (body) current, contact current, and specific absorption rate (SAR) are described. Techniques for spatial averaging are discussed and minimum measurement distance from radiating and reradiating (passive) structures and other scattering objects in the field are specified. Techniques for calibrating field measuring instruments, theoretical methods for determining exposure fields, and numerical and experimental techniques for determining SAR are also described in the 1991 measurement standard. However, since the latter are for the most part laboratory techniques, neither the determination of SAR nor instrument calibration techniques will be discussed here. Instead, only those practical techniques and instruments that are used in the field to ensure compliance with the C95.1–1991 standard will be discussed.
KeywordsLight Emit Diode Spatial Average Antenna Element Specific Absorption Rate American National Standard Institute
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