Radio Frequency Electromagnetic Fields SAFETY INFORMATION
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Contents Contents 1 Introduction 1 1.1 Target Group 1 2 RF Exposure Limits 3 2.1 RF Exposure Calculations 4 2.2 Determining Compliance Distances 5 2.
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Introduction 1 Introduction All RBSs are Radio Frequency (RF) transmitters. Very high RF exposure levels can be harmful. To protect people against such harmful effects, RF exposure limits with wide safety margins are specified by national and international health authorities. This document explains how to estimate RF exposure levels and compliance distances (minimum separations between antennas and people) for RBS radio configurations and antennas for which such data is not already specified by Ericsson.
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RF Exposure Limits 2 RF Exposure Limits Various national and international RF regulations, safety standards, and recommendations exist that are relevant to RBS RF exposure. The limits defined in these standards are similar and are often based on international guidelines set by the International Commission on Non-Ionizing Radiation Protection (ICNIRP), which is recognized by the World Health Organization (WHO). The guidelines have been incorporated in EU Council recommendation 1999/519/EC.
Radio Frequency Electromagnetic Fields Table 2 ICNIRP Reference Levels for Occupational Exposure Occupational Reference Levels Expressed as Power Density 10 – 400 MHz 10 400 – 2000 MHz W/m2 f/40 (1) W/m2 2000 – 10 000 MHz 50 W/m2 (1) f = frequency in MHz Table 3 ICNIRP Reference Levels for General Public Exposure General Public Reference Levels Expressed as Power Density 10 – 400 MHz 400 – 2000 MHz 2 W/m2 f/200 (1) W/m2 2000 – 10 000 MHz 10 W/m2 (1) f = frequency in MHz The reference leve
RF Exposure Limits P (W) is the total RMS power fed to the antenna, that is, the sum of all transmitter channels minus feeder and combiner losses. G is the numerical far-field antenna gain relative to an isotropic radiator, and d (m) is the distance from the antenna. PG is the Equivalent Isotropically Radiated Power (EIRP) of the antenna, expressed in watts.
Radio Frequency Electromagnetic Fields Compliance distances generally vary in different directions from the antenna. The analytical RF exposure assessment methods described in Section 2.1 on page 4 are used to determine compliance distances for both occupational and general public exposure. In far-field environments without significant reflections, the analytical far-field formula (equation 2) is used.
RF Exposure Limits 2.3 Example Compliance Boundary Determination The following example of a compliance boundary for the general public is for an antenna operating in the 2100 MHz frequency band. The antenna has a length of 1 meter, an antenna gain of 18 dBi, which corresponds to a numerical gain of 63, a half-power beam width of 60 degrees, and a maximum output power of 40 dBm, which corresponds to 10 W.
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General Public Safety Recommendations 3 General Public Safety Recommendations The following recommendations supplement any existing Ericsson-recommend ed technical or scientific guidelines: • If compliance boundary or other necessary exposure information is not available, estimate the maximum exposure using the methods described in Section 2.2 on page 5 and consider alternative locations for the antenna installation if the results do not comply with the relevant exposure limits for the general public.
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References 4 References Guidelines for limiting exposure to time-varying electric, magnetic, and electromagnetic fields (up to 300 GHz), International Commission on Non-Ionizing Radiation Protection (ICNIRP), Health Physics, vol. 74, no. 4, pp 494–522, April 1998. http://www.icnirp.de Electromagnetic fields and public health: mobile phones and their base stations, World Health Organization (WHO) fact sheet no. 193, revised June 2000. http://www.who.
