User's Manual

Radio Frequency Electromagnetic Fields
Table 2 ICNIRP Reference Levels for Occupational Exposure
Occupational Reference Levels Expressed as Power Density
10 – 400 MHz 400 – 2000 MHz 2000 – 10 000 MHz
10 W/m
2
f/40 W/m
2
(1)
50 W/m
2
(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 2000 – 10 000 MHz
2 W/m
2
f/200 W/m
2
(1)
10 W/m
2
(1) f = frequency in MHz
The reference levels, which vary according to frequency, have been chosen to
prevent the SAR restrictions from being exceeded. This means that additional
safety margins have been introduced. The reference levels apply primarily to
whole-body far-field exposure situations, whereas they are very conservative
for partial-body near-field exposure situations. Compliance with the reference
levels will ensure compliance with the basic restriction. If the measured value
exceeds the reference level, it does not necessarily follow that the basic
restriction will be exceeded.
The averaging time is 6 minutes. For exposure periods shorter than the
averaging time, exposure levels higher than the basic restrictions or reference
levels are accepted provided the average is lower than the limits.
In the case of RF sources with multiple frequencies, the following requirement
is specified in the ICNIRP guidelines. For an antenna that operates in n
different frequency bands, where S
i
is the power density at the i
th
frequency
and S
lim, i
is the reference level for that frequency, the requirement for total
exposure is as follows:
P009698A
(Equation 1)
S
i
S
lim,i
n
i=1
2.1 RF Exposure Calculations
The following formula is used to estimate the free-space far-field power density
S (W/m²) in the main direction of an antenna:
P009699A
(Equation 2)
PG
4
d
2
S =
4 124 46-EN/LZT 720 0399 Uen E 2008-09-29