User's Manual

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. With S = S
lim
, which is the
reference level expressed as power density (W/m
2
), the compliance distance
d
compliance
(m) in the main beam direction is calculated as follows:
P (W) is the total RMS power fed to the antenna (the sum of all transmitter
channels minus feeder and combiner losses) and G is the numerical far-field
antenna gain, which is taken from the far-field radiation pattern supplied by the
antenna manufacturer.
In most near-field situations, the far-field formula (equation 4) greatly
overestimates the compliance distance, and the near-field formula would give a
more accurate estimation of the exposure. For an antenna with an aperture
height of h meters and an azimuthal half-power beam width of
2 degrees, the
expression for the compliance distance in the main beam direction is as follows:
A recommended simple structure to define compliance distances in all
directions (a compliance boundary) is a cylinder, see Figure 1 on page 6. The
analytical assessment methods described are used to estimate the compliance
distance in front of the antenna. As a general rule, the compliance distances
behind, above, and below the antenna are about 1/20th of the distance in
front of the antenna.
Figure 1 Simple Structure of a Compliance Boundary
6
124 46-EN/LZT 720 0399 Uen E 2008-09-29