Operators, various governmental authorities and also scientists themselves
actually have fun jumping around between units wildly in their publications. Con-
sequently, the casual reader loses track of the relationships between units com-
pletely. To spare you these problems, SPECTRAN offers functionality to convert
between units or directly display measurements in the unit of your choice. Furt-
hermore, we have collected several tables for simple comparison and conversi-
on of units and values. For our mathematically adept customers, we also inclu-
ded the most important basics and formulas dealing with high frequency radiati-
on:
Power flux density of high-frequency radiation is measured, among others, in
W/m²
or
W/cm²
. Conversion is simple:
1 µW/cm² = 0,01 W/m² = 0,001 mW/cm²
and
10 µW/cm² = 0,1 W/m² = 0,01 mW/cm²
etc., respectively.
(
See also table 1 on page 64
)
More rarely, values in
dBm/m²
and
dBW/m²
can be found. Conversion is equal-
ly simple:
1 µW/cm² = 10dBm/m² = -20 dBW/m²
and.
10 µW/cm² = 20dBm/m² = -10 dBW/m²
etc., respectively.
However, the most frequently used unit is
V/m
(
see table 2 on page 64
). Here
you should remember that power flux density
S
(measured in
W/m²
) really con-
sists of two separate fields: The electric field
E
(measured in
V/m
) and the
magnetic field
H
(measured in
A/m
). However, as these do not exist separately
anymore at high frequencies, their separate indication is not really interesting for
RF exposure.
However, this is only the case outside the so-called close-up
range
. How you calculate the close-up range and how the relationship between
the different radiations works is described below.
Power flux density S (also called
electromagnetic
field or
power density
) is
calculated as follows:
If H is unknown, the following formula still allows a calculation of S, assuming
377 Ohms as the so-called “field resistance” of air:
18.0 Some high-frequency math
61
Summary of Contents for SPECTRAN HF-2025
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