Environmental Engineering Reference
In-Depth Information
1.0
0.8
0.6
0.4
0.2
modeled
measured
θ
v
= 5%
0.0
0.0
0.1
0.2
0.3
0.4
0.5
f
(GHz)
(a)
1.0
0.8
0.6
0.4
0.2
modeled
measure
d
θ
v
= 20%
0.0
0.0
0.1
0.2
0.3
0.4
0.5
f
(GHz)
(b)
Fig.
5.9
Results
for
the
described
moisture
evaluation
method:
comparison
between
S
11
,
MEAS
(
f
)
and
S
11
,
MOD
(
f
)
, after optimization, for the sand sample.
a
at
θ
=
5%.
b
at θ
=
20% [48]
θ
=
Fig. 5.10 shows the permittivity spectra of the sand sample, for
20%, as ob-
tained from (5.13) after optimization. It can be seen that the imaginary part of the
permittivity of the soil is not negligible in the low-frequency range and that it shows
a markedly dispersive behavior.
On a side note, it is worth noting that for
θ
=
20%, the apparent dielectric con-
stant (
ε
app
) directly evaluated from the time-domain TDR traces is 11.83. This result
is due to the fact that
ε
app
incorporates the effect of both the real and the imag-
inary parts of the dielectric permittivity (
ε
sc
) in the frequency range of the test
signal [39].
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