Environmental Engineering Reference
In-Depth Information
0
-5
-10
-15
-20
ε
M
U
T
= 2
ε
M
U
T
= 3
ε
MUT
= 5
ε
M
U
T
= 6
ε
MUT
= 7
m
e
as ur em en t
-25
-30
-35
-40
0
20
40
60
80
100
120
σ
MUT
(mS m
-1
)
Fig. 5.19
Comparison between simulation results (for different fixed permittivity values) and
experimental measurements performed on 8% -moistened sand #3 with a water conductivity
ranging from 0 to 107 mS m
−
1
[12]
1.960
ε
MUT
= 2
ε
MUT
= 3
1.940
ε
MUT
= 4
ε
MUT
= 5
1.920
1.900
1.880
1.860
1.840
0
20
40
60
80
100
120
thickness of the MUT (mm)
Fig. 5.20
Full-wave simulation results showing the change in the resonant frequency (
f
res
)
as a function of the thickness of the MUT, for several fixed values of ε
MUT
[12]
As a result, for an assumed dielectric permittivity, the predicted sensing
volume can be associated to the maximum sample thickness beyond which no
relevant changes in resonant frequency are present. It must be pointed out that
simulations were performed considering a MUT with fixed transverse dimensions
(20 cm
20 cm) and varying thickness; indeed, a more rigorous analysis of the sens-
ing volume should consider infinite transverse dimensions. However, considering
the directivity of the used (and simulated) antenna, the sensing volume analysis re-
ported herein can be considered adequately accurate.
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