Environmental Engineering Reference
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0.6
| S 11 , ref ( f )|
T w = 100 ns (filtered data)
T w = 100 ns (without filter)
0.5
0.4
0.3
0.2
0.1
0.0
0.81
0.84
0.87
0.90
0.93
0.96
f (GHz)
Fig. 6.9 Comparison between the
measured through the TD/FD combined approach
(with and without the application of the digital filter) and the
| S 11 ( f ) |
| S 11 , ref ( f ) |
frequencies. On the other hand, when exploring a limited frequency bandwidth, as
in the considered test-case, the optimal time windowing (for the considered AUT)
is 30 ns
<
T w <
35 ns.
6.5
Biconical Antenna Results
As a further experimental validation of the method, the second considered antenna
was a biconical antenna (Fig. 6.1(b)), generally used for Electromagnetic Compati-
bility (EMC) measurements: the wideband characteristics of this antenna anticipate
different criteria for the choice of the optimal time window [15].
Similarly to the previous case, the TDR measurements on the antenna were per-
formed by choosing several time windows, ranging from 15 ns to 150 ns; once again,
the corresponding S 11 (
f
)
was extrapolated and compared to the S 11 , ref (
f
)
in terms
of rmse (Table 6.2).
Ta b l e 6 . 2 rmse values between | S 11 ( f ) | measured (for different acquisition windows)
through the TD/FD combined approach and | S 11 , ref ( f ) | , for the biconical antenna
T w
rmse
(ns)
150
0.010
100
0.006
80
0.007
40
0.010
35
0.013
15
0.019
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