Environmental Engineering Reference
In-Depth Information
Fig. 3.16
Schematic dia-
gram illustrating the imple-
mented algorithm for the
TD/FD combined approach
and for extrapolating the
calibrated reflection scat-
tering parameter from TDR
measurements
As an example, Fig. 3.17 shows the sequence of the gating operation for isolating
the frequency-domain response of the outer connector of a cable. Considering the
non-gated time domain response of the cable, the discontinuity on the left is due to
the input connector and the discontinuity on the right is due to the output connector.
By using the gating function, the effect of the mismatch can be removed in order to
see the frequency response of just the output connector; in this way, the frequency
response of the sole output connector is obtained.
It must be pointed out, however, that gating is an extremely delicate strategy, and
it should be adopted with particular care.
Time-gated frequency-domain reflectometry can be particularly useful for removing
undesired reflections from the environment while measuring the
S
11
(
of antennas
when the anechoic chamber is not available [19]; this aspect will be further dis-
cussed in the following chapters.
f
)
3.6.4
Transmission Line Modeling and Inverse Modeling
An additional strategy for compensating for systematic errors is to model the influ-
ence of the parasitics through a transmission line (TL) model. More specifically, the
SUT is schematized as a circuit model, and the parasitics are modeled as lumped cir-
cuit elements. This approach can virtually compensate for all the systematic errors
effects.
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