Introduction - Broadband Reflectometry for Enhanced Diagnostics and Monitoring Applications - page 6

that are used for enhancing measurement accuracy. The second part (from chap-
ter four through chapter six) is a representative collection of experimental results
that demonstrate the potential of BMR for various monitoring tasks. Let us see the
content of each chapter more in detail.
In the second chapter, the basic theoretical principles behind BMR are recalled.
First, a preliminary introduction on the transmission line theory is given. Second,
the most important electrical parameters related to BMR are introduced. Particular
attention is given to the quantities that are directly measured through BMR, namely
the reflection coefficient in time domain ( ρ ( t ) ) and the reflection scattering parame-

ter ( S 11 ( ). Finally, the basic concepts behind dielectric spectroscopy are recalled.

The third chapter describes the 'actors' involved in typical BMR measurements.
First, TDR and FDR are presented and the related instrumentation is fully described.
Successively, the TDR/FDR combined approach is described in detail: as aforemen-
tioned, this approach can help exploit the benefits of both TDR and FDR, without
necessarily employing two different measurement setups. It is worth mentioning
that great emphasis is given on this issue, since it represents the solution that can
ultimately lead to the optimization of the cost-benefit ratio in the implementation
of the systems. Particular attention is also dedicated to the design of the probes,
which is crucial for obtaining accurate results. In the third chapter, also the methods
for measuring the dielectric characteristics of materials starting directly from the
analysis of TDR waveforms are presented. Additionally, the major error sources in
BMR-based measurement systems are described in detail: specific focus is given to
the strategies for enhancing measurement accuracy.
The fourth chapter deals with the quantitative and qualitative characterization of
liquid materials. In this chapter, BMR-based methods for measuring simultaneously
the levels and the dielectric characteristics of liquid materials are presented. Results
show that all the proposed methods have strong potential for practical implementa-
tion in the field of industrial monitoring.
First, an approach based solely on the analysis of TDR measurements is described
and validated. Secondly, a further enhancement of this method is accomplished by
resorting to the combination of TDR with FDR. In this second measurement method,
the accuracy is enhanced also through the adoption of a transmission line modeling
of the measurement cell and through the realization of a custom-made fixture that
allows performing an ad hoc short-open-load (SOL) calibration.
Finally, BMR-based measurements of the dielectric characteristic are extended
to edible liquids: in particular, vegetable oils are considered. This was done in view
of the possibility of performing quality and anti-adulteration control.
The fifth chapter focuses on BMR applications for monitoring water content and
static electrical conductivity of granular materials, focusing on applications on soils
and on agrofood materials.
First, a TDR-based method for inferring water content from measurements of the
apparent dielectric permittivity is presented. This approach, which relies on the in-
dividuation of so-called calibration curves , is discussed in detail and a metrological
assessment is provided.

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