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. 2022 Oct 14;22(20):7805.
doi: 10.3390/s22207805.

A Method for Extracting Debye Parameters as a Tool for Monitoring Watered and Contaminated Soils

Andrea Cataldo  1 , Iman Farhat  2 , Lourdes Farrugia  2 , Raffaele Persico  3 , Raissa Schiavoni  1
Affiliations

A Method for Extracting Debye Parameters as a Tool for Monitoring Watered and Contaminated Soils

Andrea Cataldo et al. Sensors (Basel). .

Abstract

Soil monitoring is a key topic from several perspectives, such as moisture level control for irrigation management and anti-contamination purposes. Monitoring the latter is becoming even more important due to increasing environmental pollution. As a direct consequence, there is a strong demand for innovative monitoring systems that are low cost, provide for quasi-real time and in situ monitoring, high sensitivity, and adequate accuracy. Starting from these considerations, this paper addresses the implementation of a microwave reflectometry based-system utilizing a customized bifilar probe and a miniaturized Vector Network Analyzer (m-VNA). The main objective is to relate frequency-domain (FD) measurements to the features of interest, such as the water content and/or the percentage of some polluting substances, through an innovative automatable procedure to retrieve the Debye dielectric parameters of the soil under different conditions. The results from this study confirm the potential of microwave reflectometry for moisture monitoring and contamination detection.

Keywords: Debye law; FDR measurements; bifilar probe; dielectric permittivity; microwave reflectometry; soil pollution.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
A schematic of a microwave reflectometry-based measuring system.
Figure 2
Figure 2
CST simulations comparing the performance of the probe in air with the rods made of brass and copper. (a) S11 magnitude; (b) S11 phase.
Figure 3
Figure 3
Configuration of the modelled coaxial probe. (a) CST-created 3-D model view; (b) Schematic of the probe.
Figure 4
Figure 4
The experimental setup.
Figure 5
Figure 5
Schematic of the proposed procedure to retrieve the MUT’s Debye parameters, combining both numerical simulations (CST) and experimental data.
Figure 6
Figure 6
Measurement of the S11 as a function of frequency using m-VNA and VNA R&S in air.
Figure 7
Figure 7
|S11(f)| measurements of sand with different moisture content.
Figure 8
Figure 8
Magnitude of the S11 (f) measured with the probe immersed in sand with different concentrations of water: (a) 0%, (b) 10%, (c) 20%, and (d) 30%.
Figure 9
Figure 9
(a) εs and (b) ε∞ at different soil moisture levels.
Figure 10
Figure 10
Measured |S11(f)| with the probe immersed in sand containing varying concentrations of diesel oil.
Figure 11
Figure 11
Magnitude of the S11 (f) measured with the probe immersed in sand with different concentrations of diesel oil: (a) 0%, (b) 5%, (c) 7.5%, and (d) 10%.
Figure 12
Figure 12
Trend of εs at different concentrations of diesel oil in soil.
See this image and copyright information in PMC

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