In-situ characterization of soil moisture content using a monopole probe

In this paper, a microwave non-destructive experimental tool based on a monopole antenna is used for the determination of the complex permittivity of soils. The monopole mounted on a ground plane is buried in the soil, and its reflection coefficient measured at the feed point by a vector network ana...

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Bibliographic Details
Published in:	Journal of applied geophysics Vol. 68; no. 2; pp. 182 - 193
Main Authors:	Sagnard, F.M., Guilbert, V., Fauchard, C.
Format:	Journal Article
Language:	English
Published:	Oxford Elsevier B.V 01-06-2009 Elsevier
Subjects:	Applied geophysics Earth sciences Earth, ocean, space Electromagnetic wave Electromagnetism Engineering Sciences Exact sciences and technology FDTD High resolution algorithm Input impedance Internal geophysics Moisture Monopole antenna Monopole probe Reflection coefficient Sand Soil Wave–matter interactions Wave–matter interactions Input impedance Sand Moisture Monopole antenna Soil High resolution algorithm Reflection coefficient Monopole probe Electromagnetic wave FDTD antenna microwaves algorithms impedance networks dielectric constant frequency electromagnetic waves solution soils high resolution models inverse problem soil moisture Wave-matter interactions dielectric properties in situ sand geometry
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Summary:	In this paper, a microwave non-destructive experimental tool based on a monopole antenna is used for the determination of the complex permittivity of soils. The monopole mounted on a ground plane is buried in the soil, and its reflection coefficient measured at the feed point by a vector network analyzer (VNA) depends on the dielectric properties of the surrounding medium at a given frequency. In particular, this study is focused on the evaluation of the change of dielectric properties of different soils with the moisture content. In general, the dependence of the dielectric properties of a soil with the antenna reflection coefficient is nonlinear in nature, and the solution of the inverse problem requires a sophisticated algorithm. Thus, we have used two types of modeling, analytical (Wu's approach) and numerical (FDTD), to further understand the influence of fundamental parameters (antenna geometry and soil properties) on the frequency response of the antenna reflection coefficient. These models have allowed us to develop a novel inverse algorithm for the determination of the mean real permittivity based on the position of the antenna resonant frequencies in a wide frequency range. Moreover, a high resolution algorithm based on the Prony's approach has been developed in order to fit the complex reflection coefficient and determine afterwards the complex permittivity and the volumetric moisture content of a soil. Experimental results from different types of sands have been analyzed.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0926-9851 1879-1859
DOI:	10.1016/j.jappgeo.2008.11.008