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Open AccessArticle

Spatial Retrieval of Broadband Dielectric Spectra

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Department Monitoring and Exploration Technologies, Helmholtz Centre for Environmental Research—UFZ, Permoserstrasse 15, 04318 Leipzig, Germany
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Department of Computational Hydrosystems, Helmholtz Centre for Environmental Research—UFZ, Permoserstrasse 15, 04318 Leipzig, Germany
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Institute of Material Research and Testing - MFPA at the Bauhaus-University Weimar, Coudraystrasse 9, 99423 Weimar, Germany
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Department of Advanced Electromagnetics, Technische Universität Ilmenau, Helmholtzplatz 2, 98693 Ilmenau, Germany
*
Author to whom correspondence should be addressed.
Current address: Department of Civil and Environmental Engineering, University of Waterloo, 200 University AveWest, Waterloo, ON N2L 3G1, Canada.
Sensors 2018, 18(9), 2780; https://doi.org/10.3390/s18092780
Received: 5 July 2018 / Revised: 9 August 2018 / Accepted: 16 August 2018 / Published: 23 August 2018
(This article belongs to the Special Issue Selected Papers from ISEMA 2018)
A broadband soil dielectric spectra retrieval approach ( 1 MHz– 2 GHz) has been implemented for a layered half space. The inversion kernel consists of a two-port transmission line forward model in the frequency domain and a constitutive material equation based on a power law soil mixture rule (Complex Refractive Index Model - CRIM). The spatially-distributed retrieval of broadband dielectric spectra was achieved with a global optimization approach based on a Shuffled Complex Evolution (SCE) algorithm using the full set of the scattering parameters. For each layer, the broadband dielectric spectra were retrieved with the corresponding parameters thickness, porosity, water saturation and electrical conductivity of the aqueous pore solution. For the validation of the approach, a coaxial transmission line cell measured with a network analyzer was used. The possibilities and limitations of the inverse parameter estimation were numerically analyzed in four scenarios. Expected and retrieved layer thicknesses, soil properties and broadband dielectric spectra in each scenario were in reasonable agreement. Hence, the model is suitable for an estimation of in-homogeneous material parameter distributions. Moreover, the proposed frequency domain approach allows an automatic adaptation of layer number and thickness or regular grids in time and/or space. View Full-Text
Keywords: electromagnetic scattering inverse problems; microwave propagation; dielectric materials; dielectric measurements; soil measurements; modeling electromagnetic scattering inverse problems; microwave propagation; dielectric materials; dielectric measurements; soil measurements; modeling
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MDPI and ACS Style

Bumberger, J.; Mai, J.; Schmidt, F.; Lünenschloß, P.; Wagner, N.; Töpfer, H. Spatial Retrieval of Broadband Dielectric Spectra. Sensors 2018, 18, 2780.

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