Spatial Retrieval of Broadband Dielectric Spectra

Autor: Jan Bumberger, Juliane Mai, Felix Schmidt, Peter Lünenschloß, Norman Wagner, Hannes Töpfer
Jazyk: angličtina
Rok vydání: 2018
Předmět:
Zdroj: Sensors, Vol 18, Iss 9, p 2780 (2018)
Druh dokumentu: article
ISSN: 1424-8220
18092780
DOI: 10.3390/s18092780
Popis: 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.
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