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Microwave tomography for the inspection of wood materials: imaging system and experimental results

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TitleMicrowave tomography for the inspection of wood materials: imaging system and experimental results
Publication TypeJournal Article
Year of Publication2018
AuthorsBoero, F, Fedeli, A, Lanini, M, Maffongelli, M, Monleone, R, Pastorino, M, Randazzo, A, Salvade, A, Sansalone, A
JournalIEEE Transactions on Microwave Theory and Techniques
KeywordsAntenna measurements, combined qualitative/quantitative inversion method, deterministic inversion algorithm, dielectric measurement, dielectric properties, electromagnetic wave scattering, hybrid tomographic inversion scheme, image reconstruction, Imaging, inspection, Inverse problems, Inverse scattering, microwave antennas, Microwave imaging, microwave measurement, microwave systems, Microwave theory and techniques, multistatic field measurements, multiview field measurements, network analysers, optimisation, Prototypes, qualitative image, RF hardware, switching matrix, tomography, tree trunk, vector network analyzer, Vegetation, wood, wood materials

A new microwave tomography prototype for the inspection of wood materials is described and experimentally tested in this paper. The system prototype is composed by a set of microwave antennas, used for both illuminating the sample and collecting field measurements, a custom RF hardware, and a hybrid tomographic inversion scheme. The antennas are placed in contact with the outer structure of the sample, e.g., a tree trunk, and are optimized to radiate inside the inspected region. A switching matrix connects the set of antennas with a custom vector network analyzer, which is used for acquiring multistatic and multiview field measurements at multiple frequencies. The measured data are processed by means of a combined qualitative/quantitative inversion method. In particular, in a first step, the field scattered by the inner inhomogeneities or inclusions is estimated, producing also a qualitative image of the sample. Then, these data are utilized by a deterministic inversion algorithm in order to obtain a quantitative reconstruction of the dielectric properties of the structure under test.