<p>In this thesis work, a free space microwave sensing technique to be used for power process control was investigated. Evaluation of the possibility to apply this sensing technique for determination of permittivity properties is the primary objective. Further these properties could be related to the material physical properties such as moisture content and density. Due to the fact that the permittivity properties of the material under measurement determine its measured S-parameters, such were performed throughout the whole work for the calculation of materials properties. Free space type of measurements were the primary focus of this work. Some uncertainties of free space measurement resulting from limitations in the measurement setups, instrumentation, algorithm were explored and methods to secure our measurement results to be within a specified confidence level are also discussed.</p><p>Based on the configuration of the measurement setup, two types of free space measurement were carried out. One was the reflection method where a perfect conducting metal plate is inserted between two antennas for calibration purposes and the material is placed above the plate. Only one reflection coefficient was then measured. The other was the transmission method where the measured material as placed between two antennas and all S-parameters measured. In both cases the amplitude and the phase of the S-parameters were recorded.</p><p>Three models, Debye, Cole-Cole, and Cole-Davidson have been also tested in this work to model permittivity properties of materials. Used test materials were air, plastic plate, water and icrocrystalline cellulose(MCC). Different methods using measured S-parameters for permittivity reconstruction that have been explored in previous work also were utilized in this work for same purpose. The validity of this sensing technique is determined by checking out the deviation of the recovered dielectric constant. The investigation demonstrated that the transmission method works well for reconstruction of permittivity properties as long as the material under test is low-loss. The results of the reflection method were not as satisfactory as we expected. The method was insitive to the sample thickness and shape. Also very precise measurements of the S-parameters were necessary for the correct inversion to dielectric properties, which is generally difficult due to complex measurements environment(multipath). Some of the above could be compensated with good calibration method, but it is not enough, at least with the currently existing approaches. Precise sample preparation and some improvement on the antenna should be further carried out for the reflection method to be performed better.</p>

In this thesis work, a free space microwave sensing technique to be used for power process control was investigated. Evaluation of the possibility to apply this sensing technique for determination of permittivity properties is the primary objective. Further these properties could be related to the material physical properties such as moisture content and density. Due to the fact that the permittivity properties of the material under measurement determine its measured S-parameters, such were performed throughout the whole work for the calculation of materials properties. Free space type of measurements were the primary focus of this work. Some uncertainties of free space measurement resulting from limitations in the measurement setups, instrumentation, algorithm were explored and methods to secure our measurement results to be within a specified confidence level are also discussed. Based on the configuration of the measurement setup, two types of free space measurement were carried out. One was the reflection method where a perfect conducting metal plate is inserted between two antennas for calibration purposes and the material is placed above the plate. Only one reflection coefficient was then measured. The other was the transmission method where the measured material as placed between two antennas and all S-parameters measured. In both cases the amplitude and the phase of the S-parameters were recorded. Three models, Debye, Cole-Cole, and Cole-Davidson have been also tested in this work to model permittivity properties of materials. Used test materials were air, plastic plate, water and icrocrystalline cellulose(MCC). Different methods using measured S-parameters for permittivity reconstruction that have been explored in previous work also were utilized in this work for same purpose. The validity of this sensing technique is determined by checking out the deviation of the recovered dielectric constant. The investigation demonstrated that the transmission method works well for reconstruction of permittivity properties as long as the material under test is low-loss. The results of the reflection method were not as satisfactory as we expected. The method was insitive to the sample thickness and shape. Also very precise measurements of the S-parameters were necessary for the correct inversion to dielectric properties, which is generally difficult due to complex measurements environment(multipath). Some of the above could be compensated with good calibration method, but it is not enough, at least with the currently existing approaches. Precise sample preparation and some improvement on the antenna should be further carried out for the reflection method to be performed better.

The aim of this thesis is the development of the workplace for the complex permittivity measurement by free space method. At the beginning of this thesis, the method is described. Further attention is focused on the discussions concerning electromagnetic properties of materials, comparison of the methods used for complex permittivity measurement, interactions of planar electromagnetic wave with planar infinite dielectric slab of general environment and description of radiation patterns of microwave antennas. In the rest of the thesis, the measuring workplace for the free space method is designed and fabricated. A pyramidal horn antenna is selected as a radiator. The antenna is designed with coax to waveguide transition in CST Microwave Studio, and than fabricated in two samples and measured. Finally, the fabricated measuring workplace is exploited for the complex permittivity measurement.

Owing to the ever-changing developments of battery and electric powertrain, vehicle electrification is the trend in the future. Without the presence of a combustion engine, masking effect from it reduces and noises from other components become perceivable. Among all, the cooling fan is one of the major noise sources. The design of cooling fan modules is usually carried out in the early stage before building prototype vehicles. Therefore, it is essential to come up with a method for selecting optimal fan design without performing complete vehicle testing. This is a Master's degree project in collaboration with Volvo Cars, with a focus on cooling fan noise at the charging state of electric vehicles. The main objective of this thesis is to understand the effects of fan installation. Three different setups of acoustic measurement are carried out, namely free-space, wall-mounted, and in-vehicle measurement. Correlations of these measurements are investigated through comparisons of the measurement results and the installation effects are identified through spectrum difference between free-space and in-vehicle measurement. Moreover, the implementation of spectral decomposition method enables the separation of source strength and propagation effect. Analyses of sound pressure levels are studied by looking into tonal and broadband components. In addition, sound power levels are determined by following ISO standards. Finally, a subjective rating session is held to understand the human perception of cooling fan noise. / Med anledning av den pågående utvecklingen mot elektrifiering där bilarna går mot batterier och elmotorer för framdrivning så ändras ljudbilden. Utan förbränningsmotorer som tidigare maskerade mycket av ljudet från bilarna så framträder nya ljudkällor. En sådan är kylfläkten som allt mer blir en störningskälla. Vanligtvis sker designen av kylfläktsmodulen i en tidig fas innan det finns någon prototypbil att tillgå. Detta gör att det är viktigt att utveckla metoder för att i tidig fas kunna optimera designen av kylfläkten.  Detta är ett examensarbete i samarbete med Volvo Cars med fokus på det ljud som uppstår vid laddning av eldrivna bilar. Uppsatsens huvudsakliga mål är att förstå fläktinstallationens påverkan på ljud genom att korrelera olika typer av mätningar. Detta genomfördes m.h.a tre separata konfigurationer, fritt-upphängd mätning, väggmonterad och installerad i bil. Korrelation undersöktes genom att jämföra mätresultat och analys av spektrumet. Analysen av ljudtrycksnivåerna genom att titta på dels de tonala komponenterna men också på bredbandsnivåerna. Utöver detta fastställs även ljudeffekten genom att följa gängse ISO standard. Slutligen så gjordes en subjektiv utvärdering för att få en förståelse av upplevelsen av ljudet från en kylfläkt.

Cette thèse porte sur la caractérisation non destructive de structures 2D magnéto-diélectriques inhomogènes complexes. L’ensemble des étapes allant de l’expérience au traitement du problème inverse est traité. Dans un premier temps, un modèle direct reliant le champ diffusé aux propriétés électromagnétiques du matériau a été mis en place. Ce modèle requiert des calculs par éléments finis de la propagation de l’onde électromagnétique, en présence de l’objet observé lorsque celui-ci est positionné sur un support métallique. Une validation expérimentale a été réalisée via la mise en place d'un banc de mesure multi statique. Différentes étapes d'ajustements et d'étalonnages ont permis la réduction du bruit de mesure ainsi que des biais. L’inversion est traitée principalement par une approche linéaire, avec un choix attentif de la valeur des hyper paramètres qui y sont associés. Une fois les outils mis en place, six études ont été réalisées pour la validation de notre système d’imagerie 2D des propriétés électromagnétiques de matériaux magnéto-diélectriques inhomogènes. Cela comprend l’évaluation des incertitudes de mesure, de la résolution spatiale, la mesure de différents matériaux magnétiques et l’utilisation de différents supports à géométries variées. L’ensemble des résultats expérimentaux réalisés se place dans une hypothèse de géométrie 2D. C’est pourquoi, nous avons ensuite orienté nos travaux vers la recherche d’un design innovant permettant de faire évoluer le banc de mesure en un dispositif d’imagerie 3D. Dans cette perspective, une source secondaire vient se déplacer proche de la cible pour acquérir de l’information selon la troisième dimension. / The subject of this thesis is the non-destructive characterization of complex inhomogeneous magneto-dielectric structures. Successively, the experimental developments, the modelling and the data treatments stages are addressed. A forward model that links the scattered field to the electromagnetic properties is established. This model requires some finite element computations in order to estimate the propagation of the electromagnetic wave in presence of the magneto-dielectric object which is glued on a metallic support. A multistatic bench has been designed and constructed in order to collect measured scattered fields. Several adjustments and calibration procedures have been carried out to reduce the measurement noise and biases. Next, the inverse problem has been dealt with, in order to retrieve the electromagnetic properties of the samples, from the measured scattered field. The inverse problem is mainly solved with a linear approach, with a careful selection of the hyperparameters. Once the system has been fine tuned, six studies have been realized to validate our 2D imaging system. The assessment of the measurement uncertainty, the evaluation of the spatial resolution, the characterization of various magnetics materials and the use of different supports with variable geometries have been performed. So far, all the developments were done under a 2D hypothesis. That is why, we have then focused our research on the design of a 3D innovative imaging setup. To this end, a secondary source moving close to the target has been added in order to gain information in the third direction. A numerical study has been performed to assess the expected performances of this new setup.