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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Software Defined VNA : Measure Coupling Between Elements in an Antenna Array

Söderlund, Alexander January 2023 (has links)
With improvements in hardware of antenna receivers, fully digital arrays have been made possible to use in real time systems. These systems have a greater complexity, with the advantage of more dynamic system design since the use of the communication system can be changed with only a software change. Construction of a system capable of bidirectional communication on the same frequency and at the same time, is possible with a fully digital array if the coupling between the antenna elements are known. The good thing about the system is that all components for measuring this coupling already are included in the fully digital array. A signal generator and a coherent multichannel receiver can be used to create a VNA, completely by software. This can be used to measures the coupling coefficients of the antenna elements. In this thesis the working principle of the the software defined VNA is proven, a testing environment for a antenna array is described andadjustments for real hardware are used to create a result which can be strongly correlated to measurements of a lab grade VNA used as reference.
2

Contactless detection of cardiopulmonary activity for a person in different scenarios / Détection sans contact de l'activité cardio-pulmonaire d'une personne dans différents scenarios

Samad, Sarah 24 May 2017 (has links)
De nos jours, les mesures sans contact du signal cardiaque du patient en utilisant le radar Doppler a suscité un intérêt considérable chez les chercheurs, surtout que les électrocardiographes traditionnels avec des électrodes fixes ne sont pas pratiques dans certains cas comme les nourrissons ou les victimes de brûlure. En raison de la sensibilité des micro­ondes à de petits mouvements, le radar a été utilisé comme système de surveillance de l'activité cardio-pulmonaire humaine. Selon l'effet Doppler, un signal de fréquence constante est transmis vers la cible ayant un déplacement variable puis réfléchi. Le signal réfléchit possède une variation de phase par rapport au temps. Dans notre cas, la cible est la poitrine du patient; Le signal réfléchi de la poitrine de la personne contient le signal cardiorespiratoire. Le système est basé sur un analyseur de réseau vectoriel et deux antennes cornet. Le S21 est calculé en utilisant un analyseur de réseau. La variation de phase de S21 contient des informations de l'activité cardio-pulmonaire. Des techniques de traitement sont utilisées pour extraire le signal cardiaque de la variation de la phase de S21 . Cette thèse présente une étude comparative dans la détection des signaux de battements cardiaques au niveau de la puissance rayonnée et de la fréquence opérationnelle. Les puissances rayonnées sont comprises entre 3 et -17 dBm et les fréquences opérationnelles utilisées sont 2.4, 5.8, 1 0 et 20 GHz. Cela permet de spécifier la fréquence opérationnelle optimale, qui donne un compromis entre la puissance minimale émise ainsi que la complexité du système de mesure. De plus, une étude comparative entre plusieurs méthodes de traitement de signal est proposée pour extraire la meilleure méthode qui permet de mesurer le signal cardiaque et par suite extraire ses paramètres. Des techniques de traitement basées sur des transformées en ondelettes ou le filtrage classique sont présentées et utilisées afin de faire une comparaison entre elles. Le paramètre extrait dans cette thèse est le taux des battements cardiaques. Les mesures ont été effectuées simultanément avec un électrocardiographe afin de valider les mesures du signal cardiaque. Puisque la personne peut se déplacer d'une pièce à une autre à l'intérieur de son domicile, des mesures des quatre côtés de la personne et derrière un mur sont réalisées. Ajoutons une approche de modélisation fondée sur la mesure cardio-respiratoire pour une personne qui exerce une marche en avant. De plus, une comparaison entre un système à micro-ondes à simple et deux antennes pour une personne qui prend son souffle est effectuée afin de tester la précision du système à antenne unique par rapport au a la deuxième. Par suite, des mesures sont effectuées pour une personne qui respire en utilisant un système à une seule antenne. / Nowadays, contact-less monitoring patient's heartbeat using Doppler radar has attracted considerable interest of researchers, especially when the traditional electrocardiogram (ECG) measurements with fixed electrodes is not practical in some cases like infants at risk or sudden infant syndrome or burn victims. Due to the microwave sensitivity toward tiny movements, radar has been employed as a noninvasive monitoring system of human cardiopulmonary activity. According to Doppler effect, a constant frequency signal reflected off an object having a varying displacement will result in a reflected signal, but with a time varying phase. In our case, the object is the patient's chest; the reflected signal of the person's chest contains information about the heartbeat and respiration. The system is based on a vector network analyzer and 2 horn antennas. The S21 is computed using a vector network analyzer. The phase variation of S21 contains information about cardiopulmonary activity. Processing techniques are used to extract the heartbeat signal from the S21 phase. This thesis presents a comparative study in heartbeat detection, considering different radiated powers and frequencies. The radiated powers used are between 3 and -17 dBm and the operational frequencies used are 2.4, 5.8, 10 and 20 GHz. This helps to make a compromise between the minimum power emitted and the complexity of the measurement system. In addition, a comparative study of several signal processing methods is proposed to extract the best technique for heartbeat measurement and thus to extract its parameters. Processing techniques are based on wavelet transforms and conventional filtering in order to make a comparison between them. The parameter extracted in this thesis is the heartbeat rate HR. Measurements were performed simultaneously with a PC-based electrocardiograph to validate the heartbeat rate measurement. Since the person can move from a room to another inside his home, measurements from the four sides of the person and behind a wall are performed. In addition, a modeling approach based on cardio-respiratory measurement for a person who is walking forward is presented. Furthermore, a comparison between single and two-antenna microwave systems for a non-breathing person is carried out to test the accuracy of the single-antenna system relative to the two ­antenna microwave system. After that, measurements are performed using one antenna microwave system for a person who breathes normally.
3

Composite materials filled with ferromagnetic microwire inclusions demonstrating microwave response to temperature and tensile stress

Zamorovskii, Vlad January 2017 (has links)
Amorphous and polycrystalline microwires cast from ferromagnetic Fe-based or Co-based alloys in glass envelope demonstrate unique magneto-anisotropic and high frequency impedance properties that make them very attractive for sensor applications. Magnetic anisotropies of different types result from the inverse magnetostriction effect (positive or negative) at the interface between the glass shell and the metal core, in the presence of the residual stresses induced during the Taylor-Ulitovski casting method. Therefore, the glass shell is not just isolation, but also is one of most important factors that defines the physical properties of microwires. In particular, magnetic anisotropy allows high frequency impedance to be tuned by external stimuli such as magnetic field, tensile stress, or temperature. In the project, these effects are explored for the creation of low density microwire inclusions that might introduce tuneable microwave properties to polymer composite materials. The project aims to study high frequency impedance effects in ferromagnetic wires in the presence of tensile stress, temperature, and magnetic field. The integration of microwave equipment with mechanical and thermal measurement facilities is a very challenging task. In the project, we develop new experimental techniques allowing comprehensive study of composite materials with electromagnetic functionalities. The wire surface impedance recovered from such measurements can then be used to model the microwave response from wire-filled composites in free space. The obtained results significantly expand the horizon of potential applications of ferromagnetic wires for structural health monitoring.

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