In this thesis, an estimation method adapted from MUSIC algorithm is presented for estimation of signal arrival time for impulse radio UWB systems. An accurate estimate of signal arrival time is considered essential in time-based wireless and indoor location systems. Since most wireless communications systems used for indoor position location may suffer from dense multipath situation, the accuracy of determining signal arrival time become an important issue for the time-based location systems. The fine resolution of UWB signals provides potentially accurate ranging for indoor location applications. However, the ambiguity caused by the unresolved first arrival path may still yield an error in determining the true signal arrival time. The presented method uses improved MUSIC techniques in time domains to estimate the shortest and the real signal arrival time for UWB radio link. For a two-multipath case, analysis and simulation results of multipath resolvability and the variance of estimation errors of signal arrival time are discussed.

This thesis presents the development of MUSIC algorithm based novel approaches for the estimation of Direction of Arrival (DOA) of electromagnetic sources. For the 2D-DOA estimation, this thesis proposes orthogonally polarized linear array configuration rather than the conventionally invoked two dimensional array. An elegant one dimensional search technique to compute 2D-DOA estimation for a single source scenario has been proposed. To facilitate one dimensional search for 2D-DOA estimation, a closed form relationship between the azimuth and elevation angles of the 2D-DOA is derived using the analytical expressions of radiation patterns of Rectangular Waveguide (RWG) and Circular Waveguide (CWG). The computation time for the proposed one dimensional search technique is reduced by a factor of 50 and 150 for 1 and 0:5 search interval respectively. To improve the accuracy and the resolution of 2D-DOA estimation in case of closely spaced sources, this thesis proposes novel array configurations such as orthogonally polarized planar array, orthogonally mounted linear array and orthogonally polarized linear array. Through numerous simulation studies, a relative performance comparison of 2D-DOA estimation realized through various proposed novel array configurations has been carried out to highlight the accuracy and resolution under wide range of SNR conditions. The thesis presents a discussion on the analysis of effect of spatial de correlation in lieu of the employed orthogonally polarized elements in the array configuration on the improved accuracy and resolution of the 2D-DOA estimation. This thesis also deals with the utility of the proposed orthogonally polarized array configurations for tracking of 2D-DOA angles of non-stationary signal sources. The weighting factor and forgetting factor approaches for smoothing the time-varying covariance matrix of the non-stationary sources are studied. The simulation studies on 2D-DOA tracking by invoking proposed array configurations along with the proposed smoothing techniques prove that orthogonal polarized array configuration track the DOA source angle with minimum estimation errors. The thesis proposes the replacement of computationally intensive numerical schemes in Multiple Signal Classification (MUSIC) algorithm such as eigen decomposition and singular value decomposition with the subspace tracking techniques such as Bi-Iterative Singular Value Decomposition (Bi-SVD) algorithm. Invoking the concept of sub-band processing, the thesis addresses the validity of the extension of the presented 2D-DOA estimation analysis to wide band signal. A two subband filter approach is proposed for the estimation 2D-DOA of single and two wideband sources. The simulation study of the two subband filter approach along with the orthogonal polarized array configurations confirms the better estimation accuracy as well as the lesser computation time.

This thesis first discusses the ground plane effects of a test site on the antenna factors (AFs) of hybrid antenna (biconical log-periodic dipole array). Meanwhile, the effects of mutual coupling between antenna and its image, and the variation of active phase center are also discussed. From these analyses, a hybrid method, based on the modified SSM (Standard Site Method) and the PCPM (Phase Center and Pattern Matching) applied to the hybrid antenna for NSA (Normalized Site Attenuation) measurement is proposed. By this method, the low geometry- dependent AFs of hybrid antenna can be obtained to produce more reasonable NSA values for a test site. Secondly, this thesis proposes a simple, fast, and accurate method to calibrate the free-space AFs of broadband EMC (Electromagnetic Compatibility) antennas. This method adopts a fixed-height configuration and a MUSIC (MUltiple SIgnal Classification) algorithm. This configuration significantly shortens measurement time and removes height-dependent calibration errors. Meanwhile, the MUSIC algorithm can remove unexpected reflections from the ground plane or any other reflecting objects, by which the free-space AFs can be calculated. In addition, this method can also automatically compensate for the phase center shift, which makes measurement easier and more convenient. To verify this method, the calibrated results are compared with other published standard methods: the mean differences can be as low as 0.25 dB for the LPDA (log-periodic dipole array), 0.42 dB for the hybrid antennas, and 0.36 dB for the horn antennas. Finally, this thesis provides a method of using two equivalent negative inductances from two terminals of three coupled inductors to reduce the parasitic inductances of a typical three-capacitor EMI (Electromagnetic Interference) filter. Theoretical analysis and formula deduction for the design of two equivalent negative inductances are demonstrated. The experimental results show that the insertion losses of a three-capacitor EMI filter at 50 MHz can be reduced by 16.8 dB for the DM (differential-mode) and by 19.2 dB for the CM (common-mode). In Appendix A of this thesis, an extended study of the effect of ground plane on antenna¡¦s radiation is described. A simple V-shape edge-groove design for a finite ground plane can effectively reduce the pattern ripples of a monopole. The optimal design of proposed structure can reduce the peak-to-peak pattern ripples from 26 to 4.5 dB.

Le Contrôle Non Destructif (CND) de matériaux composites multicouches pour des problèmes de qualité, viabilité, sécurité et disponibilité des systèmes qui impliquent des pièces fabriquées dans les industries aéronautiques et de l’automobile est devenu une tâche essentielle aujourd’hui. L'objectif visé par cette thèse est l’imagerie électromagnétique de structures complexes multicouches anisotropes, de plus en plus utilisées dans des applications, et encore source de sérieux défis à l'étape de leur modélisation et encore plus à l'étape souvent en enfance de leur imagerie. En utilisant une vaste gamme de fréquences, qui va des courants de Foucault jusqu’aux micro-ondes, il y a un fort besoin de rendre disponibles des procédures de modélisation et d'imagerie qui sont robustes, rapides, précises et utiles à la décision des utilisateurs finaux sur des défauts potentiels, tant donc en basse fréquence (BF) (matériaux conducteurs, type fibre de carbone) qu’en haute fréquence (HF) (matériaux diélectriques, type fibre de verre). De plus, il est important d'obtenir des résultats en des temps brefs. Cependant, cela nécessite la connaissance d’une réponse précise à des sources externes aux multicouches, en considérant les couches des composites comme non endommagées ou endommagées : on parle donc de solution du problème direct, avec le cas particulier de sources élémentaires conduisant aux dyades de Green (DGF). La modélisation et la simulation numérique du problème direct sont gérés principalement via une solution au premier ordre de la formulation intégrale de contraste de source impliquant le tenseur de dépolarisation des défauts, quand ceux-ci sont assez petits vis-à-vis de l’épaisseur de peau locale (cas BF) ou de la longueur d'onde locale (cas HF). La précision des DGF doit nécessairement être assurée alors, même si les sources se situent loin de l'origine, ce qui donne un spectre de dyades qui oscille très rapidement. La technique d'interpolation-intégration dite de Padua-Domínguez est ainsi introduite dans le but d'évaluer de façon efficace des intégrales fortement oscillantes.Néanmoins, les matériaux composites peuvent souffrir de divers défauts, lors du processus de fabrication ou pendant leurs utilisations. Vides d’air, cavités remplies de liquide, fissures, etc., peuvent affecter le fonctionnement correct des structures composites. Il est donc indispensable de pouvoir détecter la présence des défauts. Ici, l’insistance est sur la méthode bien connue d’imagerie dite MUltiple SIgnal Classification (MUSIC), qui est basée sur la décomposition en valeurs singulières (SVD) des DGF ; celle-ci est développée afin de localiser les positions de multiples petits défauts volumiques en interaction faible enfouis dans des milieux anisotropes uniaxiaux. Le principal inconvénient de la méthode MUSIC est cependant sa sensibilité par rapport au bruit. Par conséquent, des méthodes MUSIC avec une résolution améliorée et la Recursively Applied and Projected (RAP) MUSIC sont introduites afin de surmonter un tel inconvénient de l'algorithme standard et de fournir des résultats de qualité avec une meilleure résolution. De nombreuses simulations numériques illustrent ces investigations. / Non-Destructive Testing/Evaluation (NdT/E) of multi-layered composite materials for problems of quality, viability, safety and availability of systems involving manufactured parts (in aeronautics and in automotive industry, as a good example) has become an interesting and challenging task nowadays. The focus of the PhD thesis is on the electromagnetic (EM) imaging of complex anisotropic multi-slab composite panels as increasingly encountered in applications, yet source of strong challenges at modeling stage and even more at often-in-infancy imaging stage. From eddy-currents to microwaves, there is a strong need to make available modeling and imaging procedures that are robust, fast, accurate and useful to potential end-users’ decision about potential defects both at low-frequency (LF) (conductive materials, carbon-fiber like) and high-frequency (HF) (dielectric materials, glass-fiber like). Moreover, it is important to get the results in close-to-real-time. However, this requires an accurate response to external sources of the multilayers, considering the layers which these composite structures are made of as undamaged or damaged. The modeling at forward stage is managed via a first-order solution involving the dyadic Green’s functions (DGF) of the layers along with the depolarization tensor of the assumed defects when they are small enough vis-à-vis the skin depth (LF case) or the wavelength (HF case). The accuracy of the DGF has to be ensured even if the sources lie far away from the origin, which yields a fast-oscillating spectrum of the dyads. The Padua-Domínguez interpolation-integration technique is introduced herein in order to evaluate in an effective fashion fast-oscillating integrals.Damages or disorders, which these composite structures may suffer from, are of many kinds. One could mention voids, fluid-filled cavities or uniaxial defects with obvious impacts on the electromagnetic and geometric parameters of the multilayers. That is, the task to make available to end-users imaging algorithms tailored to detect the presence of defects. The well-known standard MUltiple SIgnal Classification (MUSIC) algorithm, which is based on the Singular Value Decomposition (SVD) of such DGF, is here applied to localize the positions of small multiple defects with weak interaction embedded in anisotropic uniaxial media. The main drawback of MUSIC is its sensitivity with respect to the noise. Therefore, MUSIC with enhanced resolution and Recursively Applied and Projected (RAP) MUSIC are introduced to overcome such a drawback of the standard algorithm and to provide quality results with better resolution.

In recent years, unmanned aerial vehicles (UAV), also called drones, have experienced a rapid increase, which leads to the concern of illegal use of them. Passive RF is one of the effective ways to detect drones by receiving drones’ communication signals. After receiving the signal from drones, one can utilize the prior knowledge of signal characteristics for identifying and locating the drones. The angle of arrival (AoA) measured by multiple passive RF sensors can be used for localization by triangulation. However, the accuracy of the AoA measured by the passive RF sensors is strongly affected by the environment. In particular in urban areas, the multipath effect is prominent due to the building blockage and complicated terrestrial conditions that introduce certain errors to the result. So the service provider of the sensors needs a tool to perform the environment analysis to understand the quality of the service. A fast tool that can simulate the sensor network and surrounding environment can offer a flexible solution to optimize the sensor coverage and indicate the blind zone of detection. Especially when the sensors are deployed on the mobile platform, such tool can significantly improve the defensive quality of the drone detection system by optimizing real-time deployment and indicating low observable areas. In order to plan the sensor locations and assess the performance after the deployment of the sensor at a fast speed, We propose a multipath-based model to calculate the AoA error. The model is able to utilize the input of geometrical information for simulating the AoA error within a region. In this thesis, we investigate the outdoor channel at 2.4GHz using the ray-tracing method as it is the most used channel for UAVs. Massive simulations have been carried out and real test flights have been conducted to evaluate the accuracy of the modeling. Both simulations and test flights are carried out in Kista center where buildings are from high-rises to one-floor houses with various heights. In the simulation, the AoA is obtained by MUltiple SIgnal Classification (MUSIC) algorithm. Test flights are conducted using an existing Software-defined radio (SDR) based RF sensor. We tried our best to carry out the same trajectories in both simulations and test flights to provide fair comparisons. The simulation results show that the multipath model can predict the trend of AoA error when the height changes, while not sufficient to predict the error when the 2D position changes. Thus, to more accurately characterize the signal transmission, it is essential to extend this thesis to include more detailed environmental information and adaption based on measurement. / Under de senaste åren har obemannade flygfarkoster (UAV), även kallade drönare, ökat snabbt, vilket leder till oro för olaglig användning av dem. Passiv RF är ett av de effektiva sätten att upptäcka drönare genom att ta emot drönarnas kommunikationssignaler. Efter att ha tagit emot signalen från drönare kan man använda den tidigare kunskapen om signalegenskaperna för att identifiera och lokalisera drönarna. AoA som mäts av flera passiva RF-sensorer kan användas för lokalisering genom triangulering. Noggrannheten hos AoA som mäts av de passiva RF-sensorerna påverkas dock starkt av miljön. Särskilt i stadsområden är multipath-effekten framträdande på grund av byggnadsblockering och komplicerade markförhållanden som medför vissa fel i resultatet. Därför behöver leverantören av sensorer ett verktyg för att utföra miljöanalysen för att förstå tjänstens kvalitet. Ett snabbt verktyg som kan simulera sensornätverket och den omgivande miljön kan erbjuda en flexibel lösning för att optimera sensortäckningen och ange den blinda zonen för upptäckt. Särskilt när sensorerna placeras på en mobil plattformkan ett sådant verktyg avsevärt förbättra drönardetektionssystemets försvarskvalitet genom att optimera utplaceringen i realtid och ange områden med låg observationsgrad. För att planera sensorernas placering och bedöma prestandan efter att sensorn har placerats ut i snabb takt föreslår vi en multipath-baserad modell för att beräkna AoAfelet. Modellen kan utnyttja inmatningen av geometrisk information för att simulera AoA-felet inom ett område. I denna avhandling undersöker vi utomhuskanalen vid 2:4 GHz med hjälp av raytracing- metoden eftersom det är den mest använda kanalen för UAV:er. Massiva simuleringar har utförts och verkliga testflygningar har genomförts för att utvärdera modelleringens noggrannhet. Både simuleringar och testflygningar har utförts i Kista centrum där byggnaderna är allt från höghus till envåningshus med olika höjd. I simuleringen erhålls AoA med hjälp av MUSIC-algoritmen. Testflygningar genomförs med hjälp av en befintlig SDR-baserad RF-sensor. Vi gjorde vårt bästa för att utföra samma banor i både simuleringar och testflygningar för att ge rättvisa jämförelser. Simuleringsresultaten visar att multipathmodellen kan förutsäga trenden för AoA-felet när höjden ändras, medan den inte är tillräcklig för att förutsäga felet när 2D-positionen ändras. För att mer exakt karakterisera signalöverföringen är det därför viktigt att utöka denna avhandling till att omfatta mer detaljerad miljöinformation och anpassning baserad på mätning.

For successful identification of structural defects in plates and pipes, it is essential to understand structural wave propagation characteristics such as dispersion relations. Analytical approaches to identify the dispersion relations of homogeneous, simple plates and circular pipes have been investigated by many researchers. However, for plates or pipes with irregular cross-sectional configurations or multi-layered composite structures, it is almost impossible to obtain the analytical dispersion relations and associated mode shapes. In addition, full numerical modeling approaches such as finite element (FE) methods are not economically feasible for high (e.g., ultrasonic) frequency analyses where an extremely large number of discretized meshes are required, resulting in significantly expensive computation. In order to address these limitations, Hybrid Analytical/Finite Element Methods (HAFEMs) are developed to model composite plates and pipes in a computationally-efficient manner. When a pipe system is used to transport a fluid, the dispersion curves obtained from a “hollow” pipe model can mislead non-destructive evaluation (NDE) results of the pipe system. In this study, the HAFEM procedure with solid elements is extended by developing fluid elements and solid-fluid boundary conditions, resulting in the dispersion curves of fluid-filled pipes. In addition, a HAFEM-based acoustic transfer function approach is suggested to consider a long pipe system assembled with multiple pipe sections with different cross-sections. For the validation of the proposed methods, experimental and full FE modeling results are compared to the results obtained from the HAFEM models. In order to detect structural defect locations in shell structures from defect-induced, subtle wave reflection signals and eliminate direct-excitation-induced and boundary-reflected, relatively-strong wave signals, a time-frequency MUSIC algorithm is applied to ultrasonic wave data measured by using an array of piezoelectric transducers. A normalized, structurally-damped, cylindrical 2-D steering vector is proposed to increase the spatial resolution of time-frequency MUSIC power results. A cross-shaped array is selected over a circular or linear array to further improve the spatial resolution and to avoid the mirrored virtual image effects of a linear array. Here, it is experimentally demonstrated that the proposed time-frequency MUSIC beamforming procedure can be used to identify structural defect locations on an aluminum plate by distinguishing the defect-induced waves from both the excitation-generated and boundary-reflected waves.

Through-the-wall Imaging (TWI) is crucial for various applications such as law enforcement, rescue missions and defense. TWI methods aim to provide detailed information of spaces that cannot be seen directly. Current state-of-the-art TWI systems utilise ultra-wideband (UWB) signals to simultaneously achieve wall penetration and high resolution. These TWI systems transmit signals and mathematically back-project the reflected signals received to image the scenario of interest. However, these systems are diffraction-limited and encounter problems due to multipath signals in the presence of multiple scatterers. Time reversal (TR) methods have become popular for remote sensing because they can take advantage of multipath signals to achieve superresolution (resolution that beats the diffraction limit). The Decomposition Of the Time-Reversal Operator (DORT in its French acronym) and MUltiple SIgnal Classification (MUSIC) methods are both TR techniques which involve taking the Singular Value Decomposition (SVD) of the Multistatic Data Matrix (MDM) which contains the signals received from the target(s) to be located. The DORT and MUSIC imaging methods have generated a lot of interests due to their robustness and ability to locate multiple targets. However these TR-based methods encounter problems when the targets are behind an obstruction, particularly when the properties of the obstruction is unknown as is often the case in TWI applications. This dissertation introduces a novel total sub-MDM algorithm that uses the highly acclaimed MUSIC method to image targets hidden behind an obstruction and achieve superresolution. The algorithm utilises spatio-temporal windows to divide the full-MDM into sub-MDMs. The summation of all images obtained from each sub-MDM give a clearer image of a scenario than we can obtain using the full-MDM. Furthermore, we propose a total sub-differential MDM algorithm that uses the MUSIC method to obtain images of moving targets that are hiddenbehind an obstructing material.

Le contrôle non destructif de défauts du type fissures pénétrables ou impénétrables constitue un problème inverse très intéressant parmi ceux de la physique, de l'ingénierie des matériaux et structures, des sciences médicales, etc., et en soi est donc un sujet d'importance sociétale certaine. Le but de cette thèse est de développer des méthodes de reconstruction efficaces afin de les appliquer à une variété de problèmes de fissures. Premièrement, nous proposons un algorithme non-itératif afin de déterminer les extrémités de fissures conductrices, algorithme basé sur une formulation asymptotique appropriée et une méthode d'identification de pôles simples et de résidus d'une fonction méromorphe. Puis un algorithme non-itératif de type MUSIC(MUltiple SIgnal Classification) est considéré afin d'imager une fissure pénétrable ou impénétrable à partir du champ qu'elle diffracte, ce champ pouvant être représenté grâce à une formulation asymptotique rigoureuse. Une technique d'ensembles de niveaux est alors proposé afin de reconstruire une fissure pénétrable, deux fonctions d'ensemble de niveaux étant utilisées pour la décrire puisqu'une méthode traditionnelle d'ensembles de niveaux ne le permet pas de par sa petite épaisseur. Finalement, cette thèse traite de la reconstruction des fissures courtes et étendues avec des conditions limites de Dirichlet. Nous développons alors un algorithme de type MUSIC pour reconstruire les petites fissures et un algorithme d'optimisation pour les fissures longues basé sur la formulation asymptotique. Des simulations numériques nombreuses illustrent les performances des méthodes de reconstruction proposées.

Direction Finding (DF) algorithms are used by the Swedish Defence Research Agency (FOI) in the context of electronic warfare against radio. Parallelizing these algorithms using a Graphics Processing Unit (GPU) might improve performance, and thereby increase military support capabilities. This thesis selects the DF algorithms Correlative Interferometer (CORR), Multiple Signal Classification (MUSIC) and Weighted Subspace Fitting (WSF), and examines to what extent GPU implementation of these algorithms is suitable, by analysing, implementing and evaluating. Firstly, six general criteria for GPU suitability are formulated. Then the three algorithms are analyzed with regard to these criteria, giving that MUSIC and WSF are both 58% suitable, closely followed by CORR on 50% suitability. MUSIC is selected for implementation, and an open source implementation is extended to three versions: a multicore CPU version, a GPU version (with Eigenvalue Decomposition (EVD) and pseudo spectrum calculation performed on the GPU), and a MIXED version (with only pseudo spectrum calculation on the GPU). These versions are then evaluated for angle resolutions between 1° and 0.025°, and CUDA block sizes between 8 and 1024. It is found that the GPU version is faster than the CPU version for angle resolutions above 0.1°, and the largest measured speedup is 1.4 times. The block size has no large impact on the total runtime. In conclusion, the overall results indicate that it is not entirely suitable, yet somewhat beneficial for large angle resolutions, to implement MUSIC using GPU computing.

The angle of arrival estimation of multiple sources plays a vital role in the field of array signal processing as MIMO systems can be employed at both the transmitter and the receiver end and the system capacity, reliability and throughput can be significantly increased by using array signal processing. Almost all applications require accurate direction of arrival (DOA) estimation to localize the sources of the signals. Another important parameter of localization systems is the array geometry and sensor design which can be application specific and is used to estimate the DOA. In this work, various array geometries and arrival estimation algorithms are studied and then a new scheme for multiple source estimation is proposed and evaluated based on the performance of subspace and non-subspace decomposition methods. The proposed scheme has shown to outperform the conventional Multiple Signal Classification (MUSIC) estimation and Bartlett estimation techniques. The new scheme has a better performance advantage at low and high signal to noise ratio values (SNRs). The research work also studies different array geometries for both single and multiple incident sources and proposes a geometry which is cost effective and efficient for 3, 4, and 5 antenna array elements. This research also considers the shape of the ground plane and its effects on the angle of arrival estimation and in addition it shows how the mutual couplings between the elements effect the overall estimation and how this error can be minimised by using a decoupling matrix. At the end, a novel miniaturised multi element reconfigurable antenna to represent the receiver base station is designed and tested. The antenna radiation patterns in the azimuth angle are almost omni-directional with linear polarisation. The antenna geometry is uniplanar printed logspiral with striplines feeding network and biased components to improve the impedance bandwidth. The antenna provides the benefit of small size, and re-configurability and is very well suited for the asset tracking applications.