<p>Spiral grain in trees causes trouble to the wood industry, since boards sawn from trees with large grain angle have severe problems with form stability. Measurements of the grain angle under bark enable the optimisation of the refining process. The main objective of this thesis is to study the potential in estimating the grain angle by using microwaves. To do this, electromagnetic modelling and sensitivity analysis are combined.</p><p>The dielectric properties of wood are different along and perpendicular to the wood fibres. This anisotropy is central for the estimation of the grain angle by means of microwaves. To estimate the grain angle, measurements are used together with electromagnetic modelling for the scattering from plane surfaces and cylinders. Measurement set-ups are proposed to determine the material parameters, such as the grain angle, for plane boards and cylindrical logs. For cylindrical logs both near-field and far-field measurements are investigated. In general, methods for determining material parameters exhibit large errors in the presence of noise. In this case, acceptable levels of these errors are achieved throug using few material parameters in the model: the grain angle and two dielectric parameters, characterising the electrical properties parallel and perpendicular to the fibres.</p><p>From the case with plane boards, it is concluded that it is possible to make use of the anisotropy of wood to estimate the grain angle from the reflected electromagnetic field. This property forms then the basis of the proposed methods for the estimation of the grain angle in cylindrical logs. For the proposed methods, a priori knowledge of the moisture content or temperature of the wood is not needed. Furthermore, since the anisotropy persist also for frozen wood, the method is valid for temperatures below zero degrees Celsius.</p><p>For the case with cylindrical logs, sensitivity analysis is applied to the near-field as well as the far-field methods, to analyse the parameter dependence with respect to the measurement model and the errors introduced by noise. In this sensitivity analysis, the Cram\'{e}r-Rao bound is used, giving the best possible variance for estimating the parameters. The levels of the error bounds are high, indicating a problematic estimation problem. However, the feasibility of accurate estimation will be improved through higher signal-to-noise ratios, repeated measurements, and better antenna gain. The sensitivity analysis is also useful as an analytical tool to understand the difficulties and remedies related to the method used for determining material parameters, as well as a practical aid in the design of a measurement set-up.</p><p>According to the thesis, grain angle estimation is possible with microwaves. The proposed methods are fast and suitable for further development for in-field use in the forest or in saw mills.</p> / <p>Träd med växtvridenhet orsakar problem i träindustrin eftersom brädor som sågats från träd med stor fibervinkel har problem med formstabiliteten och vrider sig då de torkas. Mätning av fibervinkeln under bark möjliggör optimering av förädlingsprocessen. I den här avhandlingen kombineras elektromagnetisk modellering och känslighetsanalys för att undersöka möjligheterna att bestämma fibervinkeln med mikrovågor.</p><p>De elektriska egenskaperna hos trä är olika längs med och vinkelrätt mot fibrerna. Den här anisotropin är utgångspunkten för att bestämma fibervinkeln med hjälp av mikrovågor. För att skatta fibervinkeln används mätningar tillsammans med elektromagnetisk modellering för spridningen från plana ytor och cylindrar. Mätuppställningar föreslås för problemet att skatta materialparametrar, såsom fibervinkeln, i plana brädor och cylindriska stockar. För cylindriska stockar undersöks både närfälts- och fjärrfältsmätningar. I allmänhet har metoder för skattning av materialparametrar stora fel då systemet innehåller brus. Här erhålls acceptabla fel genom att använda få materialparametrar i modelleringen. De materialparametrar som används är fibervinkeln och två dielektriska parametrar som karakteriserar de elektriska egenskaperna längs med och vinkelrätt mot träfibern.</p><p>Slutsatsen från fallet med plana brädor är att det är möjligt att använda anisotropin hos trä och dess påverkan på ett reflekterat elektromagnetiskt fält för att skatta fibervinkeln. Detta är grunden i de metoder som föreslås för cylindriska stockar. För samtliga metoder så gäller att varken fukthalt eller temperatur behöver vara kända på förhand. Eftersom anisotropin kvarstår också för fruset trä så är metoderna användbara även för temperaturer under noll grader Celsius.</p><p>För fallet med cylindriska stockar används känslighetsanalys på både närfälts- och fjärrfältsmetoderna för att analysera parameterberoendet i uppmätt data samt felen som introduceras av brus. I den här känslighetsanalysen används Cram\'{e}r-Rao gränsen som ger den bästa möjliga variansen för skattning av parametrarna. Nivåerna på gränserna är höga vilket indikerar att det är ett svårt estimeringsproblem. Möjligheterna att skatta parametrarna noggrant förbättras genom bättre signal-brus förhållande, upprepade mätningar samt ökad antennstyrka. Känslighetsanalysen är också användbar som ett analytiskt verktyg för ökad förståelse för problem och möjligheter relaterade till metoden för att skatta parametrarna och som ett praktiskt stöd för design av en mätuppställning.</p><p>Enligt avhandlingen är skattning av fibervinkel möjlig med mikrovågor. De föreslagna metoderna är snabba och lämpliga att utveckla vidare för användning i skogen eller i sågverk.</p>

Le système Cospas-Sarsat est un système de recherche et de sauvetage à l’échelle mondiale qui fonctionne à l’aide de satellites en orbite basse et de satellites en orbite géostationnaire. La constellation de satellites actuelle est en cours de remplacement par des satellites en orbite moyenne qui couvrent de plus grandes zones de la surface de la Terre permettant des alertes quasi instantanées. L’objectif de cette thèse est d’étudier les performances de localisation de ce nouveau système, qui a été nommé système MEOSAR (Medium Earth Orbit Search and Rescue). Nous étudions d’abord la qualité de la liaison entre la balise de détresse, le satellite, et la station de réception au sol à l’aide d’un bilan de liaison. Ensuite, nous proposons un modèle de signal basé sur des fonctions sigmoïdes afin de modéliser les transitions douces du signal de détresse. Pour ce modèle, les performances de localisation (en terme de bornes de Cramér-Rao et de la variance d’estimateurs) sont étudiées pour l’estimation de position de la balise, et pour l’estimation de différents paramètres, y compris le temps d’arrivée, la fréquence d’arrivée et la durée du symbole. Ensuite, nous étudions l’impact de l’ajout d’information a priori sur la période symbole et sur le temps de montée du signal, qui proviennent des tolérances autorisées sur les spécifications des balises de détresse. Nous étudions également l’erreur introduite par l’ajout de bruit de phase caractéristique des oscillateurs des balises, et nous considérons l’amélioration de l’estimation de position en prenant en compte les multiples émissions de la balise de détresse. Finalement, les performances de localisation du système MEOSAR sont données pour les balises de détresse de deuxième génération, qui sont en cours de développement, et qui utilisent une modulation avec étalement de spectre. / Cospas-Sarsat is an international search and rescue system that operates using low-orbit satellites and geostationary satellites. The current satellite constellation is being replaced by medium Earth orbit satellites which will cover larger areas of the surface of the Earth, permitting almost instantaneous alerts. The objective of this thesis is to study the localization performance of this new system, named MEOSAR (Medium Earth Orbit Search and Rescue). We first study the quality of the link between the beacon, the satellite and the ground receiving station through a link budget. Then, we propose a signal model based on sigmoidal functions to model the smooth transitions of the distress signal. For this model, the localization performance (in terms of Cramér-Rao bounds and estimator variances) is studied for the estimation of the beacon position and for different parameters including the time of arrival, the frequency of arrival and the symbol width. Then, we study the impact of adding prior information on the symbol width and the signal rise time, which are constructed from the allowed tolerances on the beacon specifications. We also investigate the error introduced by the addition of oscillator phase noise, and we show how the position estimation can be improved by taking into account multiple emissions of the beacon. Finally, the localization performance of the MEOSAR system is studied for second generation beacons, which are being developed using spread spectrum modulation.

Pattern theory, a mathematical framework for representing knowledge of complex patterns developed by applied mathematician Ulf Grenander, has been shown to have potential uses in automatic target recognition (ATR). Prior research performed in the mid-1990s at Washington University in St. Louis resulted in ATR algorithms based on concepts in pattern theory for forward-looking infrared (FLIR) and laser radar (LADAR) imagery, but additional work was needed to create algorithms that could be implemented in real ATR systems. This was due to performance barriers and a lack of calibration between target models and real data. This work addresses some of these issues by exploring techniques that can be used to create practical pattern-theoretic ATR algorithms. This dissertation starts by reviewing the previous pattern-theoretic ATR research described above and discussing new results involving the unification of two previously separate outcomes of that research: multi-target detection/recognition and thermal state estimation in FLIR imagery. To improve the overall utility of pattern-theoretic ATR, the following areas are re-examined: 1) generalized diffusion processes to update target pose estimates and 2) the calibration of thermal models with FLIR target data. The final section of this dissertation analyzes the fundamental accuracy limits of target pose estimation under different sensor conditions, independent of the target detection/recognition algorithm employed. The Cramér-Rao lower bound (CRLB) is used to determine these accuracy limits.

This thesis concerns detection and recognition of ground object using data from laser radar systems. Typical ground objects are vehicles and land mines. For these objects, the orientation and articulation are unknown. The objects are placed in natural or urban areas where the background is unstructured and complex. The performance of laser radar systems is analyzed, to achieve models of the uncertainties in laser radar data. A ground object recognition method is presented. It handles general, noisy 3D point cloud data. The approach is based on the fact that man-made objects on a large scale can be considered be of rectangular shape or can be decomposed to a set of rectangles. Several approaches to rectangle fitting are presented and evaluated in Monte Carlo simulations. There are error-in-variables present and thus, geometric fitting is used. The objects can have parts that are subject to articulation. A modular least squares method with outlier rejection, that can handle articulated objects, is proposed. This method falls within the iterative closest point framework. Recognition when several similar models are available is discussed. The recognition method is applied in a query-based multi-sensor system. The system covers the process from sensor data to the user interface, i.e., from low level image processing to high level situation analysis. In object detection and recognition based on laser radar data, the range value’s accuracy is important. A general direct-detection laser radar system applicable for hard-target measurements is modeled. Three time-of-flight estimation algorithms are analyzed; peak detection, constant fraction detection, and matched filter. The statistical distribution of uncertainties in time-of-flight range estimations is determined. The detection performance for various shape conditions and signal-tonoise ratios are analyzed. Those results are used to model the properties of the range estimation error. The detector’s performances are compared with the Cramér-Rao lower bound. The performance of a tool for synthetic generation of scanning laser radar data is evaluated. In the measurement system model, it is possible to add several design parameters, which makes it possible to test an estimation scheme under different types of system design. A parametric method, based on measurement error regression, that estimates an object’s size and orientation is described. Validations of both the measurement system model and the measurement error model, with respect to the Cramér-Rao lower bound, are presented.

Ingeniero Civil Eléctrico / En la Astronomía ha habido un salto cuantitativo gigantesco desde el nacimiento de la tecnología CCD y las imágenes digitales. A pesar de ello, todavía existe un espacio de mejora en lo que respecta a las técnicas para estimación de parámetros importantes que caracterizan a las estrellas. Es por eso que esta Memoria de Título se presenta como objetivo el estudiar y cuantificar el uso de nuevos enfoques de estimación modernas no aplicados aún en esta disciplina para la estimación de la posición de objetos luminosos (Astrometría). Para poder entender el problema se presenta qué es una cámara digital y su uso en la astronomía, especificamente en la astrometría, además de presentar importantes conceptos astronómicos que se usan a lo largo de la memoria, como lo son el Point Spread Function y el Full Width at Half Maximum. Por otro lado, se da un repaso a los elementos de estimación necesarios para resolver el problema, como Cramér-Rao, Cramér-Rao Bayesiano y los estimadores Esperanza Condicional, Maximum Likelihood y Least Squares. La implementación del estimador se realizará a partir de una formalización completa del problema de estimación en astrometría, donde se incluirá también el trabajo de los algoritmos necesarios para encontrar el valor numérico tanto del estimador como de su error cuadrático medio. Se mostrará también la resolución de la cota de Cramér-Rao, tanto para la versión paramétrica como la bayesiana. Se hace un análisis de las herramientras presentadas usando como figura de mérito el MSE (Error Cuadrático Medio). A partir de ello, se muestra cómo varía este valor como función del tamaño del pixel, la relación de señal-ruido y sus ganancias relativas, para posteriormente estudiar las diferencias entre la Cota Bayesiana de Cramér-Rao y el MSE de la Esperanza Condicional, el estimador propuesto para el problema. Finalmente se concluye, viendo que existen ganancias significativas del enfoque Bayesiano en regímenes de baja relación señal-ruido y gran tamaño de pixel. Además se verifica que la cota Bayesiana de Cramér-Rao es un buen predictor del MSE de la Esperanza Condicional, lo cual trae nuevas preguntas que se pueden plantear como trabajo futuro a partir de esta Memoria de Título.

Nesta dissertação de mestrado, vamos apresentar uma prova para os grandes desvios para variáveis aleatórias independentes e identicamente distribuídas com todos os momentos finitos e para a medida empírica de cadeias de Markov com espaço de estados finito e tempo discreto. Além disso, abordaremos os teoremas de Sanov e Gärtner-Ellis. / In this master thesis it is presented a proof of the large deviations for independent and identically distributed random variables with all finite moments and for the empirical measure of Markov chains with finite state space and with discrete time. Moreover, we address the theorems of Sanov and of Gartner-Ellis.

A Multiple-Input Multiple Output (MIMO) radar can be broadly defined as a radar system employing multiple transmit waveforms and having the ability to jointly process signals received at multiple receive antennas. In terms of configurations, the antennas can be widely separated or co-located. The first part of the thesis is on detection under Gaussian and non-Gaussian environments using a MIMO radar which contains several widely separated subarrays with one or more elements each. Two different situations are considered. Firstly, we consider that the interference is Gaussian but correlation between subarrays can arise due to insufficient spacing and the imperfect orthogonality of waveforms. Secondly, we consider that the interference is non-Gaussian, a situation which arises under sea and ground clutter and when the resolution is very high. The second part is on the application of MIMO techniques to Space-Time Adaptive Processing (STAP). The coherent MIMO configuration is studied in terms of antenna element distribution and inter-element spacing to improve detection and estimation performance. A preliminary study is also done on the use of spatial diversity to improve detection stability w.r.t. target Radar Cross Section (RCS) fluctuations and velocity direction changes.

ITC/USA 2012 Conference Proceedings / The Forty-Eighth Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2012 / Town and Country Resort & Convention Center, San Diego, California / A broadband passive direction finding system utilizing Luneburg lens has been investigated. With the simulated power level distribution at the detectors mounted on a Luneburg lens, both Cramér-Rao bound (CRB) and the root mean square error (RMS) based on the Correlation Algorithm (CA) for the direction of arrival (DoA) estimation have been derived and calculated. Guidelines on how to design the Luneburg lens detecting system have been studied. Finally, as a proof-of-concept demonstration, the DoA performance of a Luneburg lens fabricated using the polymer jetting technology with five detectors 10° equally spaced to receive the azimuth signal from -20° to 20° is demonstrated.

Les méthodes de trajectographie conventionnelles par mesures d'angle supposent que la source est en mouvement rectiligne uniforme tandis que l'observateur est manœuvrant. Dans cette thèse, nous remettons en cause cette hypothèse en proposant un autre modèle de cinématique de la source : le mouvement circulaire uniforme. Nous prouvons qu'une telle trajectoire est observable à partir d'un observateur en mouvement rectiligne uniforme. Puis, nous étudions l'apport de mesures additionnelles de fréquence ou la faisabilité de la trajectographie par mesures de distances. Le cas d'une source en mouvement rectiligne uniforme et d'un observateur manœuvrant est étudié pour ce dernier type de mesures. Chaque cas donne lieu à une analyse de l'observabilité de la trajectoire de la source et à la mise au point de l'estimateur du maximum de vraisemblance. Nous montrons que ce dernier s'avère le plus souvent efficace.

L'émergence des formes d'onde numériques en radar et l'engouement de la communauté scientifique pour leur versatilité éprouvée en télécom, soulèvent naturellement chez les ingénieurs radaristes la question de l'amélioration effective des performances opérationnelles par ces nouvelles formes d'onde, notamment en matière de haute-résolution. Les travaux publiés sur le sujet sont prometteurs, à ceci près qu'ils sont le plus souvent basés sur des modèles théoriques un peu éloignés de la réalité opérationnelle ou sur des scénarios simplistes relativement à la capacité haute résolution envisagée (par exemple le faible nombre de sources pris en compte). En effet la prise en compte d'un modèle d'observation réaliste (large bande, à fréquence d'échantillonnage élevée) et de scénario à grand nombre de contributeurs conduit à des estimateurs dont la complexité d'implémentation n'est pas compatible des puissances de calcul actuelles. Une approche alternative, et compatible des puissances de calcul actuelles, pour la qualification des performances haute résolution est l'utilisation des bornes inférieures d'estimation, principalement la borne de Cramèr-Rao déterministe. L'examen de la littérature courante (notamment les monographies de référence) sur la borne de Cramèr-Rao déterministe a fait apparaître des lacunes relatives à sa formulation dans le contexte radar qui nous intéresse, à savoir MIMO large bande, multisources, multiparamètres à observations multiples. En effet dans la littérature courante, les observations multiples sont définies comme des réalisations multiples indépendantes d'un même modèle d'observation, alors qu'en radar il s'agit en général de la combinaison de modèles d'observation différents (variation de la forme d'onde). Ce constat a motivé l'essentiel de ce travail, à savoir l'établissement d'une expression analytique générale de la borne de Cramèr-Rao déterministe MIMO large bande, multisources, multiparamètres à modèles d'observations multiples pour la qualification (asymptotique) des performances en estimation d'un radar actif. Ce travail fournit un outil de comparaison des performances haute-résolution des différentes formes d'onde, dont les nouvelles formes d'onde numériques. De façon générale, l'expression analytique générale de la borne de Cramèr-Rao obtenue fournit la base théorique pour le développement des futurs radars à haute résolution.