In this thesis a new approach is proposed for non-uniform linear arrays (NLA) which employs conventional subspace methods to improve the direction of arrival (DOA) estimation performance. Uniform linear arrays (ULA) are composed of evenly spaced sensor elements located on a straight line. ULA&#039 / s covariance matrix have a Vandermonde matrix structure, which is required by fast subspace DOA estimation algorithms. NLA differ from ULA only by some missing sensor elements. These missing elements cause some gaps in covariance matrix and Vandermonde structure is lost. Therefore fast subspace DOA algorithms can not be applied in this case. Linear programming methods and array interpolation methods can be used to solve this problem. However linear programming is computationally expensive and array interpolation is angular sector dependent and requires the same number of sensor in the virtual array. In this thesis, a covariance matrix augmentation method is developed by using the array interpolation technique and initial DOA estimates. An initial DOA estimate is obtained by Toeplitz completion of the covariance matrix. This initial DOA estimates eliminates the sector dependency and reduces the least square mapping error of array interpolation. A Wiener formulation is developed which allows more sensors in the virtual array than the real array. In addition, it leads to better estimates at low SNR. The new covariance matrix is used in the root-MUSIC algorithm to obtain a better DOA estimate. Several computer simulations are done and it is shown that the proposed approach improves the DOA estimation accuracy significantly compared to the same number of sensor ULA. This approach also increases the number of sources that can be identifed.

In this thesis, a Neural Network (NN) based beamforming algorithm is proposed for real time target tracking problem. The algorithm is performed for two applications, linear and cylindrical arrays. The linear array application is implemented with equispaced omnidirectional sources. The influence of the number of antenna elements and the angular seperation between the incoming signals on the performance of the beamformer in the linear array beamformer is studied, and it is observed that the algorithm improves its performance by increasing both two parameters in linear array beamformer. The cylindrical array application is implemented with twelve microstrip patch antenna (MPA) elements. The angular range of interest is divided into twelve sectors. Since three MPA elements are used to form the beam in each sector, the input size of the neural network (NN) is reduced in cylindrical array. According to the reduced size of NN, the training time of the beamformer is decreased. The reduced size of the NN has no degradation in forming the beams to the desired directions. The angular separation between the targets is an important parameter in cylindrical array beamformer.

In this thesis, the passive localization problem is studied. Robust and recursive solutions are presented by the use of Time Difference of Arrival (TDOA). The TDOA measurements are assumed to be gathered by moving sensors which makes the number of the sensors increase synthetically. First of all, a location estimator should be capable of processing the new measurements without omitting the past data. This task can be accomplished by updating the estimate recursively whenever new measurements are available. Convenient forms of the recursive filters, such as the Kalman filter, the Extended Kalman filter etc., can be applied. Recursive filter can be divided to two major groups: (a) The first type of recursive estimators process the TDOA measurements directly, and (b) the second type of the recursive estimators is the post processing estimators which process the TDOA indirectly, instead they fuse or smooth available location estimates. In this sense, recursive passive localization methods are presented for both types. In practice, issues like being spatially distant from each other and/or a radar with a rotating narrow beam may prevent the sensors to receive the same pulse. In such a case, the sensors can not construct common TDOA measurements which means that they can not accomplish the location estimation procedure. Additionally, there may be more than one sensor group making TDOA measurements. An estimator should be capable of fusing the measurements from different sensor groups. A sensor group consists of sensors which are able to receive the same pulse. In this work, solutions of these tasks are also given. Performances of the presented methods are compared by simulation studies. The method having the best performance, which is based on the Kalman Filter, is also capable of estimating the track of a moving emitter by directly processing the TDOA measurements.

An antenna array is an indispensable portion of a direction-of-arrival (DOA) estimation operation. A number of error sources in the arrays degrade the DOA estimation accuracy. Mutual coupling effect is one of the main error sources and should be corrected for any antenna array. In this thesis, a system theoretic approach is presented for mutual coupling characterization of antenna arrays. In this approach, the idea is to model the mutual coupling effect through a simple linear transformation between the measured and the ideal array data. In this context, a measurement reduction method (MRM) is proposed to decrease the number of calibration measurements. This new method dramatically reduces the number of calibration measurements for omnidirectional antennas. It is shown that a single calibration measurement is sufficient for uniform circular arrays when MRM is used. The method is extended for the arrays composed of non-omnidirectional (NOD) antennas. It is shown that a single calibration matrix can not properly model the mutual coupling effect in an NOD antenna array. Therefore, a sectorized calibration approach is proposed for NOD antenna arrays where the mutual coupling calibration is done in angular sectors. Furthermore, mutual coupling problem is also investigated for antenna arrays over a perfect electric conductor plate. In this case, reflections from the plate lead to gain/phase mismatches in the antenna elements. In this context, a composite matrix approach is proposed where mutual coupling and gain/phase mismatch are jointly modelled by using a single composite calibration matrix. The proposed methods are evaluated over DOA estimation accuracies using Multiple Signal Classification (MUSIC) algorithm. The calibration measurements are obtained using the numerical electromagnetic simulation tool FEKO. The evaluation results show that the proposed methods effectively realize the mutual coupling calibration of antenna arrays.

The prevalent frame of 'tourism as vacation' explicitly implies that one vacates 'the familiar' and escapes to 'the foreign'. Discourses of escape, therefore, function on the assumption that a rather clean and uncomplicated rupture between the familiar and foreign takes place (an assumption not only informing conventional readings and practices of tourism, but also the modern logic of states and citizenship and modern thought more broadly). A failure to account for the effects of this escapist logic on both the performance and materialization of tourism, as well as the ways in which tourism has come to reflect profound political problematics endemic to modern thought, has produced a serious gap in 'critical tourism' literature. To contest this notion of rupture, or, to disrupt escape, requires what Judith Butler terms a ‘radical re-articulation’ of tourism. In hopes to excite such a disruption, my work draws on Jacques Derrida’s texts concerning ‘non-arrival’ and ultimately re-articulates tourism as a practice of everyday life.

Darbo metu buvo nustatyti baltojo gandro gausumo ir erdvinio pasiskirstymo bei lizdaviečių pasirinkimo pokyčiai 1994–2010 metais, ištirti perėjimo buveinės pasirinkimo dėsningumai bei perėjimo sėkmingumo priklausomybė nuo kai kurių buveinės charakteristikų. Baltojo gandro perėjimo buveinės pasirinkimo tyrimai atlikti su 8,4 % pasaulinės perinčios baltojo gandro populiacijos, esančios arealo šiaurės vakarų periferijoje, susitelkusios teritorijoje, užimančioje 1,1 % arealo ploto. Buvo nustatyta, kad tyrimų teritorijoje per 1994–2010 metų laikotarpį ženkliai išaugus baltojo gandro gausumui, paukščiai prisitaikė perėti naujo tipo lizdavietėse – ant elektros oro linijų atramų. Šis prisitaikymas reprodukciniu požiūriu buvo iš dalies neadaptyvus dėl patikimai mažesnio perėjimo sėkmingumo lizduose, susuktuose ant eksploatuojamų elektros oro linijų atramų. Remiantis ilgalaikiais baltojo gandro pirmo atskridimo datos duomenimis, rinktais 1961–2000 metais, buvo nustatytas reikšmingas pavasarinio atskridimo datos į perimvietes arealo šiaurės vakarų periferijoje paankstėjimas. Taip pat buvo nustatyti veiksniai, lemiantys pirmo pavasarinio atskridimo į perimvietes datą. Darbe buvo nustatyti pagrindiniai, perinčiam baltajam gandrui grėsmę keliantys veiksniai, įvertintas jų reikšmingumas ir pasiūlytos neigiamo jų poveikio šiai Europos Sąjungoje saugomai rūšiai sumažinimo priemonės. / In this study, changes during the period 1994–2010 in White Stork abundance and spatial distribution, as well as in nest-site selection were determined; regularities in breeding habitat selection and the effect of some habitat characteristics on the breeding success were investigated. The White Stork habitat selection study was carried out in the north-western periphery of the species’ range on a sample, comprising 8.4% of the total breeding population of this species, concentrated in an area covering just 1.1% of its range. It was revealed that a considerable increase in the White Stork abundance in 1994–2010 coincided with the adaptation by birds to breeding at a new nest-site – on poles of overhead electricity lines. However, from the standpoint of reproduction, this change in the White Stork nesting behaviour was partly non-adaptive due to significantly lower breeding success in nests built on poles of operating overhead electricity lines. Data on the White Stork first spring arrival, collected during the period 1961–2000, revealed a significant advancement of spring arrival date to the breeding grounds in the north-western periphery of the range. Factors, affecting the first spring arrival to breeding grounds, were determined. The main threats facing the breeding White Storks were determined, their importance was assessed, and recommendations for the mitigation of these negative impacts were prepared for this species of the EU conservation concern.

In this study, changes during the period 1994–2010 in White Stork abundance and spatial distribution, as well as in nest-site selection were determined; regularities in breeding habitat selection and the effect of some habitat characteristics on the breeding success were investigated. The White Stork habitat selection study was carried out in the north-western periphery of the species’ range on a sample, comprising 8.4% of the total breeding population of this species, concentrated in an area covering just 1.1% of its range. It was revealed that a considerable increase in the White Stork abundance in 1994–2010 coincided with the adaptation by birds to breeding at a new nest-site – on poles of overhead electricity lines. However, from the standpoint of reproduction, this change in the White Stork nesting behaviour was partly non-adaptive due to significantly lower breeding success in nests built on poles of operating overhead electricity lines. Data on the White Stork first spring arrival, collected during the period 1961–2000, revealed a significant advancement of spring arrival date to the breeding grounds in the north-western periphery of the range. Factors, affecting the first spring arrival to breeding grounds, were determined. The main threats facing the breeding White Storks were determined, their importance was assessed, and recommendations for the mitigation of these negative impacts were prepared for this species of the EU conservation concern. / Darbo metu buvo nustatyti baltojo gandro gausumo ir erdvinio pasiskirstymo bei lizdaviečių pasirinkimo pokyčiai 1994–2010 metais, ištirti perėjimo buveinės pasirinkimo dėsningumai bei perėjimo sėkmingumo priklausomybė nuo kai kurių buveinės charakteristikų. Baltojo gandro perėjimo buveinės pasirinkimo tyrimai atlikti su 8,4 % pasaulinės perinčios baltojo gandro populiacijos, esančios arealo šiaurės vakarų periferijoje, susitelkusios teritorijoje, užimančioje 1,1 % arealo ploto. Buvo nustatyta, kad tyrimų teritorijoje per 1994–2010 metų laikotarpį ženkliai išaugus baltojo gandro gausumui, paukščiai prisitaikė perėti naujo tipo lizdavietėse – ant elektros oro linijų atramų. Šis prisitaikymas reprodukciniu požiūriu buvo iš dalies neadaptyvus dėl patikimai mažesnio perėjimo sėkmingumo lizduose, susuktuose ant eksploatuojamų elektros oro linijų atramų. Remiantis ilgalaikiais baltojo gandro pirmo atskridimo datos duomenimis, rinktais 1961–2000 metais, buvo nustatytas reikšmingas pavasarinio atskridimo datos į perimvietes arealo šiaurės vakarų periferijoje paankstėjimas. Taip pat buvo nustatyti veiksniai, lemiantys pirmo pavasarinio atskridimo į perimvietes datą. Darbe buvo nustatyti pagrindiniai, perinčiam baltajam gandrui grėsmę keliantys veiksniai, įvertintas jų reikšmingumas ir pasiūlytos neigiamo jų poveikio šiai Europos Sąjungoje saugomai rūšiai sumažinimo priemonės.

L’estimation et la localisation de sources sont des problèmes centraux en traitement d’antenne, en particulier en télécommunication, sismologie, acoustique, ingénierie médicale ou astronomie. Une antenne de capteurs est un système d’acquisition composé par de multiples capteurs qui reçoivent des ondes en provenance de sources de directions différentes: elle échantillonne les champs incidents en espace et en temps.Pour cette raison, des techniques haute résolution comme MUSIC utilisent ces deux éléments de diversité, l’espace et le temps, afin d’estimer l’espace signal engendré par les sources incidentes, ainsi que leur direction d’arrivée. Ceci est généralement atteint par une estimation préalable de statistiques de deuxième ordre ou d’ordre supérieur, comme la covariance spatiale de l’antenne, qui nécessitent donc de temps d’observation suffisamment longs.Seulement récemment, l’analyse tensorielle a été appliquée au traitement d’antenne, grâce à l’introduction, comme troisième modalité (ou diversité), de la translation en espace d’une sous-antenne de référence, sans faire appel à l’estimation préalable de quantités statistiques.Les décompositions tensorielles consistent en l’analyse de cubes de données multidimensionnelles, au travers de leur décomposition en somme d’éléments constitutifs plus simples, grâce à la multilinéarité et à la structure de rang faible du modèle sous-jacent.Ainsi, les mêmes techniques tensorielles nous fournissent une estimée des signaux eux-mêmes, ainsi que de leur direction d’arrivée, de façon déterministe. Ceci peut se faire en vertu du modèle séparable et de rang faible vérifié par des sources en bande étroite et en champs lointain.Cette thèse étudie l’estimation et la localisation de sources par des méthodes tensorielles de traitement d’antenne.Le premier chapitre présente le modèle physique de source en bande étroite et en champs lointain, ainsi que les définitions et hypothèses fondamentales. Le deuxième chapitre passe en revue l’état de l’art sur l’estimation des directions d’arrivée, en mettant l’accent sur les méthodes haute résolution à sous-espace. Le troisième chapitre introduit la notation tensorielle, à savoir la définition des tableaux de coordonnées multidimensionnels, les opérations et décompositions principales. Le quatrième chapitre présente le sujet du traitement tensoriel d’antenne au moyen de l’invariance par translation.Le cinquième chapitre introduit un modèle tensoriel général pour traiter de multiples diversités à la fois, comme l’espace, le temps, la translation en espace, les profils de gain spatial et la polarisation des ondes élastiques en bande étroite.Par la suite, les sixième et huitième chapitres établissent un modèle tensoriel pour un traitement d’antenne bande large cohérent. Nous proposons une opération de focalisation cohérente et séparable par une transformée bilinéaire et par un ré-échantillonnage spatial, respectivement, afin d’assurer la multilinéarité des données interpolées.Nous montrons par des simulations numériques que l’estimation proposée des paramètres des signaux s’améliore considérablement, par rapport au traitement tensoriel classique en bande étroite, ainsi qu’à MUSIC cohérent bande large.Egalement, tout au long de la thèse, nous comparons les performances de l’estimation tensorielle avec la borne de Cramér-Rao du modèle multilinéaire associé, que nous développons, dans sa forme la plus générale, dans le septième chapitre. En outre, dans le neuvième chapitre nous illustrons une application à des données sismiques réelles issues d’une campagne de mesure sur un glacier alpin, grâce à la diversité de vitesse de propagation.Enfin, le dixième et dernier chapitre de cette thèse traite le sujet parallèle de la factorisation spectrale multidimensionnelle d’ondes sismiques, et présente une application à l’estimation de la réponse impulsionnelle du soleil pour l’héliosismologie. / Source estimation and localization are a central problem in array signal processing, and in particular in telecommunications, seismology, acoustics, biomedical engineering, and astronomy. Sensor arrays, i.e. acquisition systems composed of multiple sensors that receive source signals from different directions, sample the impinging wavefields in space and time. Hence, high resolution techniques such as MUSIC make use of these two elements of diversities: space and time, in order to estimate the signal subspace generated by impinging sources, as well as their directions of arrival. This is generally done through the estimation of second or higher orders statistics, such as the array spatial covariance matrix, thus requiring sufficiently large data samples. Only recently, tensor analysis has been applied to array processing using as a third mode (or diversity), the space shift translation of a reference subarray, with no need for the estimation of statistical quantities. Tensor decompositions consist in the analysis of multidimensional data cubes of at least three dimensions through their decomposition into a sum of simpler constituents, thanks to the multilinearity and low rank structure of the underlying model. Thus, tensor methods provide us with an estimate of source signatures, together with directions of arrival, in a deterministic way. This can be achieved by virtue of the separable and low rank model followed by narrowband sources in the far field. This thesis deals with source estimation and localization of multiple sources via these tensor methods for array processing. Chapter 1 presents the physical model of narrowband elastic sources in the far field, as well as the main definitions and assumptions. Chapter 2 reviews the state of the art on direction of arrival estimation, with a particular emphasis on high resolution signal subspace methods. Chapter 3 introduces the tensor formalism, namely the definition of multi-way arrays of coordinates, the main operations and multilinear decompositions. Chapter 4 presents the subject of tensor array processing via rotational invariance. Chapter 5 introduces a general tensor model to deal with multiple physical diversities, such as space, time, space shift, polarization, and gain patterns of narrowband elastic waves. Subsequently, Chapter 6 and Chapter 8 establish a tensor model for wideband coherent array processing. We propose a separable coherent focusing operation through bilinear transform and through a spatial resampling, respectively, in order to ensure the multilinearity of the interpolated data. We show via computer simulations that the proposed estimation of signal parameters considerably improves, compared to existing narrowband tensor processing and wideband MUSIC. Throughout the chapters we also compare the performance of tensor estimation to the Cramér-Rao bounds of the multilinear model, which we derive in its general formulation in Chapter 7. Moreover, in Chapter 9 we propose a tensor model via the diversity of propagation speed for seismic waves and illustrate an application to real seismic data from an Alpine glacier. Finally, the last part of this thesis in Chapter 10 moves to the parallel subject of multidimensional spectral factorization of seismic ways, and illustrates an application to the estimation of the impulse response of the Sun for helioseismology.

This work deals with the further development of a method for Direction of Arrival (DOA) estimation based on the Discrete Fourier Transform (DFT) of the sensor array output. In the existing DFT-based algorithm, relatively high SNR is considered, and it is assumed that a large number of sensors are available. In this study an overview of some of the most commonly used DOA estimation techniques will be presented. Then the performance of the DFT method will be analyzed and compared with the performance of existing techniques. Two main objectives will be studied, firstly the reduction of the number of sensors and secondly the performance of the DFT based technique in the presence of noise. Experimental simulations will be presented to illustrate that in absence of noise, the proposed method is very fast and using just one snapshot is sufficient to accurately estimate DOAs. Also, in presence of noise, the method is still relatively fast and using a small number of snapshots, it can accurately estimate DOAs. The above mentioned properties are the result of taking an average of the peaks of the DFTs, X_n (k), obtained from a sequence of N_s snapshots. With N_s sufficiently large, the average over N_s snapshots approaches expected value. Also, the conditions that should be satisfied to avoid overlapping of main-lobes, and thus loosing the DOA of some signals, in the DFT spectrum are examined. This study further analyzes the performance of the proposed method as well as two other commonly used algorithms, MUSIC and conventional beamformer. An extensive simulation was conducted and different features of the spatial DFT technique, such as accuracy, resolution, sensitivity to noise, effect of multiple snapshots and the number of sensors were evaluated and compared with those of existing techniques. The simulations indicate that in most aspects the proposed spatial DFT algorithm outperforms the other techniques. / Graduate

Made available in DSpace on 2014-12-17T14:56:03Z (GMT). No. of bitstreams: 1 OsmarADJ.pdf: 1159660 bytes, checksum: 65307a903dfe1a1f71297194d1c7e2a5 (MD5) Previous issue date: 2004-12-22 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / This dissertation presents a new proposal for the Direction of Arrival (DOA) detection problem for more than one signal inciding simultaneously on an antennas array with linear or planar geometry by using intelligent algorithms. The DOA estimator is developed by using techniques of Conventional Beam-forming (CBF), Blind Source Separation (BSS), and the neural estimator MRBF (Modular Structure of Radial Basis Functions). The developed MRBF estimator has its capacity extended due to the interaction with the BSS technique. The BSS makes an estimation of the steering vectors of the multiple plane waves that reach the array in the same frequency, that means, obtains to separate mixed signals without information a priori. The technique developed in this work makes possible to identify the multiple sources directions and to identify and to exclude interference sources / Esta disserta??o apresenta uma nova proposta para os problemas de detec??o de dire??o de chegada para mais de um sinal incidindo simultaneamente sobre um arranjo de antenas de geometria planar ou linear empregando algoritmos inteligentes. O estimador de DOA ? desenvolvido utilizando as t?cnicas de Conforma??o de Feixes Digital Convencional (CBF - Conventional Beamforming), de Separa??o Cega de Fontes (BSS {Blind Source Separation) e o estimador neural MRBF (Modular Structure of Radial Basis Functions). O estimador MRBF desenvolvido tem sua capacidade ampliada gra?as ?a intera??o com a t?cnica BSS, a qual faz uma estima??o dos vetores de guiamento das m?ltiplas ondas planas que alcan?am o arranjo na mesma freq??ncia, isto ?, consegue separar sinais misturados sem informa??es a priori. A t?cnica desenvolvida neste trabalho possibilita identificar a dire??o de m?ltiplas fontes e identificar e excluir as fontes de interfer?ncia