Ultra-wideband (UWB) technology and its use in imaging and sensing have drawnsignicant interest in the last two decades. Extensive studies have contributed toutilize UWB transient scattering for automated target recognition and imagingpurposes. In this thesis a near-eld UWB synthetic aperture radar (SAR) imagingalgorithm is presented.It is shown with measurements and simulation, that it is possible to reconstruct an imageof an object in the near eld region using UWB technology and SAR imaging algorithm.However the nal SAR image is highly aected by unwanted scattered elds at each pixelusually observed as an image artifact in the nal image. In this study these artifactsare seen as a smile around the main object. Two methods are suggested in this thesiswork to suppress this artifact. The rst method combines the scattered eld informationreceived from both rear and front of the object to reconstruct two separate images, onefrom rear view and one from front view of the object respectively. Since the scatteredelds from behind the object are mirrored, the pixel by pixel multiplication of thesetwo images for objects with simple geometry will cancel the artifact. This method isvery simple and fast applicable to objects with simple geometry. However this methodcannot be used for objects with rather complex geometry and boundaries. Thereforethe Range Point Migration (RPM) method is used along with the global characteristicsof the observed range map to introduce a new artifact rejection method based on thedirectional of arrival (DOA) of scattered elds at each pixel. DOA information can beused to calculate an optimum theta for each antenna. This optimum angle along withthe real physical direction of arrival at each position can produce a weighting factor thatlater can be used to suppress the eect of undesired scattered elds producing the smileshaped artifact. Final results of this study clearly show that the UWB SAR accompaniedwith DOA can produce an image of an object free of undesired artifact from scatteredeld of adjacent antennas.

In this thesis the direction of arrival estimation of wideband signals using frequency invariant beamforming method is examined. The difficulty with the direction of arrival estimation of wideband signals is that it is not possible to obtain a single covariance matrix valid for the whole frequency spectrum of the signal. There are various methods proposed in the literature to overcome this difficulty. The common aim of all the methods is to obtain a composite covariance matrix for the overall band of the signal. In this thesis, we concentrate on a method in [12]. This method is based on a beamforming technique that provides frequency invariant beams in the band of interest. Therefore there is no need for frequency decomposition as it is done with the other wideband methods. A comparison of the frequency invariant beamforming method with coherent signal subspace methods and narrow band methods is also given.

ITC/USA 2013 Conference Proceedings / The Forty-Ninth Annual International Telemetering Conference and Technical Exhibition / October 21-24, 2013 / Bally's Hotel & Convention Center, Las Vegas, NV / In this paper, a new technique utilizing a scatterer of high dielectric constant in between electrically small antennas to achieve good Direction of arrival (DOA) estimation performance is demonstrated. The phase information of the received signal at the antennas is utilized for direction estimation. The impact of the property of the scatterer on the directional sensitivity and the output signal to noise ratio (SNR) level are studied. Finally the DOA estimation accuracy is analyzed with the proposed technique under the consumption of white Gaussian noise environment.

Since World War I, the area of acoustic undersea warfare has witnessed several research activities targeting the development of advanced systems to accurately detect and localize underwater moving targets. One of the main categories of these systems is the passive sound navigation and ranging (SONAR) that searches for the location of the ships and submarines by listening to the radiated noise produced by their propellers, machinery, and flow dynamics. The performance of the passive sonar highly depends on the particular array signal processing algorithms used in practice. Presently, one of the main challenges is to accurately estimate the target direction of arrival (DOA) in severe underwater environments. This thesis is proposed to enhance the DOA estimation in two distinct applications. This first application is to improve the spatial resolution of the uniform linear towed arrays. This is done by applying new spatial extrapolation techniques called 2D- and 3D- fast orthogonal search (FOS) for both uniform linear and rectangular arrays, respectively. The presented methods show better performance than the conventional methods with respect to signal to noise ratio (SNR), number of snapshots and angular separation. Moreover it reduces the computational complexity required by the spatial extrapolation methods based on linear prediction approach. The other application concerns with developing a new DOA estimation that provides better spatial spectrum than the one provided by conventional beamforming (CBF) when a nonuniform linear array of directional frequency analysis and recording (DIFAR) sonobuoys is employed. The introduced technique or the so called fourth order cumulant beamforming (FOCBF) and shows an outstanding performance compared to CBF especially in low SNR. Furthermore, a warping FOC-BF (WFOC-BF) method obtained by augmenting a warping beamforming technique with FOC-BF is proposed to reduce the required computational complexity by FOC-BF while preserving the same performance. / Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2012-06-27 14:59:33.941

[pt] Este trabalho de tese trata do emprego de arranjos de antenas em ambientes de comunicação móvel,dando-se ênfase ao canal de dados reverso do Sistema IS-95. Propõe-se dois estimadores: um para a direção de chegada dos sinais e outro para outros dados. Inicialmente é apresentado um estudo sobre arranjos de antenas e dos principais detalhes do sistema IS-95,especialmente a multiplicidade de acesso via divisão por códigos (CDMA).Aborda-se em seguida o problema da estimação da direção da chegada(DOA), onde se constata que os algoritmos mais conhecidos na literarura especializada, tais como Atraso-e-Soma, Capon, MUSIC e ESPRIT, não apresentam desempenho satisfatório quando empregados em ambiente CDMA. Por isso, propõe-se uma versão do método de estimação de máxima verossimilhança (ML) que utiliza a técnica denominada de EM (-Expectation Maximization-).Seu emprego permitir fracionar o problema de otimização multidimensional gerado pelo estimador ML, em últimas estimações de menor dimensão,simplificando sobremaneira a solução. O estimador proposto além da DOA,permite ainda estimar a atenuação e a defasagem dos sinais incidentes. Através de simulações, constata-se que este estimador EM apresenta um desempenho bastante satisfatório.Para tornar mais completa a análise, faz-se ainda uma comparação da variância do erro na estimação da DOA comolimitante de Cramér-Rao. Em presença de multipercursos, propõe-se quatro versões de um estimador de dados, sendo que uma delas utiliza a estrutura de treliça e objetiva a decisão sequencial dos dados. O desenvolvimento de tais estimadores faz uso de bases de espaços vetoriais para representar as funções de walsh, sendo que as operações aritméticas convencionais . Através de simulações constata-se que essas versões apresentam diferentes relações entre de desempenho e custo computacional, o que permite flexibilidade na adequação do seu emprego. / [en] This thesis deals with antenna arrays when used in mobile communication environment, but the emphasis is on the reverse data link of IS-95. Two estimators are proposed: one for the direction-of-arrival (DOA) and other for the data. Initially, study of the antenna arrays is presented together with the main details of the IS-95 System, especially the details related to the code division multiple access (CDMA). After that, the problem of dirction- of-arrival estimation is discussed. It is shown that mostly of the known estimators, such as Delay-and-Sum, Capon, MUSIC and ESPRIT, do not offer reasonable performance when used in CDMA environment. Therefore, a new Maximum- Likelihood (ML) method is proposed using the so-called Expectation Maximization (EM) algorithm. The main advantage of using such approach is due to the fact that multidimensional optimization required by ML estimation can be split into several problems of lower dimension, thus simplifying the solution. The proposed estimator, besides the DOA estimation, also allows the estimation of attenuation and phase shift of the arriving signals. Simulations show that EM-estimator offers a fair performance when compared to other methods. In order to properly access the statistical significance of this study, the of DOA-estimation erro´s variance is compared with the Cramér-Rao Lower Bound (CRLB). Under a multipath environment, four versions of a data estimator are proposed, and one of them do employ trellis. In the development of such estimators, vector basis are used to represent the Walsh functions and the module-2 operations are replaced by convenient ordinary arithmetic operations. By means of simulation, it is shown that these versions present different levels of performance and computational cost thus allowing to choose the method according to the environmentn conditions. / [es] Este trabajo de tese trata del empleo de arreglos de antenas en ambientes de comunicación móvil, con énfasis en el canal de datos reverso del Sistema IS-95. Se proponen dos estimadores: uno para la dirección de llegada de las señales y otro para el resto de los datos. Inicialmente se presenta un estudio sobre arreglos de antenas y los principales detalles del sistema IS-95,especialmente la multiplicidad de acceso vía división por códigos (CDMA). Se aborda el problema de la estimación de la dirección de llegada(DOA), donde se constata que los algoritmos más conocidos en la literarura especializada, tales como Atraso-y-Suma, Capon, MUSIC y ESPRIT, no tiene un desempeño satisfactorio cuando son utilizados en ambiente CDMA. Por eso, se propone una versión del método de estimación de máxima verosimilitud(ML) que utiliza la técnica denominada de EM (-Expectation Maximization-).Su empleo permite fraccionar el problema de optimización multidimensional generado por el estimador ML, en estimaciones de menor dimensión,simplificando la solución. El estimador propuesto, además de la DOA, permite estimar la atenuación y el defasaje de las señales incidentes. A través de simulaciones, se constata que el estimador EM tiene un desempeño bastante satisfactorio. Para un análisis más completo se comparan las varianza del error en la estimación de la DOA como límite de Cramér-Rao. En presencia de multitrayectoria, se proponen cuatro versiones de un estimador de datos, donde una de ellas utiliza la extructura de celosía y objetiva la decisión secuencial de los datos. El desarrollo de tales estimadores utiliza bases de espacios vectoriales para representar las funciones de walsh, con las operaciones aritméticas convencionales . A través de simulaciones se observa que esas versiones presentan diferentes relaciones entre de desempeño y el costo computacional, que permite flexibilidad en la adecuación de su empleo.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19712号 / 工博第4167号 / 新制||工||1643(附属図書館) / 32748 / 京都大学大学院工学研究科電気工学専攻 / (主査)教授 篠原 真毅, 教授 土居 伸二, 准教授 小嶋 浩嗣 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

This thesis considers the problem of using signals of opportunity (SOO) with known direction of arrival (DOA) for aircraft positioning. SOO is a collective name for a wide range of signals not intended for navigation but which can be intercepted by the radar warning system on an aircraft. These signals can for example aid an unassisted inertial navigation system (INS) in areas where the global navigation satellite system (GNSS) is inaccessible. Challenges arise as the signals are transmitted from non-controllable sources without any guarantee of quality and availability. Hence, it is important that any estimation method utilising SOO is robust and statistically consistent in case of time-varying signals of different quality, missed detections and unreliable signals such as outliers. The problem is studied using SOO sources with either known or unknown locations. An extended Kalman filter (EKF) based solution is proposed for the first case which is shown to significantly improve the localisation performance compared to an unassisted INS in common scenarios. Yet, a number of factors affect this performance, including the measurement noise variance, the signal rate and the availability of known source locations. An outlier rejection mechanism is developed which is shown to increase the robustness of the suggested method. A numerical evaluation indicates that statistical consistency can be maintained in many situations even with the above-mentioned challenges. An EKF based simultaneous localisation and mapping (SLAM) solution is proposed for the case with unknown SOO source locations. The flight trajectory and initialisation process of new SOO sources are critical in this case. A method based on nonlinear least squares is proposed for the initialisation process, where new SOO sources are only allowed to be initialised in the filter once a set of requirements are fulfilled. This method has shown to increase the robustness during initialisation, when the outlier rejection is not applicable. When combining known and unknown SOO source locations, a more stable localisation solution is obtained compared to when all locations are unknown. Applicability of the proposed solution is verified by a numerical evaluation. The computational time increases cubically with the number of sources in the state and quadratically with the number of measurements. The time is substantially increased during landmark initialisation.

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This thesis is related to the field of Sound Source Separation (SSS). It addresses the development and evaluation of these techniques for their application in the resynthesis of high-realism sound scenes by means of Wave Field Synthesis (WFS). Because the vast majority of audio recordings are preserved in twochannel stereo format, special up-converters are required to use advanced spatial audio reproduction formats, such as WFS. This is due to the fact that WFS needs the original source signals to be available, in order to accurately synthesize the acoustic field inside an extended listening area. Thus, an object-based mixing is required. Source separation problems in digital signal processing are those in which several signals have been mixed together and the objective is to find out what the original signals were. Therefore, SSS algorithms can be applied to existing two-channel mixtures to extract the different objects that compose the stereo scene. Unfortunately, most stereo mixtures are underdetermined, i.e., there are more sound sources than audio channels. This condition makes the SSS problem especially difficult and stronger assumptions have to be taken, often related to the sparsity of the sources under some signal transformation. This thesis is focused on the application of SSS techniques to the spatial sound reproduction field. As a result, its contributions can be categorized within these two areas. First, two underdetermined SSS methods are proposed to deal efficiently with the separation of stereo sound mixtures. These techniques are based on a multi-level thresholding segmentation approach, which enables to perform a fast and unsupervised separation of sound sources in the time-frequency domain. Although both techniques rely on the same clustering type, the features considered by each of them are related to different localization cues that enable to perform separation of either instantaneous or real mixtures.Additionally, two post-processing techniques aimed at improving the isolation of the separated sources are proposed. The performance achieved by several SSS methods in the resynthesis of WFS sound scenes is afterwards evaluated by means of listening tests, paying special attention to the change observed in the perceived spatial attributes. Although the estimated sources are distorted versions of the original ones, the masking effects involved in their spatial remixing make artifacts less perceptible, which improves the overall assessed quality. Finally, some novel developments related to the application of time-frequency processing to source localization and enhanced sound reproduction are presented. / Cobos Serrano, M. (2009). Application of sound source separation methods to advanced spatial audio systems [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/8969

Radar (RAdio Detection And Ranging) uses radio waves to detect the presence of a target and measure its position and other properties. This sensor has found many civilian and military applications due to advantages such as possible large surveillance areas and operation day and night and in all weather. The contributions of this thesis are within applied signal processing for radar in two somewhat separate research areas: 1) radar with array antennas and 2) radar with micro-Doppler measurements. Radar with array antennas: An array antenna consists of several small antennas in the same space as a single large antenna. Compared to a traditional single-antenna radar, an array antenna radar gives higher flexibility, higher capacity, several radar functions simultaneously and increased reliability, and makes new types of signal processing possible which give new functions and higher performance. The contributions on array antenna radar in this thesis are in three different problem areas. The first is High Resolution DOA (Direction Of Arrival) Estimation (HRDE) as applied to radar and using real measurement data. HRDE is useful in several applications, including radar applications, to give new functions and improve the performance. The second problem area is suppression of interference (clutter, direct path jamming and scattered jamming) which often is necessary in order to detect and localize the target. The thesis presents various results on interference signal properties, antenna geometry and subarray design, and on interference suppression methods. The third problem area is measurement techniques for which the thesis suggests two measurement designs, one for radar-like measurements and one for scattered signal measurements. Radar with micro-Doppler measurements: There is an increasing interest and need for safety, security and military surveillance at short distances. Tasks include detecting targets, such as humans, animals, cars, boats, small aircraft and consumer drones; classifying the target type and target activity; distinguishing between target individuals; and also predicting target intention. An approach is to employ micro-Doppler radar to perform these tasks. Micro-Doppler is created by the movement of internal parts of the target, like arms and legs of humans and animals, wheels of cars and rotors of drones. Using micro-Doppler, this thesis presents results on feature extraction for classification; on classification of targets types (humans, animals and man-made objects) and human gaits; and on information in micro-Doppler signatures for re-identification of the same human individual. It also demonstrates the ability to use different kinds of radars for micro-Doppler measurements. The main conclusion about micro-Doppler radar is that it should be possible to use for safety, security and military surveillance applications.