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1
Brown, Christopher L. "Goodness-of-fit and detection problems in impulsive interference." Thesis, Curtin University, 2000. http://hdl.handle.net/20.500.11937/40.
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After defining the structure to a signal detection scheme, this dissertation describes and addresses some of the unresolved issues associated with its use when the interference encountered is impulsive. The alpha-stable (alpha-S) family of distributions is used as a model of this interference due to its physical interpretation and its general form. Despite its attractive features, difficulties arise in using this distribution due to, amongst other things, the lack of a general closed form expression for its probability density function. Relevant to the detection scheme used, this affects parameter estimation, signal detector design and goodness-of-fit tests. Significant contributions are made in the latter through the introduction of characteristic function based test that uses the parametric bootstrap. A modification of this test is then made to define a test of the level of impulsive behaviour - again the parametric bootstrap is employed to maintain levels of significance for this and another test based on testing the alpha-S parameter values. The performance of these tests is examined under simulated and two sources of real, impulsive data, namely human heart rate variability and fluctuations in stock prices. Once the appropriateness of the model assumption has been verified, the final, signal detection process may take place. Detectors based on the locally optimum criterion and approximations to it are described and compared to their rank-based counterparts. Results are presented that suggest compelling arguments based on performance and computational complexity for the consideration of rank-based techniques.Keywords: Impulsive behaviour, alpha-stable distribution, stable laws, Gaussianity testing, parameter estimation, goodness-of-fit, parametric bootstrap, signal detection, locally optimum detectors, rank-based detectors.
2
Kannan, Balakrishnan. "Spatial signal processing for beamforming in impulsive noise using Bayesian principles." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621044.
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Brown, Christopher L. "Goodness-of-fit and detection problems in impulsive interference." Curtin University of Technology, School of Electrical and Computer Engineering, 2000. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=9750.
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After defining the structure to a signal detection scheme, this dissertation describes and addresses some of the unresolved issues associated with its use when the interference encountered is impulsive. The alpha-stable (alpha-S) family of distributions is used as a model of this interference due to its physical interpretation and its general form. Despite its attractive features, difficulties arise in using this distribution due to, amongst other things, the lack of a general closed form expression for its probability density function. Relevant to the detection scheme used, this affects parameter estimation, signal detector design and goodness-of-fit tests. Significant contributions are made in the latter through the introduction of characteristic function based test that uses the parametric bootstrap. A modification of this test is then made to define a test of the level of impulsive behaviour - again the parametric bootstrap is employed to maintain levels of significance for this and another test based on testing the alpha-S parameter values. The performance of these tests is examined under simulated and two sources of real, impulsive data, namely human heart rate variability and fluctuations in stock prices. Once the appropriateness of the model assumption has been verified, the final, signal detection process may take place. Detectors based on the locally optimum criterion and approximations to it are described and compared to their rank-based counterparts. Results are presented that suggest compelling arguments based on performance and computational complexity for the consideration of rank-based techniques.Keywords: Impulsive behaviour, alpha-stable distribution, stable laws, Gaussianity testing, parameter estimation, goodness-of-fit, parametric bootstrap, signal detection, locally optimum detectors, rank-based detectors.
4
Zou, Yuexian. "Robust statistics based adaptive filtering algorithms for impulsive noise suppression." Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk/hkuto/record.jsp?B22823736.
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cui, qiaofeng. "Suppression of impulsive noise in wireless communication." Thesis, Högskolan i Gävle, Avdelningen för elektronik, matematik och naturvetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-18270.
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This report intends to verify the possibility that the FastICA algorithm could be applied to the GPS system to eliminate the impulsive noise from the receiver end. As the impulsive noise is so unpredictable in its pattern and of great energy level to swallow the signal we need, traditional signal selection methods exhibit no much use in dealing with this problem. Blind Source Separation seems to be a good way to solve this, but most of the other BSS algorithms beside FastICA showed more or less degrees of dependency on the pattern of the noise. In this thesis, the basic mathematic modelling of this advanced algorithm, along with the principles of the commonly used fast independent component analysis (fastICA) based on fixed-point algorithm are discussed. To verify that this method is useful under industrial use environment to remove the impulsive noises from digital BPSK modulated signals, an observation signal mixed with additive impulsive noise is generated and separated by fastICA method. And in the last part of the thesis, the fastICA algorithm is applied to the GPS receiver modeled in the SoftGNSS project and verified to be effective in industrial applications. The results have been analyzed.6
6
Wen, Yu, and 文宇. "Robust statistics based subspace tracking in impulsive noise environment: algorithms and applications." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B44570181.
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DeJarnette, Hunter Archer. "Measuring Noise in the VHF Band and Its Effect on Low SNR Signal Detection." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/35293.
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With the increasing demand for access to the crowded radio frequency spectrum, cognitive radios have been suggested as one solution. Cognitive radios would be frequency agile and able to sense their radio environment and opportunistically use empty spectrum. Spectrum sensing, monitoring a given band of spectrum to see if it is occupied, is an essential part of a cognitive radio. The preferred method of spectrum sensing is the energy detector, which does not require any a priori information about the signal to be detected and is computationally simple to implement. Man-made noise, impulsive in nature, has also become more prevalent with the widespread use of electronic devices. In this thesis, we took measurements of man-made impulsive noise in the broadcast digital television bands to measure its presence, power, and spatial correlation. The effects of impulsive noise on the detection performance of an energy detector were analyzed. Lastly, a wideband RF receiver was designed, built, and tested on the Virginia Tech campus, which would be well suited both to spectrum sensing and taking measurements of impulsive noise.Master of Science
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Zou, Yuexian, and 鄒月嫻. "Robust statistics based adaptive filtering algorithms for impulsive noise suppression." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B22823736.
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(Uncorrected OCR)
Abstract
Abstract of thesis entitled
Robust Statistics Based Adaptive Filtering Algorithms
For Impulsive Noise Suppression
Submitted by Yuexian Zou
for the degree of Doctor of Philosophy at The University of Hong Kong in May 2000
The behavior of an adaptive filter is inherently decided by how its estimation error and the cost function are formulated under certain assumption of the involving signal statistics. This dissertation is concerned with the development of robust adaptive filtering in an impulsive noise environment based on the linear transversal filter (LTF) and the lattice-ladder filer (LLF) structures. Combining the linear adaptive filtering theory and robust statistics estimation techniques, two new cost functions, called the mean M -estimate error (MME) and the sum of weighted M -estimate error (SWME), are proposed. They can be taken as the generalizations of the well-known mean squared error (MSE) and the sum of weighted squares error (SWSE) cost functions when the
involving signals are Gaussian.
Based on the SWME cost function, the resulting optimal weight vector is governed by an M-estimate normal equation and a recursive least M -estimate (RLM) algorithm is derived. The RLM algorithm preserves the fast initial convergence, lower steady-state 11
Abstract
derived. The RLM algorithm preserves the fast initial convergence, lower steady-state error and the robustness to the sudden system change of the recursive least squares (RLS) algorithm under Gaussian noise alone. Meanwhile, it has the ability to suppress impulse noise both in the desired and input signals. In addition, using the MME cost function, stochastic gradient based adaptive algorithms, named the least mean Mestimate (LMM) and its transform dOlnain version, the transform domain least mean Mestimate (TLMM) algorithms have been developed. The LMM and TLMM algorithms can be taken as the generalizations of the least-mean square (LMS) and transform domain normalized LMS (TLMS) algorithms, respectively. These two robust algorithms give similar performance as the LMS and TLMS algorithms under Gaussian noise alone and are able to suppress impulse noise appearing in the desired and input signals. It is noted that the performance and the computational complexity of the RLM, LMM and TLMM algorithms have a close relationship with the estimate of the threshold parameters for the M-estimate functions. A robust and effective recursive method has been suggested in this dissertation to estimate the variance of the estimation error and the required threshold parameters with certain confidence to suppress the impulsive noise. The mean and mean square convergence performances of the RLM and the LMM algorithms are evaluated, respectively, when the impulse noise is assumed to be contaminated Gaussian distribution.
Motivated by the desirable features of the lattice-ladder filter, a new robust adaptive gradient lattice-ladder filtering algorithm is developed by minimizing an MME cost function together with an embedded robust impulse suppressing process, especially for impulses appearing in the filter input. The resultant robust gradient lattice-robust
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Abstract
normalized LMS (RGAL-RNLMS) algorithm perfonns comparably to the conventional GAL-NLMS algorithm under Gaussian noise alone; meanwhile, it has the capability of suppressing the adverse effects due to impulses in the input and the desired signals. The additional computational complexity compared to the GAL-NLMS algorithm is of
O(Nw log Nw) + O(NfI log N,J .
Extensive computer simulation studies are undertaken to evaluate the performance of the RLM, LMM, TLMM and the RGAL-RNLMS algorithms under the additive noise with either a contaminated Gaussian distribution or the symmetric alpha-stable (SaS ) distributions. The results substantiate the analysis and demonstrate the effectiveness and robustness of the developed robust adaptive filtering algorithms in suppressing impulsive noise both in the input and the desired signals of the adaptive filter. In conclusion, the proposed approaches in this dissertation present an attempt for developing robust adaptive filtering algorithms in impulsive noise environments and can be viewed as an extension of the linear adaptive filter theory. They may become reasonable and effective tools to solve adaptive filtering problems in a non-Gaussian environment in practice.
IVabstract
toc
Electrical and Electronic Engineering
Doctoral
Doctor of Philosophy
9
Brcic, Ramon. "Some aspects of signal processing in heavy tailed noise." Thesis, Curtin University, 2002. http://hdl.handle.net/20.500.11937/323.
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This thesis addresses some problems that arise in signal processing when the noise is impulsive and follows a heavy tailed distribution. After reviewing several of the more well known heavy- tailed distributions the common problem of which of these hest models the observations is considered. To this end, a test is proposed for the symmetric alpha stable distribution. The test threshold is found using both asymptotic theory and parametric bootstrap resampling. In doing so, some modifications are proposed for Koutrouvelis' estimator of the symmetric alpha stable distributions parameters that improve performance. In electrical systems impulsive noise is generated externally to the receiver while thermal Gaussian noise is generated internally by the receiver electronics, the resultant noise is an additive combination of these two independent sources. A characteristic function domain estimator for the parameters of the resultant distribution is developed for the case when the impulsive noise is modeled by a symmetric alpha stable distribution. Having concentrated on validation and parameter estimation for the noise model, some problems in signal detection and estimation are considered. Detection of the number of sources impinging on an array is an important first. step in many array processing problems for which the development of optimal methods can be complicated even in the Gaussian case. Here, a multiple hypothesis test for the equality of the eigenvalues of the sample array covariance is proposed.The nonparametric bootstrap is used to estimate the distributions of the test statistics removing the assumption of Gaussianity and offering improved performance for heavy tailed observations. Finally, some robust estimators are proposed for estimating parametric signals in additive noise. These are based on M-estimators but implicitly incorporate an estimate of the noise distribution. enabling the estimator to adapt to the unknown noise distribution. Two estimators are developed, one uses a nonparametric kernel density estimator while the other models the score function of the noise distribution with a linear combination of basis functions.
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Brcic, Ramon Francis. "Some aspects of signal processing in heavy tailed noise." Curtin University of Technology, Australian Telecommunications Research Institute, 2002. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=14244.
Full textAbstract:
This thesis addresses some problems that arise in signal processing when the noise is impulsive and follows a heavy tailed distribution. After reviewing several of the more well known heavy- tailed distributions the common problem of which of these hest models the observations is considered. To this end, a test is proposed for the symmetric alpha stable distribution. The test threshold is found using both asymptotic theory and parametric bootstrap resampling. In doing so, some modifications are proposed for Koutrouvelis' estimator of the symmetric alpha stable distributions parameters that improve performance. In electrical systems impulsive noise is generated externally to the receiver while thermal Gaussian noise is generated internally by the receiver electronics, the resultant noise is an additive combination of these two independent sources. A characteristic function domain estimator for the parameters of the resultant distribution is developed for the case when the impulsive noise is modeled by a symmetric alpha stable distribution. Having concentrated on validation and parameter estimation for the noise model, some problems in signal detection and estimation are considered. Detection of the number of sources impinging on an array is an important first. step in many array processing problems for which the development of optimal methods can be complicated even in the Gaussian case. Here, a multiple hypothesis test for the equality of the eigenvalues of the sample array covariance is proposed.The nonparametric bootstrap is used to estimate the distributions of the test statistics removing the assumption of Gaussianity and offering improved performance for heavy tailed observations. Finally, some robust estimators are proposed for estimating parametric signals in additive noise. These are based on M-estimators but implicitly incorporate an estimate of the noise distribution. enabling the estimator to adapt to the unknown noise distribution. Two estimators are developed, one uses a nonparametric kernel density estimator while the other models the score function of the noise distribution with a linear combination of basis functions.
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Lau, Wing-yi. "New recursive parameter estimation algorithms in impulsive noise environment with application to frequency estimation and system identification." Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B37595866.
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Lau, Wing-yi, and 劉穎兒. "New recursive parameter estimation algorithms in impulsive noise environment with application to frequency estimation and systemidentification." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B37595866.
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Hrabina, Martin. "Akustická detekce výstřelů ve volné přírodě." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2015. http://www.nusl.cz/ntk/nusl-221340.
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This work is concerned with gunshot detection and recognition. Contains overview of published works and methods used in this field. Furthermore, it lists several commercial gunshot detectors. Binary gunshot detection and recognition algorithm is proposed which discriminates between gunshot and non-gunshot sounds occuring in nature. Algorithm is tested in Matlab. Proposed algorithm is implemented in TMS320C6713 digital signal processor, achieved results are compared.
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Riffi, Temsamani Mohamed Saïd. "Analyse statistique des bruits impulsifs et estimation d'un signal en présence de bruit impulsif." Nancy 1, 1993. http://www.theses.fr/1993NAN10023.
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Généralement, dans le domaine du traitement du signal, il existe deux types de bruits: le bruit blanc gaussien et le bruit de type impulsif. Actuellement, le premier peut être éliminé facilement, puisque son comportement statistique et spectral est bien connu. Par contre, le bruit impulsif présente souvent des caractéristiques non-stationnaires telles que l'apparition d'impulsion aléatoire dans le temps. L'objectif est de connaitre le comportement de ce bruit en vue d'une modélisation permettant l'accès au filtrage et la détection de l'information. Deux parties constituent ce mémoire: - étude statistique et spectrale du bruit impulsif. Cette étude nous a permis de connaitre le comportement du bruit en question (distribution des amplitudes,. . . ), - réalisation d'un nouveau soustracteur de bruit impulsif base sur le filtrage adaptatif. Ce soustracteur permet d'extraire le bruit et d'estimer le signal utile par une version du filtre de Kalman à partir d'un seul signal, le signal bruité (signal reçu). La méthode a été appliquée sur des signaux sinusoïdaux bruites par différents bruits impulsifs
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Yeung, W. K. "Microwave imaging with impulsive signals." Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382334.
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Wang, Xun [Verfasser]. "Model based signal enhancement for impulse response measurement / Xun Wang." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2014. http://d-nb.info/1051500605/34.
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Linarès, Georges. "Détection de ruptures et classification automatique dans un environnement de bruits impulsifs." Avignon, 1998. http://www.theses.fr/1998AVIG0118.
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Ce memoire est consacre au probleme de la supervision d'environnements reels de bruits impulsifs. L'objectif est de developper une methode capable de detecter, dans un flux continu de bruits transitoires, les evenements acoustiques qui ne s'inscrivent pas dans une certaine regularite du signal. Nous montrons que les techniques classiques de detection de ruptures sont mal adaptees a la surveillance d'un milieu intrinsequement irregulier. Ceci nous amene a adopter une approche de plus haut niveau, basee sur le regroupement en classes des differentes composantes acoustiques de l'environnement. L'etude bibliographique des algorithmes de classification automatique montre leur difficulte a classifier des formes qui peuvent etre superposees. Or le recouvrement de signaux emis par differentes sources acoustiques est probable dans des milieux complexes. Nous proposons une solution neuro-mimetique originale au probleme de la modelisation dynamique du signal. Il s'agit d'une memoire associative nonsupervisee qui adapte sa structure par deux processus inter-dependants : la modelisation du signal par classification d'unites acoustiques recurrentes et la detection d'evenements provoquant la rupture du modele. L'architecture proposee permet la detection et la classification de formes acoustiques lineairement melangees. Neanmoins, la co-occurence d'une rupture et d'une forme acoustique referencee provoque une mauvaise formation du modele due au melange des prototypes des classes. La separation des classes melangees peut etre consideree comme un probleme de separation de sources. Ceci nous amene a implanter, dans l'architecture neuronale proposee, un mecanisme d'apprentissage qui s'inspire des methodes de separation aveugle de sources. Il s'agit d'un processus d'auto-organisation du classifieur neuronal qui minimise la dependance statistique des classes. Les performances de cet algorithme sont evaluees a la fois en detection de ruptures et en classification non-supervisee. Nos tests montrent le bon comportement du modele dans des situations de fort taux de superposition des formes acoustiques ainsi qu'une degradation sensible des performances en presence de bruit blanc de forte energie
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Aramaki, Mitsuko. "Analyse-synthèse de sons impulsifs : approches physique et perceptive." Aix-Marseille 2, 2003. http://www.theses.fr/2003AIX22047.
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Li, Liwei. "Microwave Photonic Signal Processing Techniques based on Finite Impulse Response Configurations." Thesis, The University of Sydney, 2013. http://hdl.handle.net/2123/9477.
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Microwave photonic signal processing based on optical delay line structure is a powerful technique for processing high speed signals. Finite impulse response microwave photonic filters are of particular interest because of their inherent flexibility in realizing arbitrary transfer functions and linear phase, together with coherent interference free and phase-induced intensity noise free. This thesis proposes a number of effective solutions to eliminate the undesirable degradation of RF response so that microwave photonic filters can be used in practice. Experimental results demonstrate successfully multi-tap microwave photonic filters with both continuous tunability over a wide range and the elimination of high frequency limitations. One major problem of current true-time-delay is the restricted number of delay lines, and another is the difficulty in controlling the signal power. To overcome these restrictions, this thesis presents an array of multiple true-time-delay elements that can be independently and continuously tuned. Moreover, a new technique is reported to overcome the tap-delay-variation, which is caused by the interaction of the equally-spaced frequency comb lines with the non-uniform group delay of the primary fiber delay line that arises from higher-order dispersion factors. In order both to eliminate non-uniform tap-delay variations and to realize independently tunable time delays, for the first time, a hybrid phase-time shifter structure is reported. It can simultaneously form true-time-delays and phase shifts to the input RF signals within one device. To overcome the problem of periodic resonances that are inherent in microwave photonic signal processors, three different approaches for realizing single bandpass response are presented. Experimental results present single bandpass RF responses with wideband tunability at high frequencies.
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Campbell, Roy Lee. "Performance assessment of the finite impulse response Adaptive Line Enhancer." Diss., Mississippi State : Mississippi State University, 2002. http://library.msstate.edu/etd/show.asp?etd=etd-05222002-085151.
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Chu, Xiaoli. "Ultra-wideband direct-sequence impulse radio wireless communications /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202005%20CHU.
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N'Da, Patrick Amoikon. "Impact du bruit impulsif sur les transmissions SDSl." Rennes, INSA, 2005. http://www.theses.fr/2005ISAR0024.
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Les bruits impulsifs présentent un effet très préjudiciable sur les transmissions SDSL. En particulier lorsque des applications du type temps réel sont transportées. Toutefois, la modification de la structure des systèmes SDSL permet au prix d'un léger délai de répondre à la problématique des bruits impulsifs sur le SDSL. Dans la première partie de cette thèse, les détails de la constitution des systèmes SDSL ont été donnés. Le chapitre deux met en évidence l'impact des bruits impulsifs sur les transmissions SDSL. Il présente en partie des résultats de validation du simulateur SDSL implémenté pour l'étude des systèmes SDSL. La synthèse des techniques étudiées pour la réduction des impacts des bruits impulsifs sur le SDSL est présentée au chapitre trois. Ce chapitre permet de montrer la difficulté de mise en œuvre d'un système de correction d'erreur respectant les différentes contraintes liées à la problématique des bruits impulsifs sur le SDSL. Des techniques proposées pour d'autres systèmes dans le cadre d'autres études sont aussi présentées afin de pouvoir en tirer parti dans le cadre du SDSL. Le quatrième chapitre détaille une procédure de retransmission permettant de répondre aux besoins de correction d'erreurs dues aux bruits impulsifs sur les systèmes SDSL multipaires. Cette procédure est entièrement décrite pour une réalisation dans les couches basses du SDSL. Elle s'appuie sur des informations de bas niveau recueillies sur la paire de cuivre torsadée. Cette solution bas niveau permet de répondre aux contraintes de délai. Dans le cinquième et dernier chapitre, on peut voir que la prise en compte de l'existence des paires voisines, pour la transmission sur chacune des paires dans le mode multipaire, apporte un gain en portée significatif. Cet apport est particulièrement notable pour les débits élevés. Le procédé dans ce cas est basé sur une annulation de paradiaphonie classique. Une approche similaire pourra être développée pour la télédiaphonie afin d'accroître les débits sur le SDSL multipaire pour les portées courtes.Impulse noises represent an important impairment for SDSL transmissions specially for real-time applications. Nevertheless, the modification of SDSL system structure allows, at the cost of some more delay, to increase the robustness against impulse noises. In the first chapter of this thesis the principles and the global structure of SDSL is presented. The second chapter show the impact of impulse noises over SDSL transmission. The third chapter is devoted to some techniques involved in the correction of impulse noises effect. The fourth chapter presents in details an ARQ technique proposed to reduce the impulse noises effects over SDSL. The fifth and last chapter deals with performance increase with respect to the data rate in multipair. This performance improvement is achieve with the help of crosstalk cancellation. The data rate increase the relatively important for high data rate. Other algorithm much more faster can applied to this system in the same manner to achieve better performance and improve the work done
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Galindo, Romero Marta. "Spatial Variations in the Acoustic Peak Pressure of Impulsive Low Frequency Anthropogenic Signals in Underwater Marine Environments." Thesis, Curtin University, 2017. http://hdl.handle.net/20.500.11937/59661.
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A method to predict spatial variations in the peak pressure level of impulsive low frequency anthropogenic signal propagating in marine environments is presented. The method is based on the correlation between the peak pressure level and the sound exposure level, and the application of extreme value theory to estimate fluctuations of the peak pressure around its mean value in varying ocean environments. The method was examined using signals from offshore seismic surveys and pile driving.
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Murphy, Damian Thomas. "Digital waveguide mesh topologies in room acoustics modelling." Thesis, University of York, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313846.
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Kahaei, Mohammad Hossein. "Performance analysis of adaptive lattice filters for FM signals and alpha-stable processes." Thesis, Queensland University of Technology, 1998. https://eprints.qut.edu.au/36044/7/36044_Digitised_Thesis.pdf.
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The performance of an adaptive filter may be studied through the behaviour
of the optimal and adaptive coefficients in a given environment. This thesis
investigates the performance of finite impulse response adaptive lattice filters for
two classes of input signals: (a) frequency modulated signals with polynomial
phases of order p in complex Gaussian white noise (as nonstationary signals),
and (b) the impulsive autoregressive processes with alpha-stable distributions (as
non-Gaussian signals).
Initially, an overview is given for linear prediction and adaptive filtering. The
convergence and tracking properties of the stochastic gradient algorithms are discussed
for stationary and nonstationary input signals. It is explained that the
stochastic gradient lattice algorithm has many advantages over the least-mean
square algorithm. Some of these advantages are having a modular structure,
easy-guaranteed stability, less sensitivity to the eigenvalue spread of the input autocorrelation
matrix, and easy quantization of filter coefficients (normally called
reflection coefficients).
We then characterize the performance of the stochastic gradient lattice algorithm
for the frequency modulated signals through the optimal and adaptive
lattice reflection coefficients. This is a difficult task due to the nonlinear dependence
of the adaptive reflection coefficients on the preceding stages and the input
signal. To ease the derivations, we assume that reflection coefficients of each
stage are independent of the inputs to that stage. Then the optimal lattice filter
is derived for the frequency modulated signals. This is performed by computing
the optimal values of residual errors, reflection coefficients, and recovery errors.
Next, we show the tracking behaviour of adaptive reflection coefficients for
frequency modulated signals. This is carried out by computing the tracking model
of these coefficients for the stochastic gradient lattice algorithm in average. The
second-order convergence of the adaptive coefficients is investigated by modeling
the theoretical asymptotic variance of the gradient noise at each stage. The
accuracy of the analytical results is verified by computer simulations.
Using the previous analytical results, we show a new property, the polynomial
order reducing property of adaptive lattice filters. This property may be used to
reduce the order of the polynomial phase of input frequency modulated signals.
Considering two examples, we show how this property may be used in processing
frequency modulated signals. In the first example, a detection procedure in carried
out on a frequency modulated signal with a second-order polynomial phase
in complex Gaussian white noise. We showed that using this technique a better
probability of detection is obtained for the reduced-order phase signals compared
to that of the traditional energy detector. Also, it is empirically shown that
the distribution of the gradient noise in the first adaptive reflection coefficients
approximates the Gaussian law. In the second example, the instantaneous frequency
of the same observed signal is estimated. We show that by using this
technique a lower mean square error is achieved for the estimated frequencies at
high signal-to-noise ratios in comparison to that of the adaptive line enhancer.
The performance of adaptive lattice filters is then investigated for the second
type of input signals, i.e., impulsive autoregressive processes with alpha-stable
distributions . The concept of alpha-stable distributions is first introduced. We
discuss that the stochastic gradient algorithm which performs desirable results
for finite variance input signals (like frequency modulated signals in noise) does
not perform a fast convergence for infinite variance stable processes (due to using
the minimum mean-square error criterion). To deal with such problems, the
concept of minimum dispersion criterion, fractional lower order moments, and
recently-developed algorithms for stable processes are introduced.
We then study the possibility of using the lattice structure for impulsive stable
processes. Accordingly, two new algorithms including the least-mean P-norm
lattice algorithm and its normalized version are proposed for lattice filters based
on the fractional lower order moments. Simulation results show that using the
proposed algorithms, faster convergence speeds are achieved for parameters estimation
of autoregressive stable processes with low to moderate degrees of impulsiveness
in comparison to many other algorithms. Also, we discuss the effect of
impulsiveness of stable processes on generating some misalignment between the
estimated parameters and the true values. Due to the infinite variance of stable
processes, the performance of the proposed algorithms is only investigated using
extensive computer simulations.
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Saaifan, Khodr [Verfasser]. "Advanced Detection Schemes of Digital Signals in Impulse Noise / Khodr Saaifan." Aachen : Shaker, 2015. http://d-nb.info/1080763694/34.
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Paluri, Suraj, and Sandeep Patluri. "A Study of Impulse Response System Identification." Thesis, Karlstad University, Faculty of Technology and Science, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-1069.
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In system identification, different methods are often classified as parametric or non-parametric methods. For parametric methods, a parametric model of a system is considered and the model parameters are estimated. For non-parametric methods, no parametric model is used and the result of the identification is given as a curve or a function.
One of the non-parametric methods is the impulse response analysis. This approach is dynamic simulation. This thesis introduces a new paradigm for dynamic simulation, called impulse-based simulation. This approach is based on choosing a Dirac function as input, and as a result, the output will be equal to the impulse response. However, a Dirac function cannot be realized in practice, and an approximation has to be used. As a consequence, the output will deviate from the impulse response. Once the impulse response is estimated, a parametric model can be fitted to the estimation.
This thesis aims to determine the parameters in a parametric model from an estimated impulse response. The process of investigating the models is a critical aspect of the project. Correlation analysis is used to obtain the weighting function from the estimates of covariance functions.
Later, a relation formed between the parameters and the estimates (obtained by correlation analysis) in the form of a linear system of equations. Furthermore, simulations are carried out using Monte Carlo for investigating the properties of the two step approach, which involves in correlation analysis to find h-parameters and least squares and total least squares methods to solve for the parameters of the model. In order to evaluate the complete capability of the approach to the noise variation a study of signal to noise ratio and mean, mean square error and variances of the estimated parameters is carried out.
The results of the Monte Carlo study indicate that two-step approach can give rather accurate parameter estimates. In addition, the least squares and total least squares methods give similar results.
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Wu, Tsan-Ming. "Statistical impulse reponse modeling and dereverberation for room acoustics." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/14932.
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Wu, Qing. "Characterization of Impulse Noise and Hazard Analysis of Impulse Noise Induced Hearing Loss using AHAAH Modeling." OpenSIUC, 2014. https://opensiuc.lib.siu.edu/theses/1467.
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Millions of people across the world are suffering from noise induced hearing loss (NIHL), especially under working conditions of either continuous Gaussian or non-Gaussian noise that might affect human's hearing function. Impulse noise is a typical non-Gaussian noise exposure in military and industry, and generates severe hearing loss problem. This study mainly focuses on characterization of impulse noise using digital signal analysis method and prediction of the auditory hazard of impulse noise induced hearing loss by the Auditory Hazard Assessment Algorithm for Humans (AHAAH) modeling. A digital noise exposure system has been developed to produce impulse noises with peak sound pressure level (SPL) up to 160 dB. The characterization of impulse noise generated by the system has been investigated and analyzed in both time and frequency domains. Furthermore, the effects of key parameters of impulse noise on auditory risk unit (ARU) are investigated using both simulated and experimental measured impulse noise signals in the AHAAH model. The results showed that the ARUs increased monotonically with the peak pressure (both P+ and P-) increasing. With increasing of the time duration, the ARUs increased first and then decreased, and the peak of ARUs appeared at about t = 0.2 ms (for both t+ and t-). In addition, the auditory hazard of experimental measured impulse noises signals demonstrated a monotonically increasing relationship between ARUs and system voltages.
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Sahmoudi, Mohamed. "Processus alpha-stables pour la séparation et l'estimation robustes des signaux non-gaussiens et/ou non-stationnaires." Paris 11, 2004. http://www.theses.fr/2004PA112283.
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L’objectif principal de ce travail de thèse est de développer de nouvelles techniques robustes pour le traitement des signaux non-gaussiens et/ou nonstationnaires dans des environnements impulsifs. Plus précisément, le travail de cette thèse de doctorat se situe au carrefour des deux problématiques suivantes: I- Séparation aveugle de mélanges linéaires de sources impulsives : Ce problème a été peu étudié pour certains cas statistiquement ardus. En effet, lorsque les sources sont modélisées par des lois alpha-stables, les méthodes classiques ne s’appliquent plus, car la densité de probabilité n’a pas d’expression analytique explicite et les moments d’ordre 2 ou d’ordre supérieur à 2 sont infinis. Dans ce cas, nous avons introduit quatres approches originales. Une approche basée sur le critère de dispersion minimum. Une deuxième approche basée sur l’idée des statistiques normalisées que nous avons introduite pour adapter les méthodes existantes basées sur les statistiques d’ordre deux ou d’ordre supérieur. Une troisième approche en utilisant des fonctions de contrastes, sous contrainte d’orthogonalité. Une quatrième approche de structure semi-paramétrique. Nous combinons une version stochastique de l’algorithme EM et l’approximation des PDF alpha-stables par les fonctions logspline afin d’estimer la PDF et la matrice du mélange simultanément. II- Estimation de signaux FM non-stationnaires multicomposantes dans un environnement impulsif: Pour contribuer à la résolution de ce problème, nous avons proposé des méthodes paramétriques et d’autres non-paramétriques basées sur l’analyse temps-fréquenceIn this thesis, we introduce some new blind source separation approches for heavy-tailed and/or nonstationary signals. The impulsive, or heavy-tailed signals are modeled as real-valued symmetric alpha-stable processes characterized by infinite second and higher order moments. For the heavy-tailed signals separation, the proposed approaches uses the minimum dispersion criterion, the normalized statistics, some contrast function and a semi-parametric version of the maximum likelihood principle respectively. For the nonstationary FM signals in heavy-tailed noise, we propose some parametric and non-parametric methodes. Parametric methodes are based on the polynomial phase transform and the subspace method MUSIC. The non-parametric methodes are based on the use of the time-frequency representation of the signals. In a first appraoch, we use a preprocessing stage to mitigate the impulsive noise effect, while in the second one we design a new robust time-frequency distribution
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Schulte, Walter B. "The frequency response, impulse response, and transfer function of an ocean waveguide /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FSchulte.pdf.
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Thesis (M.S. in Applied Science (Signal Processing))--Naval Postgraduate School, June 2004.Thesis advisor(s): Lawrence J. Ziomek. Includes bibliographical references (p. 47). Also available online.
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Salmer, Christophe. "Contribution à l'étude de la stabilité d'impulsion à impulsion d'un émetteur état solide pour radar." Lille 1, 1999. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/1999/50376-1999-275.pdf.
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La stabilité d'impulsion à impulsion est une caractéristique primordial d'un radar de surface. Elle représente la variation de phase et d'amplitude entre impulsions successives du signal hyperfréquence et entraîne une dégradation (perte de détection, création de fausse alarme) du fonctionnement du radar. Notre travail a principalement consisté en une meilleure définition et compréhension de ce problème complexe de stabilité qui présente une importance capitale lors de la conception et de la certification d'un équipement radar. Après un rappel du principe général de fonctionnement d'un radar impulsionnel, nous avons défini la stabilité de phase et d'amplitude d'impulsion à impulsion, introduit les différentes causes d'instabilité et présenté leurs conséquences. Puis, nous avons aussi insisté sur les différentes approches mathématiques quantifiant ces phénomènes et montré en particulier que suivant le type de méthode retenue (temporelle ou fréquentielle) les résultats obtenus pouvaient varier de façon significative. Nous avons expliqué ces écarts par le fait que les méthodes temporelles caractérisent principalement la stabilité de l'émetteur seul alors que la méthode fréquentielle caractérisé plutôt la stabilité du système radar global. L'essentiel de notre travail a été consacré à l'analyse des causes d'instabilité des modules émetteurs état solide et à la mise en oeuvre de méthodologies spécifiques pour les caractériser. Nous avons en particulier montré l'influence prédominante des effets thermiques transitoires sur la stabilité d'un émetteur état solide loin devant les effets liées aux fluctuations de tension d'alimentation et de désadaptation d'impédance. L'étude des phénomènes de recombinaison de plusieurs signaux issus d'amplificateurs ou de chaînes d'amplification utilises dans les modules émetteurs et des conséquences sur la stabilité a permis d'obtenir des résultats très significatifs et nouveaux. Nous avons confirmé que dans la quasi totalité des cas, la recombinaison s'accompagnait d'une amélioration de la stabilité. Cette amélioration est surtout notable pour la stabilité de phase et semble liée principalement à la compensation des composantes déterministes de l'instabilité.
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Feirstine, Kelly Renee. "A Study of the Impact of Hardware Design Choices on the System Impulse Response of a Signal-level Radar Simulation." Wright State University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=wright1156968416.
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Logette, Patrice. "Etude et réalisation d'un processeur acousto-optique numérique de traitement des signaux." Valenciennes, 1997. https://ged.uphf.fr/nuxeo/site/esupversions/bbfd31df-2499-46a6-843d-52f346b1db41.
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Un système hybride acousto-optique/numérique axe principalement sur le filtrage F. I. R. A été développé au laboratoire dans le cadre d'une thèse antérieure. L'objet du présent travail est, d'une part, d'améliorer le système existant et, d'autre part, de tester les aptitudes du système ainsi modifié à effectuer d'autres types de calcul. Nous commençons par un résumé des travaux relatifs à l'ancien système, afin de bien positionner le problème. Nous exposons ensuite la conception du nouveau système. Une première partie décrit les modifications des circuits électroniques, avec l'utilisation de circuits de logique programmable de marque Altera. Une seconde partie est dédiée à l'aspect commande. On y détaille le programme de pilotage du système, la création et l'utilisation de modules indépendants pour chaque type de calcul, ainsi que les utilitaires associés (simulation, génération d'algorithmes). Nous terminons par une présentation de quelques exemples de calculs (FIR, IIR, DFT, DCT, corrélation) et évaluons les performances de notre système pour chacun de ces types d’opérations. Le bilan est assez satisfaisant dans l'ensemble, bien que l'apport des circuits Altera ne se soit pas révélé à la hauteur de nos espérances. Le filtrage IIR est le moins performant et nécessiterait la recherche d'autres algorithmes. Cependant, pour être réellement opérationnel, il faudrait améliorer la partie acousto-optique, ou à moyen terme, passer au tout numérique. Nous pourrions, alors, disposer d'un système simple et pratique pour simuler, tester ou valider, sur maquette, des algorithmes ou des sous-systèmes développés au laboratoire dans divers domaines du traitement de signal.
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Chaouki, Saïd. "Logiciel de traitement du signal." Rouen, 1987. http://www.theses.fr/1987ROUES024.
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Etude d'un algorithme pour le traitement d'un signal. Cet algorithme est composé de différents programmes indépendants permettant le calcul des polynômes orthonormaux, le calcul récursif, le calcul de la transformée de Fourier, de densité spectrale, réponse impulsionnelle d'un filtre numérique. Application à la reconnaissance des formes et simulation du processus de Lévy
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Rivenq, Atika. "Etude de systèmes anti-collision basés sur les techniques radar pour véhicules routiers." Valenciennes, 1996. https://ged.uphf.fr/nuxeo/site/esupversions/08c0d176-22f2-43e1-9790-c2656a116cac.
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L’objectif de ce travail est de concevoir un radar anticollision micro-onde qui sera embarqué sur les véhicules pour renforcer la sécurité routière. Deux technologies radars ont été testées : le radar à impulsions et le radar à modulation de fréquence. Les deux radars sont adaptés à la détection d'obstacles, mais ne permettent pas la détection de certains intervalles de distances. La solution a été d'associer ces deux radars dans un seul ensemble que nous appelons radar bi mode. Ce dernier a été ainsi réalisé et teste avec succès en temps réel. Dans cette étude, nous nous sommes intéressés aux radars basés sur le récepteur à corrélation considéré comme récepteur optimal. Cette technique a été associée à un codage numérique utilisant les séquences pseudo-aléatoires. Une solution plus économique utilisant une corrélation à un bit a été proposée. Une étude théorique originale a été présentée pour évaluer les performances de ce radar et surtout en rapport signal au bruit a la sortie du récepteur. Plusieurs cas ont été étudies par des simulations qui viennent renforcer l'étude théorique présentée. Finalement des tests utilisant un prototype du radar à corrélation montrent la faisabilité de la technique appliquée au domaine de l'anticollision
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August, Nathaniel J. "Medium Access Control in Impulse-Based Ultra Wideband Ad Hoc and Sensor Networks." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/27594.
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This thesis investigates distributed medium access control (MAC) protocols custom tailored to both impulse-based ultra wideband (I-UWB) radios and to large ad hoc and sensor networks. I-UWB is an attractive radio technology for large ad hoc and sensor networks due to its robustness to multipath fading effects, sub-centimeter ranging ability, and low-cost, low-power hardware. Current medium access control (MAC) protocols for I-UWB target small wireless personal area networks (WPANs) and cellular networks, but they are not suitable for large, multihop ad hoc and sensor networks. Therefore, this paper proposes a new type of MAC protocol that enables ad hoc and sensor networks to realize the benefits of I-UWB radios. First, we propose a method to overcome the challenges of quickly, reliably, and efficiently sensing medium activity in an ultra wideband network. This provides a base MAC protocol similar to carrier sense multiple access (CSMA) in narrowband systems. Next, we propose to exploit the unique signaling of I-UWB to improve performance over the base MAC protocol without the associated overhead of similar improvements in narrowband systems. I-UWB enables a distributed multichannel MAC protocol, which improves throughput. I-UWB also facilitates a busy signal MAC protocol, which reduces wasted energy from corrupt packets. Finally, because the I-UWB Physical Layer and MAC Layer affect the network and application layers, we propose a cross-layer adaptive system that optimizes performance. Physical Layer simulations show that both the base protocol and the improvements are practical for an I-UWB radio. Networks level simulations characterize the performance of the proposed MAC protocols and compare them to existing MAC protocols.Ph. D.
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Mercure, Virginie. "La peinture comme impulsion pour un dynamisme psychique." Thesis, Université Laval, 2013. http://www.theses.ulaval.ca/2013/29340/29340.pdf.
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La conscience d’un individu se développe au fil du temps par expérimentation, imitation et conditionnement. Sa compréhension du monde se construit à partir de déductions logiques qui s’appuient à la fois sur un désir d’acceptation sociale et sur son émotivité propre. Pour conserver l’équilibre psychique ainsi acquis, l’attitude qu’il adopte, dictée par cette vision du monde, peut devenir de plus en plus rigide. Il serait cependant possible de prendre en charge l’évolution de la conscience par une mise en mouvement volontaire de l’esprit. Celle-ci permettrait la participation positive de l’inconscient à l’évolution des connaissances et ainsi faciliterait l’adaptation de l’attitude aux constants changements de l’environnement. Pour moi, la peinture représente un outil favorisant ce dynamisme psychique.
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Giorgadze, Nino. "Factors Influencing Impulse Buying in Retail Stores." Master's thesis, Vysoká škola ekonomická v Praze, 2014. http://www.nusl.cz/ntk/nusl-193315.
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Impulse buying is a widely pervasive phenomenon. Statistics shows that more and more shoppers are experiencing irresistible urge to purchase unplanned and in most cases unnecessary product. Existing researches fall short in identifying most suitable tools that marketers can adopt in order to promote impulsive sales. Therefore, this thesis provides deep analysis of those, controllable factors that influence impulse buying. Particularly four external cues are examined: product display, promotional signage, sensory elements and social atmospherics. Research has deductive approach. First, existing academic articles and research papers are analyzed. Then two different methods of primary data collection are covered. Self-reported online survey is used as a main research tool. Received data of 193 respondents is analyzed in SPSS software using Pearson correlation test and standard multiple regression analysis. Results of store experiment and interviews are covered next. The research concludes that product display has strongest impact on impulse buying, influences and encourages consumer unplanned purchase decisions. Thus, marketers are advised to promote product presentation in the stores.
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Tesfamariam, Gebremichael Te-ame [Verfasser], Abdelhak M. [Akademischer Betreuer] Zoubur, and Dilip S. [Akademischer Betreuer] Mali. "Signal Processing Techniques for Landmine Detection Using Impulse Ground Penetrating Radar (ImGPR) / Gebremichael Te-ame Tesfamariam. Betreuer: Abdelhak M. Zoubur ; Dilip S. Mali." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2013. http://d-nb.info/1107770718/34.
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Mauuary, Didier. "Détection, estimation et identification pour la tomographie acoustique océanique : étude théorique et expérimentale." Grenoble INPG, 1994. http://www.theses.fr/1994INPG0033.
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La tomographie acoustique oceanique s'est developpee depuis une quinzaine d'annees en apparaissant comme un moyen jusque-la inexistant d'observer la dynamique des oceans sur des espaces de grandes echelles (100, 1000 km) et sur de longues periodes (1 mois, 1 an). Mais le principe de faisabilite de la methode est encore au cur du probleme surtout pour les zones experimentees par les laboratoires francais et europeens. Les resultats experimentaux ont remis en cause les procedes classiques de traitement du signal. Les instruments et la chaine de pretraitement ont fait l'objet d'une etude complete. Nous mettons en evidence les proprietes de la reponse impulsionnelle instrumentale et l'impact du doppler sur le systeme de mesure des temps de propagation des trajets multiples. Les proprietes spatiales du doppler et la sensibilite des signaux utilises en font une grandeur qui peut etre maintenant exploitee sous la forme d'une antenne a ouverture synthetique. Les methodes avancees de traitement du signal necessaires pour estimer les temps de propagation des trajets multiples et pour les identifier aux trajectoires predites par un modele acoustique sont formalisees avec les outils statistiques de decision. L'estimation bayesienne de temps de retard est analysee en detail et les domaines ou elle ameliore la precision des estimateurs sont donnes. Un nouveau concept, resolvant le probleme de l'identification, est propose. Il utilise d'une maniere fondamentale une information d'origine oceanique et un modele acoustique de trace de rayons. Les algorithmes qui en decoulent permettent d'identifier statistiquement les trajets acoustiques instables ou non resolus. Tous les concepts proposes sont valides sur des donnees experimentales
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Singh, Latchman. "Speech enhancement for forensic applications." Thesis, Queensland University of Technology, 1998. https://eprints.qut.edu.au/36080/1/36080_Singh_1998.pdf.
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Forensic audio recordings are usually made with a single covert microphone in non-ideal conditions. In non-ideal conditions the recordings are highly susceptible
to various types of noise. The noise is usually broadband noise, co-talker interference, impulsive noise, narrow band noise or convolutional noise. There are existing speech enhancement techniques available to suppress most of the noise types mentioned, but when the noise is of a considerable level the performance of most enhancement techniques tend to decrease significantly. This thesis presents a study of speech enhancement techniques that are applicable to the enhancement of forensic audio recordings or that can be used in a forensic
recording environment. It considers both pre-processing and post-processing speech enhancement techniques. This thesis investigates the improvement of some of the existing speech enhancement techniques as well as proposing some new ones. The performance of the improved and proposed speech enhancement techniques were evaluated objectively using the segmental signal-to-noise ratio
(SNRseg) and subjectively using the mean opinion score (MOS). A review of the current speech enhancement techniques is presented in the thesis and is also used
as a reference in some comparisons. The current speech enhancement techniques considered are those that are
applicable to forensic audio recordings. The performance of the existing techniques are assessed in the comparisons with the speech enhancement
techniques proposed by this thesis.
Two pre-processing speech enhancement techniques are presented in this thesis. The first pre-processing speech enhancement technique is designed to improve
existing broadband noise suppression techniques by the use of frequency shift keying (FSK) signals. It is based on a simple concept, which is to insert a known
tone of sufficient amplitude into the silent segments of a speech signal prior to transmission. At the receiver the detection of silent or non-speech segments used
in estimating the noise, becomes a simpler and more accurate task due to the inserted tone. The second pre-processing speech enhancement technique is designed to suppress a wide range of noises and it is based on zero padding. Zero padding involves inserting a zero value sample in between each speech signal sample prior to transmission. The inserted zero value samples allow accurate characterisation of the noise in the adjacent speech samples. At the receiver the noise is estimated from the sample positions allocated for the zero value samples. Several post-processing speech enhancement techniques are presented in this thesis. The first post-processing speech enhancement technique is designed for the suppression of co-talker interference and it uses a combination of dynamic time warping (DTW) and dual channel adaptive filtering. This technique is proposed for the suppression of co-talker interference, when the co-talker interference or noise reference signal is obtainable at a later instance as in the case of many covert forensic recordings. The corrupted speech signal and the noise reference signal are aligned using DTW and then the co-talker interference is suppressed using a dual channel adaptive filter.
The second post-processing speech enhancement technique is designed for broadband noise suppression and is based on spectral subtraction but it incorporates the masking properties of the human auditory system for improved
performance. Auditory masking is used to find the masking threshold, below which the noise is no longer perceivable. Only those noise components above the
masking threshold are suppressed. This approach is taken to reduce any byproducts such as musical noise.
The third post-processing speech enhancement technique is designed for broadband noise suppression and is based on spectral subtraction but it exploits the human auditory systems perception of frequency. Critical band analysis is used to group frequencies that are similarly perceived, which are then treated as a single
entity by the enhancement technique.
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Jaoua, Nouha. "Estimation Bayésienne non Paramétrique de Systèmes Dynamiques en Présence de Bruits Alpha-Stables." Phd thesis, Ecole Centrale de Lille, 2013. http://tel.archives-ouvertes.fr/tel-00929691.
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Dans un nombre croissant d'applications, les perturbations rencontrées s'éloignent fortement des modèles classiques qui les modélisent par une gaussienne ou un mélange de gaussiennes. C'est en particulier le cas des bruits impulsifs que nous rencontrons dans plusieurs domaines, notamment celui des télécommunications. Dans ce cas, une modélisation mieux adaptée peut reposer sur les distributions alpha-stables. C'est dans ce cadre que s'inscrit le travail de cette thèse dont l'objectif est de concevoir de nouvelles méthodes robustes pour l'estimation conjointe état-bruit dans des environnements impulsifs. L'inférence est réalisée dans un cadre bayésien en utilisant les méthodes de Monte Carlo séquentielles. Dans un premier temps, cette problématique a été abordée dans le contexte des systèmes de transmission OFDM en supposant que les distorsions du canal sont modélisées par des distributions alpha-stables symétriques. Un algorithme de Monte Carlo séquentiel a été proposé pour l'estimation conjointe des symboles OFDM émis et des paramètres du bruit $\alpha$-stable. Ensuite, cette problématique a été abordée dans un cadre applicatif plus large, celui des systèmes non linéaires. Une approche bayésienne non paramétrique fondée sur la modélisation du bruit alpha-stable par des mélanges de processus de Dirichlet a été proposée. Des filtres particulaires basés sur des densités d'importance efficaces sont développés pour l'estimation conjointe du signal et des densités de probabilité des bruits
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Nascimento, Felipe da Trindade do. "Algoritmos Genéticos para Síntese de Filtros Aplicados em Controle por Modo Deslizante." Universidade do Estado do Rio de Janeiro, 2010. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=7527.
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Nesta Dissertação propõe-se a aplicação de algoritmos genéticos para a síntese de filtros
para modular sinais de controladores a estrutura variável e modo deslizante. A modulação
do sinal de controle reduz a amplitude do sinal de saída e, consequentemente, pode
reduzir o consumo de energia para realizar o controle e o chattering. Esses filtros também
são aplicados em sistemas que possuem incertezas paramétricas nos quais nem todas as
variáveis de estado são medidas. Nesses sistemas, as incertezas nos parâmetros podem
impedir que seus estados sejam estimados com precisão por observadores. A síntese
desses filtros necessita da obtenção da envoltória, que é o valor máximo da norma de cada
resposta impulsiva admissível no sistema. Após este passo, é sintetizado um filtro que
seja um majorante para a envoltória. Neste estudo, três métodos de busca da envoltória
por algoritmos genéticos foram criados. Um dos métodos é o preferido, pois apresentou
os melhores resultados e o menor tempo computacional.This thesis proposes the application of genetic algorithms for the synthesis of filters which modulate signals of variable structure sliding mode controllers. The modulation of the control signal reduces the amplitude of the output signal and thus can reduce power consumption and chattering. These filters are also applied to systems with parametric uncertainties and unmeasured state variables. In these systems, the uncertainties can impair the accurate estimation of the state by means of observers. For the synthesis of these filters, it is necessary to obtain the envelope which is the maximum norm of each impulse response admissible for the system. After this step, a filter is synthesized to be an upper bound for the envelope. In this study, three methods of search of the envelope by genetic algorithms were developed. One of these methods has been giving the best results and needs the least computational time.
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Barbounaki, Stavroula. "Modélisation et traitement numérique des impulsions électriques générées par le passage des globules rouges à travers des micropores." Paris 5, 1997. http://www.theses.fr/1997PA05S030.
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Pour évaluer la déformabilité érythrocytaire qui est un facteur important du comportement rhéologique du sang au niveau de la microcirculation, il existe plusieurs techniques. Parmi ces techniques, on distingue celle de mesure du temps de transit des globules rouges a travers des micropores. Cette technique de filtration permet d'étudier la variation de la conductance électrique du filtre à travers lequel passent les globules rouges considérés comme particules non conductrices. Afin de pouvoir mieux comprendre ce phénomène, un modèle théorique approprié à été mis au point pour valider la méthode utilisée et interpréter qualitativement et quantitativement les résultats expérimentaux obtenus. Par ailleurs, un nouveau système l'analyseur des impulsions électriques générées par le passage des cellules à travers des micropores a été développé. Ce système, rapide et convivial à l'utilisateur, présente plusieurs possibilités de réglages des paramètres expérimentaux. L'analyse du signal acquis permet l'étude de la forme des impulsions électriques qui portent une information intéressante sur le passage des globules rouges et sur les phénomènes d'entrée et de sortie du pore. De plus, le système offre la possibilité d'étudier par analyse statistique la distribution des cellules vis à vis des paramètres mesures et de détecter les éventuelles sous populations globulaires dont la présence est très importante surtout dans les cas pathologiques. La modélisation théorique aide à définir certains paramètres indispensables à la détection et à l'interprétation de la forme des impulsions obtenues par le nouveau système. Les différentes expériences réalisées permettent d'illustrer les possibilités offertes par le nouveau système et aussi de confronter les valeurs théoriques avec les résultats expérimentaux.
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Fayolle, Gérard. "Conceptions et applications de circuits à mémoire de courant basse tension." Grenoble 1, 1998. http://www.theses.fr/1998GRE10151.
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Ce travail presente deux circuits bases sur les memoires de courant. Les applications developpees sont capables de travailler avec des alimentations en tension de 3v et moins. Pour ces realisations, il a ete necessaire de developper a la fois de nouvelles memoires de courants ainsi que des architectures originales pour repondre a tous les criteres des cahiers des charges. La premiere realisation est un fir pour une application video dont la fonction est, en sortie d'un filtre continu, d'y transferer une partie des contraintes de rejection. La phase lineaire que presente ce type de filtre se prete parfaitement bien a cette application tres sensible au delai de groupe. L'architecture developpee utilise un adressage cyclique qui permet de fortement reduire les degradations engendrees par les memoires de courant tout en conservant la dynamique. Le deuxieme circuit est un modulateur sigma-delta d'ordre 2 dont les performances requises sont une resolution superieure a 12 bits dans la bande 300-3400 hz, une surface d'integration reduite et une faible consommation. Pour arriver a obtenir la precision necessaire avec la faible tension d'alimentation, une nouvelle memoire a ete developpee. Sa particularite est d'utiliser un transistor de memorisation en zone triode qui lui confere une grande linearite. Elle laisse esperer des resultats en terme de linearite et de resolution proche de 14 bits.
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Schulte, Walter B. III. "The frequency response, impulse response, and transfer function of an ocean waveguide." Thesis, Monterey, California. Naval Postgraduate School, 2004. http://hdl.handle.net/10945/1516.
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Approved for public release, distribution is unlimitedIn this thesis, the ocean was modeled as a waveguide with an ideal pressure - release surface, and an ideal rigid bottom. The ocean waveguide was then treated as a linear, time - invariant, space - variant (TISV) filter or communication channel. The filter is time - invariant because no motion was modeled and because the properties of the ocean were assumed to be constant. The filter is space - variant because of the presence of the two boundaries, that is, the ocean surface and ocean bottom. This thesis investigates the ocean as a linear TISV filter by evaluating 1) the complex frequency response, 2) the impulse response, and 3) the transfer function of the ocean with respect to depth. It is shown that the TISV impulse response of the ocean contains information that can be used to help localize a target in range and whether the target is above or below the receiver. Computer simulation results were obtained by evaluating the three filter functions for several different test cases.
Ensign, United States Navy
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Fourt, Olivier. "Traitement des signaux à phase polynomiale dans des environnements fortement bruités : séparation et estimation des paramètres." Paris 11, 2008. http://www.theses.fr/2008PA112064.
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Les travaux de cette thèse sont consacrés aux différents problèmes de traitement des Signaux à Phase Polynomiale dans des environnements fortement dégradés, que se soit par de fort niveaux de bruit ou par la présence de bruit impulsif, bruit que nous avons modélisé en ayant recourt à des lois alpha-stables. La robustesse au bruit est un sujet classique de traitement du signal et si de nombreux algorithmes sont capables de fonctionner avec de forts niveaux de bruits gaussiens, la présence de bruit impulsif a souvent pour conséquence une forte dégradation des performances voir une impossibilité d'utilisation. Récemment, plusieurs algorithmes ont été proposés pour prendre en compte la présence de bruit impulsif avec toutefois une contrainte: ces algorithmes voient généralement leurs performances se dégrader lorsqu'ils sont utilisés avec du bruit gaussien, et en conséquence nécessitent une sélection préalable de l'algorithme adapté en fonction de l'usage. L'un des points abordé dans cette thèse a donc été la réalisation d'algorithmes robustes à la nature du bruit en ce sens que leurs performances sont similaires, que le bruit additif soit gaussien ou alpha-stable. Le deuxième point abordé a été la réalisation d'algorithmes rapides, une capacité difficile à cumuler à la robustesseThe research works of this thesis deal with the processings of polynomial phase signals in heavily corrupted environnements, whatsoever noise with high levels or impulse noise, noise modelled by the use of alpha-stable laws. Noise robustness is a common task in signal processing and if several algorithms are able to work with high gaussian noise level, the presence of impulse noise often leads to a great loss in performances or makes algorithms unable to work. Recently, some algorithms have been built in order to support impulse noise environnements but with one limit: the achievable results decrease with gaussian noise situations and thus needs as a first step to select the good method versus the kind of the noise. So one of the key points of this thesis was building algorithms who were robust to the kind of the noise which means that they have similar performances with gaussian noise or alpha-stable noise. The second key point was building fast algorithms, something difficult to add to robustness
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Peterek, Jan. "Časově proměnná filtrace signálů EKG." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-220042.
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The aim of this master’s thesis is to create a multiband stop derived from Lynn filters for suppressing mains hum and baseline variation (drift). The first part of the thesis is focused on brief theoretical introduction to the distortion types affecting ECG signal and twelve lead connection. The following practical part describes free realizations of ECG filter and ECG signal filtration. The filter has been tested both on distorted and on non-distorted signal. Finally filters’ error rate was computed from CSE database signals.
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Rouissi, Fatma. "Optimisation de la couche PHY des systèmes de communication sur le réseau d'énergie en présence de bruit impulsif." Thesis, Lille 1, 2008. http://www.theses.fr/2008LIL10042/document.
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Les travaux de cette thèse concernent l'étude et la proposition de nouvelles solutions d'adaptation d'un système de transmission CPL haut débit aux caractéristiques du canal ligne électrique en accordant un intérêt particulier au bruit impulsif qui représente une contrainte sévère encore difficile à surmonter. Le premier objectif concerne la conduite d'une analyse statistique des mesures du bruit impulsif puis l'étude et la définition d'un modèle à la fois simple et fidèle qui servira à dimensionner et évaluer par simulation les techniques à proposer. Les campagnes de mesure réalisées dans les milieux indoor et automobile ont permis de dégager les caractéristiques du bruit dans les deux environnements et de les comparer pour déduire l'agressivité du bruit indoor et la difficulté de sa compensation. Dans la phase de modélisation du bruit, trois modèles ont d'abord été présentés et étudiés: la classe A du modèle de Middleton, l'approche basée sur les chaînes de Markov et l'approche stochastique. Ensuite, une approche hybride, permettant à la fois une simplicité et une efficacité à reproduire les caractéristiques temporelles, a été proposée. La comparaison des mesures aux différents modèles étudiés ainsi qu'à celui proposé a montré l'efficacité de l'approche hybride qui sera adoptée dans la suite de ce travail. Le deuxième objectif concerne la proposition d'une nouvelle méthode de compensation de l'effet du bruit impulsif qui soit à la fois performante mais à faible complexité d'implantation matérielle. D'abord, la solution d'ajout de modules d'annulation de bruit au niveau du récepteur a été étudiée en proposant des techniques d'annulation de bruit basées sur l'estimation de sa puissance, ensuite différentes structures de codage canal ont été développés, et leurs performances ont été vérifiées et comparées en présence de plusieurs types de scénarios de bruit impulsifThis thesis deals with the study and the suggestion of new solutions to improve high bit rate power line communications. A special interest is given to impulsive noise presence which is the most difficult transmission constraint to overcome. The first aim of this work is to analyze statistically measure results then to propose a simple and efficient noise model that will be used in a simulation tool to define accurately suitable noise cancellation techniques. Experimental measurements done in both Indoor and vehicle PLC channels allowed to deduce noise characteristics in the two environments, to compare these characteristics and to prove high effect of Indoor impulsive noise. ln next step, three models were studied: c1ass A of Middleton mode 1, Markov chains-based model and the stochastic approach. Then, a new hybrid model, that combines the stochastic approach and Markov chains, was proposed. This model is simple, easy to implement and allows a satisfying fitting to noise temporal characteristics. Comparisons of models to measured noise show the efficiency of the hybrid approach that will be used afterward. The second aim of this work is to defme new appropriate and cost-effective methods to compensate impulsive noise effect. The frrst solution is to add a noise canceller module in the PLC system receiver. This solution was studied by proposing techniques to cancel noise by estimating its power. The second solution is to use error correction methods. ln this case, three channel coding structures were developed and their performances were studied in the presence of different impulsive noise scenarios