Thèses sur le sujet « Signal distorsion »
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Pagot, Jean-Baptiste. « Modeling and monitoring of new GNSS signal distortions in the context of civil aviation ». Phd thesis, Toulouse, INPT, 2016. http://oatao.univ-toulouse.fr/17864/1/PAGOT_JB.pdf.
Texte intégralDa, Silva Jeferson Jhone. « Développement d'outils pour le suivi non-invasif de la pression intracrânienne par des produits de distorsion acoustiques ». Thesis, Université Clermont Auvergne (2017-2020), 2019. http://www.theses.fr/2019CLFAS010.
Texte intégralNon-invasive measurement of intracranial pressure (ICP) has been a research topic for decades, as invasive methods carry risks of hemorrhages and infections. Non-invasive monitoring by cochlear responses has been suggested as a reliable method. One of the most common solutions considered in these methods is the Distortion Products of Otoacoustic Emissions (DPOAE). The DPOAE measurement is quick and simple, as it only requires sending a sound stimulation and recording the cochlear acoustic response using a single probe (such as an earphone). The DPOAE phase shift is the parameter that allows us to monitor the ICP variations. As this is a relative measure, it is necessary to have an individual reference that should not be changed during or between measurements. In addition, the age of the patient influences the DPOAE levels which generally reduce with aging. They are also fragile and very sensitive to the acoustic environment, especially the noise from the patient. This work first presents the development of a signal processing method based on signal distribution analysis for automatic identification and rejection of noisy sections, in order to improve the robustness of the signal extraction from acoustic background noise. The developed method was compared to the rejection thresholds based on operator visual analysis (standard method). The results indicated a statistically lower noise level and more stable signals when using the automatic method. A second study presents a probe positioning and air leak detection technique (AFPS), based on the frequency response analysis of the pressure measured in the external ear canal after wideband stimulation. In this study, a tilt table was used to induce a slight variation in the ICP in four positions (60°, 0°, -20° and again 60°) into two series of measurements. We analyzed the reproducibility between the two tests and the effects on the test results of probe displacement and air leakage when they were identified. These analyses indicated that the AFPS is able to correctly classify the signals according to the occurrence of air leaks or probe movement. In the last experiment, both techniques (automatic rejection and AFPS) were adapted to be used in real time, to identify and correct any problems before or during the test. We compared the modified device and the commercial device in two test sessions, so that each device was used for both ears. In each session, three tests were performed (T1, T2 and T3), each with five values recorded for each of the three positions (45°, 0° "lying down" and -10°). These three tests were performed to allow the analysis of the reproducibility of the measurements, without and with a probe replacement effect, and its accuracy (expressed as the standard deviation of the differences). The AFPS increases robustness, providing more consistent values in all analyses, especially if the probe is repositioned. Automatic rejection reduces the variability between the five measurements taken for the same position, thus increasing the stability and accuracy of the responses
Thiesse, Jean-Marc. « Codage vidéo flexible par association d'un décodeur intelligent et d'un encodeur basé optimisation débit-distorsion ». Phd thesis, Université de Nice Sophia-Antipolis, 2012. http://tel.archives-ouvertes.fr/tel-00719058.
Texte intégralRossello, Norbert. « Optimisation par traitement de signal et automatique de la pureté spectrale de forts signaux d'émission : application aux émissions sonar ». Nice, 1990. http://www.theses.fr/1990NICE4416.
Texte intégralMuquet, Bertrand. « Nouveaux schémas de réception et décodage pour les systèmes OFDM sans fil avec préfixe cyclique ou zero-padding ». Paris, ENST, 2001. http://www.theses.fr/2001ENST0022.
Texte intégralGuénégo, Béatrice. « Conversion numérique de signaux biologiques de faibles intensités pour les applications biomédicales ». Electronic Thesis or Diss., université Paris-Saclay, 2023. http://www.theses.fr/2023UPAST230.
Texte intégralAccording to the World Health Organization, cardiac ischemia is the world's leading cause of death. Ischemia is an insufficient vascularization of myocardial cells, which, if prolonged, leads to the necrosis of part of the heart, i.e., a cardiac infarction, endangering the patient's life. However, if ischemia is treated in time, it can have no impact on the patient's health. An embedded system that detects cardiac ischemia over long periods, without requiring medical staff monitoring, and provides alerts would enable patients to be taken care of earlier, increasing their chances of avoiding a heart attack.The electrocardiogram (ECG) is a measurement of the heart's electrical activity, commonly used in medicine to make an initial diagnosis. Examining the signal morphology and the time intervals between different events gives hints of eventual pathologies. The diagnosis of ischemia is based on variations in the part of the ECG named ST segment. Some embedded systems using the ECG to detect cardiac arrhythmias already exist, but none target cardiac ischemia. In this context, the originality of this work is in the design of an integrated system that can detect ST segment variations for ischemia diagnosis. The main difficulties of such a system's design are ST segment preservation during the acquisition stage and the conception of a signal processing method adapted to integrated circuits (power consumption, complexity, ST segment preservation).In this thesis, we studied the design of an integrated system for ECG acquisition and processing for cardiac ischemia detection. The various circuits, simulations, and layouts were realized in 180 nm using XFAB xh018 technology. The standard giving minimum performance for electrocardiograms published by the International Electrotechnical Commission (IEC) was used to quantify ST-segment distortion. We first designed an analog acquisition stage from the system to the transistor level. Simulations of this stage were then carried out to confirm its compliance with the IEC standard and to estimate its power consumption. As the design of an analog-to-digital converter is not new to the state of the art, it was not addressed during this thesis. Then, we conceived an integrated implementation of the discrete wavelet transform, used to eliminate noise and obtain information on the signal's fiducial points while retaining the possibility of reconstructing the signal. We first simulated an implementation of Mallat's algorithm in Python, which was then realized in VHDL, and finally, the place and route step was carried out for several wavelets. Layouts and post-layout simulation results were used to determine which wavelet offered the best trade-off between signal distortion, baseline wander elimination, power consumption, and circuit area.This work covers the design and dimensioning of the essential blocks of an ECG acquisition chain dedicated to ST segment detection that can be integrated. It may be completed by implementing an embedded decision-making method before the physical realization of the chip
Payan, Frédéric. « Optimisation du compromis débit/distorsion pour la compression géométrique de maillages surfaciques triangulaires ». Phd thesis, Université de Nice Sophia-Antipolis, 2004. http://tel.archives-ouvertes.fr/tel-00011445.
Texte intégralgéométriques permettent l'utilisation de modèles théoriques pour le
débit et la distorsion des sous-bandes de coefficients. Finalement,
nous proposons un codeur géométrique incluant une allocation rapide et performante qui optimise la quantification des coefficients pour que la qualité visuelle de l'objet reconstruit soit maximisée sous la contrainte d'un débit total fixé. Expérimentalement, l'algorithme
proposé donne de meilleurs résultats que toutes les méthodes de l'état de l'art.
Hamoud, Houssam Eddine. « Linéarisation par pré-distorsion numérique d'amplificateurs de puissance pour les nouvelles générations des systèmes de télécommunications ». Thesis, Limoges, 2019. http://www.theses.fr/2019LIMO0110.
Texte intégralModern communications systems converge towards multi-standard operation combined with high PAPR modulation formats where the power amplifier must first be optimized in efficiency and where linearity will then be corrected by adding a predistorter. If this solution seems functional, it seems inadequate and ineffective on 5G systems where the targeted bandwidths pose both architectural problems (complexity of the observation path) and problems of accuracy of the usual behavioural models based on a simplification of the Volterra series in its discrete form (GMP, DDR) in the face of exacerbated memory effects but also of energy efficiency of the linearized system (DPD+PA). In this context, it becomes necessary to move towards a predistorter model less dependent on the characteristics of the signal to be linearized, in particular by the TPM (Two path Memory) model developed at XLIM, based on a simplification of the Volterra series in its continuous form, is independent of the characteristics of the signal to be linearized.Our work focused on evaluating the linearity performance of the classical models (GMP, DDR) and the TPM model on different power amplifiers either from simulations or from physical measurements of the PA. To do this, we have set up a simulation environmentand an evaluation bench for predistortion models with physical PA in order to quantify ACPR performance according to the variation in signal characteristics (power, frequency, statistics). All these experiments made it possible to verify, on the one hand,the poor robustness of traditional approaches (GMP/DDR) and, on the other hand, the stability of the performance of the TPM approach, whatever the scenario envisaged. This study therefore paves the way for a new generation of pre-distributor which, if extracted once and for all, would only require an update on slow dynamic phenomena (ageing) and would make it possible to consider a simplified architecture of the DPD observation path; thus improving the overall energy efficiency of the linearizedsystem
Akam, Bita Isidore Paul. « Sur une approche de l'analyse en composantes indépendantes à la compression des images multi composantes ». Phd thesis, Université Joseph Fourier (Grenoble), 2007. http://tel.archives-ouvertes.fr/tel-00151987.
Texte intégralPicard, Guillaume. « Traitement statistique des distorsions non-linéaires pour la restauration des enregistrements sonores ». Phd thesis, Télécom ParisTech, 2006. http://pastel.archives-ouvertes.fr/pastel-00002315.
Texte intégralAgostini, Marie Andrée. « New Trends in High Definition Video Compression - Application to Multiple Description Coding ». Phd thesis, Université de Nice Sophia-Antipolis, 2009. http://tel.archives-ouvertes.fr/tel-00451684.
Texte intégralCheaito, Ali. « Analytical anaysis of in-band and out-of-band distorsions for multicarrier signals : Impact of non-linear amplification, memory effects and predistorsion ». Thesis, Rennes, INSA, 2017. http://www.theses.fr/2017ISAR0001/document.
Texte intégralOFDM multicarrier techniques are now widely deployed in most wireless communication systems, in particular in cellularnetworks (L TE), broadcast networks (DVB) and WiFi networks. However, multi-carrier modulations are characterized by avery large dynamic amplitude measured by the Peak to Average Power Ratio (PAPR). which prevents radio frequencydesigners to feed the signal at the optimal point of the Power Amplifier (PA) which reduces the PA energy efficiency. Inliterature, the PAPR reduction and linearization techniques are the main approaches to solve the PAPR problem, the PAnonlinearities problem. as well as the low PA efficiency problem.The approach developed in this thesis was to study an intelligent solution for future implementations to control thereduction of PAPR and the linearization steps in a flexible way according to some predefined parameters so that theybecome adaptive and self-configurable. More specifically, our work focused on the analytical analysis of in-band measureby the Error Vector Magnitude (EVM) and out-of-band distortions measured by the Adjacent Chanel Power Ratio (ACPR)for clipped multicarrier signals taking into account the impact of non-linear amplification, memory effects and predistortion.In particular. many analytical results complemented by simulation results to evaluate the EVM and ACPR are proposed.These analytical expressions depend on the PA characteristics taking into account or not the PA memory effects and theuse of clipping and pre-distortion techniques. lt is worthwhile to note that our proposed theoretical analyses could be veryuseful for optimizing future transmitter efficiency and linearity in the field of broadcasting applications for the deployment oDVB-T2 transmitters as well as for L TE cellular networks
Lajoinie, Jérôme. « Contribution à la conception optimale en terme de linéarité et consommation des amplificateurs de puissance en fonctionnement multiporteuses ». Limoges, 2000. http://aurore.unilim.fr/theses/nxfile/default/db9f1c38-f96b-4798-9ae8-94e63c48d9fb/blobholder:0/2000LIMO0007.pdf.
Texte intégralThe signals used in modern telecommunication systems are very complex in the sense that multicarrier signals, digitally modulated and spread spectrum signals are required. The main characteristic of these signals is their time variant envelope. To characterize the linearity of power amplifiers used in these systems, one of the criterions, which is essential today is the NPR (Noise Power Ratio). After the description of the means of power amplifier characterizations under CW and multicarrier operations as well as CAD tools, an in depth study of the multicarrier linearity factor used (the NPR) is undertaken. A design method for power amplifier in terms of linearity and consumption was developed. This method is based on the optimisation of a new specific figure of merit (C/(N+I)=f(Pdc/N) which directly integrates the total signal to noise ratio of the system in a joint optimization of consumption and NPR. A systematic study of the optimal loading impedance and the operation classes of amplifiers is performed. One shows the interest of taking into account load and source impedances at the 2nd harmonic. The new design methodology is applied to the realization of two amplifiers optimized in linearity and consumption. An experimental checking validates the successive steps of the design. A complete characterization on a NPR measurement set-up of the two produced amplifiers is presented
Cornille, Nicolas. « Accurate 3D Shape and Displacement Measurement using a Scanning Electron Microscope ». Phd thesis, INSA de Toulouse, 2005. http://tel.archives-ouvertes.fr/tel-00166423.
Texte intégralLa thèse met l'accent sur la nouvelle technique de calibrage et de correction des distorsions développée car c'est une contribution majeure pour la précision de la mesure de forme et de déformations 3D aux échelles de grandeur étudiées. Elle prouve que, contrairement aux travaux précédents, la prise en compte de la dérive temporelle et des distorsions spatiales d'images est indispensable pour obtenir une précision de mesure suffisante. Les principes permettant la mesure de forme par vidéogrammétrie et le calcul de déformations 2D et 3D sont aussi présentés en détails. Dans le but de valider nos travaux et démontrer en particulier la précision de mesure obtenue, des résultats expérimentaux issus de différentes applications sont présentés tout au long de la thèse. Enfin, un logiciel rassemblant différentes applications de vision par ordinateur a été developpé.
Picard, Guillaume. « Traitement statistique des distorsions non-linéaires pour la restauration des enregistrements sonores / ». Paris : École nationale supérieure des télécommunications, 2007. http://catalogue.bnf.fr/ark:/12148/cb41024512c.
Texte intégralMahé, Gaël. « Correction centralisée des distorsions spectrales de la parole sur les réseaux téléphoniques ». Phd thesis, Université Rennes 1, 2002. http://tel.archives-ouvertes.fr/tel-00114668.
Texte intégralNous proposons un algorithme d'égalisation spectrale aveugle consistant à aligner, sur une bande de fréquences limitée (200-3150 Hz), le spectre à long terme du signal traité sur un spectre de référence (spectre de la recommandation P.50 de l'UIT-T). Des évaluations subjectives mettent en évidence une restauration satisfaisante du timbre original des locuteurs, dans la limite de la bande d'égalisation choisie.
Il apparaît toutefois que la quantification en loi A des échantillons de sortie de l'égaliseur induit un bruit gênant en réception. Deux approches sont donc proposées pour masquer perceptivement ce bruit par un reformage spectral. L'une est fondée sur la réinjection à l'entrée du quantificateur de l'erreur de quantification filtrée. L'autre explore selon un algorithme de type Viterbi les séquences temporelles des niveaux de quantification possibles, de manière à maximiser un critère probabiliste de masquage du bruit. Une évaluation subjective montre finalement d'une part que le bruit non reformé est préféré au bruit reformé, plus sporadique mais plus "rauque", d'autre part qu'une voix dont le timbre a été corrigé, au prix de ce bruit de quantification, est préférée à la même voix en réception d'une liaison téléphonique sans correction de timbre (et non bruitée).
Afin d'améliorer l'adéquation du spectre de référence de l'égaliseur aux différents locuteurs, une classification des locuteurs selon leur spectre, en deux ou quatre classes, est étudiée, et des critères de classement robustes aux distorsions de la liaison téléphonique sont définis. Cette classification permet d'utiliser non plus un spectre de référence unique, mais un spectre de référence par classe. Il en résulte une réduction de la distorsion spectrale induite par l'égaliseur, ce qui se traduit, pour certains locuteurs, par une amélioration significative de la correction de timbre.
Vivet, Damien. « Perception de l'environnement par radar hyperfréquence. Application à la localisation et la cartographie simultanées, à la détection et au suivi d'objets mobiles en milieu extérieur ». Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2011. http://tel.archives-ouvertes.fr/tel-00659270.
Texte intégralGuigue, Lisa. « Evaluation clinique de la pression artérielle centrale à partir de la mesure par cathétérisme radial en utilisant la modélisation de l'arbre artériel, de la liaison hydraulique et du capteur. Intégration de la fonction dans un dispositif de surveillance de la qualité de la mesure de la pression artérielle ». Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAS036.
Texte intégralAortic pressure is generally recognized as a good index of the hemodynamic state of a patient. In intensive care units, aortic pressure is indirectly estimated via a radial catheter-tansducer system. The present study aims to remove the obstacles to a reliable evaluation of central pressure via the radial catheter-transducer system commonly used in clinics. These obstacles can be due to :1.technical problems occurring between the radial catheter and the sensor;}2.pathophysiological problems affecting the arterial tree between the heart and peripheral arteries. Several clinical situations have been identified in which alterations of the physical properties of the vasculature do not allow a reliable estimation of central arterial pressure using the common radial setting. One of these phenomena is the so called central-to-radial arterial pressure gradient.CATARSI, a medical device developped by AII SAS, affords a solution to the first group of problems by providing an index of the quality of the signal provided by the radial catheter-transducer system.Under pathophysiological conditions affecting the arterial vascualture of the patient, early detection of a mismatch between peripheral and central arterial pressure would also be of great clinical value. In this view, a new functionality could be develop to implement CATARSI. However, to achieve this goal, it is first necessary to understand, evaluate and modelize the precise pathophysiological mechanisms involved in these particular situations.The study contains three steps :1.Experimental evaluation, by oscillometry and catheterization, of AP propagation-time on the human arterial tree (aortic, radial, femoral arterial pressure) during a central-to-radial arterial pressure gradient. This evaluation has been carried out on patients undergoing Cardio Pulmonary Bypass (CPB). Several measurements have been performed: before, during and after CPB.2.Development and optimization of a method allowing the detection of an uncoupling between central and peripheral arterial pressure thanks to AP signal analysis in real time and a potential complementary measurement performed with CATARSI.3.Several central to radial arterial modelling propositions in order to present a better evaluation of central arterial pressure estimated by radial arterial pressure
Saad, El Dine Mohamad. « Linéarisation des amplificateurs de puissance à haut rendement en combinant les techniques de pré distorsion numérique et le contrôle de polarisation ». Limoges, 2011. http://aurore.unilim.fr/theses/nxfile/default/159b8ebd-0d26-4b99-9c48-fc7f17ff3bf4/blobholder:0/2011LIMO4021.pdf.
Texte intégralModern communication systems require the use of modulation schemes that lead to non envelope constant microwave signals. The peak to average power ratio (PAPR) of these signals is large. In such conditions, power amplifiers used in transmitters are critical devices because they need to be optimized in terms of both electrical efficiency and linearity which are antagonist parameters if conventional power amplifier architectures are considered. Consequently there is a major interest in research activities dealing with new power amplifier architectures that enable to obtain either high efficiency or good linearity performances. This can be reached if linearization techniques are applied to high efficiency power amplifiers designs. In such a context it is of prime interest to develop a laboratory set up that includes dynamic biasing of power amplifiers and digital predistortion capabilities to investigate novel high efficiency and linear amplification solutions. This has been accomplished in this work and applied to the optimisation of both efficiency and linearity of a 10 Watt GaN amplifier at S Band. Finally an experimental study that consists in low pass filtering the dynamic drain bias voltage is reported. The goal is to find a possible solution to enhance the efficiency of the bias modulator circuit without impacting to much linearity performances