<p>This thesis demonstrates the high- level modelling and design of oversampled delta- sigma noise shapers for D/A conversion. It presents an overview and study on digital- to- analog converters (DAC) followed by the noise shapers. It helps us to understand how to design a noise shaper model and algorithmic expressions are presented. The models are verified through high level simulations. The usage of models is to reduce the design time and get a good understanding for fundamental limitations on performance. Instead of time consuming circuit- level simulations, we point out the behavioural- level and algorithmic- level simulations of the noise shaper and the entire system comprising of interpolation filter, noise shaper followed by pulse amplitude modulation and reconstruction filtering. We have used the delta- sigma modulators to reduce the number of bits representing the digital signal. It is found that the requirement on oversampled DACs are tough. It is emphasised that the design of an oversampling converter is a filter designproblem. There is a large number of trade- offs that can be made between the different building blocks in the OSDAC.</p>

This thesis demonstrates the high- level modelling and design of oversampled delta- sigma noise shapers for D/A conversion. It presents an overview and study on digital- to- analog converters (DAC) followed by the noise shapers. It helps us to understand how to design a noise shaper model and algorithmic expressions are presented. The models are verified through high level simulations. The usage of models is to reduce the design time and get a good understanding for fundamental limitations on performance. Instead of time consuming circuit- level simulations, we point out the behavioural- level and algorithmic- level simulations of the noise shaper and the entire system comprising of interpolation filter, noise shaper followed by pulse amplitude modulation and reconstruction filtering. We have used the delta- sigma modulators to reduce the number of bits representing the digital signal. It is found that the requirement on oversampled DACs are tough. It is emphasised that the design of an oversampling converter is a filter designproblem. There is a large number of trade- offs that can be made between the different building blocks in the OSDAC.

Afin de réaliser des traitements locaux sur des données de diverses natures (volumes, images ou signaux) contenant des éléments informatifs dans certaines bandes de fréquence, nous nous intéressons dans cette thèse à l’étude de bancs de filtres (BdF). Plus précisément, nous étudions l’existence et la synthèse de BdF de réponses impulsionnelles finies (RIF) inverses d’un BdF d’analyse RIF redondant complexe fixé. Nous proposons en particulier des méthodes testant l’inversibilité de la matrice d’analyse et la construction d’un inverse explicite à l’aide de la formulation polyphase. À partir de ce dernier, nous proposons une paramétrisation réduite de l’ensemble des BdF de synthèse permettant d’optimiser leurs réponses selon différents critères. Cette étude est étendue au cas multidimensionnel notamment par l’utilisation de la notion de résultant. Ces outils permettant de représenter efficacement certaines informations structurées dans des données, il devient possible de les préserver tout en rejetant d’éventuelles perturbations. Le premier cadre considéré est celui du bruit gaussien. Nous avons utilisé le principe de Stein pour proposer deux méthodes de débruitage : FB-SURELET-E et FBSURELET-C. Elles sont comparées à des méthodes récentes de débruitage conduisant à de bons résultats en particulier pour des images texturées. Un autre type d’application est ensuite considéré : la séparation des structures orientées. Afin de traiter ce problème, nous avons développé une méthode de filtrage anisotrope. Les algorithmes réalisés sont finalement testés sur des données issues de différents domaines applicatifs (sismique, microscopie, vibrations) / Our main purpose in this PhD thesis is to perform local frequential (or directional) processing in different kind of data (volumes, images or signals). To this end, filter banks (FBs) are studied. More precisely, we first investigate the existence and the construction of synthesis FBs inverse to a given FIR complex analysis FB. Through the study of the polyphase analysis matrix, we are able to propose methods to test the invertibility and to build one inverse FB. Using this inverse, we provide a parametrization of the set of synthesis FB, with which we optimize filter responses with different criteria. The same study is performed in the multidimensional case. Since FBs provide an efficient representation of structured information in data, it is then possible to preserve them while rejecting unwanted perturbations. By associating Stein’s principle and those FB, we proposed two methods to denoise signals and images corrupted by Gaussian noise. These methods, named FB-SURELET-E and FB-SURELET-C, are compared to recent denoising methods and are found to offer good results, especially for textured images. Another type of application is then investigated : separation of oriented structures. To this end, we have developed an anisotropic filtering method. The different proposed methods are finally applied on images and signals from various fields : seismic images and cubes, transmission electron microscopy (TEM) images of catalysts and vibration signals from car engines

Advances in electronic systems have lead to the demand for high resolution, high bandwidth Analog-to-Digital Converters (ADCs). Oversampled ADCs are well- known for high accuracy applications since they benefit from noise shaping and they usually do not need highly accurate components. However, as a consequence of oversampling, they have limited signal bandwidth. The signal bandwidth (BW) of oversampled ADCs can be increased either by increasing the sampling rate or reducing the oversampling ratio (OSR). Reducing OSR is a more promising method for increasing the BW, since the sampling speed is usually limited by the technology. The advantageous properties (e.g. low in-band quantization, relaxed accuracy requirements of components) of oversampled ADCs are usually diminished at lower OSRs and preserving these properties requires complicated and power hungry architectures. In this thesis, different combinations of delta-sigma and pipelined ADCs are explored and new techniques for designing oversampled ADCs are proposed. A Hybrid Delta-Sigma/Pipelined (HDSP) ADC is presented. This ADC uses a pipelined ADC as the quantizer of a single-loop delta-sigma modulator and benefits from the aggressive quantization of the pipelined quantizer at low OSRs. A Noise-Shaped Pipelined ADC is proposed which exploits a delta-sigma modulator as the sub-ADC of a pipeline stage to reduce the sensitivity to the analog imperfection. Three prototype ADCs were fabricated in 0.18μm CMOS technology to verify the effectiveness of the proposed techniques. The performance of these architectures is among the best reported for high bandwidth oversampled ADCs. / Graduation date: 2011

De nombreuses applications de communication numériques font face à des canaux de transmission sélectifs en temps et en fréquence que nous pouvons assimiler à des systèmes linéaires variants dans le temps. À travers ces travaux de thèse, nous montrons que les modulations multiporteuses suréchantillonnées constituent une technique de transmission adaptée à ce type d'environnement. Cependant, la complexité algorithmique des émetteurs-récepteurs présentent un frein majeur à leur adoption. Fort de ce constat, nous nous intéressons à la sous-famille des modulations multiporteuses suréchantillonnées à filtres courts (WCP-OFDM), dont la complexité algorithmique est comparable à celle de l'OFDM avec préfixe cyclique. Après avoir exprimé les conditions de reconstructions parfaites, nous développons des égaliseurs de faible complexité et étudions la problématique du rapport de puissance crête sur puissance moyenne du signal en sortie d'émetteur. Enfin, nous analysons les performances de ces modulations à travers plusieurs scénarios de propagation radiomobiles. Les résultats de simulation confirment l'intérêt du WCP-OFDM, associé à des filtres prototypes bien localisés en temps et en fréquence pour faire face aux canaux doublement sélectifs. / Many digital communication applications are facing time and frequency selective channels that can be modelled by linear time-variant systems. Through this thesis work, we show that oversampled multicarrier modulations provide a suitable transmission technique for such an environment. However, the complexity of the transmitter-receiver remains a major obstacle for their adoption. Based on this observation, we focus on the sub-family of oversampled multicarrier modulation with short filters (WCP-OFDM), whose complexity is similar to cylic prefix OFDM. After introducing the perfect reconstruction conditions, we develop low-complexity equalizers and we study the peak-to-average power ratio issue at the output of the transmitter. Finally, we evaluate the performances of these moduations over several mobile radio propagation scenarios. Simulation results confirm the benefits of WCP-OFDM, with time-frequency localized prototypes filters, over doubly selective channels.

In video transmission there is a need to compose a wide-band signal from a numberof narrow-band sub-signals. A flexible solution offers the possibility to place any narrow-band sub-signal anywhere in the wide-band signal, making better use of the frequency space of the wide-band signal. A multi-standard supportive solution will also consider the three standard bandwidths of digital and analog video transmissions, both terrestrial and cable (6; 7 and 8 MHz), in use today. This thesis work will study the efficiency of a flexible aggregation solution, in terms of computational complexity and error vector magnitude (EVM). The solution uses oversampled complex modulated filter banks and inner channelizers, to reduce the total workload on the system. Each sub-signal is channelized through an analysis filter bank and together all channelized sub-signals are aggregated through one synthesis filter bank to form the wide-band composite signal. The EVM between transmitted and received sub-signals are investigated for an increasing number of sub-signals. The solution in this thesis work is performing good for the tested number of up to 100 narrow-band sub-signals. The result indicates that the multi-standard flexible aggregation solution is efficient for an increasing number of transmitted sub-signals.