Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Kwok Pui-ho. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves [79]-85). / Abstracts in English and Chinese. / Chapter CHAPTER 1 --- INTRODUCTION --- p.1 / Chapter CHAPTER 2 --- NONLINEAR BEHAVIOR OF RF POWER AMPLIFIERS --- p.5 / Chapter 2.1 --- Single Tone Excitation --- p.6 / Chapter 2.1.1 --- AM-AM Conversion --- p.7 / Chapter 2.1.2 --- AM-PM Conversion --- p.9 / Chapter 2.2 --- Two-Tone Excitation --- p.11 / Chapter 2.2.1 --- Intermodulation Distortion --- p.12 / Chapter 2.3 --- Digitally Modulated Signal Excitation --- p.13 / Chapter 2.3.1 --- Spectral Regeneration --- p.14 / Chapter 2.3.2 --- Adjacent Channel Power Ratio (ACPR) --- p.16 / Chapter CHAPTER 3 --- LINEARIZATION TECHNIQUES --- p.18 / Chapter 3.1 --- pre-distortion --- p.20 / Chapter 3.2 --- Feed-forward Techniques --- p.23 / Chapter 3.3 --- Harmonics Control Techniques --- p.24 / Chapter CHAPTER 4 --- SPECTRAL REGROWTH ANALYSIS USING VOLTERRA SERIES METHOD --- p.26 / Chapter 4.1 --- Introduction To Volterra Series Analysis --- p.27 / Chapter 4.1.1 --- Linear and Nonlinear Systems --- p.27 / Chapter 4.1.2 --- Evaluation of Volterra transfer function --- p.29 / Chapter 4.1.3 --- Volterra Series Analysis of Spectral Regrowth --- p.31 / Chapter 4.2 --- Nonlinear Model of GaAs MESFET Device --- p.33 / Chapter 4.3 --- Evaluation Of Nonlinear Responses --- p.35 / Chapter 4.3.1 --- First-Order Response --- p.36 / Chapter 4.3.2 --- Second-Order Response --- p.38 / Chapter 4.3.3 --- Third-Order Response --- p.39 / Chapter CHAPTER 5 --- EFFECT OF HARMONIC TUNING ON SPECTRAL REGROWTH --- p.42 / Chapter 5.1 --- Simulation of Digitally Modulated Signal --- p.43 / Chapter 5.2 --- Effect of Source Second Harmonic Termination --- p.44 / Chapter CHAPTER 6 --- EXPERIMENTAL VERIFICATION --- p.48 / Chapter 6.1 --- Circuit Design and Construction --- p.49 / Chapter 6.2 --- Setup and Measurement --- p.55 / Chapter 6.3 --- Experimental Results --- p.56 / Chapter 6.3.1 --- Small Signal Measurement --- p.56 / Chapter 6.3.2 --- Single Tone Characterization --- p.57 / Chapter 6.3.3 --- Two-Tone Characterization --- p.59 / Chapter 6.3.4 --- ACPR Characterization --- p.60 / Chapter 6.4 --- Comparison of Measurement and Simulation --- p.66 / Chapter CHAPTER 7 --- NONLINEAR TRANSCONDUCTANCE COEFFICIENTS EXTRACTION --- p.68 / Chapter 7.1 --- Large Signal Model --- p.69 / Chapter 7.2 --- Extraction of Nonlinear Transconductance --- p.71 / Chapter 7.2.1 --- Extraction of g1 --- p.71 / Chapter 7.2.2 --- Extraction of g2 and g3 --- p.72 / Chapter CHAPTER 8 --- CONCLUSION --- p.76 / FUTURE WORK RECOMMENDATION --- p.78 / REFERENCE

The research investigates several critical design issues of continuous-time (CT) [Sigma Delta] modulators. The first is to investigate the sensitivity of CT [Sigma Delta] modulators to high-frequency clock spurs. These spurs down-convert the high-frequency quantization noise, degrading the dynamic range of the modulator. The second is to study the robustness of continuous-time loop filters under large RC product variations. Large RC variations in the CMOS process strongly degrade the performance of continuous-time [Sigma Delta] modulators, and reduce the production yield. The third is to model the harmonic distortion of one-bit continuous-time [Sigma Delta] modulators due to the interaction between the first integrator and the feedback digital-to-analog converter (DAC). A closed-form expression of the 3'rd-order harmonic distortion is derived and verified. Conventional CT [Sigma Delta] modulators employ all active integrators: each integrator needs an active amplifier. The research proposes a 5th-order continuous-time [Sigma Delta] modulator with a hybrid active-passive loop filter consisting of only three amplifiers. The passive integrators save power, and introduce no distortion. The active integrators provide gain and minimize internal noise contributions. A single-bit switched-capacitor DAC is employed as the main feedback DAC for high clock jitter immunity. An additional current steering DAC stabilizes the loop with the advantage of simplicity. To verify the proposed techniques, a prototype continuous-time [Sigma Delta] modulator with 2-MHz signal bandwidth is designed in a 0.25-¹m CMOS technology targeting for GPS or WCDMA applications. The experimental results show that the prototype modulator achieves 68-dB dynamic range over 2-MHz bandwidth with a 150-MHz clock, consuming 1.8 mA from a 1.5-V supply.

Cette thèse est consacrée à l'étude de la localisation d'objets enfouis dans acoustiques sous-marins en utilisant les méthodes de traitement d'antenne et les ondes acoustiques. Nous avons proposé un modèle bien adapté en tenant compte le phénomène physique au niveau de l'interface eau/sédiment. La modélisation de la propagation combine donc la contribution de l'onde réfléchie et celle de l'onde réfractée pour déterminer un nouveau vecteur directionnel. Le vecteur directionnel élaboré à partir des modèles de diffusion acoustique est utilisé dans la méthode MUSIC au lieu d'utiliser le modèle d'onde plane habituel. Cette approche permet d'estimer à la fois coordonnées d'objets (angle et distance objet-capteur) de forme connue, quel que soit leur emplacement vis à vis de l'antenne, en champ proche ou en champ lointain. Nous remplaçons l'étape de décomposition en éléments propres par des algorithmes plus rapides. Nous développons un algorithme d'optimisation plus élaboré consiste à combiner l'algorithme DIRECT (DIviding RECTangles) avec une interpolation de type Spline, ceci permet de faire face au cas d'antennes distordues à grand nombre de capteurs, tout en conservant un temps de calcul faible. Les signaux reçus sont des signaux issus de ce même capteur, réfléchis et réfractés par les objets et sont donc forcément corrélés. Pour cela, nous d'abord utilisons un opérateur bilinéaire. Puis nous proposons une méthode pour le cas de groupes indépendants de signaux corrélés en utilisant les cumulants. Ensuit nous présentons une méthode en utilisant la matrice tranche cumulants pour éliminer du bruit Gaussien. Mais dans la pratique, le bruit n'est pas toujours gaussien ou ses caractéristiques ne sont pas toujours connues. Nous développons deux méthodes itératives pour estimer la matrice interspectrale du bruit. Le premier algorithme est basé sur une technique d'optimisation permettant d'extraire itérativement la matrice interspectrale du bruit de la matrice interspectrale des observations. Le deuxième algorithme utilise la technique du maximum de vraisemblance pour estimer conjointement les paramètres du signal et du bruit. Enfin nous testons les algorithmes proposés avec des données expérimentales et les performances des résultats sont très bonnes. / This thesis is devoted to the study of the localization of objects buried in underwater acoustic using array processing methods and acoustic waves. We have proposed a appropriate model, taking into account the water/sediment interface. The propagation modeling thus combines the reflected wave and the refracted wave to determine a new directional vector. The directional vector developed by acoustic scattering model is used in the MUSIC method instead of the classical plane wave model. This approach can estimate both of the object coordinates (angle and distance sensor-object) of known form, in near field or far field. We propose some fast algorithms without eigendecompostion. We combine DIRECT algorithm with spline interpolation to cope with the distorted antennas of many sensors, while maintaining a low computation time. To decorrelate the received signals, we firstly use a bilinear operator. We propose a method for the case of independent groups of correlated signals using the cumulants. Then we present a method using the cumulants matrix to eliminate Gaussian noise. But in practice, the noise is not always Gaussian or the characteristics are not always known. We develope two iterative methods to estimate the interspectral matrix of noise. The first algorithm is based on an optimization technique to extract iteratively the interspectral matrix of noise. The second algorithm uses the technique of maximum likelihood to estimate the signal parameters and the noise. Finally we test the proposed algorithms with experimental data. The results quality is very good.

This doctoral thesis is focused on problems of modulators based on six-ports. It begins with description of current state of the art of six-ports used like modulators, their transfer functions and SIW technology. A design part of this thesis consists from experimental six-port based on substrate integrated waveguide (SIW) technology. There is presented step-by-step development of this six-port using this technology and also there is introduced micro-strip technology based six-port. Final design of six-ports and variable impedances were measured, the results are discussed and compared with expected ones in next chapters. Second part of this thesis deals with influences of internal parameters of six-ports to final signal transmission and derives theirs transfer functions for more than one reflection in structure. The computation results are compared with experimental measurements for fixed loads. With using of ideal loads sweeps, modulations with shaped input signals were calculated. For designed variables impedances, there was founded the optimal biasing points for demanded IQ diagram and discussed which from tested active circuit is suitable. In the last part there are shown results of experiment with these variable loads connected to both types of designed six-ports.