Orientador: Samuel da Silva / Resumo: Muitas aplicações da engenharia envolvem estruturas essencialmente não-lineares onde várias técnicas têm sido recentemente estudadas e investigadas por muitos pesquisadores. Dentre as várias abordagems, as que usam séries de Volterra têm apresentado propriedades úteis para fornecer um melhor entendimento para identificação e análise. Neste contexto, a presente tese propõem novas contribuições em como usar as séries de Volterra para caracterização, identificação e análise dinâmica de sistemas não-lineares usando sinais de entrada e saída e sinais somente de saída. Inicialmente, apresenta-se uma metodologia para análise de sistemas mecânicos não-lineares através das funções de resposta em frequência de alta-ordem (HOFRFs) e o conceito de HOFRFs estendidas com dados apenas de saída é introduzido e descrito em detalhes. Após isso, uma abordagem para identificação de sistemas não-lineares com base nas séries de Volterra através da expansão na base ortonormal de Kautz é proposta. Essa técnica permite identificar os seus núcleos mais facilmente e permite separar as contribuições dos termos lineares e não-lineares usando somente sinais de saída. Além disso, uma metodologia para análise modal de sistemas fracamente não-lineares sujeito a excitações com vários níveis de amplitude é também apresentada. A contribuição desse novo método reside no fato de que as HOFRFs são simplesmente estimadas como função das FRFs lineares. Basicamente, essa metodologia estende o conceito ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Most recent engineering applications involve structures essentially nonlinear where several techniques have been recently studied and investigated by many researchers. Among them, the methods based on Volterra series expansion have presented powerful properties to provide a better understanding for identification and analysis. In this context, the present thesis proposes new contributions in how to use Volterra series for characterization, identification and dynamical analysis of nonlinear systems based on input and output signals and output-only signals. Initially, a methodology for analysis of nonlinear mechanical systems through higher-order frequency response functions (HOFRFs) is presented and the concept of extended HOFRFs based on output-only is introduced and described in detail. Afterwards, an approach for identification of nonlinear systems based on Volterra series through the expansion onto orthonormal Kautz basis is proposed. This technique allows to identify the Volterra kernels easily and enable to split the contribution of the linear and nonlinear terms using input-output as well as output-only signals. Furthermore, a methodology for modal analysis of weakly nonlinear systems under multilevel excitation is also proposed. The contribution of this new approach lies in the fact that HOFRFs are simply computed as functions of the linear FRFs. Basically, it extends the conventional experimental modal analysis methods in order to characterize and treat no... (Complete abstract click electronic access below) / Doutor

Submitted by OSCAR SCUSSEL null (oscar.scussel@gmail.com) on 2017-04-29T13:57:37Z No. of bitstreams: 1 PhDThesisScussel.pdf: 4308679 bytes, checksum: 08a1260ebbd5cc5320910fff695b1037 (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-05-03T16:39:39Z (GMT) No. of bitstreams: 1 scussel_o_dr_ilha.pdf: 4308679 bytes, checksum: 08a1260ebbd5cc5320910fff695b1037 (MD5) / Made available in DSpace on 2017-05-03T16:39:39Z (GMT). No. of bitstreams: 1 scussel_o_dr_ilha.pdf: 4308679 bytes, checksum: 08a1260ebbd5cc5320910fff695b1037 (MD5) Previous issue date: 2017-03-27 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Muitas aplicações da engenharia envolvem estruturas essencialmente não-lineares onde várias técnicas têm sido recentemente estudadas e investigadas por muitos pesquisadores. Dentre as várias abordagems, as que usam séries de Volterra têm apresentado propriedades úteis para fornecer um melhor entendimento para identificação e análise. Neste contexto, a presente tese propõem novas contribuições em como usar as séries de Volterra para caracterização, identificação e análise dinâmica de sistemas não-lineares usando sinais de entrada e saída e sinais somente de saída. Inicialmente, apresenta-se uma metodologia para análise de sistemas mecânicos não-lineares através das funções de resposta em frequência de alta-ordem (HOFRFs) e o conceito de HOFRFs estendidas com dados apenas de saída é introduzido e descrito em detalhes. Após isso, uma abordagem para identificação de sistemas não-lineares com base nas séries de Volterra através da expansão na base ortonormal de Kautz é proposta. Essa técnica permite identificar os seus núcleos mais facilmente e permite separar as contribuições dos termos lineares e não-lineares usando somente sinais de saída. Além disso, uma metodologia para análise modal de sistemas fracamente não-lineares sujeito a excitações com vários níveis de amplitude é também apresentada. A contribuição desse novo método reside no fato de que as HOFRFs são simplesmente estimadas como função das FRFs lineares. Basicamente, essa metodologia estende o conceito de métodos convencionais de analise modal experimental para caracterizar e tratar efeitos não-lineares. Os resultados via exemplos numéricos e experimentais apresentados ao longo da tese mostram as contribuições, benefícios e eficácia da proposta. / Most recent engineering applications involve structures essentially nonlinear where several techniques have been recently studied and investigated by many researchers. Among them, the methods based on Volterra series expansion have presented powerful properties to provide a better understanding for identification and analysis. In this context, the present thesis proposes new contributions in how to use Volterra series for characterization, identification and dynamical analysis of nonlinear systems based on input and output signals and output-only signals. Initially, a methodology for analysis of nonlinear mechanical systems through higher-order frequency response functions (HOFRFs) is presented and the concept of extended HOFRFs based on output-only is introduced and described in detail. Afterwards, an approach for identification of nonlinear systems based on Volterra series through the expansion onto orthonormal Kautz basis is proposed. This technique allows to identify the Volterra kernels easily and enable to split the contribution of the linear and nonlinear terms using input-output as well as output-only signals. Furthermore, a methodology for modal analysis of weakly nonlinear systems under multilevel excitation is also proposed. The contribution of this new approach lies in the fact that HOFRFs are simply computed as functions of the linear FRFs. Basically, it extends the conventional experimental modal analysis methods in order to characterize and treat nonlinear effects. The results based on numerical and experimental examples presented along the thesis show the contributions, benefits and effectiveness of the proposal. / FAPESP: 2012/09135-3 / CNPq: 47058/2012-0 / CNPq: 203610/2014-8

<p>Most work on amplifier linearity has focused on the transconductance (gm) linearity, but there is increasing evidence that the voltage-dependence of the gate-source capacitance (Cgs) plays an important role in the linearity of emerging devices. This work addresses the capacitance contribution by incorporating the nonlinearities attributed to the voltage dependency of Cgs of a general FET on a circuit-level Cg amplifier model.</p> <p>An amplifier model including a voltage-dependent Cgs, and a voltage-dependent gm is studied using harmonic analysis and Volterra series. A closed form expression for the  third-order intercept point (IP3) of the amplifier, which depends on the nonlinear coefficients of Cgs, is obtained. A simple design rule, and a formula for the reduction of the IP3 due to the voltage-dependent Cgs are also presented. </p> <p>As application examples, the linearity of an amplifier based on a specific device is analyzed for two cases by extracting the nonlinear circuit parameters of the device. First for an analytic model of a bulk mosfet. Second for a one-dimensional, ballistic, coaxially gated Si nanowire. For low frequencies of design, the distortion introduced by gm is predominant, but for high frequencies it is obscured by the distortion coming from Cgs.</p> <p>We conclude that taking into account the voltage-dependence of Cgs is crucial when predicting the linearity behavior of a Cg amplifier, either designed for high-frequency operation, or based on a device operating near the quantum capacitance limit. </p>

El objetivo de este trabajo es el desarrollo de técnicas para la simulación y optimización del diseño de circuitos osciladores y lazos de enganche en fase de microondas. La intención de estas técnicas es que puedan ser utilizadas por el diseñador para optimizar las prestaciones de este tipo de circuitos durante la etapa de diseño. Por este motivo, se ha intentado que en todo momento las técnicas puedan ser utilizadas en combinación con un programa comercial de simulación de circuitos de microondas.En el caso de los circuitos osciladores, inicialmente se han optimizado sus prestaciones cuando se utilizan como osciladores controlados por tensión. De esta forma, se han desarrollado una serie de técnicas que, en combinación con simulaciones en un programa comercial, permiten la linealización y extensión de la característica tensión-frecuencia. Mediante una técnica de control de estabilidad, se ha optimizado la respuesta dinámica del oscilador ante entradas variantes en el tiempo. En concreto, se ha aumentado la rapidez de respuesta eliminando transitorios lentos oscilantes que distorsionan la señal de salida deseada. Esta técnica se ha aplicado al caso particular de osciladores controlados por tensión utilizados para generar señales chirp, como puede ser en radares Frequency Modulated Continuos Wave (FMCW). Se ha analizado también el fenómeno del "injection-pulling", en el que una señal interferente desplaza la frecuencia de oscilación. Para ello, se ha desarrollado una formulación tipo transitorio de envolvente cuyos coeficientes pueden ser identificados mediante simulaciones de balance armónico en un simulador comercial. La técnica permite incrementar la robustez del circuito oscilador ante estas señales interferentes. Dados los problemas observados en el simulador comercial para simular la característica de ruido de fase en osciladores con estructuras acopladas, se ha desarrollado una técnica de simulación de ruido de fase que solventa estos problemas. La técnica obtiene la característica de ruido de fase a través de simulaciones de transitorio de envolvente en combinación con el uso de generadores auxiliares. Estas simulaciones pueden realizarse sin problemas usando un simulador comercial. Los resultados de todas las técnicas han sido corroborados mediante medidas en varios tipos de osciladores de microondas. Finalmente, se ha realizado un estudio preliminar para combinar el uso de series de Volterra con la técnica de transitorio de envolvente para la simulación de la respuesta transitoria de los osciladores.En el caso de los lazos de enganche en fase, se ha desarrollado un programa propio que realiza un análisis no lineal de lazos acoplados o "Coupled Phase-Locked Loops" (CPLL). Estos sistemas son utilizados en aplicaciones tales como en control de apuntamiento de antenas "phased-array". El programa, basado en una formulación tempo-frecuencial del sistema, permite la obtención de los rangos de operación del CPLL mediante una caracterización no lineal de los elementos que componen el lazo. Se delimitan los rangos de histéresis, y se analiza la variación de estos rangos en función de los parámetros del sistema. Se analiza la estabilidad de las soluciones estacionarias, teniendo en cuenta parámetros tales como el retardo del lazo. Mediante el control de la estabilidad y un análisis de tipo transitorio de envolvente, se optimiza la rapidez del sistema en el seguimiento de entradas moduladas. Finalmente, se analiza el ruido de fase, separando la perturbación en fase en distintas componentes. Esta separación permite clarificar el efecto del ruido en el control de apuntamiento de un array de antenas. Las predicciones de las técnicas han sido validadas mediante medidas en un sistema CPLL a 2 GHz. / The objective of this work is the development of techniques for the simulation and optimization of the design of microwave oscillator circuits and phase-locked loops. The intention of these techniques is that they can be used by the designer to optimize the features of these kinds of circuits during the design stage. For this reason, a lot of effort has been put along this thesis to ensure that the techniques can be used in combination with commercial microwave circuit simulators.In the case of the oscillator circuits, initially, their features have been optimized when used as voltage controlled oscillators (VCO). In this way, different techniques are proposed for the computer aided design of these circuits. The first technique allows setting the operation frequency band for specific values of the tuning voltage. The second technique imposes a linear frequency-voltage characteristic with the aid of an auxiliary generator. To follow this characteristic, the circuit is solved in terms of an ideal capacitance, synthesized, at a later stage, with the tuning varactor embedded in a linear network. In the third technique, the oscillator response to a sawtooth input, used to generate a chirp signal, is improved, eliminating spurious frequencies, not observable in steady state. To illustrate the techniques, a VCO operating in the C-band has been optimized and used to generate a chirp signal with low nonlinear frequency distortion. The injection-pulling phenomenon in oscillator circuits has been also analyzed. Injection pulling by interference signals is an undesired phenomenon in front-end oscillators, which causes a shift of the oscillation frequency and degrades the output spectrum. A semi-analytical formulation for the insightful analysis of injection-pulling phenomena in the presence of a modulated carrier or chirp signal is presented. The formulation enables an efficient analysis of interference problems difficult to simulate with harmonic balance or standard envelope transient. It allows the modification of the original design in order to reduce the injection pulling to the desired levels. The techniques have been applied to an oscillator at 6 GHz. Considering the problems found in commercial software to simulate the phase noise characteristic of coupled oscillator topologies, a numerical technique for the determination of the phase-noise spectrum of free-running oscillators is presented. The technique is based on envelope transient and can be applied to any commercial simulator on which this analysis method is available. The main advantage of the technique is that it allows simulating the near carrier phase noise spectrum, including possible resonances. The elements providing the oscillator phase-noise spectrum are obtained from envelope-transient simulations of low-computational cost. Comparisons are performed between the presented technique and other existing techniques, such as the carrier modulation approach. The technique has been successfully tested on the simulation of the near carrier phase noise spectrum of an oscillator circuit at 6.3 GHz. Finally, a preliminary study has been carried out to combine the use of Volterra series with the envelope transient technique for the simulation of oscillator transients.Regarding the phase-locked loops, in this thesis, harmonic-balance (HB) and envelope-transient formulations of coupled phase-locked loops (CPLLs) are presented. The CPLL has the added difficulty of its autonomous behavior since no reference oscillator is present. The new formulation takes into account the autonomy of the system, introducing a special set of state variables, which depend on the autonomous frequencies. The hysteresis phenomenon in CPLLs is analyzed in detail, efficiently obtaining the pull-in and hold-in ranges through HB. The pole analysis of the perturbed HB system enables an accurate prediction of instabilities and resonances. Due to the CPLL autonomy, there exists an inherent noise accumulation effect. This effect is taken into account, analyzing the perturbation in terms of accumulation and deviation components. The envelope formulation allows simulating the CPLL behavior in presence of modulation signals. The influence of the stability of the steady-state solution on the modulated signals is investigated. The simulation results have been successfully compared with the measurements in a manufactured CPLL system at 2 GHz.

Cette thèse porte sur la caractérisation de structures mécaniques, au travers de leurs paramètres structuraux, à partir d'observations perturbées par des bruits de mesure, supposés additifs blancs gaussiens et centrés. Pour cela, nous proposons d'utiliser des modèles à temps discret à parties linéaire et non-linéaire séparables. La première permet de retrouver les paramètres recherchés tandis que la seconde renseigne sur la non-linéarité présente. Dans le cadre d'une modélisation non-récursive par des séries de Volterra, nous présentons une approche à erreurs-dans-les-variables lorsque les variances des bruits ne sont pas connues ainsi qu'un algorithme adaptatif du type LMS nécessitant la connaissance de la variance du bruit d'entrée. Dans le cadre d'une modélisation par un modèle récursif polynomial, nous proposons deux méthodes à partir d'algorithmes évolutionnaires. La première inclut un protocole d'arrêt tenant compte de la variance du bruit de sortie. Dans la seconde, les fonctions fitness sont fondées sur des fonctions de corrélation dans lesquelles l'influence du bruit est supprimée ou compensée. / This PhD deals with the caracterisation of mechanical structures, by its structural parameters, when only noisy observations disturbed by additive measurement noises, assumed to be zero-mean white and Gaussian, are available. For this purpose, we suggest using discrete-time models with distinct linear and nonlinear parts. The first one allows the structural parameters to be retrieved whereas the second one gives information on the nonlinearity. When dealing with non-recursive Volterra series, we propose an errors-in-variables (EIV) method to jointly estimate the noise variances and the Volterra kernels. We also suggest a modified unbiased LMS algorithm to estimate the model parameters provided that the input-noise variance is known. When dealing with recursive polynomial model, we propose two methods using evolutionary algorithms. The first includes a stop protocol that takes into account the output-noise variance. In the second one, the fitness functions are based on correlation criteria in which the noise influence is removed or compensated.

Les systèmes de communications optiques jouent un role important pour satisfaire la demande incessante de trafics de données. Cette demande, induite par des applications gourmandes en termes de bande passante et débit, necéssite une augmentation de la capacité des réseaux optiques d’accès et par conséquent une augmentation des capacités de réseaux de transports métropolitains et longues distances. La prochaine génération de systèmes WDM longue distance devrait opérée à des débits de 400Gbps ou 1Tbps. Cette montée en débit s’appuiera sur des nouvelles formes d’ondes avancées de type mono-porteuse (Nyquist-WDM) ou multi-porteuse (OFDM multi-bande). Ces approches sont basées sur le multipléxage de plusieurs porteuses espacées par des intervalles de garde réduits. D’autre part, pour générer ces très haut débits, des modulations multi-états sont utilisées pour chaque porteuse grâce à leur efficacité spectrale élevée. Ces types de systèmes, qui combinent à la fois les approches multi-bande et les modulations multi-états, sont extrêmement vulnérables aux effets nonlinéaires de la fibre optique. En fait, les effets nonlinéaires sont dépendants de la puissance de transmission et inversement proportionels à l’intervalle de garde. Cela rend leur compensation indispensable pour maintenir des bonnes performances des systèmes en terme de distance de transmission. Grâce à l’emploi de récepteurs à détection cohérente, des techniques de traitement du signal numérique sont utlisées pour combattre les effets nonlinéaires. Dans cette thèse, nous avons proposé des nouvelles techniques basées sur les séries de Volterra et les égaliseurs à retour de decision pour compenser respectivement les effets nonlinéaires intrabande et les interférences nonlinéaires inter-bande. / Optical communication systems have evolved since their deployment to meet the growing demand for high-speed communications. Over the past decades, the global demand for communication capacity has increased exponentially and the most of the growth has occurred in the last few years when data started dominating network traffic. In order to meet the increase of traffic demands fueled by the growth of internet services, an increase of access network capacity and consequently metro and long-haul network capacities is required. Next generation of long-haul WDM transmission systems is expected to operate at 400Gbps or 1Tbps bit rate. Superchannel approaches, such as Nyquist WDM and multi-band OFDM, allow both high spectral efficiency and small guardband which makes them promising candidates to generate these high bit rates in combination with multi-level modulations formats. Such transmission systems are strongly disturbed by fiber nonlinear effects which increase with the data rate and the small guard band. Therefore, fiber nonlinearities compensation is required to get the desired performance in terms of transmission reach. DSP based approaches such as digital back propagation and third-order Volterra based nonlinear equalizer have been already proposed to deal with intra-channel or intra-band nonlinear effects. In the context of superchannel systems, we have proposed two new compensation techniques to deal with fiber nonlinear effects. The first one, called fifth-order inverse Volterra based nonlinear equalizer, compensate for intra-band nonlinear effects. The second approach, which is the interband/ subcarrier nonlinear interference canceler, is proposed to combat the nonlinear interference insuperchannel systems.