Modélisation distribuée et évolutive du GaN HEMT

L’industrie de télécommunication et les satellites se base majoritairement sur les technologies Si et GaAs. La demande croissante des hauts débits de données entraine une facture élevée en énergie. En outre, la saturation de la bande des basses fréquences, le besoin des débits élevés et les exigences de la haute puissance imposait l’utilisation de la bande hautes fréquences. Dans le but de résoudre les problèmes cités auparavant, la technologie GaN est introduite comme un candidat prometteur qui peut offrir de la haute puissance, taille du circuit plus faible avec une meilleure stabilité mécanique aux environnements hostiles/milieux agressifs. À titre d’exemple, l‘agence spatiale européenne sont en cours de développement d’un circuit à base du GaN sur substrat en Si pour faible cout, une hautes performance et une grande fiabilité. La technologie GaN est assez mature pour proposer de nouveaux systèmes intégrés utilisés pour les puissances microonde ce qui permet une réduction considérable de la taille du système. Étant un semiconducteur à grande bande interdite, GaN peut offrir une haute puissance sous hautes températures (>225oC) avec une bonne stabilité mécanique. Elle présente un facteur de bruit faible, qui est intéressant notamment pour les circuits intégrés aux ondes millimétriques. À noter que la mobilité du GaN par rapport à la température est assez élevée pour proposer des amplificateurs dans la bande W. Avec le progrès du procédé de fabrication du GaN, notre objectif est l’introduction de cette technologie dans des applications industrielles. À cette fin, on désire avoir un modèle du dispositif qui correspond à la meilleure performance. Ensuite, on veut le valider dans une modélisation du circuit. Cette thèse, basée sur la technologie GaN unique développée au 3IT, a pour objectif l’amélioration de l’outil de conception en réduisant son erreur avec une validation de son utilisation dans la conception du circuit. Ce travail est réalisé pour la première fois au 3IT avec des résultats de simulation pour une conception idéale d’un circuit MMIC ainsi que sa démonstration. Une caractérisation des échantillons a été réalisée avec objectif d’extraction de données qui vont servir à l’alimentation de modélisation des transistors sur l’outil ADS. Une fois complétée, la modélisation a été validée par une modélisation des petits et grands signaux et a été testée par une mesure load-pull. Enfin, ce modèle a été utilisé lors de la conception d’un amplificateur pour les applications RF. L’innovation de ce travail réside dans la modélisation de la résistance d’une grille large sous forme de quadripôles parallèles à structure 3D (ou à résistances de grille distribuées) du transistor MOSHEMT GaN. La conception et la fabrication de l’amplificateur à haute puissance (HPA) aux fréquences microondes (≤4GHz) sont réalisés au LNN du 3IT et inclus une couche d’oxyde de grille afin de réduire le courant de fuite notamment pour les tensions Vgs élevées, la grille du transistor forme un serpentin pour fournir une puissance de sortie élevée avec un encombrement spatial minimal et une grille présentant une électrode de champ pour permettre d’augmenter la tension de claquage.Abstract : The telecommunication and satellite industry is mainly relying on Si and GaAs technologies as the demand for a high data rate is continuously growing, leading to higher power consumption. Moreover, the lower frequency band's saturation, the need for high data rate, and high-power force to utilize the high-frequency band. In pursuit of solving the issues mentioned earlier, GaN technology has been introduced as a promising candidate that can offer high power at a smaller circuit footprint and higher mechanical stability in harsh environments. For example, currently, the European space agency (ESA) is developing an integrated circuit with GaN on Si substrate for low cost, high performance, and high reliability. GaN technology is sufficiently mature to propose integrated new systems which are needed for microwave power range. This technology reduces the size of the system considerably. GaN is a wide bandgap semiconductor which can offer remarkably high power at high temperature (>225℃), and it is very stable mechanically. It presents a low noise factor, very interesting for a millimeter-wave integrated circuit. Finally, the mobility of GaN vs. temperature is sufficiently elevated to propose a power amplifier in W-Band. With the improvement of the GaN process, our objective is to introduce this technology for industrial applications. For this purpose, we wish to have a better model of the device that corresponds to the best performance and then validate it by using this model in a circuit. Based on the 3IT's GaN process, which is unique in its context, this thesis aims to improve the design kit by reducing the design model's error and validating it by using it in circuit design. This work is the first to realize in 3IT with simulation results to design an MMIC circuit for demonstration. I first characterized the new samples by performing different measurements than using these measurement data; transistor is modeled in ADS software. Once the model was completed, it is validated by small-signal modeling, and then the large-signal model is tested with non-linear capacitances, current source, and transconductance modeling. Finally, we used this model to design a power amplifier for RF application. The innovation comes from modeling large gate resistance as distributed gate resistance for GaN MOSHEMT transistor and then designing high-power amplifier (HPA) in the frequency range (≤ 4GHz) while using 3IT GaN process which includes first oxide layer to have low gate current and more voltage of Vgs, the second transistor is meander to have high power and third, field plate - gate for high breakdown voltage

Une proposition pour de nouveaux moyens pour simuler les transformations d'un paysage urbain : le cas des devantures commerciales du Mile End

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal

Three Essays on Methodologies for Dynamic Modeling of Emerging Socio-technical Systems:The Case of Smart Grid Development

Socio-technical energy transitions are long-term and major transformations in incumbent energy infrastructures. They include fundamental changes in technologies as well as institutions and social patterns. Transition studies are primarily focused on frameworks for analyzing the entire transition process by investigating the historical cases of transitions. A multi-phase approach to transition posits this process begins with a pre-development phase characterized by technological and institutional lock-ins, and resistance from incumbent actors. This period is critical for a forward-looking approach to transitions, since early developments shape path-dependent and irreversible processes leading to the emergence of new transition pathways. However, our understanding about the mechanisms and dynamics of this phase is still very limited. This is mainly due to lack of data, weak conceptualization and the necessity of developing new methods proper to deal with these limitations. This dissertation develops methodologies for investigating some complex questions arising in the pre-development phase, by focusing on the case of smart grid development. The first essay uses insights from modeling interventions in complex systems and builds a System Dynamics model to investigate the cost allocation problem of smart metering roll-out. The second essay takes ideas from Technological Innovation System approach and develops a method to analyze the emergence of spatial diversity in smart grid development by combining Social Network Analysis and Agent-Based Modeling. The third essay builds on ideas from network theory and evolutionary modeling to develop a method for identifying the main path of knowledge development and analyzing knowledge trajectories in smart grid initiatives

Contribution à l’étude des non-linéarités au sein d’une association amplificateur-transducteur : atténuation des distorsions par un mode de contrôle en courant

Undertaken with the LAUM, this work aims at first tocharacterize non linear distortions relative to electrodynamicloudspeakers with a view to miniaturizing units designed in thelaboratory. Furthermore, a special point about the advantages and drawbacks resulting from voltage or current driving has been investigated. After a brief review about the prominent definitions used in thefield of electro-acoustics, the main properties and specificitiesof transducers are discussed while considering at first linear devices. Considering a generic transducer of the state of theart, the main parameters are given in terms of transfer functions. Then, a current-driving policy is discussed whiletaking account of the actual power operational amplifier properties. Furthermore, the rejection of the mechanical resonance is investigated without any kind of alteration of theideal infinity of the Control Drive Index value. Specific filtering structures are calculated regarding a given transducer and considered either in feedforward or feedback arrangements within the circuitry. After such a first order analysis non linear behaviours areconsidered. At first a straightforward typology of non linearsystems is presented so as to highlight the most importantdefinitions. Then, a special analytical approach is given,allowing us to analyse the harmonic generation from a currentdriven loudspeaker with a mono frequency regime. Such anapproach is extended and generalized by way of original numerical models designed with Simulink®, PSpice® and SLPSsoftware, considering bi tonal stimuli signals. Then, such anapproach is considered with transducers and amplifiers of thestate of the art, allowing us to validate the whole relevantrationale. Thus, the micro speakers actually developed in thelaboratory should be investigated and optimized in the shortrun, considering their relevant electronic conditioning policy.Ce travail réalisé au LAUM, concerne en premier lieu la caractérisation des distorsions, notamment non linéaires,observables sur des haut-parleurs en vue de les miniaturiser.En outre l’étude se rapporte au mode de contrôle de tels transducteurs au regard des avantages et des inconvénients présentés par l’électronique d’un pilotage en intensité.Après rappel des principales définitions permettant d’appréhender les mesures électroacoustiques, la structure et les propriétés des haut-parleurs font l’objet d’une première analyse, discutée dans le cadre des hypothèses de linéarité.Les exemples et les caractéristiques décrits en termes de fonctions de transfert sont présentés autour d’un transducteur générique de l’état de la technique. Les principes de la commande en courant sont ensuite présentés, compte tenu des caractéristiques globales des amplificateurs opérationnels de puissance disponibles actuellement. En maintenant l’intégrité de l’indice de contrôle en courant (Control Drive Index), la réjection du pic de résonance mécanique et des hautes fréquences sont discutés autour de structures de filtrages, soit incorporées à la boucle de feedback et adaptées au transducteur, soit disposées en feed forward. Au-delà de ces considérations de premier ordre les comportements non linéaires sont examinés. Après une analyse fondamentale se rapportant aux définitions et aux caractéristiques de non-linéarité, une évaluation analytique en régime mono fréquentiel est présentée, pour un transducteur commandé en courant. L’analyse est ensuite généralisée au moyen de modèles numériques originaux réalisés sous Simulink®, PSpice® et SLPS avec des sollicitations bitonales.Considérant divers dispositifs de l’état de la technique, des résultats conformes à ceux de la littérature récente et validés par l’expérience sont obtenus. Ainsi, les prototypes de micro haut-parleurs réalisés au laboratoire seront à court terme caractérisés avec plusieurs modes de conditionnement

Online incremental learning from scratch with application to handwritten gesture recognition

In recent years we have witnessed a significant growth of data to be processed by machines in order to extract all the knowledge from those data. For agile decision making, the arrival of new data is not bounded by time, and their characteristics may change over time. The knowledge stored in machines needs to be kept up to date. In traditional machine learning, this can be done by re-learning on new data. However, with the constant occurrence of high data volume, the process becomes overloaded, and this kind of task becomes unfeasible. Online learning methods have been proposed not only to help with the processing of high data volume, but also to become more agile and adaptive towards the changing nature of data. Online learning brings simplicity to the updates of the model by decoupling a single update from the whole updating process. Such a learning process is often referred to as incremental learning, where the machine learns by small increments to build the whole knowledge. The aim of this research is to contribute to online incremental learning for pattern recognition and more specifically, by handwritten symbol recognition. In this work, we focus on specific problems of online learning related to the stability-plasticity dilemma and fast processing. Driven by the application and the focus of this research, we apply our solutions to Neuro-Fuzzy models. The concept of Neuro-Fuzzy modeling is based on dividing the space of inseparable and overlying classes into sub-problems governed by fuzzy rules, where the classification is handled by a simple linear model and then used for a combined result of the model, i.e., only a partially linear one. Each handwritten symbol can be represented by a number of sets of symbols of one class that resemble each other but vary internally. Thus, each class appears difficult to be described by a simple model. By dividing it into a number of simpler problems, the task of describing the class is more feasible, which is our main motivation for choosing Neuro-Fuzzy models. To contribute to real-time processing, while at the same time maintaining a high recognition rate, we developed Incremental Similarity, a similarity measure using incremental learning and, most importantly, simple updates. Our solution has been applied to a number of models and has shown superior results. Often, the distribution of the classes is not uniform, i.e., there are blocks of occurrences and non-occurrences of some classes. As a result, if any given class is not used for a period of time, it will be forgotten. Since the models used in our research use Recursive Least Squares, we proposed Elastic Memory Learning, a method for this kind of optimization and, we have achieved significantly better results. The use of hyper-parameters tends to be a necessity for many models. However, the fixing of these parameters is performed by a cross-validation. In online learning, cross-validation is not possible, especially for real-time learning. In our work we have developed a new model that instead of fixing its hyper-parameters uses them as parameters that are learned in an automatic way according to the changing trends in the data. From there, the whole structure of the model needs to be self-adapted each time, which yields our proposal of a self-organized Neuro-Fuzzy model (SO-ARTIST). Since online incremental learning learns from one data point at a time, at the beginning there is only one. This is referred to as starting from scratch and leads to low generalization of the model at the beginning of the learning process, i.e., high variance. In our work we integrated a model based on kinematic theory to generate synthetic data into the online learning pipeline, and this has led to significantly lower variance at the initial stage of the learning process. Altogether, this work has contributed a number of novel methods in the area of online learning that have been published in international journals and presented at international conferences. The main goal of this thesis has been fulfilled and all the objectives have been tackled. Our results have shown significant impact in this area