Il y a à l'heure actuelle un grand besoin d'antennes reconfigurables dans la bande des 60 GHz pour des applications de télédétection et de télécommunications sans fil très hauts débits. Les solutions traditionnelles de reconfiguration sont basées sur des semiconducteurs ou des composants RF-MEMS, qui connaissent un coût, une complexité et des pertes croissantes en bande millimétrique. Dans cette thèse, une approche originale a été développée : elle est basée sur la reconfiguration mécanique d'antennes et dispositifs millimétriques microrubans sur substrat élastomère ultrasouple PDMS grâce à des actionneurs MEMS grands déplacements. Premièrement, les choix de conception, la technique de simulation éléments finis (HFSS), et surtout la microfabrication d'antennes sur membrane PDMS ainsi que les techniques de mesure en impédance et rayonnement sont abordés.Deux axes ont ensuite été étudiés : les antennes accordables en fréquence, et les antennes et composants pour le balayage angulaire (déphaseurs et antennes à balayage mécanique de type scanner). Des procédés technologiques innovants ont été développés (reports de métallisations épaisses biocompatibles et d'aimants permanents en couches minces sur membrane PDMS) et différentes techniques d'actionnement (pneumatique, magnétique, par électromouillage) ont été mises en œuvre. Les performances en terme d'accord en fréquence (8,2 %) et de balayage angulaire (-90/+100°) dépassent l'état de l'art des antennes du même type en bande millimétrique, et ceci en utilisant une technologie peu complexe, ultra bas-coût et prometteuse pour la montée en fréquence. / There is currently an increasing need for reconfigurable antennas in the 60 GHz band for remote sensing applications and wireless communications. Traditional reconfiguration solutions are based on semiconductors or RF-MEMS but these components face cost, complexity and losses issues at millimeter-waves.In this thesis, an original approach was developed: it is based on the mechanical reconfiguration of millimeter-wave microstrip antennas and devices printed on ultrasoft PDMS substrates, thank to large displacements MEMS actuators. First, the design choices, the finite element simulation technique (HFSS), and the microfabrication of antennas supported by PDMS membranes as well as the impedance and radiation measurements techniques have been discussed. Two axis have then been studied: frequency-tunable antennas, and beam-steering components (phase shifters and "scanner" type antennas). Innovative technological processes were developed (transfer of biocompatible metal patterns and permanent magnet thin films on PDMS membranes) and several actuation techniques (pneumatic, magnetic, electrowetting) were implemented. Performances in terms of frequency tuning (8.2%) and scan angles (-90 / 100 °) are beyond the state of the art for similar antennas in the millimeter-wave band, and are achieved by using a very simple, ultra low-cost technique that is expected to be effective at even higher frequencies.

In the past decade, there has been an increased interest in low-cost, low-power, high data rate wireless systems for both commercial and defense applications. Some of these include air defense systems, remote sensing radars, and communication systems that are used for unmanned aerial vehicles, ground vehicles, and even the individual consumer. All of these applications require state-of-the-art technologies to push the limits on several design factors such as functionality, weight, size, conformity, and performance while remaining cost effective. There are several potential solutions to accomplish these objectives and a highly pursued path is through the utilization of advanced integrated system platforms with high frequency, versatile, multilayered materials. This work intends to explore advanced 3-D integration for state-of the art components in wireless systems using LCP multilayer organic platforms. Several packaging techniques are discussed that utilize the inherent benefits of this material. Wire bond, via interconnect, and flip-chip packages are implemented at RF and millimeter-wave (mm-wave) frequencies to explore the benefits of each in terms of convenience, reliability, cost, and performance. These techniques are then utilized for the demonstration of bulk acoustic waveguide (BAW) filter applications and for the realization of highly integrated phased-array antenna systems.

Pushing wireless data traffic onto small cells is important for alleviating congestion in the over-loaded macrocellular network. However, the ultimate potential of such load balancing and its effect on overall system performance is not well understood. With the ongoing deployment of multiple classes of access points (APs) with each class differing in transmit power, employed frequency band, and backhaul capacity, the network is evolving into a complex and “organic” heterogeneous network or HetNet. Resorting to system-level simulations for design insights is increasingly prohibitive with such growing network complexity. The goal of this dissertation is to develop realistic yet tractable frameworks to model and analyze load balancing dynamics while incorporating the heterogeneous nature of these networks. First, this dissertation introduces and analyzes a class of user-AP association strategies, called stationary association, and the resulting association cells for HetNets modeled as stationary point processes. A “Feller-paradox”-like relationship is established between the area of the association cell containing the origin and that of a typical association cell. This chapter also provides a foundation for subsequent chapters, as association strategies directly dictate the load distribution across the network. Second, this dissertation proposes a baseline model to characterize downlink rate and signal-to-interference-plus-noise-ratio (SINR) in an M-band K-tier HetNet with a general weighted path loss based association. Each class of APs is modeled as an independent Poisson point process (PPP) and may differ in deployment density, transmit power, bandwidth (resource), and path loss exponent. It is shown that the optimum fraction of traffic offloaded to maximize SINR coverage is not in general the same as the one that maximizes rate coverage. One of the main outcomes is demonstrating the aggressive of- floading required for out-of-band small cells (like WiFi) as compared to those for in-band (like picocells). To achieve aggressive load balancing, the offloaded users often have much lower downlink SINR than they would on the macrocell, particularly in co-channel small cells. This SINR degradation can be partially alleviated through interference avoidance, for example time or frequency resource partitioning, whereby the macrocell turns off in some fraction of such resources. As the third contribution, this dissertation proposes a tractable framework to analyze joint load balancing and resource partitioning in co-channel HetNets. Fourth, this dissertation investigates the impact of uplink load balancing. Power control and spatial interference correlation complicate the mathixematical analysis for the uplink as compared to the downlink. A novel generative model is proposed to characterize the uplink rate distribution as a function of the association and power control parameters, and used to show the optimal amount of channel inversion increases with the path loss variance in the network. In contrast to the downlink, minimum path loss association is shown to be optimal for uplink rate coverage. Fifth, this dissertation develops a model for characterizing rate distribution in self-backhauled millimeter wave (mmWave) cellular networks and thus generalizes the earlier multi-band offloading framework to the co-existence of current ultra high frequency (UHF) HetNets and mmWave networks. MmWave cellular systems will require high gain directional antennas and dense AP deployments. The analysis shows that in sharp contrast to the interferencelimited nature of UHF cellular networks, mmWave networks are usually noiselimited. As a desirable side effect, high gain antennas yield interference isolation, providing an opportunity to incorporate self-backhauling. For load balancing, the large bandwidth at mmWave makes offloading users, with reliable mmWave links, optimal for rate. / text

Vacuum microwave tubes, such as klystron, traveling-wave tube, gyrotron are high efficiency devices, where the RF interaction structure facilitates efficient energy transfer from the kinetic energy of the high energy electron beam to the electromagnetic wave. Traveling-wave Tube is the most versatile microwave power amplifier widely used for terrestrial communication, radar and aerospace applications. The waveguide based slow-wave structures like Millman, Karp, inter digital, grated waveguide, ring-plane, ring-bar, millitron and folded-waveguide structure gathered importance for application in millimeter-wave traveling-wave tubes. Among these millimeter-wave interaction structures, the folded-waveguide slow-wave structure became the most popular due to its robust structure, high power capability, low RF loss, simpler coupling, reasonably wide bandwidth and ease of fabrication for millimeter-wave to terahertz frequencies. Hence this thesis aims to analyse the folded-waveguide slow-wave structure for broad-banding and efficiency enhancement. The existing approaches for the analysis of cold circuit parameters (dispersion and interaction impedance characteristics) of folded-waveguide slow-wave structure are reinvestigated and found that these have limitation, as the effects of E-plane bend and beam-hole discontinuities are ignored in the parametric analysis. A cascaded matrix equivalent circuit model includes the effect of E-plane and beam-hole discontinuities for the analysis, but reported only for the serpentine folded-waveguide slow-wave structure. The cold test measurement technique was reported only for the dispersion characteristics. Hence the measurement technique has to be extended for the measurement of interaction impedance. The author proposes to orient the present doctoral work to (i) extend the proposed cascaded transmission matrix equivalent model for the analysis of rectangular folded-waveguide slow-wave structure, (ii) develop a non-resonant perturbation technique for the measurement of interaction impedance characteristics of the folded-waveguide slow-wave structure and also to (iii) establish new analysis models for the folded-waveguide slow-wave structure. The effect of E-plane bend and beam-hole discontinuities on the RF characteristics have been considered and simple, yet accurate closed form expressions for the computation of dispersion and interaction impedance characteristics have been established by three different approaches namely: transmission line equivalent circuit model, conformal mapping equivalent circuit model and quasi-TEM approach. The analysis results are benchmarked against 3-D electromagnetic modeling. The non-resonant perturbation theory is developed for the interaction impedance measurement. Typical Ka-band structures are fabricated by wire-EDM process and cold test measurements are carried out to benchmark the analysis approaches. The equivalent circuit models based on lumped circuit model are simpler than the cascaded matrix equivalent circuit model and can give closed form expressions for the prediction of dispersion and interaction impedance characteristics. The quasi-TEM approach can be extended for the complicated structure like ridge-loaded FWG-SWS. Broad-banding of the conventional folded-waveguide slow-wave structure is attempted by ridge-loading on the broad wall of the structure. The ridge-loaded folded-waveguide slow-wave structure is analyzed by parametric approach, cascaded transmission matrix equivalent circuit model and quasi-TEM approach and validated against numerical simulation. The analysis is extended for exploring the efficacy of the ridge-loading on broad-banding of the traveling-wave tube. Finally efficiency enhancement of the folded-waveguide slow-wave structure is attempted by introducing grating on the broad wall of the structure. The analysis is carried out by numerical simulation for exploring the efficacy of the grating on efficiency enhancement of the traveling-wave tube.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-08-07T18:53:34Z No. of bitstreams: 1 TELES DE SALES BEZERRA - DISSERTAÇÃO PPGCC 2017..pdf: 20064982 bytes, checksum: 40cc1a5d9429d5090373078fb560639d (MD5) / Made available in DSpace on 2018-08-07T18:53:34Z (GMT). No. of bitstreams: 1 TELES DE SALES BEZERRA - DISSERTAÇÃO PPGCC 2017..pdf: 20064982 bytes, checksum: 40cc1a5d9429d5090373078fb560639d (MD5) Previous issue date: 2017-12-21 / Capes / Os Sistemas de Comunicações móveis sem fio estão em uma crescente em relação a demanda por infraestrutura de comunicação, explicado pelo aumento do fornecimento de serviços aos usuários nas últimas décadas. Um dos recursos que está em escassez é o uso da banda, em que diversas técnicas tentam reutilizá-la, na tratativa de aumentar a disponibilidade de uso do espectro. Uma das opções de expansão do espectro, e consequentemente dos atuais serviços de redes móveis é o uso de outras faixas do espectro eletromagnético, que ainda não eram utilizadas nas comunicações móveis, como as ondas milimétricas. As comunicações que operam nas faixas de ondas milimétricas enfrentam obstáculos técnicos, como a necessidade de evolução de equipamentos específicos, problemas de cobertura e o quanto esses aspectos afetam a Qualidade de Serviço (QoS), em resumo, a viabilidade da comunicação requer uma avaliação cuidadosa. Há receio de que comunicações por ondas milimétricas sejam muito menos favoráveis que o uso de espectros mais usuais, principalmente nos problemas relacionados a cobertura. Projetistas de redes contam com diversas ferramentas para prever as características do ambiente, com o intuito de prever dificuldades na cobertura de sinal, para isso, fazem uso de modelos de previsão de perdas. Neste trabalho foi realizado um estudo sobre os problemas de cobertura e propagação de ondas milimétricas em ambientes urbanos fechados, sendo um prédio de escritórios e um shopping center. Para tanto, foram utilizados diversos modelos de previsão de perdas, a partir dos quais foi possível identificar que mesmo com o uso de modelos de perdas recomendados para ondas milimétricas, a minimização dos erros na predição é pequena, e comparada com modelos genéricos. / Wireless Mobile Communications Systems are on the rise in demand for resources, explained by the increased provision of services to users over the past few decades. One of the resources that is in shortage is the use of the band, in which several techniques try to reuse it, in the attempt to increase the availability of use of the spectrum. One of the options for spectrum expansion, and consequently of current mobile network services, is the use of other bands in the electromagnetic spectrum that were not yet used in mobile Communications such as millimeter waves. Communications that operate in the millimeter wave bands face technical obstacles, such as the need to evolve specific equipment, coverage problems and how these aspects affect Quality of Service, in short, the viability of communication requires a careful evaluation. There are fears that millimeter-wave Communications are far less favorable than the use of more usual spectra, especially in coverage-related problems. Network designers rely on several tools to predict the characteristics of the environment, in order to predict difficulties in signal coverage. For this, they use loss prediction models. In this work was carried out a study on the problems of coverage and propagation of millimeter waves in closed urban environments, being an office building and a shopping center. For this, several loss prediction models were used, through which we can identify that even with the use of recommended loss models for millimeter waves, the minimization of prediction errors is small, and compared with generic models.

L’objectif de ce travail est de concevoir et de caractériser un front-end millimétriqueutilisant des lignes de propagation à ondes lentes S-CPW optimisées en technologies CMOS avancées.Ces lignes présentant des facteurs de qualité 2 à 3 fois supérieurs à ceux des lignes classiques de typemicroruban ou CPW.Dans le premier chapitre, l’impact de l’évolution des noeuds technologiques CMOS sur lesperformances des transistors MOS aux fréquences millimétriques et sur les lignes de propagation ainsiqu’un état de l’art concernant les performances des front-end sont présentés. Le deuxième chapitreconcerne la réalisation des lignes S-CPW dans différentes technologies CMOS et la validation d’unmodèle phénoménologique électrique équivalent. Le troisième chapitre est dédié à la conceptiond’amplificateurs de puissance à 60 GHz utilisant ces lignes S-CPW en technologies CMOS 45 et65 nm. Cette étude a permis de mettre en évidence l’apport des lignes à ondes lentes aux performancesdes amplificateurs de puissance fonctionnant dans la gamme des fréquences millimétriques. Uneméthode de conception basée sur les règles d’électro-migration et permettant une optimisation desperformances a été développée. Finalement, un amplificateur faible bruit et un commutateur d’antennetravaillant à 60 GHz et à base de lignes S-CPW ont été conçus en technologie CMOS 65 nm afin degénéraliser l’impact de ce type de lignes sur les performances des front-end millimétriques. / The objective of this work is to design and characterize a millimeter-wave front-end usingthe optimized slow-wave transmission lines S-CPW in advanced CMOS technologies. The qualityfactor of these transmission lines is twice to three times higher than that of the conventionaltransmission lines such as microstrip lines and coplanar waveguides.In the first chapter, the influence of CMOS scaling-down on the performance of transistors atmillimeter-wave frequencies and on the transmission lines was studied. In addition, a state of the artwith regard to the performance of the front-end was presented. The second chapter concerns about therealization of the S-CPW lines in different CMOS technologies and the validation of an electricalequivalent model. The third chapter is dedicated to the design of 60-GHz power amplifiers using theseS-CPW lines in CMOS 45 and 65 nm technologies. This study highlighted the performanceenhancement of power amplifiers operating at millimeter-wave frequencies by using the slow-wavetransmission lines. A design method based on the electro-migration rules was also developed. Finally,a low noise amplifier and an antenna switch operating at 60 GHz were designed in CMOS 65 nm inorder to generalize the impact of such transmission lines on the performance of the millimeter-wavefront-end.

Ce travail de thèse s’inscrit dans la recherche des solutions économiquementviables pour des réseaux personnels à hauts débits (plusieurs Gbps à plusieursdizaines de Gbps) opérationnels en bande millimétrique autour de 60 GHz. Aucas où ces réseaux servent un nombre élevé d’utilisateurs, ils comprendront unemultitude d’antennes afin d’assurer l’accès sans fil rapide. Afin de réduire aumaximum le coût d’un module d’antenne, les réseaux doivent fournir un signalanalogue à des porteuses millimetriques. Une solution prometteuse pour les systèmesde distribution qui correspond à ces besoins sont des structures à fibreoptique, laquelle permet une transmission à faibles pertes et à haute bande passante.On parle de l’approche "radio-sur-fibre" (en anglais, radio-over-fiber). Laproblématique est de pouvoir générer et moduler un signal aux fréquences millimétriqueslors de la transmission optique - et ce avec des composant bas coûts.La technique utilisée dans le cadre de cette thèse est l’emploi des diodes laser àverrouillage de modes. Ces derniers vont pouvoir générer des hautes fréquencestout en ne nécessitant qu’une alimentation continue, et ils peuvent être modulésde manière directe ou externe. Les lasers à semi-conducteurs employés ici sontd’une génération encore à l’état d’étude puisqu’il s’agit des lasers à boites (ouîlots) quantiques. Ces lasers ont montrés de très bonnes capacités à générer dessignaux électriques aux fréquences autour de 60 GHz, bien qu’ayant encore, pourl’instant, à une stabilité de fréquence (ou de phase) limitée. Dans le cadre des systèmesde communication opto/micro-ondes, peu de travaux approfondis ont étémenés sur ces structures.Au cours de cette thèse, plusieurs études ont été effectuées. La première portesur les propriétés générales d’un système construit à partir de ce type de laser(puissances disponibles, figure de bruit, linéarité etc.). Une deuxième étude aété consacrée aux effets de la propagation des signaux dans les systèmes baséssur les lasers à verrouillage de modes, notamment de la dispersion chromatiquelaquelle a un effet considérable sur les distances de transmission. Les deux étudesmettent en avant l’importance d’une limitation du nombre de modes générés parla diode laser afin d’optimiser non seulement le gain du lien et la puissance RFrécupérée, mais aussi la figure de bruit du système. Lors d’une troisième étude, lastabilité en fréquence/phase s’est révélée critique, car le bruit de fréquence/phaselimite la qualité de la transmission en introduisant un plancher d’erreur mêmepour des rapports signal-a-bruit très élevés. Des différentes générations de lasersà boites (îlots) quantiques et à verrouillage de modes ont été testées. Le problèmedu bruit de fréquence et de phase persiste et ne peut pas être résolu en utilisantles techniques classiques comme les boucles à verrouillage de phase conventionnelles.Une solution pour ce problème a été développée pour les systèmes detransmission; elle permet simultanément un ajustement de fréquence supérieure(précision de quelques Hz à quelques kHz) à celle donnée par le processus de fabricationdes diodes lasers (précision de quelques GHz), ainsi qu’une stabilisationde fréquence et de phase. / This dissertation is related to the search for an economically sustainable solutionfor high data rate (several Gbps to several tens of Gbps) personal area networksoperating in the millimeter-wave region around 60 GHz. If such networks supplya large number of users, they need to encompass a multitude of antenna pointsin order to assure wireless access to the network. With the aim of reducing thecost of an antenna module, the networks should at best provide quasi "readyto-radiate" signals to the modules, i.e. at millimeter-wave carrier frequencies.Thanks to their low transmission loss and their high bandwidth, optical fiber distributionarchitectures represent a promising solution. The technique is referredto as the so-called "radio-over-fiber" approach whereby the analog radio signalwill be transported to the access point by an optical wave. The challenge herebyis the generation and modulation of an optical signal by a millimeter-wave radiosignal using preferably cost-efficient system components. The technique proposedherein is based on the use of mode-locked laser diodes which can generatesignals at very high frequencies under the condition of continuous current supply.Mode-locked laser diodes can be modulated both directly and externally. Thediodes employed in this work are based on so-called quantum dots (or quantumdashes); these are material structures which are themselves still subject to intensivephysical research. Signals at millimeter-wave frequencies (around 60 GHz)can easily be generated by such lasers. However, their frequency and phase stabilityis as yet limited. In the context of radio-over-fiber communication systems,these structures have not yet been studied in detail.In the course of this dissertation, several aspects are considered. A first systemstudy treats the basic properties of a system built from this type of laser source(available signal power, system noise figure, linearity etc.). A second study isdevoted to an investigation of propagation effects like dispersion, which considerablyinfluence the attainable transmission distances. An essential result of bothstudies is the importance of limiting the laser spectrum to a small number of lasermodes for an optimization of link gain, generated RF power, and system noisefigure. A third study deals with the limited frequency and phase stability whichturn out to be critical factors for transmission quality. The study of several generationsof quantum dot/dash lasers has revealed that the problems of frequencyand phase noise persist and cannot be solved using classical techniques involvinge.g. conventional phase-locked loops. In this dissertation, a solution is presentedwhich not only allows a more precise adjustment of the laser frequency (precisionin the order of Hz to kHz) than that given by the manufacturing process of thelaser (precision in the order of GHz), but also enables a stabilization of frequencyand phase. / Die vorliegende Dissertation steht im Zusammenhang mit der Suche nach wirtschaftlichtragfähigen Lösungen zum Aufbau hochdatenratiger Heimnetzwerke(einige Gbps bis einige zehn Gbps), so genannter Personal area-Netzwerke imMillimeterwellenbereich um 60 GHz. Sollen diese Netze eine große Anzahl vonNutzern versorgen, wird eine Vielzahl von Zugangspunkten - also Antennenmodulen- benötigt, um den drahtlosen Netzanschluss zu ermöglichen. Um dieKosten eines Antennenmoduls soweit wie möglich zu senken, sollen die Netzequasi "abstrahlfertige" Signale an die Module liefern, d. h. auf Trägerfrequenzenim Millimeterwellenbereich. Glasfaserbasierte Verteilsysteme werden dankihrer geringen Leitungsverluste und ihrer hohen Bandbreite diesem Anspruchgerecht. Man spricht hier vom so genannten Radio-over-fiber-Ansatz, wobei dasanaloge Signal von einer optischen Welle zum Zugangspunkt transportiert wird.Die Herausforderung liegt hierbei in der Generierung und Modulation eines optischenSignals mit einem Nutzsignal imMillimeterwellenbereich - und das unterVerwendung möglichst kostengünstiger Komponenten. Die hier vorgeschlageneTechnik basiert auf der Nutzung von modengekoppelten Laserdioden, welcheallein bei Gleichstromversorgung Signale bei hohen Frequenzen erzeugen undsowohl direkt als auch extern moduliert werden können. Die Dioden, welche hierzur Verwendung kommen, basieren auf so genannten Quantenpunkten (englisch:quantum dot/quantum dash); es sind Strukturen, die selbst noch Gegenstand intensiverphysikalischer Forschung sind. Signale bei Frequenzen um 60 GHz könnenleicht von diesen Lasern erzeugt werden, wenn auch bisher nur bei begrenzterFrequenz- und Phasenstabilität. Im Kontext von Radio-over-fiber-Systemenwurden diese Strukturen noch nicht untersucht.Im Rahmen dieser Dissertation wurden mehrere Aspekte betrachtet. Eine ersteSystemstudie behandelt die grundlegendenEigenschaften eines Systems, welchesauf dieser Art von Lasern basiert (verfügbare Leistung, Rauschzahl, Linearitätusw.). Eine zweite Untersuchung ist der Erforschung von Ausbreitungseffektenwie etwa Dispersion gewidmet, welche die erreichbaren Entfernungen maßgeblichbeeinflusst. Ein wesentliches Ergebnis beider Studien ist die Relevanzeiner Begrenzung des Laserspektrums auf wenige Moden zur Optimierung vonGewinn, Hochfrequenz-Leistung und Rauschzahl. Eine dritte Studie untersuchtdie Frequenz-und die Phasenstabilität, welche sich als kritisch für die Übertragungsqualitäterweisen. Die Untersuchung von mehreren Generationen von modengekoppeltenQuantenpunktlasern hat ergeben, dass das Problem des FrequenzundPhasenrauschens fortbesteht und nicht auf konventionellem Weg wie z.B.durch die Verwendung von klassischen Phasenregelkreisen gelöst werden kann.Im Rahmen der Arbeit wurde eine Lösung für dieses Problem gefunden, welcheerstens eine bessere Feineinstellung der Frequenz erlaubt (Genauigkeit von Hzbis kHz), als sie durch den Laserfertigungsprozess gegeben ist (Genauigkeit vonGHz), und zweitens eine Stabilisierung von Frequenz und Phase ermöglicht.

The research work reported in this thesis is focused on the chiral analysis, quantification of enantiomeric composition, assignment of absolute configuration of molecules with chosen functional groups. The weak intra-molecular hydrogen bonding interactions are detected by exploiting several multinuclear and multi-dimensional techniques. Pulse sequences have been designed to manipulate the spin dynamics to derive specific information from the complex NMR spectra encountered in diverse situations. Broadly, the thesis can be classified in to three sections. The section I containing two chapters reports the introduction of new chiral auxiliaries and protocols developed for enantiomeric discrimination, measurement of enantiomeric contents, assignment of absolute configuration for molecules possessing specific functional groups using chiral solvating and derivatizing agents. The section II, reports NMR experimental evidence for the observation of the rare type of intramolecular hydrogen bonds involving organic fluorine in biologically important organic molecules, that are corroborated by extensive DFT based theoretical calculations. The section II also discusses the H/D exchange mechanism as a tool for quantification of HB strengths in organic building blocks. The section III reports the two different novel NMR methodologies designed for deriving information on the scalar interaction strengths in an orchestrated manner. The designed sequences are able to completely eradicate the axial peaks, prevents the evolution of unwanted couplings and also yields ultrahigh resolution in the direct dimension, permitting the accurate measurement of scalar couplings for a particular spin. The brief summary about each chapter is given below. Chapter 1 provides a general introduction to one and two dimensional NMR spectroscopy. The pedagogical approach has been followed to discuss the conceptual understanding of spin physics and the NMR spectral parameters. The basic introduction to chirality, existing approaches in the literature for discrimination of enantiomers and the assignment of absolute configuration of molecules with chosen functional groups and their limitations are briefly discussed. The brief introduction to hydrogen bond, experimental methods to obtain the qualitative information about the strengths of hydrogen bonds, and the theoretical approaches employed in the thesis to corroborate the NMR experimental findings have been provided. The mechanism of H/D exchange, the utilization of exchange rates to derive strengths of intra-molecular hydrogen bond in small molecules have also been discussed. This chapter builds the bridge for the rest of the chapters. Each of these topics are discussed at length in the corresponding chapters. Part I: NMR Chiral Analysis: Novel Protocols Chapter 2 discusses a simple mix and shake method for testing the enantiopurity of primary, secondary and tertiary chiral amines and their derivatives, amino alcohols. The protocol involves the in-situ formation of chiral ammonium borate salt from a mixture of C2 symmetric chiral BINOL, trialkoxyborane and chiral amines. The proposed concept has been convincingly demonstrated for the visualization of enantiomers of a large number of chiral and pro-chiral amines and amino alcohols. The protocol also permits the precise measurement of enantiomeric composition. The significant advantage of the protocol is that it can be performed directly in the NMR tube, without any physical purification. The structure of the borate complex responsible for the enantiodifferentiation of amines has also been established by employing multinuclear NMR techniques and DFT calculations. From DOSY and 11B NMR experiments it has been ascertained that there are only two possible complexes or entities which are responsible for differentiating enantiomers. From the combined utility of DFT calculations and the 11B NMR chemical shifts, the structure of the borate complex has been determined to be an amine-coordinated complex with the N atom of the amine. Chapter 3 discusses a simple chiral derivatizing protocol involving the coupling of 2-formylphenylboronic acid and an optically pure [1,1-binaphthalene]-2,2-diamine for the rapid and accurate determination of the enantiopurity of hydroxy acids and their derivatives, possessing one or two optically active centres. It is established that this protocol is not only rapid method for discrimination of enantiomers but also highly effective for assigning the absolute configuration of various chiral hydroxy acids and their derivatives. The developed protocol involves the coupling of 2-formylphenylboronic acid with (R)-[1,1-binaphthalene]-2,2-diamine, and 2-formylphenylboronic acid with (S)-[1,1-binaphthalene]-2,2-diamine as chiral derivatizing agents. The absence of aliphatic peaks from the derivatizing agent, large chemical shift separation between the discriminated peaks of diastereomers, and the systematic change in the direction of displacement of peaks for an enantiomer in a particular diastereomeric complex, permitted the unambiguous assignment of absolute configuration. Part II : Rare Type of Intramolecular Hydrogen Bonding In chapter 4 The rare occurrence of intramolecular hydrogen bonds of the type N–H˖˖˖F–C, in the derivatives of imides and hydrazides in a low polarity solvent, is convincingly established by employing multi-dimensional and multinuclear solution state NMR experiments. The observation of 1hJFH, 2hJFN, and 2hJFF of significant strengths, where the spin polarization is transmitted through space among the interacting NMR active nuclei, provided strong and conclusive evidence for the existence of intra-molecular hydrogen bonds. Solvent induced perturbations and the variable temperature NMR experiments unambiguously supported the presence of intramolecular hydrogen bond. The two dimensional HOESY and 15N–1H HSQC experiments reveals the existence of multiple conformers in some of the investigated molecules. The 1H DOSY experimental results discarded any possibility of self or cross-dimerization of the molecules. The results of DFT based calculations, viz., Quantum Theory of Atoms In Molecules (QTAIM) and Non Covalent Interaction (NCI), are in close agreement with the NMR experimental findings. In chapter 5 the rates of hydrogen/deuterium (H/D) exchange determined by 1H NMR spectra have been utilized to derive the strength of hydrogen bonds and to monitor the electronic effects in the site-specific halogen substituted Benz amides and anilines. The theoretical fitting of the time dependent variation in the integral areas of 1H NMR resonances to the first order decay function permitted the determination of H/D exchange rate constants (k) and their precise half-lives (t1/2) with high degree of reproducibility. The comparative study also permitted the determination of relative strengths of hydrogen bonds and the contribution from electronic effects on the H/D exchange rates. Part III: Novel NMR Methodologies for the Precise Measurement of 1H-1H Couplings Chapter 6 describes two novel NMR methodologies developed for the precise measurement of 1H-1H couplings. Poor chemical shift dispersion and the pairwise interaction among the entire coupled network of protons results in the severely complex and overcrowded one dimensional 1H NMR spectra, hampering both the resonance assignments and the accurate determination of nJHH. The available two-dimensional selective refocusing (SERF) based experiments suffer from the evolution of magnetization from uncoupled protons as intense uninformative axial peaks. This creates ambiguity in the identification of peaks belonging to the coupled partners of a selectively excited proton, hindering the extraction of their interaction strengths. This challenge has been circumvented by designing two novel experimental technique, cited as “Clean-G-SERF” and “PS-Clean-G-SERF”. The Clean-G-SERF technique completely eradicates the axial peaks and suppresses the evolution of unwanted couplings while retaining only the couplings to the selectively excited proton. The method permits the accurate determination of spin-spin couplings even from a complex proton NMR spectrum in an orchestrated manner. The PS-Clean-G-SERF technique has been designed for the complete elimination of axial peaks and undesired couplings, with a blend of ultra-high resolution achieved by real time broad band mononuclear decoupling has been discussed in this chapter. The spin dynamics involved in both these pulse sequences have been discussed. The diverse applications of both these novel experiments have been demonstrated.

Abstract The past two decades have witnessed an unprecedented proliferation of mobile devices equipped with extremely innovative wireless technologies. Short range networks, such as wireless personal area networks (WPANs), wireless sensor networks (WSNs) and wireless body area networks (WBANs) have been defined and researched to deliver high speed home connectivity, environment and health monitoring. This thesis tackles design, analysis and simulation of medium access control (MAC) protocols tailored for short range networks. These have in common the use of battery operated devices but also certain design challenges connected with MAC protocols are common upon selecting the physical layer technology. Ultra wideband (UWB) technology and 60 GHz technology (which is referred to also as millimeter wave communications) are two valid examples of the wireless revolution of the past decade. Several existing standards, such as IEEE 802.15.3, ECMA-368, IEEE 802.15.4 and its amendment IEEE 802.15.4a, are considered in this thesis for MAC analysis in conjunction with UWB technology. With regard to millimeter wave communications the characteristics of the IEEE 802.15.3c standard are taken into account. Apart for the IEEE 802.15.3c all the MAC protocols have been modeled in the network simulator Opnet. One contribution of this thesis is to produce an innovative and in-depth analysis of the management aspects (e.g. ECMA-368 distributed beaconing) stemming from the above mentioned standards by means of analytical and simulation models. This study approach allows selecting the MAC features suitable for the applications and the technologies of interest. The key performance metric used to analyze all the protocols is energy efficiency, but also throughput is investigated. Another contribution brought by this thesis consists in the innovative way of studying slotted-based MAC protocols as an integrated concept connected with the type of network, the type of application and the selected physical technologies. This thesis also shows MAC performance in conjunction with UWB when false alarm, miss-detection and receiver capture (capture is modeled by means of an existing interference model) are taken into consideration. Most of the unrealistic, though common, assumptions in MAC analysis are removed and the performance of selected medical applications is evaluated through Opnet simulations. The well known binary exponential backoff is analyzed with an innovative though simplified one-dimensional Markov chain approach in the context of directional MAC for 60 GHz communications. As shown in the remainder of this thesis, the simplification introduced does not hinder the accuracy of the results, but rather allows accounting even for a finite number of retransmissions with a simple chain extension. / Tiivistelmä Kahden viime vuosikymmenen aikana innovatiivisella langattomalla tekniikalla varustettujen viestintälaiteiden määrä on kasvanut räjähdysmäisesti. Lyhyen kantaman verkkoja kuten langattomia henkilökohtaisen alueen verkkoja (WPAN), langattomia anturiverkkoja (WSN) ja langattomia vartaloalueen verkkoja (WBAN) on määritelty ja tutkittu, jotta voitaisiin tuottaa korkeanopeuksisia kotiyhteyksiä sekä välineitä ympäristön ja terveydentilan seurantaan. Tämä väitöskirja käsittelee lyhyen kantaman viestintään suunniteltujen linkinohjauskerroksen MAC-protokollien suunnittelua, analysointia ja simulointia. Näissä kaikissa käytetään akkukäyttöisiä laitteita, mutta myös tietyt MAC-protokollien suunnittelun haasteet ovat tavallisia fyysisen kerroksen teknologiaa valittaessa. Ultra-laajakaistainen (UWB) teknologia ja 60 GHz teknologia (eli millimetriaallonpituusalueen tietoliikenne) ovat hyviä esimerkkejä kuluneen vuosikymmenen langattomasta vallankumouksesta. Tässä väitöskirjassa huomioidaan UWB teknologiaan liittyvää MAC-kerroksen analyysiä tehtäessä useat olemassa olevat standardit, kuten IEEE 802.15.3, ECMA-368, IEEE 802.15.4 ja sen lisäys IEEE 802.15.4a. Millimetriaallonpituusalueen tietoliikenteessä huomioidaan myös IEEE 802.15.3c standardin erityispiirteet. IEEE 802.15.3c:tä lukuun ottamatta kaikki MAC-protokollat on mallinnettu Opnet verkkosimulaattorilla. Tämä tutkimus tarjoaa innovatiivisen ja syväluotaavan tutkimuksen näiden standardien pohjalta ja analyyttisten ja simuloitujen mallien avulla kehitetyistä hallinnallisista lähestymistavoista (esim. ECMA-368 hajautettu majakkasignaali). Näiden avulla voidaan valita kohteena oleviin sovelluksiin ja teknologioihin parhaiten soveltuvia MAC-ominaisuuksia. Kaikkien protokollien analysointiin käytetty ensisijainen suorituskykymittari on energiatehokkuus, mutta myös datanopeuksia on tarkasteltu. Tässä tutkimuksessa esitellään myös innovatiivinen tapa tutkia MAC protokollia integroituina konsepteina suhteessa verkon ja sovellusten tyyppiin sekä fyysisen kerroksen teknologiaan. Lisäksi tämä väitöskirja esittelee MAC suorituskykyä UWB verkossa silloin, kun siinä otetaan huomioon väärät hälytykset, väärä havainnointi ja vastaanottimen signaalinkaappaus (vastaanoton mallintamiseksi käytetään olemassa olevaa interferenssimallia). MAC analyysistä poistetaan useimmat epärealistiset, vaikkakin tavalliset, olettamukset, ja verkkojen suorituskykyä tarkastellaan valittujen kriittisten parametrien monitoroinnissa Opnet-simulaatioiden avulla. Tunnettua binäärijakoinen eksponentiaalinen perääntyminen -algoritmia analysoidaan innovatiivisella, yksinkertaistetulla yksiulotteisella Markov-ketju -mallilla 60 GHz:n suunta-antenni MAC:n yhteydessä. Kuten tässä tutkimuksessa tullaan osoittamaan, esitelty yksinkertaistus ei rajoita tulosten tarkkuutta, vaan mukaan voidaan lukea jopa rajallinen määrä uudelleenlähetyksiä yksinkertaisen Markovin ketjun laajennuksen avulla.

Cette thèse porte sur l’analyse et la conception de générateurs de fréquence millimétrique à faible bruit de phase destinés à des applications de communication sans fil de très haut débit sur une technologie BiCMOS 0.25m. Spécifiquement, des applications backhauling sont visées sur le protocole de communication P2P (point-to-point), pour un système de radio hétérodyne (à faible fréquence intermédiaire) approprié pour les bandes entre 30–38GHz et de faible profondeur de modulation (2-3 bits /symbole). Une étude rigoureuse du comportement du bruit de phase en 1/f2 d’un oscillateur contrôlé en tension (du type paire différentielle croisée) en fonction de la fréquence d’oscillation est développée. Des facteurs essentiels pour la conception de ces oscillateurs tels que la plage de fréquence et la charge de la paire croisée sur le résonateur sont pris en compte dans l’analyse. L’étude révèle que lorsque la fréquence augmente, l’oscillateur passe à travers deux régimes d’opération différents, ici appelés région QL-limited et région QC- limited, qui résultent de la dépendance du facteur de qualité du résonateur à sa partie inductive (pour les basses fréquences d’oscillation) et sa partie capacitive (pour les hautes fréquences d’oscillation). De plus, l’impact de la plage de fréquence sur l’évolution du bruit de phase en 1/f2 a été considéré en utilisant un circuit classique à base d’un varactor et d’un condensateur du type MiM. Des équations simples et précises ont été calculées pour les paramètres du circuit afin d’obtenir une fréquence centrale souhaitée avec la variation de la capacité requise. Pour ce circuit, il a été démontré (et vérifié à travers des simulations du circuit) que le pire scénario du facteur de qualité peut être associé à la constante de temps d’un condensateur. Ce dernier a permis d’estimer aisément le facteur de qualité minimal de la partie capacitive du résonateur LC de l’oscillateur, pour une plage de fréquence donnée, en fonction de la fréquence d’oscillation. D’une manière similaire, et basée sur une analyse à petit signal, la constante de temps de la capacité de sortie de la paire croisé a été déterminée. Notamment cette constante de temps présente un comportement constant sur une large gamme de fréquences, ce qui permet d’évaluer facilement son facteur de qualité. Cette étude fournit les bases théoriques qui permettent l’évaluation du bruit de phase en 1/f2 d’une source de signal basée sur un oscillateur en mode fondamental, super-harmonique ou sous-harmonique. En effet, la supériorité des oscillateurs sous-harmoniques est démontrée et des équations simples sont proposées pour déterminer la performance maximale et les conditions dans lesquelles elles peuvent être atteintes. Enfin, un système de génération de signal est ainsi conçu et vérifié par des mesures sur un prototype. Le système est composé d’un VCO sous-harmonique suivi d’un tripleur de fréquence (ILFT) –verrouillé par injection. Le circuit est implémenté sur une technologie SiGe:C BiCMOS 0.25 m. Le tripleur implémente une configuration à émetteur commun, polarisé en courant, qui exploite la seconde harmonique du VCO afin d’améliorer l’efficacité de la génération du signal responsable de verrouiller le ILFT. A 30.8 GHz, le système atteint un bruit de phase de -112 dBc/Hz à 1MHz d’offset. La consommation totale de courant est de 38mA pour une tension d’alimentation de 2.5V. Un deuxième prototype a été réalisé pour un système de génération multibande, offrant ainsi trois sorties RF à 18 GHz, 34GHz et 68 GHz. Avec une plage de fréquence de 10% (mesurée par rapport à la fréquence centrale) pour chaque sortie RF. Le bruit de phase mesuré à 1MHz d’offset est respectivement de -113dBc/Hz, -107dBc/Hz et -100dBc/Hz.. / This thesis deals with the analysis and design of Low phase Noise Local-Oscillator(LO) sources suitable for backhauling applications on the frequencies 30-38GHz. The LO is intended to be used in a low-IF architecture for low order modulations (2-3 bits/symbol). This work was developed in collaboration with NXP Semiconductorsat CAEN, France, within the project RF2THz of the European program CATRENE.The original contributions in this work include a rigorous study of the 1/f2 phasenoise characteristics of the VCO (bipolar cross-coupled pair Voltage-Controlled-Oscillator) with the oscillating frequency. Key factors in the design of VCOs such as tuning range and the tank load given by the cross-coupled pair are considered in the analysis. The study reveals that as the frequency scales, the VCO passes through two different zones, named the QL-limited and the QC-limited region, that results from the dependence of the resonator quality factor on its inductive part (for low oscillating frequencies) and its capacitive part (for high oscillating frequencies). Moreover, the impact of the tuning range on the 1/f2 phase noise evolution was captured by using a classical circuit based on an AC-coupled varactor and a MiM capacitor. Simple and accurate equations were derived for the circuit parameters in order to achieve a desired central frequency with the required capacitance variation. For this circuit, it is demonstrated (and verified through circuit simulations) that the lowest quality factor scenario can be associated to the time-constant of a lossy capacitor. The latter allows to estimate easily the minimum quality factor of the capacitive part of the VCO LC tank, for a given tuning range, as a function of the oscillating frequency. In a similar way, and based on a small signal analysis, the time-constant of the output capacitance of the bipolar cross-coupled pair was derived. Interesting, this time constant shows a constant behavior over a wide frequency range, thereby allowing to estimate easily its quality factor. This study set the bases for an analytical framework that enables the evaluation of the 1/f2 phase noise performances of local oscillator sources working either on fundamental,super-harmonic or sub-harmonic mode. The superiority in terms of 1/f2 phase noise of local oscillators based on sub-harmonic oscillators is thus demonstrated and simple equations are derived to determine the maximum performance and the conditions on which this can be achieved. Finally, a signal generation system intended for a low-IF point-to-point fixed radio system in the Ka-Band band is thus designed and verified through prototype measurements.The system is composed by a sub-harmonic VCO followed by an injectionlocked frequency tripler (ILFT) and it is designed in a 0.25m BiCMOS SiGe:C technology. The ILFT implements a cascode current-biased common emitter configuration that exploits the second harmonic of the VCO to enhance the efficiency in the generation of the injecting signal responsible for the ILFT locking. At 30.8GHz, the system achieves a phase noise of -112dBc/Hz at 1MHz offset. The total current consumption is 38mA for a supply voltage of 2.5V. A second prototype is designed for a multiband LO generation, providing thus three RF outputs at 18GHz, 34GHz and 68GHz. With a measured tuning range of 10% for each RF output, the measured phase noise at 1MHz is -113dBc/Hz, -107dBc/Hz and -100dBc/Hz respectively.