International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California / The architecture of the High Rate (600 Mega-bits per second) Digital Demodulator (HRDD) ASIC capable of demodulating BPSK and QPSK modulated data is presented in this paper. The advantages of all-digital processing include increased flexibility and reliability with reduced reproduction costs. Conventional serial digital processing would require high processing rates necessitating a hardware implementation other than CMOS technology such as Gallium Arsenide (GaAs) which has high cost and power requirements. It is more desirable to use CMOS technology with its lower power requirements and higher gate density. However, digital demodulation of high data rates in CMOS requires parallel algorithms to process the sampled data at a rate lower than the data rate. The parallel processing algorithms described here were developed jointly by NASA’s Goddard Space Flight Center (GSFC) and the Jet Propulsion Laboratory (JPL). The resulting all-digital receiver has the capability to demodulate BPSK, QPSK, OQPSK, and DQPSK at data rates in excess of 300 Mega-bits per second (Mbps) per channel. This paper will provide an overview of the parallel architecture and features of the HRDR ASIC. In addition, this paper will provide an overview of the implementation of the hardware architectures used to create flexibility over conventional high rate analog or hybrid receivers. This flexibility includes a wide range of data rates, modulation schemes, and operating environments. In conclusion it will be shown how this high rate digital demodulator can be used with an off-the-shelf A/D and a flexible analog front end, both of which are numerically computer controlled, to produce a very flexible, low cost high rate digital receiver.

abstract: Phase locked loops are an integral part of any electronic system that requires a clock signal and find use in a broad range of applications such as clock and data recovery circuits for high speed serial I/O and frequency synthesizers for RF transceivers and ADCs. Traditionally, PLLs have been primarily analog in nature and since the development of the charge pump PLL, they have almost exclusively been analog. Recently, however, much research has been focused on ADPLLs because of their scalability, flexibility and higher noise immunity. This research investigates some of the latest all-digital PLL architectures and discusses the qualities and tradeoffs of each. A highly flexible and scalable all-digital PLL based frequency synthesizer is implemented in 180 nm CMOS process. This implementation makes use of a binary phase detector, also commonly called a bang-bang phase detector, which has potential of use in high-speed, sub-micron processes due to the simplicity of the phase detector which can be implemented with a simple D flip flop. Due to the nonlinearity introduced by the phase detector, there are certain performance limitations. This architecture incorporates a separate frequency control loop which can alleviate some of these limitations, such as lock range and acquisition time. / Dissertation/Thesis / M.S. Electrical Engineering 2012

Das Ziel dieser Arbeit ist, die elektronischen Eigenschaften von CZTS zu verstehen. Ein leistungsfahigesWerkzeug zu diesem Zweck ist die Rontgen-Nahkanten Absorptions-Spektroskopie (XANES). Die Interpretation von XANES-Spektren komplexer Materialien ist nicht trivial und erfordert daher theoretische Modellierung. Alle Rechnungen in dieser Arbeit wurden mittels der im exciting Code implementierten Linearized-Augmented-Plane- Wave-Methode, welche alle Elektronen gleichberechtigt behandelt, durchgefuhrt. Die genaue Beschreibung der Anregungen von Kernzustanden wird durch ein zweistufiges Verfahren erreicht. Zunachst wird die elektronische Struktur berechnet, indem die Kohn-Sham-Gleichungen (KS) der Dichtefunktionaltheorie (DFT) gelost werden. Die Absorptionsspektren unter Berucksichtigung der Elektron-Loch-Wechselwirkung (e-h) werden durch die Losung der Bethe-Salpeter Gleichung (BSE) der Vielteilchen-Storungstheorie (MBPT) unter Einsatz der KS-Zustonde als Ausgangspunkt beschrieben. / The aim of this work is to understand the electronic properties of CZTS. X-ray absorption near edge structure (XANES) is a powerful tool for this purpose. Interpreting XANES of complex materials is nontrivial and thus requires theoretical modeling. Here, all the calculations are performed using an all-electron full-potential augmented plane-wave method as implemented in the exciting code. The accurate description of the core level excitations is performed by a two-step procedure. First, the electronic structure is calculated by solving the Kohn-Sham (KS) equation of density functional theory (DFT). The absorption spectra including electron-hole (e-h) is described by the solution of the Bethe-Salpeter equation (BSE) of many-body perturbation theory (MBPT) using the KS states as starting point.

An investigation of electrochemical storage device materials has been undertaken in four parts. The bulk and interfacial resistance of Na+ beta-alumina tubes were separated using a galvanostatic charge-discharge method. Sodium silicide was characterized to better understand its synthesis. BiMn2O5 was produced using a sol-gel method and tested for pseudocapacity. Different lithium ion anode and cathode materials were deposited using a new electrophoretic deposition method. A novel galvanostatic charge-discharge method was developed for the determination of bulk and interface resistance in Na+ beta-alumina solid electrolytes [BASE]. Dense and duplex BASE tubes were tested by varying the exposed surface area. The results of dense BASE tube pairs were used to determine the bulk and interfacial resistance components, while duplex BASE tubes were tested to determine the reduction in interfacial resistance. It was found that duplex tubes had reduced the interfacial resistance by 75%, when compared to a uniformly dense electrolyte. Sodium silicide was characterized using various methods to better understand the phase and the Na-Si phase diagram. EMF experiments using Na+ BASE tubes was used to determine the activity in the silicon rich region of the phase diagram, which showed a sodium activity of 0.5 at 550°C. TGA/DSC was used to determine phase transformation temperatures, as well as the heat of formation for NaSi, which was recorded to be below 1 kJ mol-1. A sol-gel precipitation method was used to produce fine BiMn2O5 powders used for supercapacitors. The powders resulting from a consistent method were tested for pseudocapacitance using bulk and thin film electrodes. Bulk electrodes had a gravimetric capacitance of 10 F g-1, while thin film electrodes only reached 2.6 F g-1. Lithium ion battery anode (Li4Ti5O12) and cathode (LiFePO4, LiMn2O4, LiMn1.5Ni0.5O4) materials were electrophoretically deposited with the assistance of PAZO-Na and CMC-Na. Cathodes were successfully deposited on aluminium substrates, and were tested in the potential window 2 – 4.3 V. The LiFePO4 cathodes showed capacity of 146.7 mAh g-1 at C/10, while showing capacity retention of 103% after 50 cycles. / Thesis / Doctor of Philosophy (PhD) / The goal of this work is to examine materials used in different types of electrochemical storage devices. The modification of resistive properties of β-alumina electrolytes are examined for use in high temperature sodium batteries. Electrophoretic deposition methods are used to rapidly make thin electrodes for lithium ion batteries and supercapacitors. The stoichiometric compound NaSi, a potentially safer and greener method of producing hydrogen gas, is characterized for a better understanding of its properties, and therefore production.

The system diagrams for the digital radio compatible with NASA's S-Band Space Network operating from 2025.8 - 2117.9 MHz (forward link) to 2200 - 2300 MHz (return link) are presented. The digital radio implementation includes binary phase shift keying (BPSK), quadrature phase shift keying (QPSK) and staggered quadrature phase shift keying (SQPSK). We have derived the system requirements for these modulation schemes from the Space Network User Guide (SNUG) and thereafter, derived system diagrams for the communication links. The designed system diagrams for the transceiver were implemented using Simulink models and USRP2 platform.

Des applications comme les contre-mesures optiques nécessitent des sources puissantes et avec une bonne qualité de faisceau dans le moyen infrarouge. Le laser à cascade quantique (LCQ) est une solution prometteuse mais la puissance fournie par ces lasers n’est pas suffisante. La combinaison cohérente de plusieurs de ces sources devrait permettre de sommer leurs puissances tout en conservant la qualité de faisceau d’un émetteur unique et constitue donc une solution intéressante pour contourner l’actuelle limitation en puissance des LCQ.Nous présentons une étude théorique et expérimentale de la combinaison de faisceaux cohérente de LCQ dans une cavité externe commune utilisant un coupleur de faisceaux. La mise en phase est ici totalement passive puisque fondée sur la minimisation des pertes dans la cavité globale : on parle d’auto-organisation. Un modèle général permettant de quantifier l’efficacité de combinaison et la stabilité de telles cavités est développé. Dans un premier temps, on montre expérimentalement que la combinaison cohérente de deux LCQ dans une cavité Michelson est une solution efficace et stable. Pour combiner plus d’émetteurs il est nécessaire de concevoir des coupleurs de faisceaux dans le moyen infrarouge efficaces. Pour cela, nous avons étudié deux types de réseaux : les réseaux de phase binaire (réseaux de Dammann) et des structures à gradient d’indice composées de motifs sub-longueur d’onde. Le dessin et l’optimisation de telles structures fait appel à la théorie des milieux artificiels et nécessite l’utilisation d’un code de résolution rigoureuse des équations de Maxwell (RCWA). Enfin, la combinaison cohérente de cinq LCQ en cavité externe avec un coupleur de faisceaux est démontrée expérimentalement et la combinaison d’un plus grand nombre de LCQ est discutée. En conclusion, nous présentons une solution originale pour réaliser la combinaison cohérente passive de LCQ et ainsi apporter une solution à l’augmentation de puissance dans le moyen infrarouge. / Powerful sources in the mid-infrared with a good beam quality are highly needed for applications such as optical countermeasures. The quantum cascade laser (QCL) is a promising solution but the maximum power achievable is not sufficient. The coherent beam combining of several QCL could lead to higher output power in the same beam and thus is an interesting solution to circumvent the current power limitation of these sources.We present a theoretical and experimental study of the coherent beam combining of QCL in a common external cavity with a beam combiner. The phase locking is totally passive since it is only based on loss minimization in the external cavity: it is a self-organization process. A general model is developed to quantify the combining efficiency and the stability that can be obtained from this method. Experimentally, the coherent combining of two QCL in a Michelson cavity is studied first and demonstrated to be efficient and stable. In order to combine more emitters, an efficient beam combiner must be designed in the mid-infrared. For that purpose, two type of gratings, a classical binary phase grating (or Dammann grating) and a more complex gradient-index structure made of local sub-wavelength patterns are designed and compared. The calculation and optimization of this sub-wavelength structure is based on the artificial media theory and is achieved with rigorous coupled wave analysis (RCWA). Finally, the coherent combining of five QCL in an external cavity with a binary phase grating is demonstrated and the scalability to the combining of more emitters is discussed. In conclusion, we present an original solution to combine coherently several QCL and thus address the power scaling issue in the mid-infrared.

Die vorliegende Arbeit liefert einen Beitrag zum Verständnis der komplexen Wechselwirkungen zwischen Nanopartikeln und Polymeren in dünnen Schichtsystemen. Dazu wurden in einem geeignetem Modellsystem drei verschiedene Einflussparameter auf die Nanopartikelverteilung im Polymer und zwischen einer hydrophilen und einer hydrophoben Grenzfläche analysiert. Für eine erste Abschätzung der Verträglichkeit der einzelnen Komponenten wurden Wechselwirkungsparameter, binäre und ternäre Phasendiagramme ermittelt. Die experimentelle Charakterisierung der Nanopartikelverteilung erfolgte mittels Rasterkraftmikroskopie, Rasterelektronenmikroskopie und Transmissionselektronenmikroskopie. Die erhaltenen Ergebnisse wurden mit denen der theoretischen Vorbetrachtungen verglichen um herauszufinden, ob Vorhersagen zur Nanopartikelverteilung in einem Polymer möglich sind. In dieser Arbeit konnte gezeigt werden, dass die Nanopartikelverteilung im Polymer mit den untersuchten Parametern gezielt beeinflusst werden kann.

Die vorliegende Arbeit liefert einen Beitrag zum Verständnis der komplexen Wechselwirkungen zwischen Nanopartikeln und Polymeren in dünnen Schichtsystemen. Dazu wurden in einem geeignetem Modellsystem drei verschiedene Einflussparameter auf die Nanopartikelverteilung im Polymer und zwischen einer hydrophilen und einer hydrophoben Grenzfläche analysiert. Für eine erste Abschätzung der Verträglichkeit der einzelnen Komponenten wurden Wechselwirkungsparameter, binäre und ternäre Phasendiagramme ermittelt. Die experimentelle Charakterisierung der Nanopartikelverteilung erfolgte mittels Rasterkraftmikroskopie, Rasterelektronenmikroskopie und Transmissionselektronenmikroskopie. Die erhaltenen Ergebnisse wurden mit denen der theoretischen Vorbetrachtungen verglichen um herauszufinden, ob Vorhersagen zur Nanopartikelverteilung in einem Polymer möglich sind. In dieser Arbeit konnte gezeigt werden, dass die Nanopartikelverteilung im Polymer mit den untersuchten Parametern gezielt beeinflusst werden kann.

This thesis deals with optical synthesis of unmodulated and modulated microwave signals. Generation of microwave signals based on optical heterodyning is discussed in detail. The effect of phase noise of laser on heterodyned output has been studied for different phase noise profiles. Towards this, we propose a generic algorithm to numerically model the linewidth broadening of a laser due to phase noise. Generation of microwave signals is demonstrated practically by conducting an optical heterodyning experiment. Signals ranging in frequency from 12.5 MHz to 27 GHz have been generated. Limitations of optical heterodyning based approach in terms of phase noise performance and frequency stability are discussed and practically demonstrated. A hardware-efficient Optical Phase Locked Loop (OPLL) is proposed to overcome these issues. Phase noise tracking performance of the proposed OPLL has been experimentally demonstrated. Phase noise values as low as -105 dBc/Hz at 10 KHz offset have been achieved. Optical modulators, owing to their extremely low electro-optic response time, can support high frequency modulating signals. This makes them highly attractive in comparison to their microwave counterparts. In this thesis, we propose techniques to generate microwave signals modulated at very high bit rates by down-converting the corresponding modulated optical signals to microwave domain. Down-conversion required for this process is achieved by optical heterodyning. The proposed concept has been theoretically analyzed, simulated and experimentally validated. Amplitude Modulated and ASK modulated microwave signals have been generated as Proof-of-Concept. Limitations posed by OPLL in generation of angle modulated microwave signals by optical heterodyning have been brought out. Schemes overcoming these limitations have been proposed towards generation of BPSK and QPSK modulated microwave signals. Integrated Optics (IO) technology has been studied as a means of implementation of the proposed concepts. IO components like Sinusoidal bends, Y-branch splitters and Electro-Optic-Modulators (EOMs) have been designed towards optical synthesis of modulated microwave signals. Propagation of modulated optical signal through these IO components has also been studied. An all-optic scheme based on Optical Beam Forming is proposed for transmission of QPSK modulated signal. Limitation of phase-shifting based approach, in terms of beam-squint, has been brought out. True-Time-Delay based approach has been proposed for applications demanding wide instantaneous bandwidth to avoid beam-squint. Algorithms / numerical methods required for analyses and simulations associated with the above-mentioned tasks have been evolved. This study is envisaged to provide useful insight into the realization of high-speed, compact, light-weight data transmitting systems based on Integrated Optics for future onboard spacecraft applications. This work, we believe, is a step towards realization of an Integrated Optic System-on-Chip solution for specific microwave data transmission applications.

Le contexte environnemental (réchauffement climatique) et économique (épuisement des ressources en énergies fossiles) entraîne une nécessaire mutation du paysage énergétique mondial. L’hydrogène est présenté comme un vecteur d’énergie propre pouvant, par l’intermédiaire d’une pile à combustible, fournir de l’électricité pour diverses applications (nomade, portable, automobile et stationnaire). Cependant, son développement reste tributaire de son mode de stockage. Parmi les composés présentant de bonnes capacités de stockage, le borohydrure de sodium NaBH4 se distingue puisqu’il permet aussi un dégagement contrôlé de l’hydrogène d’après la réaction d’hydrolyse suivante : ( ) (2 ) ( ) ( ) 4 ( ) 4 2 2 2 2 NaBH ++ x H O l→NaBO . xH O + H g Il constitue ainsi une solution sûre et facile d’utilisation, et est donc envisageable pour des applications grand public. La thèse avait pour objectif l’approfondissement des connaissances relatives à la réaction catalysée d’hydrolyse du borohydrure de sodium selon deux axes principaux: la catalyse de la réaction et l’étude des produits d’hydrolyse. Concernant le premier axe, notre objectif était de mieux comprendre et d’améliorer la cinétique de la réaction d’hydrolyse, les catalyseurs étudiés étant à base de cobalt. Un catalyseur « modèle » a été utilisé et comparé à des nanoparticules métalliques synthétisées et d’autres espèces chimiques à base de cobalt (oxyde, hydroxyle et carbonate). Le modèle cinétique de Langmuir-Hinshelwood a permis de décrire la cinétique de l’hydrolyse. Un mécanisme réactionnel basé sur les adsorptions en surface du catalyseur de BH4 - et de H2O a été proposé. Enfin, la nature des sites actifs en surface a été discutée. En ce qui concerne le second axe de la thèse, nous avions deux objectifs : identifier les phases formées en fonction des conditions expérimentales et approfondir les connaissances thermodynamiques du système binaire NaBO2-H2O pour définir les différents équilibres se formant à l’issu de la réaction d’hydrolyse. Pour ce faire, les borates ont d’abord été synthétisés, puis caractérisés en termes de structure cristallographique et de stabilité en température. C’est ainsi qu’un nouveau borate de sodium, Na3[B3O4(OH)4] ou NaBO2•2/3H2O, a été obtenu. D’autre part, l’étude des équilibres liquide+solide, solide+solide et liquide+vapeur nous a permis d’établir le diagramme binaire NaBO2-H2O à pression atmosphérique. / As an alternative solution to fossil fuels, hydrogen is may be the most advanced technology. However, its large scale development is today harshly hindered by the issues it encounters, its storage being certainly the most significant. Various storage methods are under investigation but solid storage as in sodium borohydride NaBH4 appears to be convenient with regard to its storage capacities, safety and cost. The hydrogen stored in NaBH4 can be released by hydrolysis at ambient temperature. The hydrolysis reaction leads to the formation of 4 hydrogen molecules and borates: ( ) (2 ) ( ) ( ) 4 ( ) 4 2 2 2 2 NaBH ++ x H O l → NaBO . xH O + H gThe efficiency of this reaction suffers from two problems. First, slow kinetics of hydrogen release is observed for this reaction. Second, the “hydration” of NaBO2 is detrimental to the storage capacities of the system NaBH4-H2O. Indeed, the higher the pseudo-hydration degree (i.e. x), the lower the gravimetric hydrogen storage capacity. Both issues are the topics we have studied in the present work. Hydrogen release can be accelerated by using a cobalt catalyst. Hence, we focused on various cobalt-based catalysts. A reference catalyst was first chosen, and then tested and compared to lab-prepared cobalt nanoparticles and other cobalt-based materials (oxide, hydroxide and carbonate). The Langmuir-Hinshelwood kinetic model well captured the kinetics of the hydrolysis reaction. Accordingly, a reaction mechanism based on the adsorptions of both BH4 - and H2O on the catalyst surface has been proposed. The adsorptions are expected to occur on specific surface sites which nature has been discussed. The gravimetric hydrogen storage capacity of NaBH4-H2O can be increased by decreasing the pseudo-hydration degree (i.e. x) of the borates. However, this implies that the thermodynamics of the NaBO2•xH2O compounds are well known as they are crucial for favouring the formation of water-free borates. Borates were then synthesized and characterized in terms of crystallographic structure, pseudo-hydration degree and thermal stability. In this context, a new sodium borate has been synthesized: Na3[B3O4(OH)4] or NaBO2•2/3H2O. Besides, we studied the liquid+solid, liquid+vapor and solid+solid equilibria that permitted to set the binary phase diagram NaBO2-H2O at atmospheric pressure