Radiation chemistry is concerned with understanding the chemical kinetics following the application of ionising radiation. There are two main methods for modelling recom- bination and spin dynamics in radiation chemical systems: The Monte Carlo random flights algorithm, in which the trajectories of the diffusing species are followed ex- plicitly and the Independent Reaction Times (IRT) algorithm, where reaction times are sampled from appropriate marginal distribution functions. This thesis reports develop- ments to both methods, and applies them to better understand experimental findings, particularly spin relaxation effects. Chapter 4 introduces current simulation techniques and presents newly developed algorithms and simulation programs (namely Hybrid and Slice) for modelling spatially dependent spin effects. A new analytical approximation for accurately treating ion-pair recombination in low-permittivity solvents in also presented in this chapter. Chapter 5 explores the photodissociation of H₂O₂, where there is some controversy in the literature on the spin state of the precursor. This chapter explores the possibility of reproducing the observed spin polarisation phase using the Radical Pair Mechanism. Chapter 6 presents two new algorithms for treating reactive products in the IRT framework. These have been tested for two chemical systems: (i) photodissociation of H₂O₂ where the ·OH are scavengeable; (ii) water photolysis which produces H⁺, ·OH and e⁻__aq. In the latter case a careful handling of three body correlations is required. Chapter 7 presents simulation results which suggest a strong correlation between scavenging and ion recombination in low permittivity solvents. A path decomposition method has been devised that allows IRT simulations to be corrected for this effect. Chapter 8 presents evidence for spin-entanglement and cross-recombination to act as an extra source of relaxation for ion-recombination in low permittivity solvents. It is hypothesised this effect contributes to the anomalous relaxation times observed for certain cyclic hydrocarbons. Chapter 9 presents an extension of the IRT simulation method to micelles. The kinetics are shown to be accurately described using the mean reaction time and the exponential approximation.

Västergarn is one of the smallest parishes on the island of Gotland. It’s a place of rich history and has been subject to numerous excavations throughout the years. The University of Gotland has conducted seminar excavations at Västergarn between the years of 2005-2012. During these excavations a lot of horse related finds have been found. By studying these finds archaeologist can learn a lot about the horses and the people who once lived in Västergarn. The purpose of this paper is to shed some light on the urban and rural horse in Västergarn. How big were the horses? Were the horses used for riding or farming? What can the finds tell us about the people who lived in Västergarn and their view on horse handling?

O propósito deste estudo clínico, prospectivo e randomizado foi comparar cefalometricamente as alterações dentoalveolares e esqueléticas decorrentes do tratamento da mordida aberta anterior, utilizando o aparelho esporão colado associado à mentoneira, durante um período de 12 meses. As amostras foram constituídas de 30 pacientes cada, sendo um grupo controle, com idade média inicial de 8,36 anos e um grupo experimental, com idade média inicial de 8,14 anos, de ambos os gêneros, leucodermas, em fase da dentadura mista, com incisivos e molares permanentes totalmente irrompidos, relação molar de Classe I de Angle e overbite negativo de pelo menos 1 mm. O período de avaliação foi de 1 ano e correspondeu ao intervalo entre a obtenção das telerradiografias inicial e final. O grupo controle não foi submetido a tratamento. A terapêutica empregada no grupo experimental compreendeu o uso do aparelho esporão lingual , colado na face lingual dos incisivos centrais superiores e inferiores, associado à mentoneira, usada durante o período noturno, com uma força de 450 a 500g por lado, direcionada a 45º acima do plano oclusal. Para a comparação entre os grupos utilizou-se o teste t não pareado, a um nível de significância de 5%. Os resultados permitiram concluir que o aparelho esporão colado associado à mentoneira proporcionou alterações dentoalveolares e esqueléticas (Ar.GoMe) estatisticamente significantes. O grupo experimental apresentou uma lingualização e extrusão dos incisivos superiores e apenas extrusão dos incisivos inferiores quando comparado ao grupo controle. O fechamento médio do overbite foi de 5,23 mm para o grupo experimental, enquanto que para o grupo controle foi de 1,98mm. O grupo experimental apresentou um fechamento do ângulo goníaco com significância estatística, quando comparado ao grupo controle. Concluiu-se que o protocolo de tratamento empregado proporcionou alterações dentoalveolares na região anterior dos arcos dentários, que foram responsáveis pelo fechamento da mordida aberta anterior na fase da dentadura mista, e alterações esqueléticas, devido ao fechamento do ângulo goníco. / The aim of this prospective clinical study was to cephalometrically investigate the dentoalveolar and skeletal changes produced by a bonded spurs appliance with high-pull chincup therapy in children with anterior open-bite malocclusions, for a period of 12 months. The samples comprising 30 white patients each, of both genders, in mixed dentition phase, with permanent incisors and first molars completely erupted, presenting a Class I malocclusion with anterior open bite. The control group had an initial mean age of 8.36 years, while the experimental group had an average of 8.14 years old. The evaluation period comprised the interval of 1 year between the initial and final lateral cephalometric radiographs. The control group was not submitted to any type of orthodontic treatment. The experimental group used bonded spurs appliance associated with high-pull chincup therapy, with a force level of 450 to 500 g per side, passing 45º above the oclusal plane. Comparison between groups was conducted by the unpaired t test. The results allowed the conclusion that the bonded spurs appliance associated to high-pull chincup therapy provided significant dentoalveolar and skeletal alterations in the experimental group when compared to a control group. The maxillary and mandibular incisors extruded and lingually tipped and the madibular incisors extruded only. The mean closure of the anterior open bite was 5.23 mm for the experimental group and 1.98mm for the control group. The experimental group demonstrated a decrease of the gonial angle when compared to the control group. Based on the results of this study, the association of high-pull chincup therapy with bonded spurs appliance provided dentoalveolar changes at the anterior region of the dental arches that were responsible for closure of the anterior open bite in patients treated in the mixed dentition and a decrease of the gonial angle.

With the advances in wireless communication technology over last two decades, the use of fractional-N frequency synthesizers has increased widely in modern wireless communication applications due to their high frequency resolution and fast settling time. The performance of a fractional-N frequency synthesizer is degraded due to the presence of unwanted spurious tones (spurs) in the output spectrum. The Digital Delta-Sigma Modulator can be directly responsible for the generation of spur because of its inherent nonlinearity and periodicity. Many deterministic and stochastic techniques associated with the architecture of the DDSM have been developed to remove the principal causes responsible for production of spurs. The nonlinearities in a frequency synthesizer are another source for the generation of spurs. In this thesis we have predicted that specific nonlinearities in a fractional-N frequency synthesizer produce spurs at well-defined frequencies even if the output of the DDSM is spur-free. Different spur free DDSM architectures have been investigated for the analysis of spurious tones in the output spectrum of fractional-N frequencysynthesizers. The thesis presents simulation and experimental investigation of mechanisms for spur generation in a fractional-N frequency synthesizer. Simulations are carried out using the CppSim system simulator, MATLAB and Simulink while the experiments are performed on an Analog Devices ADF7021, a high performance narrow-band transceiver IC.

Aurimas Bieliauskas, Nemuno vagos reguliavimas būnomis: magistro tezės/ mokslinis vadovas doc. Arvydas Šikšnys. Darbo apimtis: 50 psl., 1 lentelė, 21 paveikslas, 7 priedai. Šiame darbe nagrinėjamas 3 km ilgio Nemuno vandens kelio ruožas ties Leitės žiotimis ir tiriami įvairūs upės vagos reguliavimo variantai. Skaitmeniniuose hidrodinamikos modeliuose buvo tiriamas vagos reguliavimo poveikis upės hidrauliniam režimui esant įvairioms hidrologinėms sąlygoms. Išnagrinėtas vagos reguliavimas būnomis, kurių pagrindinė paskirtis - sumažinti vandens tėkmės greičius prie kranto linijos ir apsaugoti upės krantus nuo vandens erozijos, o laivakelio zonoje - padidinti tėkmės greičius ir sumažinti čia nusėdančių nešmenų kiekius. Pasirinktas Nemuno ruožas ties Leitės žiotimis pasižymi sudėtingomis vaginių procesų sąlygomis. Tai be įprastinių, daugybės antropogeninių veiksnių formuojamas ruožas. Kita vertus, tai labai svarbus ruožas kraštovaizdžio – gamtosaugos, rekreacijos, kultūros, ekonomikos ir kitais požiūriais. Darbo tikslas – išanalizuoti ir įvertinti Nemuno vagos reguliavimo būnomis įvairiais variantais poveikį upės hidrauliniam-hidrologiniam režimui. Modeliavimui buvo panaudota programa MIKE 21, buvo išanalizuoti 3 skirtingi vagos reguliavimo variantai, nustatyta būnų įtaka upės hidraulinėms charakteristikoms, apskaičiuoti darbų kiekiai. / Aurimas Bieliauskas. The riverbed regulation with spurs of the river Nemunas: master theses/ scientific guide doc. Arvydas Šikšnys. The amount of work: 50 pages, 1 tables, 21 pictures, 5 supplements. In this work is analyzed the modeling of riverbed of the Nemunas 3 km length the Nemunas beside the mouth of the Leitė river mouth. In the numerical hydrodynamic models there were searching effects of the river bed regulation of the river hydraulic regime in various conditions. In the analytical part there is analyzed the process of the riverbed regulation which the main purpose there is the reduction of the water velocity near banks and conservation of the banks from the water erosion. Another purpose there is the regulation of the water velocity in the waterway zone and reduction in the silt there. This is typical, without odd, the strip formed with many anthropogenic factors. In other way, this is very essential strip of landscape – ecology, recreation, cultural, economical and in other aspects, wherefore this research of channel section of the Nemunas river has undoubted scientific and practical substantiality. The aim of this work is to analyzing and estimation of the waterway regulation in numerous aspects and influence on the river hydraulic- hydrologic regime. The modeling had been made with program MIKE 21 and had analyzed free different variants of the river bed. While doing analysis there was found the influence of the river hydraulic characteristics and there was... [to full text]

O propósito deste estudo clínico, prospectivo e randomizado foi comparar cefalometricamente as alterações dentoalveolares e esqueléticas decorrentes do tratamento da mordida aberta anterior, utilizando o aparelho esporão colado associado à mentoneira, durante um período de 12 meses. As amostras foram constituídas de 30 pacientes cada, sendo um grupo controle, com idade média inicial de 8,36 anos e um grupo experimental, com idade média inicial de 8,14 anos, de ambos os gêneros, leucodermas, em fase da dentadura mista, com incisivos e molares permanentes totalmente irrompidos, relação molar de Classe I de Angle e overbite negativo de pelo menos 1 mm. O período de avaliação foi de 1 ano e correspondeu ao intervalo entre a obtenção das telerradiografias inicial e final. O grupo controle não foi submetido a tratamento. A terapêutica empregada no grupo experimental compreendeu o uso do aparelho esporão lingual , colado na face lingual dos incisivos centrais superiores e inferiores, associado à mentoneira, usada durante o período noturno, com uma força de 450 a 500g por lado, direcionada a 45º acima do plano oclusal. Para a comparação entre os grupos utilizou-se o teste t não pareado, a um nível de significância de 5%. Os resultados permitiram concluir que o aparelho esporão colado associado à mentoneira proporcionou alterações dentoalveolares e esqueléticas (Ar.GoMe) estatisticamente significantes. O grupo experimental apresentou uma lingualização e extrusão dos incisivos superiores e apenas extrusão dos incisivos inferiores quando comparado ao grupo controle. O fechamento médio do overbite foi de 5,23 mm para o grupo experimental, enquanto que para o grupo controle foi de 1,98mm. O grupo experimental apresentou um fechamento do ângulo goníaco com significância estatística, quando comparado ao grupo controle. Concluiu-se que o protocolo de tratamento empregado proporcionou alterações dentoalveolares na região anterior dos arcos dentários, que foram responsáveis pelo fechamento da mordida aberta anterior na fase da dentadura mista, e alterações esqueléticas, devido ao fechamento do ângulo goníco. / The aim of this prospective clinical study was to cephalometrically investigate the dentoalveolar and skeletal changes produced by a bonded spurs appliance with high-pull chincup therapy in children with anterior open-bite malocclusions, for a period of 12 months. The samples comprising 30 white patients each, of both genders, in mixed dentition phase, with permanent incisors and first molars completely erupted, presenting a Class I malocclusion with anterior open bite. The control group had an initial mean age of 8.36 years, while the experimental group had an average of 8.14 years old. The evaluation period comprised the interval of 1 year between the initial and final lateral cephalometric radiographs. The control group was not submitted to any type of orthodontic treatment. The experimental group used bonded spurs appliance associated with high-pull chincup therapy, with a force level of 450 to 500 g per side, passing 45º above the oclusal plane. Comparison between groups was conducted by the unpaired t test. The results allowed the conclusion that the bonded spurs appliance associated to high-pull chincup therapy provided significant dentoalveolar and skeletal alterations in the experimental group when compared to a control group. The maxillary and mandibular incisors extruded and lingually tipped and the madibular incisors extruded only. The mean closure of the anterior open bite was 5.23 mm for the experimental group and 1.98mm for the control group. The experimental group demonstrated a decrease of the gonial angle when compared to the control group. Based on the results of this study, the association of high-pull chincup therapy with bonded spurs appliance provided dentoalveolar changes at the anterior region of the dental arches that were responsible for closure of the anterior open bite in patients treated in the mixed dentition and a decrease of the gonial angle.

Les émetteurs-récepteurs actuels tendent à devenir multi-standards c’est-àdireque plusieurs standards de communication peuvent cohabiter sur la même puce. Lespuces sont donc amenées à traiter des signaux de formes très différentes, et les composantsanalogiques subissent des contraintes de conception de plus en plus fortes associées au supportdes différentes normes. Les auto-interférences, c’est à dire les interférences généréespar le système lui-même, sont donc de plus en plus présentes, et de plus en plus problématiquesdans les architectures actuelles. Ces travaux s’inscrivent dans le paradigmede la « radio sale » qui consiste à accepter une pollution partielle du signal d’intérêtet à réaliser, par l’intermédiaire d’algorithmes, une atténuation de l’impact de ces pollutionsauto-générées. Dans ce manuscrit, on s’intéresse à différentes auto-interférences(phénomène de "spurs", de "Tx leakage", ...) dont on étudie les modèles numériques etpour lesquelles nous proposons des stratégies de compensation. Les algorithmes proposéssont des algorithmes de traitement du signal adaptatif qui peuvent être vus comme des« algorithmes de soustraction de bruit » basés sur des références plus ou moins précises.Nous dérivons analytiquement les performances transitionnelles et asymptotiques théoriquesdes algorithmes proposés. On se propose également d’ajouter à nos systèmes unesur-couche originale qui permet d’accélérer la convergence, tout en maintenant des performancesasymptotiques prédictibles et paramétrables. Nous validons enfin notre approchesur une puce dédiée aux communications cellulaires ainsi que sur une plateforme de radiologicielle. / Radio frequency transceivers are now massively multi-standards, which meansthat several communication standards can cohabit in the same environment. As a consequence,analog components have to face critical design constraints to match the differentstandards requirements and self-interferences that are directly introduced by the architectureitself are more and more present and detrimental. This work exploits the dirty RFparadigm : we accept the signal to be polluted by self-interferences and we develop digitalsignal processing algorithms to mitigate those aforementioned pollutions and improve signalquality. We study here different self-interferences and propose baseband models anddigital adaptive algorithms for which we derive closed form formulae of both transientand asymptotic performance. We also propose an original adaptive step-size overlay toimprove transient performance of our method. We finally validate our approach on a systemon chip dedicated to cellular communications and on a software defined radio.

Les émetteurs-récepteurs actuels tendent à devenir multi-standards c’est-àdireque plusieurs standards de communication peuvent cohabiter sur la même puce. Lespuces sont donc amenées à traiter des signaux de formes très différentes, et les composantsanalogiques subissent des contraintes de conception de plus en plus fortes associées au supportdes différentes normes. Les auto-interférences, c’est à dire les interférences généréespar le système lui-même, sont donc de plus en plus présentes, et de plus en plus problématiquesdans les architectures actuelles. Ces travaux s’inscrivent dans le paradigmede la « radio sale » qui consiste à accepter une pollution partielle du signal d’intérêtet à réaliser, par l’intermédiaire d’algorithmes, une atténuation de l’impact de ces pollutionsauto-générées. Dans ce manuscrit, on s’intéresse à différentes auto-interférences(phénomène de "spurs", de "Tx leakage", ...) dont on étudie les modèles numériques etpour lesquelles nous proposons des stratégies de compensation. Les algorithmes proposéssont des algorithmes de traitement du signal adaptatif qui peuvent être vus comme des« algorithmes de soustraction de bruit » basés sur des références plus ou moins précises.Nous dérivons analytiquement les performances transitionnelles et asymptotiques théoriquesdes algorithmes proposés. On se propose également d’ajouter à nos systèmes unesur-couche originale qui permet d’accélérer la convergence, tout en maintenant des performancesasymptotiques prédictibles et paramétrables. Nous validons enfin notre approchesur une puce dédiée aux communications cellulaires ainsi que sur une plateforme de radiologicielle. / Radio frequency transceivers are now massively multi-standards, which meansthat several communication standards can cohabit in the same environment. As a consequence,analog components have to face critical design constraints to match the differentstandards requirements and self-interferences that are directly introduced by the architectureitself are more and more present and detrimental. This work exploits the dirty RFparadigm : we accept the signal to be polluted by self-interferences and we develop digitalsignal processing algorithms to mitigate those aforementioned pollutions and improve signalquality. We study here different self-interferences and propose baseband models anddigital adaptive algorithms for which we derive closed form formulae of both transientand asymptotic performance. We also propose an original adaptive step-size overlay toimprove transient performance of our method. We finally validate our approach on a systemon chip dedicated to cellular communications and on a software defined radio.

Η πληθώρα των εφαρμογών που μπορεί να εξυπηρετήσει η τεχνολογία Υπερευρείας Ζώνης (UWB), από τα ασύρματα προσωπικά δίκτυα υψηλών ταχυτήτων, μέχρι τα ασύρματα δίκτυα αισθητήρων με δυνατότητες ακριβούς εντοπισμού θέσης, και τα ασύρματα δίκτυα ιατρικών αισθητήρων, έχει προκαλέσει έντονο ερευνητικό ενδιαφέρον γύρω από τις υλοποιήσεις UWB συστημάτων. Η ασυνήθιστα μεγάλη περιοχή συχνοτήτων που έχει ανατεθεί στο UWB, από τα 3.1-10.6 GHz, επιτρέπει την επίτευξη υψηλών ταχυτήτων με απλά σχήματα διαμόρφωσης, ωστόσο, λόγω της διαμοίρασης του φάσματος με τις υφιστάμενες τεχνολογίες ασύρματης δικτύωσης, οι UWB εκπομπές πρέπει να περιορίζονται σε ισχύ κάτω από το κατώφλι των -41.3 dBm/MHz, ικανοποιώντας πολύ αυστηρές μάσκες εκπομπής που εισάγουν έντονες προκλήσεις στη σχεδίαση των πομπών. Η υλοποίηση αναδιατάξιμων UWB πομπών σε σύγχρονες CMOS τεχνολογίες, με υψηλή φασματική ευελιξία, ταχύτητα και ποιότητα διαμόρφωσης, καθώς και με χαμηλή κατανάλωση, αποτέλεσε το αντικείμενο της συγκεκριμένης διατριβής. Υιοθετώντας την αρχιτεκτονική Multi-Band Impulse-Radio (MB-IR) σε συνδυασμό με την τεχνική Direct Sequence BPSK, η έρευνα προσανατολίστηκε προς την ανάπτυξη καινοτόμων μονάδων βασικής ζώνης, με στόχο την ενεργειακά αποδοτική αντιστροφή Γκαουσιανών μορφοποιημένων παλμών υψηλής ποιότητας φάσματος και διάρκειας μικρότερης ακόμα και από 1 nsec. Προς αυτή την κατεύθυνση, αναπτύχθηκε μια καινοτόμα γεννήτρια Γκαουσιανών παλμών με πολύ χαμηλούς πλευρικούς λοβούς στο φάσμα, τυπικά κάτω από -40 dB, ώστε να υποστηρίζονται οι αυστηρότερες μάσκες εκπομπής ή και μελλοντικές. Η σχεδίασης της προτεινόμενης γεννήτριας είχε ως κριτήριο την ευέλικτη ρύθμιση της διάρκειας των παραγόμενων παλμών, και αξιοποίησε τη χαρακτηριστική μεταφοράς τάσης ενός ωμικά φορτωμένου, ασύμμετρου CMOS αντιστροφέα. Η γεννήτρια βασίζεται κυρίως σε ψηφιακά κυκλώματα πολύ χαμηλής τάσης και, σε σύγκριση με τις υφιστάμενες υλοποιήσεις, παρουσιάζει σημαντικό προβάδισμα στον τομέα της ταχύτητας, καθώς και στο πλάτος εξόδου, η μεγάλη τιμή του οποίου χαλαρώνει σημαντικά τη σχεδίαση του RF front end. Η γεννήτρια μελετήθηκε διεξοδικά, διεξήχθη ανάλυση κλιμάκωσης, έγινε εξαγωγή σχεδιαστικών εξισώσεων και αναπτύχθηκαν εργαλεία λογισμικού για την αυτοματοποιημένη σχεδίασή της. Για περαιτέρω αύξηση της ταχύτητας των παλμικών σημάτων εφαρμόσθηκε ειδική σχεδίαση, η οποία αντιπραγματεύεται την ταχύτητα με το επίπεδο των λοβών του φάσματος. Για την αποδοτική BSPK διαμόρφωση των Γκαουσιανών παλμών αναπτύχθηκε ειδική τοπολογία “Μεταγωγής Σήματος Πυροδότησης Πλήρους Ισορροπίας με Up-Conversion”. Η τοπολογία αυτή, σε αντίθεση με τις ανταγωνιστικές τοπολογίες, αποφεύγει την αντιστροφή του παλμού με αναλογικά κυκλώματα υψηλής κατανάλωσης, αλλά και την αναλογική μεταγωγή, καθώς η διαμόρφωση λαμβάνει χώρα πριν από την παραγωγή των παλμών. Παράλληλα, επιτυγχάνονται υψηλοί ρυθμοί, καθώς και υψηλή ποιότητα διαμόρφωσης λόγω των ισορροπημένων μονοπατιών της τοπολογίας. Η γεννήτρια μαζί με το διαμορφωτή αποτελούν τις καινοτόμες παρεμβάσεις στη μονάδα Βασικής Ζώνης του προτεινόμενου πομπού. Για την ολοκλήρωση της λειτουργικότητας του πομπού, αναπτύχθηκε ένα RF front end, το οποίο αποτελείται από έναν διπλά ισορροπημένο μίκτη, έναν LO buffer, ένα μετατροπέα διαφορικού σήματος σε απλό, και έναν ενισχυτή ισχύος, ο οποίος είναι προσαρμοσμένος στα 50 Ohms, χωρίς να απαιτεί κανένα εξωτερικό στοιχείο. Το RF front end ολοκληρώθηκε μαζί με τη μονάδα βασικής ζώνης, και ο ολοκληρωμένος πομπός κατασκευάστηκε σε τεχνολογία CMOS 130 nm. Το ολοκληρωμένο προσαρτήθηκε στην RF πλακέτα συστήματος με την τεχνική Chip on Board. Για την επιτυχία του συστήματος με την πρώτη προσπάθεια έγινε συσχεδίαση σε επίπεδο IC-Package-PCB, δίνοντας ιδιαίτερη έμφαση στα ζητήματα Signal/Power Integrity. Ο πομπός παρουσίασε την υψηλότερη ταχύτητα από τις ανταγωνιστικές MB-IR UWB υλοποιήσεις, ίση με 1.5 Gbps, με αντίστοιχη ενεργειακή αποδοτικότητα 21 pJoule/bit και μέτρο διανυσματικού σφάλματος 5.5%. Ο πομπός βελτίωσε τους πλευρικούς λοβούς στο φάσμα περισσότερο από 10 dB, ενώ η διατριβή, εκμεταλλευόμενη την αναδιαταξιμότητα του πομπού, παρουσιάζει, επιπλέον, τις πρώτες μετρήσεις σε ταχύτητες εκατοντάδων Mbps για ικανοποίηση της χαμηλής ζώνης της πρόσφατα θεσμοθετημένης, και εξαιρετικά αυστηρής, ευρωπαϊκής μάσκας εκπομπής. / The multitude of applications that Ultra-Wideband (UWB) technology can serve, from high-speed Wireless Personal Area Networks, to Wireless Sensor Networks with precision Geolocation abilities, and Wireless Medical Networks, has attracted intense research interest in the implementation of UWB systems. The unusually wide range of frequencies assigned to UWB, from 3.1-10.6 GHz, allows UWB systems employing low order modulation schemes to enjoy high throughput at low power consumption. However, since UWB shares the spectrum with existing wireless networking technologies, UWB emissions must be limited to a power spectral density below the threshold of -41.3 dBm/MHz, satisfying very stringent emission masks and introducing great challenges in the design of UWB transmitters. The subject of this thesis is the design of low power, fully integrated, reconfigurable CMOS UWB transmitters, with high spectral flexibility, high speed and high modulation quality. Adopting the Multi-Band Impulse-Radio architecture, in conjunction with the Direct Sequence BPSK modulation, the research focused on the development of a baseband unit, able to precisely invert Gaussian shaped, subnanosecond pulses. The key contributions of this thesis are a CMOS Gaussian Pulse Generator and a BSPK modulation topology, which jointly constitute the proposed baseband unit. The Pulse Generator (PG) is based on non-linear shaping, so as to facilitate the configurability of the output pulse duration, and exploits the voltage transfer characteristic of a Resistive Loaded Asymmetrical CMOS Inverter, which results in spectral sidelobes typically better than -40 dB. The PG incorporates mostly-digital low voltage circuits, while the MOSFET devices that undertake the pulse shaping avoid exclusive operation in weak inversion, in contrast to previous implementations. Consequently, the proposed CMOS PG is able to support higher throughput, as well as higher output amplitude, which relaxes considerably the design of the RF front end. This thesis presents a systematic design procedure and a scaling analysis of the non-linear pulse shaper. Moreover, in order to further increase the speed, a special PRF boost technique is proposed, which trades off speed and spectral efficiency for the spectral sidelobes level. Regarding the BPSK modulator, this work introduces the “Trigger Switching Fully Balanced Up-Conversion” topology, which avoids the use of power-hungry and distortion-prone analog circuits for the accurate inversion of the subnanosecond shaped pulses, as well as avoids the application of analog waveform switching to the baseband pulses, since the baseband modulation takes place before the generation of the pulses. The digital nature of the switching lends itself to high data rates, while the balanced paths of the topology ensure high modulation quality with minimal design effort. Wafer probing measurements confirmed the high performance of the baseband unit. The functionality of the transmitter was completed by the development of an RF front end which consists of a double balanced mixer, an LO buffer, a differential to single-ended (DtoSE) converter, and a power amplifier which is ready to drive a 50 Ohms load without requiring any off-chip components. The integrated transmitter, which incorporates the proposed baseband unit and the RF front end, was fabricated in 130 nm CMOS technology. The transmitter RFIC was directly attached to the system RF PCB using the Chip-on-Board packaging option. The First-Pass success of the system was ensured by paying particular attention to Signal/Power Integrity issues and following an IC-Package-PCB co-design procedure. The transmitter was measured up to 1.5 Gbps, which, to the author’s knowledge, was the highest speed amongst the competitive Multi-Band Impulse-Radio UWB implementations in the literature. The corresponding energy efficiency was 21 pJoule/bit and the Error Vector Magnitude (EVM) 5.5%, while the proposed transmitter improved the spectral sidelobes by over 10 dB. Exploiting the reconfigurability of the transmitter, this thesis presents the first measurements at multi-Mbps speeds that completely meet the final version of the European spectrum emission mask.