The ever-increasing demand for high date rate is beyond what is provided by the present wireless and wired access networks. Radio-over-fiber (RoF) technology which can provide broadband wireless access has been considered the most practical and efficient solution. In recent years, RoF with coherent detection has been shown to have better performance than that with direct detection in terms of receiver sensitivity and spectral efficiency. However, RoF with coherent detection suffers from phase noise introduced from both the transmitter and local oscillator (LO) laser sources, which degrades the performance significantly. This study is focused on coherent RoF links for broadband wireless access networks. The thesis consists of four parts. In the first part, a new approach to cancel the phase noise and the unstable frequency difference introduced from the transmitter and LO laser sources based on digital signal processing (DSP) in an RoF link with coherent detection is presented. The proposed schemes rival the RoF link with direct detection in complexity while maintaining a high receiver sensitivity. In addition, a high spectral efficiency coherent RoF link with phase noise cancellation, which can detect both intensity- and phase- modulated signals carried by the same optical carrier, is studied and demonstrated. In the second part, to achieve full-duplex transmission and increase the capacity of an RoF link, radio over wavelength division multiplexing passive optical network (WDM-PON) is studied. To eliminate the requirements of light sources and wavelength management at the optical network units (ONUs), which reduces the cost and eases the installation for a radio over WDM-PON system, a new approach to reuse the downstream wavelength at the ONU with coherent detection and DSP at the optical line terminal (OLT) is investigated. The performance in terms of error vector magnitude (EVM) and bit rate error (BER) is evaluated for both downlink and uplink. In the scheme, the coherent detection improves the receiver sensitivity for the uplink and compensate for the degraded data transmission performance due to the utilization of a wavelength-reused downstream optical signal. Furthermore, since the future internet traffic will become highly symmetric, a symmetrical radio over a colorless WDM passive optical network (PON) with wavelength reuse based on polarization multiplexing and coherent detection is proposed and studied. In the third part, a coherent RoF link based on optical single sideband with no optical carrier (OSSB) modulation with low-cost free-running laser sources for ultra-dense wavelength division multiplexing passive optical networks (UDWDM-PONs) is studied. In a UDWDM-RoF-PON, the channel spacing is very small, thus a WDM filter may not be able to de-multiplex the ultra-dense channels. However, through coherent detection, the channel separation can be realized by using electrical filters at the output of the coherent receiver. In addition, to utilize the spectrum in each channel more efficiently, OSSB modulation is employed. In the proposed scheme, an RoF signal based OSSB modulation with coherent detection is experimentally demonstrated. The channel spacing can be as narrow as 3 GHz. Finally, for 5th generation wireless systems (5G), multi-input and multi-output (MIMO) is a key technology which can multiple the capacity. To seamlessly integrate MIMO into RoF links, it is required that an RoF link can transmit multiple wireless signals over a single wavelength. To enable 4 × 4 MIMO, in the fourth part, an RoF link to transmit four wireless signals with an identical microwave center frequency without using frequency-division multiplexing (FDM) over a single optical wavelength based on optical independent sideband (OISB) modulation and optical orthogonal modulation incorporating optical coherent detection and digital signal processing (DSP) is studied. To increase the spectral efficiency further, a novel high spectral efficiency (20.62 bit/s/Hz) RoF link based on coherent detection and DSP with the spectral efficiency improved by employing both intensity and phase modulation and polarization multiplexing to transmit four microwave signals over a single optical carrier is investigated.

Les capteurs de type MEMS (Micro Electro Mechanical Systems) sont des microsystèmes mettant en œuvre différents domaines de la physique (électronique, mécanique, chimie, optique,...) et permettant de mesurer différentes grandeurs physiques (accélération, pression, température...). Parmi ces micro-capteurs, les MEMS vibrants se caractérisent par leur structure présentant un micro-résonateur mis en vibration à sa fréquence de résonance et la variation de cette fréquence est représentative du mesurande. Cette thèse s'intéresse principalement à analyser et identifier les limites de résolution fréquentielle de ces capteurs vibrants en effectuant une modélisation multiphysique. Dans un premier temps, nous avons modélisé le comportement multiphysique d'un capteur MEMS vibrant en détaillant trois types de transduction (piézoélectrique, électrostatique et optique). La seconde partie a permis de valider les équations développées en se basant sur les simulations sous Cadence (langage multiphysque Verilog-A) et en les validant par des mesures expérimentales. La dernière partie traite de l'optimisation d'un micro-accéléromètre de type VIA (Vibrating Inertial Accelerometer) et l'étude de l'annulation des non linéarités permettant d'améliorer la résolution d'un capteur MEMS vibrant / MEMS (Micro Electro Mechanical Systems) sensors are micro-systems implementing various fields of physics (electronical, mechanical, chemical, optical, ...) and measuring various physical quantities (acceleration, pressure, temperature ...). The vibrating MEMS are characterized by a micro-resonator vibrating at its resonant frequency. The frequency variation is proportional to the measurand. This thesis is concerned with analyzing and identifying the frequency resolution limits of these vibrating sensors by performing multiphysics modeling. The first step is to model the multiphysics behavior of a vibrating MEMS sensor with three transduction types (piezoelectrical, electrostatical and optical). Secondly, the equations developed are validated, based on simulations with Cadence (multiphysique language Verilog-A) and their comparaison with experimental measurements. The last section presents the micro-accelerometer VIA (Vibrating Inertial Accelerometer) optimization and the nonlinearities cancellation study for improving the resolution of vibrating MEMS sensor

Oscillators are ubiquitous to radio frequency circuits, where frequency translations and channel selection play a central role in the analogue communications channel. Oscillators also form part of digital systems as a time reference. Typical heterodyne receivers require an intermediate frequency channel. The associated oscillators and variable filters can only be centred perfectly at a single frequency, and degrade performance at the boundaries of the channel. These circuits also require image-rejecting filters and phase-locked loops in order to enable down-conversion. The penalties for these components are increased circuit area and power consumption. A direct down-conversion circuit will reduce the number of components in the system. A requirement added by the structural change is a passive sub-harmonic mixer. Quadrature oscillators may be achieved by cross-coupling two nominally identical LC differential voltage-controlled oscillators. Because of the widespread use of voltage-controlled oscillators in wireless communication systems, the development of comprehensive nonlinear analysis is pertinent in theory and applications. A key characteristic that defines the performance of an oscillator is the phase noise measurement. The voltage-controlled oscillator is also a key component in phase-locked loops, as it contributes to most of the out-of-band phase noise, as well as a significant portion of in-band noise. Current state-of-the-art modulation techniques, implemented at 60 GHz, such as quadrature amplitude modulation, and orthogonal frequency domain multiplexing, require phase noise specifications superior to 90 dBc/Hz at a 1 MHz offset. It has been shown that owing to the timing of the current injection, the Colpitts oscillator tends to outperform other oscillator structures in terms of phase noise performance. The Colpitts oscillator has a major flaw in that the start-up gain must be relatively high in comparison to the cross-coupled oscillator. The oscillation amplitude cannot be extended as in the cross-coupled case. The oscillator’s bias current generally limits the oscillation amplitude. The phase noise is defined by a stochastic differential equation, which can be used to predict the system’s phase noise performance. The characteristics of the oscillator can then be defined using the trajectory. The model projects the noise components of the oscillator onto the trajectory, and then translates the noise into the resulting phase and amplitude shift. The phase noise performance of an oscillator may be improved by altering the shape of the trajectory. The trajectory of the oscillator is separated into slow and fast transients. Improving the shape of the oscillator’s slow manifold may improve its phase noise performance, and improving the loaded quality factor of the tank circuit may be shown to directly improve upon close-in phase noise. The approach followed describes oscillator behaviour from a circuit-level analysis. The derived equations do not have a closed form solution, but are reformulated using harmonic balance techniques to yield approximate solutions. The results from this closed form approximation are very close to both the numerical solutions of the differential equations, as well as the Simulation Program with Integrated Circuit Emphasis solutions for the same circuits. The derived equations are able to predict the amplitude and frequency in the single-phase example accurately, and are extended to provide a numerical platform for defining the amplitude and frequency of a multiphase oscillator. The analysis identifies various circuit components that influence the oscillator’s phase noise performance. A circuit-level modification is then identified, enabling the decoupling of some of the factors and their interactions. This study demonstrates that the phase noise performance of a Colpitts oscillator may be significantly improved by making the proposed changes to the oscillator. The oscillator’s figure of merit is improved even further. When a given oscillator is set at its optimum phase noise level, the collector current will account for approximately 85% of the phase noise; with the approach in this work, the average collector current is reduced and phase noise performance is improved. The key focus of the work was to identify circuit level changes to an oscillator’s structure that could be improved or changed to achieve better phase noise performance. The objective was not to improve passive components, but rather to identify how the noise-to-phase noise transfer function could be improved. The work successfully determines what can be altered in an oscillator that will yield improved phase noise performance by altering the phase noise transfer function. / The concept is introduced on a differential oscillator and then extended to the multiphase oscillator. The impulse sensitivity function of the modified multiphase oscillator is improved by altering the typical feedback structure of the oscillator. The multiphase oscillator in this work is improved from -106 dBc/Hz to -113 dBc/Hz when considering the phase noise contribution from the tank circuits’ bias current alone. This is achieved by uniquely altering the feedback method of the oscillator. This change alters the noise-to-phase noise properties of the oscillator, reducing phase noise. The improvement in the phase noise does not account for further improvements the modification would incorporate in the oscillator’s limit cycle. For a given tank circuit, supply current and voltage, compared to an optimised Colpitts oscillator, the modifications to the feedback structure proposed in this work would further improve the figure of merit by 9 dB. This is not considering the change in the power consumption, which would yield a further improvement in the figure of merit by 7 dB. This is achieved by relaxing the required start-up current of the oscillator and effecting an improvement in the impulse sensitivity function. Future research could include further modelling of the phase shift in the feedback network, including the transmission lines in the feedback networks using the harmonic balance technique in a numerical form. The feedback technique can also be modified to be applicable to single and differential oscillators. / Dissertation (MEng)--University of Pretoria, 2017. / National Research Foundation / The Department of Science and Technology, South Africa / GEW Technologies (Pty) Ltd / Electrical, Electronic and Computer Engineering / MEng / Unrestricted

Les progrès sur la technologie électronique pendant les dernières années avaient permis l’utilisation des techniques numériques dans la métrologie de temps et fréquence où bas bruit et haute précision sont nécessaires. Ces techniques génèrent systèmes plus flexibles pour l’implémentation et pour la configuration. De cette façon, c’est possible d’obtenir systèmes de mesure avec capacités étendues, fonctionnalités ajoutées et plus facile ad utiliser.Les convertisseurs analogique-numérique (ADCs) et numérique-analogique (DACs), considérée comme l’interface avec le monde analogique, représentent la limite de la performance du système en termes de bruit. De plus, en général, les plateformes commerciales basées sur FPGA sont cadencées par un oscillateur à quartz dont précision et stabilité de fréquence ne sont pas adapté pour plupart des applications de temps e fréquence. Dans ce cas, c’est possible d’utiliser le Phase Locked Loop (PLL) intégré dans la FPGA pour générer l’horloge du système à partir d’une référence de fréquence externe. Cependant, en considérant que le bruit de phase du PLL pourrait dégrader la stabilité de la référence et ainsi limiter la performance d’entier système, le PLL devient un composant critique pour l’instrumentation numérique. L’information disponible actuellement dans la littérature décrit en détail les spécifications de ces composants a offset de fréquence loin de la porteuse. Cependant, l’information proche à la porteuse est une préoccupation plus importante pour les applications de temps et fréquence.Dans ce cadre, ma thèse de doctorat est concentrée sur l’étude des limitations des composants critiques de l’instrumentation numérique pour la métrologie de temps et fréquence. L’objectif est de caractériser le bruit introduit par ces composants et ainsi obtenir un modèle que permettra de prédire leurs effets sur une application spécifique. On propose une méthode pour extraire les paramètres des modelés lequel est testé et validé sur la plateforme commercial Red Pitaya. Cette plateforme est une open source embedded system dont résolution et vitesse (14 bit, 125 MSps) sont raisonnablement proche de l’état de l’art des ADCs et DACs (16 bit, 350 MSps or 14 bit, 1 GSps/3GSPs) et c’est potentiellement suffisant pour l’implémentation de un instrument complet. Les résultats de la caractérisation conduisent aux limitations de la plateforme et donnent une directrice pour le design de l’instrument.Basé sur les résultats obtenus de la caractérisation du bruit, l’implémentation de un instrument numérique pour le transfert de fréquence par fibre optique est été réalisée sur la plateforme Red Pitaya. Dans ce projet, une implémentation numérique pour la détection et compensation du bruit de phase induit par la fibre est proposé. Sur la base des résultats de la caractérisation, il était prévu une limitation de la mesure du bruit de phase donnée par le PLL. Les premières mesures de cette implémentation ont été réalisées sur un lien de fibre de 150 km + 150 km placées dans les mêmes câbles entre l'INRiM (Turin) et le Laboratoire Souterrain de Modane (LSM) à la frontière Italie-France. A partir de ces résultats, le bruit introduit par le système numérique a été vérifié en accord avec les résultats de la caractérisation. Additionnel tests et améliorations seront effectués pour avoir un système capable d’être utilisé sur le lien italien pour la fréquence et le temps de Turin à Florence qui est longue de 642 km et à son extension dans le reste de l'Italie prévue dans le prochain avenir.Actuellement, une plateforme plus performante est en cours d'évaluation, à travers les techniques et concepts développés au cours de la thèse. Ce projet a pour but l’implémentation d'un phasemètre à l’état de l’art de la technologie dont l'architecture est basée sur le DAC. La caractérisation du DAC est en cours de développement et les mesures préliminaires sont également rapportées ici. / Improvements on electronic technology in recent years have allowed the application of digital techniques in time and frequency metrology where low noise and high accuracy are required, yielding flexibility in systems implementation and setup. This results in measurement systems with extended capabilities, additional functionalities and ease of use.The Analog to Digital Converters (ADCs) and Digital to Analog Converters (DACs), as the system front-end, set the ultimate performance of the system in terms of noise. Moreover, most commercial platforms based on FPGA are clocked by quartz oscillators whose accuracy and frequency stability are not suitable for many time and frequency applications. In this case, it is possible to take advantage of the internal Phase Locked Loop (PLL) for generating the internal clock from an external frequency reference. However, the PLL phase noise could degrade the oscillator stability thereby limiting the entire system performance becoming a critical component for digital instrumentation. The information available currently in literature, describes in depth the features of these devices at frequency offsets far from the carrier. However, the information close to the carrier is a more important concern for time and frequency applications.In this frame, my PhD work is focused on understanding the limitations of the critical blocks of digital instrumentation for time and frequency metrology. The aim is to characterize the noise introduced by these blocks and in this manner to be able to predict their effects on a specific application. This is done by modeling the noise introduced by each component and by describing them in terms of general and technical parameters. The parameters of the models are identified and extracted through the corresponding method proposed accordingly to the component operation. This work was validated by characterizing a commercially available platform, Red Pitaya. This platform is an open source embedded system whose resolution and speed (14 bit, 125 MSps) are reasonably close to the state of the art of ADCs and DACs (16 bit, 350 MSps or 14 bit, 1 GSps/3GSPs) and it is potentially sufficient for the implementation of a complete instrument. The characterization results lead to the noise limitations of the platform and give a guideline for instrumentation design techniques.Based on the results obtained from the noise characterization, the implementation of a digital instrument for frequency transfer using fiber link was performed on the Red Pitaya platform. In this project, a digital implementation for the detection and compensation of the phase noise induced by the fiber is proposed. The beat note, representing the fiber length variations, is acquired directly with a high speed ADC followed by a fully digital phase detector. Based on the characterization results, it was expected a limitation in the phase noise measurement given by the PLL. First measurements of this implementation were performed using the 150 km-long buried fibers, placed in the same cables between INRiM and the Laboratoire Souterrain de Modane (LSM) on the Italy-France border. The two fibers are joined together at LSM to obtain a 300 km loop with both ends at INRiM. From these results the noise introduced by the digital system was verified in agreement with characterization results. Further test and improvements will be performed for having a finished system which is intended to be used on the Italian Link for Frequency and Time from Turin to Florence that is 642-km long and to its extension in the rest of Italy that is foreseen in the next future.Currently, a higher performance platform is under assessment by applying the tools and concepts developed along the PhD. The purpose of this project is the implementation of a state of the art phasemeter whose architecture is based on the DAC. The DAC characterization is under development and preliminary measurements are reported here.

L’utilisation des technologies MEMS dans la navigation aéronautique présente deux difficultés majeures.D’une part, le bon fonctionnement des appareils de mesure de l’aviation civile requiert l’anticipation des défaillances susceptibles de se produire durant des décennies. D’autre part, le remplacement des capteurs macroscopiques traditionnels par des cellules MEMS ne peut se faire qu’à niveau de performances équivalent. Vis-à-vis de ces deux enjeux de fiabilité et de performance, le comportement fortement non-linéaire des résonateurs MEMS est souvent considéré comme un frein voire une limite infranchissable aux progrès technologiques.Cependant, l’exploitation de ces phénomènes non-linéaires constitue en réalité une source extrêmement riche d’améliorations. Au prix d’une complexité mathématique accrue et d’efforts de conception spécifiques, la modélisation précise des phénomènes non-linéaires affectant le comportement des MEMS donne accès à des informations précieuses, aussi bien pour la détection de défaillances que pour l’amélioration des performances.Dans cette thèse, on développe une procédure de caractérisation linéaire et non-linéaire de cellules MEMS résonantes. Après avoir démontré l’intérêt et vérifié expérimentalement la précision d’une telle caractérisation, on montre comment la connaissance des caractéristiques non-linéaires permet de déterminer des points de fonctionnement optimaux en termes de stabilité fréquentielle des capteurs oscillants, et donc de précision et de justesse des mesures. / The use of MEMS technologies in navigation measurements faces two main challenges.On the one hand, reliability improvement requires a deep understanding of MEMS failure mechanisms. These components are meant for long-term use and are subject to harsh mechanical and thermal constraints during their expected lifetime, usually longer than a decade. On the other hand, the replacement of macroscopic navigation sensors by MEMS components remains impossible as long as the performances of MEMS sensors do not match those of their macroscopic equivalents. With respect to these two challenges, the nonlinear behavior of MEMS resonators is usually seen as an obstacle, if not an insurmountable barrier to technological progress.However, nonlinear phenomena are actually a rich source of potential improvements. At the cost of increased mathematical complexity and specific design efforts, a precise model of MEMS nonlinear behaviors gives access to valuable information about the internal structure of the device. This information may then be used for failure detection and performance optimization.In this thesis, a linear and nonlinear characterization method is developed and experimentally-demonstrated. The knowledge of such nonlinear characteristics allows the determination of optimal operating points in terms of frequency stability and, hence, measurement accuracy.

Le développement technologique dans le domaine des télécommunications, ainsi que des systèmes de détection, a accru ces dernières années la nécessité de signaux de référence présentant une très haute pureté spectrale. L'augmentation des débits, la saturation des bandes de fréquence ainsi que les performances imposées pour la détection radar ont ouvert la voie à la génération micro-onde par l'optique. Ces références de fréquence sont souvent issues d'oscillateurs optoélectroniques (OEO). Ces oscillateurs intègrent un élément de stockage de l'énergie au travers de résonateurs ou de longues lignes à retard fibrées afin d'augmenter leur facteur qualité et permettant ainsi d'atteindre des performances supérieures aux signaux multipliés à partir de sources basses fréquences ou directement à partir d'oscillateurs micro-ondes à résonateur diélectrique (DRO). Une topologie originale d'oscillateurs optoélectroniques a été proposée à la fin des années 1990 par une équipe américaine : il s'agit de remplacer le résonateur passif nécessitant un verrouillage du laser sur ce dernier par un résonateur actif, intégrant un amplificateur optique. Ce résonateur actif, un laser à blocage de modes, permet un couplage entre l'oscillation optique du laser et l'oscillation optoélectronique. On parle alors d'oscillateur optoélectronique couplé (COEO). Les performances du COEO sont étroitement liées à la pureté spectrale du signal issu du laser à blocage de modes. Ce travail de thèse traite de l'étude et de l'optimisation de ces systèmes. Une étude approfondie sur le bruit dans les amplificateurs optiques a tout d'abord été menée afin de déterminer quel type d'amplificateur choisir pour le COEO et sous quelles conditions l'amplification optique apporte un bruit de phase minimal. Ensuite, un COEO à 10 GHz a été réalisé, présentant un très faible bruit de phase atteignant - 132 dBc/Hz à 10 kHz de la porteuse. Un modèle a par ailleurs été implémenté, permettant de déterminer a posteriori l'efficacité du couplage et ainsi la bande de verrouillage entre l'oscillation optoélectronique et le laser à blocage de modes. Ce couplage interne dépend fortement de la dynamique du système. Cependant, les différents effets non linéaires qui ont lieu dans l'amplificateur à semiconducteur et les fibres ne permettent pas d'obtenir un modèle analytique. Un modèle itératif a alors été proposé afin d'obtenir les propriétés de l'enveloppe complexe lentement variable du peigne de fréquence généré en sortie du laser dont la photodétection conduit à la puissance RF générée par le COEO. Le COEO génère un peigne de fréquence suffisamment large pour produire des harmoniques RF supérieurs à la fréquence de répétition du laser à blocage de modes, si les modes longitudinaux espacés de plusieurs intervalles spectraux libres (ISL) sont en phase. Le modèle itératif développé permet, à partir des paramètres expérimentaux de déterminer le spectre optique ainsi que la distribution de phase à l'intérieur de celui-ci. Il est possible alors d'augmenter la puissance d'une harmonique en sortie de la photodiode par un ajout d'éléments dispersifs. Cette multiplication de fréquence permet la génération de signaux à haute pureté spectrale en bande millimétrique. Une démonstration expérimentale à 90 GHz a été proposée, basée sur un COEO fonctionnant à 30 GHz. Ces résultats sont prometteurs et une intégration du COEO dans un boîtier thermalisé ainsi qu'une gestion plus fine de la dispersion des fibres peut permettre des améliorations significatives sur le bruit de phase du système. / The important rise of telecommunication systems in the past decades, together with the sensitivity improvement of radar systems, has increased the necessity for high spectral purity frequency references at high frequencies. The saturation of classical microwave bandwidths motivated the search of frequency references at higher frequencies, such as K-band. Frequency multiplication from highly stable sources, such as quartz sources, is limited by the increase of the noise floor, which is often prohibitive at millimeter wave frequencies. On the contrary, microwave generation using optics becomes a very efficient technique in this frequency range. Indeed, passive optical resonators or delay lines feature a high Q factor which can be used to stabilize the microwave frequency. The best phase noise performance is today obtained with long delay line oscillators. However, a spurious mode suppression technique has to be implemented in this type of OEOs. The use of an active optical resonator is a third solution, which avoids any locking technique between the laser and the passive resonator. The first architecture of this type has been proposed at the end of the 1990's. In such a system, a mode-locked laser is coupled to a microwave oscillator (COEO). COEO phase noise performances are strongly dependent on the spectral purity of the mode locked laser signal. This thesis work focus on the study and the optimization of this system. Optical amplifiers noise is firstly investigated, in order to determine the optimal conditions to minimize their phase noise contribution to the COEO. A 10 GHz SOA based COEO has been realized and features a low phase noise level reaching - 132 dBc/Hz at 10 kHz from the carrier. An analytical model has also been developed to obtain the locking range of the coupled oscillations. This frequency range is strongly dependent on the coupling efficiency between optical oscillation and the optoelectronic oscillation. This parameter cannot be calculated analytically and an iterative model has been proposed to determine the amplitude and phase of the optical spectrum. Therefore, one can calculate the RF power on the photodiode, on which the coupling efficiency is depending. Since COEO features a large optical frequency comb where each tooth of the comb is phase locked thanks to the mode locked laser, harmonic generation from COEO is possible. Wide frequency comb from high frequency COEO allow millimeter wave generation. The iterative model developed in this work enable to determine the RF power of one specified harmonic from experimental parameters. Harmonic selection can also be performed through the management of the chromatic dispersion. Such frequency multiplication has been implemented to generate a high purity 90 GHz signal from a 30 GHz COEO.These results are promising and an integration of the system in a thermalized box is under process.

[pt] Nesta dissertação foram projetados e desenvolvidos osciladores apresentando ruído de fase otimizado. Em virtude das limitações dos equipamentos analisadores de espectro na precisa medição do ruído de fase dos osciladores desenvolvidos nos laboratórios do CETUC, foi implementada a técnica de medição Método do Detector de Fase. Esta técnica consiste no desenvolvimento de um segundo oscilador com as mesmas características do existente, e com auxílio de misturadores, realizar o batimento dos mesmos para freqüências próximas a DC, onde nesta região a medição do ruído de fase torna-se viável. Entretanto, em aplicações dedicadas, verificou-se que o batimento entre dois osciladores operando em torno de 10 GHz produz uma freqüência intermediária instável, variando de 10 kHz à 50 kHz. Para evitar a realização de uma medição extremamente instável, utilizou-se o método de sincronização de freqüências (Injection Locking) entre os osciladores. Foi também destacada a influência do ruído de cintilação (Flicker Noise) na medida final do ruído de fase. A melhor medida aferida foi em torno de -100 dBc/Hz @ 3,25 kHz. Foi verificado através de diversas simulações que a freqüência de cintilação int c f , situada em 10 MHz, apresenta grande influência sobre as medições do ruído de fase realizadas à 3,25 kHz da portadora, degradando-o em cerca de 30dB. / [en] In this dissertation, oscillators presenting optimized phase noise had been projected and develloped. Because of the limitation of the specter analyzer devices in the accurate measurements of the oscillators phase noise developed in the CETUC laboratories, it was implemented the measurement technique called Phase Detector Method. This technique consists on the development of a second oscillator with the same characteristics of the already existent one and, with aid of mixers, multiplies these signals together and provides the difference of the two signals next to DC, where, in this region, the measurement of the phase noise becomes viable. However, in dedicated applications, it was verified that the beating between two oscillators operating around 10GHz produces instable intermediate frequency, varying between 10kHz to 50kHz. To prevent the accomplishment of an extremely unstable measurement, the method of synchronization of frequency (Injection Locking) between the oscillators was used. Also the influence of the Flicker Noise in the final measure of the phase noise was detached. The best measure was around -100dBc/Hz@3,25kHz. It was verified through lots of simulations that the flicker corner frequency int c f , situated in 10MHz, presents great influence on the measures of the phase noise carried through to the 3,25kHz of the carrier, degrading it in about 30dB.

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