The advent of high-fT silicon CMOS/BiCMOS technologies has led to a dramatic upsurge in the research and development of radio and microwave frequency integrated circuits (ICs) in silicon. The integration of silicon-germanium heterojunction bipolar transistors (SiGe HBTs) into established "digital" CMOS processes has provided analog performance in silicon that is not only competitive with III-V compound-semiconductor technologies, but is also potentially lower in cost. Combined with improvements in silicon on-chip passives, such as high-Q metal-insulator-metal (MIM) capacitors and monolithic spiral inductors, these advanced RF CMOS and SiGe BiCMOS technologies have enabled complete silicon-based RF integrated circuit (RFIC) solutions for emerging wireless communication standards; indeed, both the analog and digital functionalities of an entire wireless system can now be combined in a single IC, also known as a wireless "system-on-a-chip" (SoC). This approach offers a number of potential benefits over multi-chip solutions, such as reductions of parasitics, size, power consumption, and bill-of-materials; however, a number of critical challenges must be considered in the integration of such SoC solutions. The focus of this research is the application of SiGe BiCMOS technology to on-going challenges in the development of receiver components for high speed wireless data networks. The research seeks to drive SoC integration by investigating circuit topologies that eliminate the need for off-chip components and are amenable to complete on-chip integration. The first part of this dissertation presents the design, fabrication, and measurement of a 5--6GHz sub-harmonic direct-conversion-receiver (DCR) front-end, implemented in the IBM 0.5um 5HP SiGe BiCMOS process. The design consists of a fully-differential low-noise amplifier (LNA), a set of quadrature (I and Q)x~2 sub-harmonic mixers, and an LO conditioning chain. The front-end design provides a means to address performance limitations of the DCR architecture (such as DC-offsets, second-order distortion, and quadrature phase and amplitude imbalances) while enabling the investigation of high-frequency IC design complications, such as package parasitics and limited on-chip isolation. The receiver front-end has a measured conversion gain of ~18dB, an input second-order intercept point of +17.5dBm, and a noise figure of 7.2dB. The quadrature phase balance at the sub-harmonic mixer IF outputs was measured in the presence of digital switching noise; 90<degree> balance was achieved, over a specific range of LO power levels, with a square wave noise signal injected onto the mixer DC supply rails. The susceptibility of receiver I/Q balance to mixed-signal effects in a SoC environment motivates the second part of this dissertation --- the design of a phase and amplitude tunable, quadrature voltage-controlled oscillator (QVCO) for the on-chip synthesis of quadrature signals. The QVCO design, implemented in the Freescale (formerly Motorola) 0.18um SiGe:C RFBiCMOS process, uses two identical, differential LC-tank VCOs connected such that the two oscillator outputs lock in quadrature to the same frequency. The QVCO designs proposed in this work provide the additional feature of phase-tunability, i.e. the relative phase balance between the quadrature outputs can be adjusted dynamically, offering a simulated tuning range of ~90<degree>+/-10â ¹degree> in addition, a variable-gain buffer/amplifier circuit that provides amplitude tunability is introduced. One potential application of the QVCO is in a self-correcting RF receiver architecture, which, using the phase and amplitude tunability of the QVCO, could dynamically adjust the IF output quadrature phase and amplitude balance, in near real-time, in the analog-domain. The need for high-quality inductors in both the DCR and QVCO designs motivates the third aspect of this dissertation --- the characterization and modeling of on-chip spiral inductors with patterned ground shields, which are placed between the inductor coil and the underlying substrate in order to improve the inductor quality factor (Q). The shield prevents the coupling of energy away from the inductor spiral to the typically lossy Si substrate, while the patterning disrupts the flow of induced image currents within the shield. The experimental effort includes the fabrication and testing of a range of inductors with different values, and different types of patterned ground shields in different materials. Two-port measurements show a ~50% improvement in peak-Q and a ~20% degradation in self-resonant frequency for inductors with shields. From the measured results, a scalable lumped element model is developed for the rapid simulation of spiral inductors with and without patterned ground shields. The knowledge gained from this work can be combined and applied to a range of future RF/wireless SoC applications. The designs developed in this dissertation can be ported to other technologies (e.g. RF CMOS) and scaled to other frequency ranges (e.g. 24GHz ISM band) to provide solutions for emerging applications that require low-cost, low-power RF/microwave circuit implementations. / Ph. D.

Les recherches que nous présentons dans ce mémoire s'inscrivent dans le cadre du développement de nouvelles structures et de l'étude de matériaux accordables en vue d'une intégration industrielle comme radôme actif.Plus particulièrement, ils consistent en la réalisation d'un dispositif micro-onde permettant à la fois un filtrage et une agilité fréquentiels en espace libre. Des structures basées sur des surfaces sélectives en fréquences, pour l'aspect filtrage, et sur des matériaux de type ferroélectrique, pour l'aspect accordabilité, sont développées. Des modélisations et des simulations électromagnétiques montrent que le changement de permittivité du matériau, obtenu par application d'un champ électrique externe, permet le pilotage fréquentiel de la transmission de la structure. Une mise en oeuvre expérimentale complète ces travaux, au cours de laquelle des prototypes ont été fabriqués par des techniques de photolithographie, puis caractérisés en espace libre grâce à un banc ABmm. Les mesures micro-ondes valident ainsi les résultats de simulations menées en amont et montrent les possibilités de contrôler la fréquence de transmission du radôme. / The research we present in this memory registers within the framework to develop new structures and to study tunable materials for an industrial integration as an active radome. Specifically, they consist of achieving a free space microwave device for both a filtering behaviour and a frequency agility behaviour. Structures based on frequency selective surfaces, for the filtering aspect, and on ferroelectric materials for the tuning aspect, are developed. Modeling and simulations show that the change of the material permittivity, obtained by applying an external electric field, enable piloting the transmission frequency of the structure. An experimental implementation complete this work and prototypes have been fabricated by photolithography techniques and then characterized in free space with a bench ABmm. Thus, microwave measurements validate the results of simulations and show the possibility to control the frequency transmission of the radome.

Les lasers à électrons libres (LELs) à simple passage représentent actuellement la possibilité la plus prometteuse pour fournir des impulsions lumineuses de haute énergie (µJ à mJ) à des échelles de durée femtoseconde (1 fs = 10⁻¹⁵s) et des longueurs d’ondes ultra-courtes (résolution nanométrique i.e., jusqu’aux domaines de l’extrême-ultraviolet et des rayons X). Les LELs émettant dans l’extrême-ultraviolet sont une technologie encore jeune, si bien que de nombreuses questions restent ouvertes. Celles posées au sein de ce manuscrit concernent la configuration dite injectée, dans laquelle le processus est initié par une source externe cohérente (le “seed"). Nous nous concentrons particulièrement dans cette thèse sur les caractéristiques transverses et longitudinales de la lumière, sa cohérence, les propriétés de la phase temporelle et les liens directs entre le seed et l’émission LEL. La technique de génération dans un gaz noble d’harmoniques d’ordres élevés d’un laser femtoseconde (GHE) se montre à la fois complémentaire et en compétition avec les LELs. En compétition car les impulsions produites ont des qualités similaires à celles obtenues avec un LEL ; complémentaire car le rayonnement GHE peut être utilisé comme seed ou en combinaison avec la lumière LEL, par exemple pour effectuer des expériences mettant en jeu de multiples faisceaux. Bien que la GHE fournisse des impulsions moins puissantes, l’implémentation d’une telle source requiert un effort significativement moins important. Le taux de conversion harmonique, l’accordabilité et la qualité spatiale du faisceau généré, et la manière dont ces paramètres dépendent du laser générateur sont les problématiques traitées au sein de ce manuscrit. La volonté de la communauté scientifique d’effectuer des expériences novatrices demande des études profondes et l’optimisation des sources de GHE et des LELs. En particulier, sur la source LEL injectée FERMI@Elettra de Trieste, l’induction d’une dérive de fréquence dans le rayonnement a conduit à des résultats marquants. Entre autres, une méthode de génération d’impulsions scindées avec différentes longueurs d’ondes a été analysée et développée. Une telle possibilité ouvre la voie à l’utilisation des LELs injectés en tant que source autonome pour des installations de type pompe-sonde à deux couleurs. Plus généralement, l’étude des phénomènes mis en jeu dans les processus de GHE et du LEL ainsi que la caractérisation des propriétés de leur lumière sont des sujets intrinsèquement excitants, ayant des connexions directes avec de nombreux aspects fondamentaux de la physique. / Single-pass free-electron lasers (FELs) are currently the most promising facilities for providing light pulses with high energies (µJ to mJ) at femtosecond time scales (1 fs = 10⁻¹⁵s) and with ultrashort wavelengths (nanometer resolution i.e., down to extreme-ultraviolet and X-ray spectral regions). Extreme-ultraviolet FELs are still quite young so that many questions remain open. Those addressed within this manuscript concern the so-called seeded configuration, where an external coherent source (the “seed") initiates the process. In particular, we focus in this thesis on the transverse and longitudinal characteristics of the light, its coherence, the properties of the temporal phase and the direct correlations between the seed and the FEL emission. With regard to FELs, high-order harmonics of femtosecond laser pulses generated in noble gases (HHG technique) exhibit both competitive and complementary features. Competitive, because the produced pulses have similar assets as the ones provided by an FEL. Complementary, because the generated harmonics can be used as a seed or, in combination with FEL light, to perform multi-beam experiments. Even though less powerful pulses are produced by a HHG source, its implementation requires a significantly smaller effort. The efficiency of harmonic conversion, the tunability and spatial quality of the generated beam, and how these parameters depend on the driving laser are the issues discussed within this manuscript. The general will of the scientific community to perform novel experiments requires deep studies and optimization of FEL and HHG sources. In particular, on the seeded FEL facility FERMI@Elettra of Trieste, the induction of chirp in the radiation has led to remarkable results. Among others, a method of generation of split pulses with different wavelengths has been construed and developed. Such a possibility paves the way for the use of seeded FEL facilities as stand-alone sources for two-colour pump-probe setups. More generally, the study of phenomena involved in the FEL and HHG processes, together with the characterization of the light properties, are intrinsically exciting matters that have direct connections with fundamental aspects of physics. / Laser na proste elektrone (LPE, ang. free-electron laser - FEL) z enojnim prehodom je trenutno najbolj obetaven vir femtosekundnih (1 fs = 10⁻¹⁵ s) svetlobnih pulzov z visoko energijo (μJ do mJ) in ultra kratko valovno dolžino (nanometrska ločljivost, t.j., vse do spektralnega območja ekstremne ultravijolične in rentgenske svetlobe). LPE-ji, ki delujejo na področju ekstremne ultravijolične svetlobe, so razmeroma novi svetlobni viri, kar pomeni, da so glede njihovega delovanja odprta še mnoga vprašanja. V pričujočem doktorskem delu smo se ukvarjali predvsem z dvostopenjsko konfiguracijo, pri kateri LPE ojači zunanje (koherentno) elektromagnetno valovanje (seed). Osredotočili smo se na transverzalne in longitudinalne lastnosti proizvedene svetlobe, koherenco, lastnosti časovne faze ter na direktne korelacije med zunanjim virom (seed) in sevanjem LPE-ja. Poleg LPE-jev so v vzponu tudi svetlobni viri, ki temeljijo na generaciji visokih harmonikov (GVH, ang. high-order harmonic generation - HHG) v žlahtnih plinih. Ti svetlobni viri so zaradi podobnih lastnosti pulzov konkurenčni LPE-jem, po drugi strani pa predstavljajo komplementarne izvore svetlobe, ker jih je mogoče uporabiti v dvostopenjski LPE konfiguraciji kot vir zunanjega elektromagnetnega valovanja (seed) ali v kombinaciji z LPE-jem v eksperimentih z dvema ali več žarki. Kljub temu, da so ti svetlobni viri šibkejši v primerjavi z LPE-ji, je njihova izvedba bistveno lažja. V dizertaciji obravnavamo izkoristek harmonične pretvorbe virov, ki temeljijo na principu GVH, nastavljivost in prostorsko kakovost žarkov, ter odvisnost omenjenih parametrov od gonilnega laserja. Zaradi vse večje težnje po novih eksperimentih na vseh znanstvenih področjih sta ključna zelo natančno poznavanje delovanja in optimizacija LPE-jev in virov, ki temeljijo na GVH. Med bolj pomembne dosežke na LPE-ju FERMI@Elettra v Trstu spadajo možnost spreminjanja trenutne frekvence proizvedene svetlobe (ang. chirp) na podlagi katere je bila razvita metoda za generacijo razdeljenih pulzov z različnimi valovnimi dolžinami. S pomočjo te metode bo možno dvostopenjske LPE-je uporabljati kot samostojne vire svetlobe za poskuse v t.i. načinu « pump-probe ». V dizertaciji so predstavljene študije pojavov, ki so prisotni pri generaciji svetlobe v LPE-jih ter virih, ki temeljijo na GVH. Ti pojavi so, skupaj z metodami karakterizacije proizvedene svetlobe, tesno povezani s temeljnimi principi v fiziki.

Les antennes présentes dans la plupart des systèmes communicants comme les véhicules automobiles, les avions et les trains se multiplient et sont soumises à une contrainte d’intégration de plus en plus sévère. De nombreuses techniques de miniaturisation d’antennes existent et passent toutes par un compromis entre la taille et les performances (bande passante et/ou rendement de rayonnement). Pour les systèmes cités ci-dessus, les antennes sont souvent placées devant ou à proximité d’un réflecteur métallique (toit de véhicule, carlingue d’aéronef). Dans ce cas, l’épaisseur de système antennaire est une contrainte majeure et les métamatériaux de type Conducteur Magnétique Artificiel (CMA) ouvrent des perspectives intéressantes grâce à leurs propriétés électromagnétiques non conventionnelles. Cependant, pour les applications sub-GHz (RFID, LTE, PMR…), les CMA sont limités par les dimensions des cellules unitaires nécessaires à leur mise en œuvre (λg/4) ainsi que leur bande réduite de fonctionnement. Réduire leurs dimensions permet de rendre leur utilisation compatible avec le contexte des antennes miniatures intégrées. Ajouter l’agilité fréquentielle permet de palier le problème de la bande passante réduite dans le cas des antennes et des CMA miniaturisés en ajustant le fonctionnement du système antennaire sur une large bande passante. Cette thèse de doctorat propose d’étudier et de développer un nouveau système antennaire à faible profil composé d’une antenne miniature associée à une métasurface compacte reconfigurable en fréquence et compatible avec le standard NB-IoT dans la bande basse LTE (700 MHz – 960 MHz). / Antennas are now very integrated in several connected systems like cars, airplanes and trains. Many antenna miniaturization techniques exist and all go through a compromise between size and performance (bandwidth and/or radiation efficiency). For the systems mentioned above, the antennas are often placed near a metallic reflector (vehicle roof, aircraft cabin). Within this context, Artificial Magnetic Conductors (AMC) present an attractive reflector for low profile antennas which can take advantage of intrinsic zero reflection phase response to boost antenna performance without the need for thick quarter wave backplane. However, for sub-GHz applications (RFID, LTE, PMR ...), AMC are limited by the size of the unit cells necessary for their implementation (λg/4) as well as their reduced operating bandwidth. AMC miniaturization makes their use compatible with small antennas. Adding tunability restores the possibility of adjusting the operating frequency over a large bandwidth. This PhD thesis proposes to study and develop a new electrically small, low-profile antenna based on miniaturized and tunable AMC for the NB-IoT standard in low LTE band (700 MHz – 960 MHz).

Magnetic vortices are fundamental topologically protected magnetic structures which have evolved into a large and intense field of research and hold promise for future technological applications. The fundamental frequency of the magnetic vortex in a disk is directly proportional to the magnitude of the local saturation magnetization and individual sample design resulting in a single vortex precession frequency. Commercial applications like RF oscillators in wireless transmitters and receivers, however, require tuning of the output frequency by external parameters, such as applied fields or spin-polarized currents. It is shown here that the limited tunability of a magnetic vortex in a permalloy disk can be lifted when submitted to local chromium ion implantation by introducing areas in the disk with different saturation magnetization. A static magnetic field is applied to displace the vortex core between these two regions to enable detection of different frequencies corresponding to the respective regions. This realization of multiple resonance frequencies in one and the same magnetic disk is shown experimentally via electrical detection exploiting anisotropic magnetoresistance effects and the results are supported by micromagnetic simulations. In the experiments presented here, the gyrotropic mode is excited at resonance with spin-polarized alternating currents. Systematic investigations (in terms of excitation amplitude, external static field amplitude, angle between static field and current) on the disks without chromium ion implantation clearly indicate that the vortex core is driven by a combination of Oersted field and spin-torque. These measurements also help to identify the linear and non-linear regions of vortex dynamics electrically on single disks. The results shown in this work pave the way for enabling highly tuneable wireless transmitters and receivers based on magnetic vortex structures.

<p dir="ltr">Rapid evolution in wireless technology and the increasing demand for high bandwidth communication for 5G/6G and the Internet of Things (IoT) have necessitated a growing number of components in radio front-end modules in an increasingly overcrowded radio frequency (RF) spectrum. Low-cost ad-hoc radios have drawn consumer interest, enabling new devices like microelectromechanical (MEMS) resonators for on-chip clocking, frequency-selective filters, RF signal processing, and spectral sensing for their small footprint and low power consumption. Gallium nitride (GaN) is an attractive electromechanical material due to its high coupling coefficient, acoustic velocity, and low viscoelastic losses. These benefits enable high-Q MEMS resonators in GaN monolithic microwave integrated circuits (MMICs) with scaling capability up to mm-wave frequencies, making this technology platform a contender for high-performance programmable radios in RF/mm-wave, sensors for harsh environments, and information processing in quantum systems.</p><p dir="ltr">The bias-dependent control mechanism of the 2D electron gas (2DEG) in GaN heterostructures can be exploited to design different switchable and tunable devices for reconfigurable MEMS components. This work presents, for the first time, a comprehensive study of the electromechanical performances of different transduction mechanisms in switchable GaN MEMS resonators. A unique OFF-state shunt design, where the 2DEG in an AlN/GaN heterostructure is utilized to control electromechanical transduction in Lamb mode resonators, is also experimentally demonstrated in this work. To make a valid comparison among switchable transducers, equivalent circuit models are developed to extract key parameters from the measurements by fitting them in both ON and OFF states. The switchable transducer with Ohmic interdigitated transducers (IDTs) and Schottky control gate shows superior performance among the designs under consideration with complete suppression of the mechanical mode in the OFF state and a maximum frequency-quality factor product of 5x10¹²s^-1 and a figure-of-merit of 5.18 at 1GHz in the ON state.</p><p dir="ltr">Over the past few years, there have been numerous efforts to scale the frequencies of MEMS devices in the GaN platform towards mm-wave frequencies. However, challenges remain due to the multi-layer thick buffer, typical in the growth of GaN epilayer on a substrate. This work presents the investigation of SweGaN QuanFINEbuffer-free and ultrathin GaN-on-SiC for the performance of surface acoustic wave (SAW) devices beyond 10GHz. Finite element analysis (FEA) is performed to find the range of frequencies for the Sezawa mode in the structure. Transmission lines and resonators are designed, fabricated, and characterized. Modified Mason circuit models are developed for each class of devices to extract critical performance metrics and benchmark with the state-of-the-art and theoretical limits for GaN. Sezawa modes are observed at frequencies up to 14.3GHz, achieving a record high in GaN MEMS to the best of our knowledge. A maximum piezoelectric coupling of 0.61% and frequency-quality factor product of 6x10¹²s^-1 are achieved for Sezawa resonators at 11GHz, with a minimum propagation loss of 0.26dB/λ for the two-port devices. The devices also exhibit high linearity with input third-order intercept points (IIP3) of 65dBm at 9GHz.</p><p dir="ltr">This work also investigates tunable acoustoelectric (AE) devices in the QuanFINE platform, leveraging its inherent 2DEG in the AlGaN/GaN heterostructure. Using 9.7GHz Sezawa mode acoustic delay lines, we report the highest frequency of AE in GaN to date. Active and passive AE devices are designed for voltage-dependent non-reciprocity and propagation loss without modification to the standard process for the High Electron Mobility Transistors (HEMTs) in MMICs. Drain/source Ohmic contacts control the drift velocity of the 2DEG, and the Schottky gate modulates 2DEG carrier concentration, resulting in a 30dB/cm separation between forward and reverse acoustic waves for a 2.56kV/cm lateral DC electric field and a maximum change in propagation loss of 50dB/cm for -5V DC at the control gate, respectively. The QuanFINEtechnology with AlGaN/GaN heterostructure enables a platform for switchable MEMS resonators and tunable acoustoelectric devices in MMICs for reconfigurable front end approaching mm-wave frequencies.</p>

Les filtres spectraux à réseaux résonants, ou GMRF (Guided-Mode Resonance Filters), sont une nouvelle génération de filtres à bande étroite et constituent une alternative très prometteuse aux filtres conventionnels multicouches Fabry-Pérot. Le pic de résonance d'un GMRF peut être très fin spectralement et de longueur d'onde de centrage accordable en fonction de l'angle d'incidence. Ces propriétés sont particulièrement importantes pour la spectroscopie. Les travaux antérieurs ont permis de mettre en œuvre une structure originale comportant deux réseaux 1D croisés. Les performances de ce filtre surpassent celles des filtres conventionnels par leur réponse spectrale subnanométrique, leur accordabilité, et leur capacité à s'affranchir de l'influence de la polarisation de l'onde incidente sous incidence oblique. Le but de ce travail est d'explorer les performances ultimes de ce type de dispositif en termes de résolution et taux de réjection, par une approche mêlant théorie, technologie et caractérisation. Nous présentons des résultats expérimentaux d'un filtre en réflexion indépendant de la polarisation, accordable sur 40 nm avec 8.3nm/° d'accordabilité, ayant une réflexion de 10-3 sur une plage de 90nm en dehors de la résonance et un facteur de qualité supérieur à 5000. / Guided Mode Resonance Filters ( GMRF ) are a new generation of narrowband optical filters and are a very promising alternative to conventional multilayer Fabry-Perot filters. The resonance peak of GMRF can be spectrally extremely thin and with a centering wavelength tunable according to the angle of incidence of the light. These properties are particularly important for spectroscopy. Previous works have helped to implement an original structure with two 1D crossed gratings. The performance of this filter overpasses those of conventional filters in their spectral subnanometric response, tunability and their ability to overcome the influence of the polarization of the incident wave under oblique incidence. The aim of this work is to explore the final performances of such devices in terms of resolution and rejection rate, thanks to an approach combining theory, fabrication technology and characterization. We present experimental results of a polarization independent reflective filter, tunable over 40nm with a tunability of 8.3nm / °, having a reflection of 10-3 on a 90nm range outside the resonance and a quality factor over 5000.