Le fil rouge guidant nos travaux de recherche correspond à la convergence des techniques hyperfréquences, des micro- et nano-technologies et plus récemment de la fluidique, amenant le développement de microsystèmes hyperfréquences innovants pour des applications en télécommunication et en biologie. Nous retraçons, au travers de notre habilitation à diriger des recherches, nos travaux sur les approches multidisciplinaires permettant le développement de microsystèmes hyperfréquences communicants pour lesquels notre leitmotiv fut de tirer au mieux partie des potentialités des micro et nano-technologies. Des composants et circuits RF-MEMS (RadioFrequency MicroElectroMechanical Systems), à l'intégration des nanotechnologies au sein de microsystèmes hyperfréquences, à la miniaturisation de fonctions passives ainsi qu'à leur co-intégration avec des circuits actifs au sein de microsystèmes. Nous présentons de plus notre projet de recherche visant à explorer l'alliance des microsystèmes hyperfréquences avec d'autres disciplines telles que la fluidique et la biologie pour de nouvelles fonctionnalités et applications. Nous tenterons de répondre aux questions scientifiques : "comment les microsystèmes hyperfréquences peuvent aller au delà des fonctionnalités et applications traditionnelles, quelles sont les opportunités ainsi ouvertes ?"

L'évolution de notre société est spectaculaire. Les nouvelles technologies apportent sans cesse des bouleversements dans nos vies, dont nous n'avons d'ailleurs pas toujours conscience tellement ces changements sont rapides et naturels. Qui aujourd'hui ne possède pas un téléphone portable extra miniature, possédant de multiples fonctionnalités intégrées: appareil photo, boussole, loupe...? Qui n'a pas entendu parlé des progrès phénoménaux réalisés en médecine avec, par exemple, la technique d'Imagerie par Résonance Magnétique (IRM) ou encore l'utilisation par les chirurgiens d'outils extrêmement précis, assistés par ordinateur? Parmi ce contexte très général de révolutions technologiques, ma simple contribution se situe dans le développement de microsystèmes hyperfréquences, que ce soit :  pour les communications et transfert d'informations avec des modules toujours plus performants et agiles (multifonctionnalité),  et plus récemment pour les domaines de la biologie et du médical avec le développement de systèmes d'analyse par ondes électromagnétiques hautes fréquences. La démarche scientifique adoptée vise à établir, grâce aux microtechnologies, de nouvelles perspectives d'exploitation des microsystèmes hyperfréquences, au-delà des technologies conventionnelles. Ceci commence par l'élaboration de circuits passifs à fort coefficient de qualité, leur intégration tridimensionnelle vers toujours plus de miniaturisation et fréquences de fonctionnement plus élevées, l'évaluation de matériaux inédits (notamment à base de nanotubes de carbone) qui apportent de nouvelles possibilités aux concepteurs HF, de concepts innovants de composants à forte reconfigurabilité, que ce soit par une approche mécanique avec les MEMS RF, ou encore avec des liquides, jusque de nouvelles applications pour les domaines de la biologie et du médical, l'environnement et même l'agro-alimentaire.

Le packaging des MEMS-RF est un sujet de recherche qui a été étudié de manière intensive ces dernières années. En effet, la fiabilité des composants micromécaniques est directement dépendante de l’humidité et de la poussière avoisinant la structure. C’est pourquoi la recherche d'un package parfaitement hermétique à très faible coût, sans influence sur les performances RF reste d’actualité, même si un grand nombre de publications et de solutions ont été présentées auparavant. Ces travaux de recherche porte sur la conception, la réalisation et la caractérisation de commutateurs MEMS-RF ohmiques packagés par deux techniques différentes. La première partie de cette thèse a été consacrée d’étudier une encapsulation par film mince. Une couche métallique d’or électrolysée est utilisée pour former le capot, ensuite le nitrure de silicium est utilisé pour sceller le capot. Cette technique a présenté plusieurs avantages où nous obtenons une petite taille, l’augmentation du nombre de composants par substrat tout en réduisant le cout de fabrication. Malgré tous ces avantages, cette technique engendre aux composants des faibles effets parasites sur leurs performances RF. La deuxième technique qui a été étudié dans ce travail, est l’encapsulation par collage de tranche. Le principe de cette encapsulation est de sceller un substrat de capots micro-usinés en silicium avec un substrat contenant les composants MEMS-RF. Ensuite, une découpe de deux substrats est nécessaire pour obtenir les commutateurs MEMS-RF encapsulés. Le scellement utilisé durant cette thèse était le glass frit qui garantit une très bonne herméticité. Des mesures d’herméticité sont faites par le cnes montrent que les commutateurs mems-rf sont encapsulés hermétiquement en indiquant un taux de fuite de 8.8e-12 atm.cc/s. Les performances RF du commutateur MEMS-RF sont déjà présentées et qui montrent que cette technique d’encapsulation ne présente aucune influence sur ces performances. / RF MEMS packaging is an important research topic that is intensively studied for years. Indeed, Micro-mechanical devices that are protected from humidity, dust and working in a clean controlled atmosphere consequently improve their reliability. Meanwhile, the search for a perfectly hermetic package at very low cost with no influence on the RF performances is still a challenge even if a lot of publications and solutions have been presented so far. This research focuses on the design, realization and characterization of encapsulated RF MEMS switches using two different techniques. The first part of this thesis has been to study a Wafer Level Thin Film Packaging (WLTFP) using a metallic cap, then we have utilize the silicon nitride to seal this cap. This encapsulation technique presents several advantages where we have extremely small volume cavity, no double-wafer alignment required, and substantial increase in the number of devices per wafer reducing cost. Despite all these advantages, this technique generates to the components a low parasitic effects on their RF performances. Another type of packaging has been studied during this thesis is Wafer to Wafer Packaging. The principle of this encapsulation is to seal a micro-machined wafer of caps on the wafer containing RF MEMS switches to be protected. The both wafers are then cut together and we obtain directly the packaged switches. The RF MEMS packaging using this technique permits to obtain a hermetic package (leak rate of 8.8e-12 atm.cc/s measured by the French Space Agency-CNES) with no influence on the device characteristics. The RF characterization of the switch having a silicon cap bonded using a dielectric sealing paste have shown that the insertion loss in the ON state and the isolation in the OFF state is practically the same before and after capping.

<p>The ferrimagnetic electrical insulator yttrium iron garnet (YIG) has been proved a promising magnonic platform that allows for a variety of application within microwave fre- quency range. This dissertation focuses on the development of novel spin wave resonators and filters for next-generation radio frequency technology.</p> <p>Chapter 1 begins with an introduction to modern radio frequency communication tech- nology and motivation of our research on novel radio frequency devices.</p> <p>Chapter 2 discusses about the properties of yttrium iron garnet (YIG) thin film platform and theory of magnetostatic waves (MSW) within the magnetic thin film system. Three different types of magnetostatic wave modes, known as magnetostatic forward volume wave (MSFVW), magnetostatic backward volume waves (MSBVW) and magnetostatic surface wave (MSSW), are illustrated in this section. They have very distinct dispersion relations and require different transduction technology, which leads to disparate designs for devices utilizing different modes. The damping mechanism and linewidth of the magnetostatic modes will also be discussed in this chapter.</p> <p>Chapter 3 will showcase a new YIG-on-Si platform created using novel YIG bonding technology and the first ever on-chip MSFVW hairpin resonator on the YIG-on-Si platform. In the first part, we would like to show finite element analysis of YIG-on-Si MSFVW hairpin resonator and prove the capability of the hairpin transducer incorporated with YIG thin film to yield lower self-inductance and stronger excitation field. These unique properties are beneficial for generating high coupling between magnon and microwave domains. In the following sections, the bonding technology essential for creation of YIG-on-Si platform and key fabrication technology of hairpin devices are explained in detailed. With well defined fabrication process established, we will demonstrate that the hairpin magnetostatic wave resonator obtained through the process is magnetically tunable with a high coupling efficiency over 50%. An out-of-plane Z-directional tunable magnetic field results in forward volume spin-wave resonance with frequency in the 5G band. This technology enables us to build on-chip devices of desirable high coupling and magnetic tuning on the new YIG-on-Insulator platform and provides possibility of magnetic tuning and band-pass filter at radio-frequency range.</p> <p>Chapter 4 demonstrates a planar monolithic yttrium iron garnet (YIG) Chebyshev bandstop filter on traditional gadolinium gallium garnet (GGG) substrate with tunable frequency, low insertion loss and high rejection. This filter is created in YIG micro-machining technol- ogy that allows direct placement of metal transducers on YIG for strong spin-wave coupling. With an out-of-plane 3900 Oe bias field, the bandstop filter exhibits 55 dB maximum stop- band rejection at a center frequency of 6 GHz, with 2 dB passband insertion loss and 37.8 dBm passband <strong>IIP3</strong>. By applying different bias fields, the stopband center frequency is tuned from 4 GHz to 8 GHz while maintaining more than 30 dB rejection. Incorporated with proper design of tunable compact electromagnet, this new filter design can provide attenuation of spurs appearing across the 5G and X-band spectrum.</p> <p>In chapter 5, we will explore the properties of YIG thin-film materials in depth. Both YIG-on-Si and YIG-on-GGG platform under different conditions will be examined. Results of X-ray diffraction (XRD), ferromagnetic resonance (FMR), scanning tunneling microscope (STM) on the YIG thin films will be presented. Those results will cast light onto the study of limiting factors of our YIG-on-Si and YIG-on-GGG devices.</p>

Wireless and mobile communications are already playing an important role in our lives, and this will can only grow more and more due to the predominant importance and use of modern smartphones, tablets and any kind of connected devices. With this is mind, the spectrum for wireless and mobile communications is becoming incredibly overcrowded, leading to increasing requirements for RF front-end filters. This progress has encouraged an impressive need for developing low-cost, high performance, mass-producible, small footprint, and highly integrated front-end solutions for microwave and millimeter-wave systems and applications including emerging 5G and future wireless platforms. In this context, high quality factor resonators are usually typical basic building blocks of many high performance passive and active circuits, and its design has become even more challenging in the last decade. As a result, Substrate Integrated Waveguide (SIW) technology has attracted scientific community and industry attention as a very good candidate for developing such desired high-Q planar microwave devices. Recently, SIW is demonstrating to be a successful approach for implementing microwave and mm-wave filters with high Q-factor, easy integration with other planar circuits, and for mass-production manufacturing processes in many technologies (i.e. Printed Circuit Board (PCB) and Low Temperature Co-fired Ceramics (LTCC) technologies among them). Its enormous similarity with waveguides is probably one of the main reasons why the development of SIW-based components and circuits is rapidly growing among the research community. Other potential features that, combined with the former advantages, could be of huge interest in a wide range of wireless and mobile applications are a lively set of research subjects, such as compactness, advanced filtering responses, and recently frequency-agility capabilities. These key features have been recently introduced in the design of microwave filters for the next-generation wireless systems. Taking into account the above-mentioned background, the work carried out during the course of this PhD Thesis has been directed towards a further study of SIW technology to propose, analyze and develop an innovative and original resonator topology. The proposed topology is based on the extension of the classical coaxial waveguide resonator to SIW technology, and must take advantage of the characteristics of SIW devices to allow the design of improved and innovative microwave resonator filters for advanced wireless systems. This PhD Thesis includes the latest improvements made on this topic, from the working principles of the basic coaxial SIW block, until different applications for the design of compact quasi-elliptic and reconfigurable microwave filters. The results are promising and demonstrate the validity of the proposed topology for the design of high-Q microwave filters, as well as its potential application to implement complex designs. The general knowledge gained from these cases of study can be considered a good base for further developing this technology, which can help to improve its EM performance, and also contribute to a more general use in the market. / Las comunicaciones inalámbricas y móviles juegan un papel importante en nuestras vidas, y esto sólo puede ir a más debido a su enorme importancia y al uso de los modernos teléfonos inteligentes (del inglés, smartphones), tabletas y toda clase de dispositivos inalámbricos. Con todo esto en mente, el espectro electromagnético para comunicaciones inalámbricas y móviles se está saturando cada día más, lo que conlleva un constante aumento de los requisitos para los filtros de radio-frecuencia usados en las cabeceras de dichos sistemas. Este progreso ha llevado a un creciente interés en desarrollar componentes de microondas de bajo coste, alto rendimiento, pequeño tamaño, que permitan implementar soluciones altamente integradas para sistemas de alta frecuencia (i.e. microondas y ondas milimétrica) y sus aplicaciones, incluyendo entre ellas la emergente conexión 5G y las futuras plataformas inalámbricas. En este contexto, los resonadores de elevado factor de calidad constituyen generalmente los bloques básicos para el diseño de muchos circuitos pasivos (entre ellos filtros) y activos de alto rendimiento. Su diseño se ha convertido por tanto en un reto aún mayor en la última década. Como resultado de ello, la tecnología de guía de ondas integradas en substrato (Substrate Integrated Waveguide, SIW) ha atraído la atención de la comunidad científica e industrial, al revelarse como una buena aproximación para el desarrollo de dispositivos planares de microondas con excelentes prestaciones eléctricas, y en particular para la implementación de filtros de microondas y onda milimétrica de bajas pérdidas y elevada integración con circuitos en tecnología planar. Además, su flexibilidad se caracteriza también por su adecuación a diferentes procesos de fabricación y producción en masa, en tecnologías tales como los circuitos impresos (Printed Circuit Board, PCB) o la tecnología de materiales cerámicos multi-capa co-sinterizados a baja temperatura (Low Temperature Co-fired Ceramics, LTCC) entre otras. Su enorme similitud con las ya largamente estudiadas guías de onda es, probablemente, una de las principales razones por las cuales el desarrollo de dicho circuitos está creciendo rápidamente entre la comunidad de investigadores. Cabe mencionar como, además de las anteriores ventajas, otras características de la tecnología SIW que podrían ser de gran interés en una amplia gama de aplicaciones inalámbricas y móviles son la miniaturización, la posibilidad de implementar respuestas avanzadas de filtrado y, recientemente, las capacidades de sintonía en frecuencia de los componentes de microondas. De este modo, el trabajo desarrollado a lo largo de esta Tesis Doctoral se ha orientado hacia el planteamiento, análisis y desarrollo de una topología de resonador innovadora y original. Dicha topología se basa en una extensión de las cavidades coaxiales en guía de onda metálica a una implementación integrada en substrato inspirada en la tecnología SIW. Esta Tesis Doctoral recapitula los últimos avances que se han producido sobre este tema, empezando desde la descripción de los principios fundamentales de funcionamiento de las estructuras, hasta la demostración de varias aplicaciones concretas útiles para el diseño de filtros de microondas muy compactos, con respuestas filtrantes avanzadas y reconfigurables. Los resultados que se van a mostrar a continuación son prometedores, y demuestran la validez de la topología propuesta. El conocimiento general obtenido de los diferentes prototipos fabricados y caracterizados experimentalmente puede considerarse una buena base para seguir desarrollando esta tecnología, lo que puede ayudar a mejorar su rendimiento electromagnético, así como a contribuir a un uso más extendido de estos dispositivos en el mercado. / Les comunicacions sense fils i mòbils juguen un paper important en les nostres vides, i això només pot anar a més a causa de la gran importància i l'ús dels moderns telèfons intel·ligents (de l'anglès, smartphones), tablets i tota classe de dispositius sense fil. Tenint en compte tot açò, l'espectre electromagnètic per a comunicacions sense fils i mòbils s'està saturant cada dia més, el que comporta un constant augment dels requisits per als filtres de radiofreqüència usats en les capçaleres d'aquests sistemes. Aquest progrés ha portat a un creixent interès en desenvolupar components de microones de baix cost, alt rendiment, volum reduït, que permeten implementar solucions altament integrades per a sistemes d'alta freqüència (ie. microones i ones mil·limètriques) i les seves aplicacions, incloent l'emergent connexió 5G i les futures plataformes sense fils. En aquest context, els ressonadors d'elevat factor de qualitat constitueixen generalment els blocs bàsics per al disseny de molts circuits passius (entre ells filtres) i actius d'alt rendiment. El seu disseny s'ha convertit per tant en un repte encara més gran en l'última dècada. Com a resultat d'això, la tecnologia de guia d'ones integrades en substrat (Substrate Integrated Waveguide, SIW) ha atret l'atenció de la comunitat científica i industrial, al revelar-se com una bona aproximació per al desenvolupament de dispositius planars de microones amb excel·lents prestacions elèctriques , i en particular per a la implementació de filtres de microones i ones mil·limètriques de baixes pèrdues i elevada integració amb circuits en tecnologia planar. A més, la seua flexibilitat es caracteritza també per la seua adequació a diferents processos de fabricació i producció en massa, en tecnologies com ara els circuits impresos (Printed Circuit Board, PCB) o la tecnologia de materials ceràmics multicapa co-sinteritzats a baixa temperatura (Low Temperature Co-Fired Ceramics, LTCC) entre d'altres. La seua enorme similitud amb les ja llargament estudiades guies d'ona és, probablement, una de les principals raons per les quals el desenvolupament d'aquests circuits està creixent ràpidament entre la comunitat d'investigadors. Cal destacar com, a més de les anteriors avantatges, altres característiques de la tecnologia SIW que podrien ser de gran interès en una àmplia gamma d'aplicacions sense fils i mòbils són la miniaturització, la possibilitat d'implementar respostes avançades de filtrat i, recentment, les capacitats de sintonia en freqüència dels components de microones. Aquestes característiques clau s'han introduït recentment en el disseny de filtres microones per als sistemes sense fils de pròxima generació, convertint-se en objecte prioritari d'estudi per part de la comunitat científica. D'aquesta manera, el treball desenvolupat al llarg d'aquesta tesi doctoral s'ha orientat cap al plantejament, anàlisi i desenvolupament d'una topologia de ressonador innovadora i original. Aquesta topologia es basa en una extensió de les cavitats coaxials en guia d'ona metàl·lica a una implementació integrada a substrat inspirada en la tecnologia SIW. Aquesta tesi doctoral recapitula els últims avanços que s'han produït sobre aquest tema, començant des de la descripció dels principis fonamentals de funcionament de les estructures, fins a la demostració de diverses aplicacions concretes útils per al disseny de filtres i microones molt compactes, amb respostes de filtrat avançades i reconfigurables. Els resultats que es mostraran a continuació són prometedors, i demostren la validesa de la topologia proposada. El coneixement general obtingut dels diferents prototips fabricats i caracteritzats experimentalment es pot considerar com una bona base per seguir desenvolupant aquesta tecnologia, el que pot ajudar a millorar el seu rendiment electromagnètic, així com a contribuir a un ús més estès d'aquests dispositius en el mer / Sirci, S. (2017). Substrate Integrated Coaxial Filters with Fixed and Tunable Responses [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/78838

<div>The allocated frequency bands for the incoming fifth generation (5G) wireless communication technologies spread broadly from sub 6 GHz to K and potentially W bands. The evolution of the future generations toward higher frequency bands will continue and presents significant challenges in terms of excessive system complexity, production and maintenance costs. Reconfigurable radio architecture with frequency-tunable components is one of the most feasible and cost-effective solutions to meet such challenges. Among these technologies, evanescent-mode (EVA) cavity tunable resonator have demonstrated many of the needed features such as wide tunability, low loss and high linearity. Such a technology typically employs a movable membrane that controls the resonant frequency of a post-loaded cavity. </div><div><br></div><div>The first part of this work focuses on advancing such technology into the mm-wave frequency bands and beyond. Manufacturing tolerance and tuner performance are the two main limiting factors addressed here. This work develops a cost-effective micro-fabrication and package assembly flow which addresses the manufacturing related limitations. On the other hand, introducing micro-corrugated diaphragms and gold-vanadium co-sputtered thin film deposition technology, significantly reduces (4 times) the tuning voltage and enhances tuning stability (7 times). We demonstrate a tunable two-pole band-pass filter (BPF) prototype as the first EVA cavity tunable filter operating in the K-Ka band. </div><div><br></div><div>The second part of this work extensively discusses an optimal RF design flow based on the developed manufacturing technology. It considers all technology constrains and allows the actualization of a high Q transfer function with minimum bandwidth variation within an octave tuning range. Moreover, a new fully passive input/output feeding mechanism that facilitates impedance matching over the entire tuning range is presented. The devised RF methodology is validated through the design and testing of a two-resonator BPF. Measurements demonstrate a tuning range between 20-40 GHz, relative bandwidth of 1.9%-4.7%, and impedance matching over the entire tuning range which is upto 2 times better than previously reported state-of-the-art MEMS tunable filters of this type.</div><div><br></div><div>The third part of this work further advances the technology by proposing the first MEMS-based low-power bi-directional EVA tuning approach that employs both the main bias circuitry as well as a new corrective biasing technique that counteracts viscoelastic memory effects. The two key enabling technologies are extensively discussed: a) a new metal-oxide-metal (MOM) sealed cavity that maintains high quality without requiring complicated metal bonding; and b) a new electrostatic bi-directional MEMS tuner that implements the needed frequency tuning without lowering the resonator quality factor. </div><div><br></div><div>Furthermore, we explore important design and fabrication trade-offs regarding sensitivity to non-ideal effects (residual stress, fabrication imperfections). Measurement of the new prototype bi-directional design, prove that this technology readily corrects residual post-bias displacement of 0.1 um that shifts the frequency by over 1 GHz with less than 2.5 V. It takes over 100 seconds to recover this error in the uni-directional case. This correction does not adversely affect the filter performance.</div>

This thesis presents the RF and mechanical design of a metal-to-metal contact RF MEMS switch. Metal-to-metal contact RF MEMS switches are especially preferred in low frequency bands where capacitive switches suffer from isolation due to the limited reactance. Frequency band of operation of the designed switch is from DC to beyond X-band. Measured insertion loss of the structure is less than 0.2 dB, return loss is better than 30 dB, and isolation is better than 20 dB up to 20 GHz. Isolation is greater than 25 dB below 10 GHz. Hence, for wideband applications, this switch offers very low loss and high isolation. Time domain measurement is necessary for the investigation of the dynamic behavior of the devices, determination of the &lsquo / pull in&rsquo / and &lsquo / pull out&rsquo / voltages of the membranes, switching time and power handling of the devices. Also, failure and degradation of the switches can be monitored using the time domain setup. For these purposes a time domain setup is constructed. Moreover, failure mechanisms of the RF MEMS devices are investigated and a power electronic circuitry is constructed for the biasing of RF MEMS switches. Advantage of the biasing circuitry over the direct DC biasing is the multi-shape, high voltage output waveform capability. Lifetimes of the RF MEMS devices are investigated under different bias configurations. Finally, for measurement of complicated RF MEMS structures composed of large number of switches, a bias waveform distribution network is constructed where conventional systems are not adequate because of the high voltage levels. By this way, the necessary instrumentation is completed for controlling a large scale RF MEMS system.

In der vorliegenden Arbeit wird ein Mikroresonator für die kernmagnetische Resonanzspektroskopie kleinster Probenvolumen entwickelt. Der Resonator besteht aus einem Mikrodetektor und einer elektrisch steuerbaren Kapazität für den Resonanzabgleich. Beide Bauteile sind speziell an die Anforderungen des Messverfahrens angepasst. Der Mikrodetektor, welcher die Funktion der Erregung der Kernspins und die Detektion des Messsignals erfüllt, weist aufgrund seiner besonderen Geometrie ein weitgehend homogenes statisches Magnetfeld im Bereich des Probenvolumens auf. Daraus resultieren eine Verbesserung der spektralen Auflösung und eine Steigerung der Empfindlichkeit. Die elektrisch steuerbare Kapazität weist eine hohe elektrische Güte und eine hohe Spannungsfestigkeit auf, wodurch die Verwendung von hohen Pulsleistungen möglich ist. Der Nachweis der Funktionalität des Systems erfolgt durch die Integration des Mikroresonators in einen Probenkopf, welcher zur Messung von Test- und Referenzsignalen eingesetzt wird. Anhand der Messwerte wird gezeigt, dass die neue Entwicklung eine sehr hohe Empfindlichkeit und eine deutlich höhere spektrale Auflösung als andere Detektorsysteme dieser Art aufweist und somit besonders gut für die Messung von sehr kleinen Probenvolumen geeignet ist. / The thesis describes the development of a micro resonator for nuclear magnetic resonance (NMR) spectroscopy of very small sample volumes. The resonator consists of a microcoil and an electrically adjustable capacitance for resonance tuning. Both components are specially designed for the purpose of NMR. The microcoil excites the nuclear spins and detects the measurement signal. Due to the special cylindrical geometry, the detector provides a very homogenous spatial distribution of the static magnetic field at the location of the sample. This leads to improved spectral resolution and increased sensitivity. The electrically adjustable capacitance provides a high quality factor and high voltage stability. Hence, short excitation pulses with high bandwidth can be applied. The components are integrated into a specially designed probe. The functionality of the system is demonstrated by test and reference measurements. The measurement results verify the high sensitivity and the high spectral resolution. Hence, the system is applicable and well suited for NMR measurements of small sample volumes.

This thesis presents research towards enabling micromachined millimeter and submillimeter wave focal plane arrays (FPAs). The FPAs operate under the following principle: a switch network consisting of microelectromechanical (MEMS) switches, integrated with micromachined waveguides, is used to feed an array of antenna elements, located in the focal plane of a high-gain quasi-optical system. Hence, it is possible to switch between a set of narrow beams in different directions. Such beam steering systems are needed for future millimeter and submillimeter wave imaging and communication systems. The contributions to future MEMS-switchable FPAs presented here are organized in three papers, as described below. Paper I presents a criterion on the spacing between adjacent FPA elements which results in -3 dB overlap between the switched beams, for the special case when an extended hemispherical dielectric lens is used as the optical system. A key step towards this criterion is a closed-form relation between the scan angle and the FPA element's position, which results in an expression for the effective focal length of extended hemispherical lenses. A comparison with full-wave simulations demonstrates an excellent agreement with the presented theoretical results. Finally, it is shown that the maximum feasible FPA spacing when using an extended hemispherical lens is about 0.7 wavelengths. Paper II presents a numerical study of silicon-micromachined planar extended hemispherical lenses, with up to three matching regions used to reduce internal reflections. The effective permittivity of the matching regions is tailor-made by etching periodic holes in the silicon wafer. The optimal thickness and permittivity of the matching regions were determined using TRF optimization, in order to yield the maximum wide-band aperture efficiency and small side-lobes. We introduce a new matching region geometry, referred to as shifted-type matching regions, and it is demonstrated that using three shifted-type matching regions results in twice as large aperture efficiency as compared to using three conventional concentric-type matching regions. Paper III presents a submillimeter-wave single-pole single-throw (SPST) 500-750 GHz MEMS waveguide switch, based on a MEMS-reconfigurable surface inserted between two waveguide flanges. A detailed design parameter study is carried out to select the best combination of the number of horizontal bars and vertical columns of the MEMS-reconfigurable surface, for achieving a low insertion loss in the transmissive state and a high isolation in the blocking state. A method is presented to model the non-ideal electrical contacts between the vertical cantilevers of the MEMS surface, with an excellent agreement between the simulated and measured isolation. It is shown that the isolation can be improved by replacing an ohmic contact by a new, capacitive contact. The measured isolation of the switch prototype is better than 19 dB and the measured insertion loss is between 2.5 and 3 dB. / Denna avhandling presenterar forskning som syftar till att möjliggöra fokalplans-gruppantenner (FPAs) för våglängder i millimeter och submillimeterområdet. Principen för en sådan FPAs funktion är följande: ett nätverk bestående av mikroelektromekaniska (MEMS) switchar, används för att välja mellan de olika antenn-elementen i en gruppantenn, som placerats i fokalplanet av ett optiskt system. Därmed blir det möjligt att välja från en uppsättning av smala lober i olika riktningar. Sådana lob-styrningssystem behövs för framtida radar- och kommunikationssystem i millimeter och submillimeterområdet. Resultaten är uppdelade i tre vetenskapliga artiklar, som beskrivs nedan. I den första artikeln (Paper I) presenteras ett villkor för avståndet mellan närliggande FPA-element som resulterar i -3 dB överlappning mellan de switchade loberna, för specialfallet då en förlängd hemisfärisk lins används som optiskt system. Det viktigaste steget mot att hitta detta villkor är att bestämma en analytisk relation mellan avsökningsvinkeln och FPA-elementens position. Detta resulterar i ett uttryck för den effektiva fokallängden för denna typ av lins. En utmärkt överensstämelse har funnits mellan dessa relationer och simuleringar. Slutligen visas det att de största möjliga FPA-avstånden för en förlängd hemisfärisk lins är ungefär 0.7 våglängder, vilket uppnås för linser med låg permittivitet. I den andra artikeln (Paper II) presenteras en numerisk studie av plana förlängda hemisfäriska linser, som kan produceras från en kiselskiva. Linserna har upp till tre matchningsregioner, som används för att reducera interna reflektioner. Den effektiva permittiviteten av de matchande regionerna skräddarsys genom etsning av periodiska hål i kiselskivan. Den optimala tjockleken och permittiviteten av de matchande regionerna har bestämts med hjälp av TRF-optimering, för att ge maximal bredbandig direktivitet och minimala sidlober. En ny geometri introduceras för matchningsregionerna, som vi kallar matchningsregioner av skiftad typ. Vi visar att användning av tre matchningsregioner av skiftad typ resulterar i en dubbelt så hög apertur-effektivitet, jämfört med att använda tre konventionella matchningsregioner av koncentrisk typ. I den tredje artikeln (Paper III) presenteras en MEMS-switch för rektangulära vågledare, för frekvensområdet 500-750 GHz. Baserat på en designparameterstudie har den bästa kombinationen av antalet horisontella rader och vertikala kolumner hos den MEMS-konfigurerbara ytan valts ut, för att uppnå låga förluster i det öppna tillståndet och hög isolation i det blockerande tillståndet. I artikeln presenteras en metod för att modellera icke-perfekta elektriska kontakter mellan de fixerade och de rörliga delarna i MEMS-ytan. Denna metod uppvisar en utmärkt överensstämmelse mellan den simulerade och den uppmätta isolationen. Vi visara att isolationen kan förbättras med hjälp av en ny typ av kapacitiv kontakt. Den uppmätta isolationen hos den presenterade switch-prototypen är högre än 19 dB, och den uppmätta förlusten är mellan 2.5 och 3 dB. / <p>QC 20161206</p>

This thesis presents novel radio frequency microelectromechanical (RF MEMS) circuits based on the three-dimensional (3-D) micromachined coplanar transmission lines whose geometry is re-configured by integrated microelectromechanical actuators. Two types of novel RF MEMS devices are proposed. The first is a concept of MEMS capacitors tuneable in multiple discrete and well-defined steps, implemented by in-plane moving of the ground side-walls of a 3-D micromachined coplanar waveguide transmission line. The MEMS actuators are completely embedded in the ground layer of the transmission line, and fabricated using a single-mask silicon-on-insulator (SOI) RF MEMS fabrication process. The resulting device achieves low insertion loss, a very high quality factor, high reliability, high linearity and high self actuation robustness. The second type introduces two novel concepts of area efficient, ultra-wideband, MEMS-reconfigurable coupled line directional couplers, whose coupling is tuned by mechanically changing the geometry of 3-D micromachined coupled transmission lines, utilizing integrated MEMS electrostatic actuators. The coupling is achieved by tuning both the ground and the signal line coupling, obtaining a large tuneable coupling ratio while maintaining an excellent impedance match, along with high isolation and a very high directivity over a very large bandwidth. This thesis also presents for the first time on RF nonlinearity analysis of complex multi-device RF MEMS circuits. Closed-form analytical formulas for the IIP3 of MEMS multi-device circuit concepts are derived. A nonlinearity analysis, based on these formulas and on  measured device parameters, is performed for different circuit concepts and compared to the simulation results of multi-device  conlinear electromechanical circuit models. The degradation of the overall circuit nonlinearity with increasing number of device stages is investigated. Design rules are presented so that the mechanical parameters and thus the IIP3 of the individual device stages can be optimized to achieve a highest overall IIP3 for the whole circuit.The thesis further investigates un-patterned ferromagnetic NiFe/AlN multilayer composites used as advanced magnetic core materials for on-chip inductances. The approach used is to increase the thickness of the ferromagnetic material without increasing its conductivity, by using multilayer NiFe and AlN sandwich structure. This suppresses the induced currents very effectively and at the same time increases the ferromagnetic resonance, which is by a factor of 7.1 higher than for homogeneous NiFe layers of same thickness. The so far highest permeability values above 1 GHz for on-chip integrated un-patterned NiFe layers were achieved. / <p>QC 20140328</p>