Dissertations / Theses on the topic 'High Frequency Applications'
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Davari, Pooya. "High frequency high power converters for industrial applications." Thesis, Queensland University of Technology, 2013. https://eprints.qut.edu.au/62896/1/Pooya_Davari_Thesis.pdf.
Full textLee, Joshua Khai Ho. "High performance transconductance amplifiers for high frequency RF applications." Thesis, Oxford Brookes University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432702.
Full textbi, xiaofei. "Compressed Sampling for High Frequency Receivers Applications." Thesis, Högskolan i Gävle, Avdelningen för elektronik, matematik och naturvetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-10877.
Full textDespotopoulos, Solon. "SiGe HFETs for analogue high frequency applications." Thesis, Imperial College London, 2003. http://hdl.handle.net/10044/1/8727.
Full textKöroğlu, Mustafa Hadi. "High frequency integrated filters for wireless applications." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/14458.
Full textMassicotte, Mathieu. "Graphene electronics for high frequency, scalable applications." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=110547.
Full textL'avènement du graphène produit à grande-échelle par dépôt chimique en phase vapeur (CVD) ouvre une voie vers l'électronique haute-fréquence (HF) à base de graphène. Synthétiser du graphène possédant une grande mobilité des porteurs de charge et l'incorporer à des dispositifs HF constitue cependant un important défi. Nous présentons ici le fruit de nos efforts pour comprendre et contrôler le mécanisme de croissance CVD du graphène sur le cuivre, caractériser les films ainsi produits, et fabriquer des transistors et dispositifs HF à base de graphène. Parallèlement, nous décrivons la synthèse de grands flocons dendritiques de graphène que nous appelons graphlocons. Les propriété électroniques et la magnetorésistance de ces échantillons ont été mesurées de 300 K à 100 mK et la mobilité la plus élevée obtenue est de 460 cm^2/Vs avec une densité de porteurs de charge résiduels de 1.6x10^12 cm^-2 . Les paramètres S de haute fréquence ont été mesurés de 0.04 à 20 GHz mais aucune dépendance en température ou champ magnétique n'a été observée. Ce travail fourni un point de départ pour améliorer les propriétés structurales et électroniques du graphène produit par CVD, et pour explorer de nouveaux phénomènes dans le domaine des GHz. .
McCarthy, Jane. "Composite magnetostrictive materials for high frequency applications." Thesis, University of Brighton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365089.
Full textZhang, Xiaokai. "Novel magnetic composites for high frequency applications /." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 190 p, 2009. http://proquest.umi.com/pqdweb?did=1654494811&sid=2&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Full textLin, Fang. "High-Q high-frequency CMOS bandpass filters for wireless applications." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/14869.
Full textEscalante, Soberanis Mauricio Alberto. "High frequency data analysis for wind energy applications." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/54821.
Full textApplied Science, Faculty of
Mechanical Engineering, Department of
Graduate
LI, QUAN, and q. li@cqu edu au. "HIGH FREQUENCY TRANSFORMER LINKED CONVERTERS FOR PHOTOVOLTAIC APPLICATIONS." Central Queensland University. N/A, 2006. http://library-resources.cqu.edu.au./thesis/adt-QCQU/public/adt-QCQU20060830.110106.
Full textBoustedt, Katarina. "Flip chip for high frequency applications : materials aspects /." Örebro : Institutionen för teknik Department of Technology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-1519.
Full textSkulason, Helgi. "High-frequency characterization and applications of graphene devices." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119524.
Full textDans cette thèse, nous avons expérimentalement sondé les micro-ondes électrodynamiques de graphène de grande surface, plus particulièrement les mesures de graphène sans contact pour en extraire les propriétés de la matière et la mise en œuvre de dispositifs non-réciproques générateurs de micro-ondes. Notre objectif consiste à exploiter l'interaction entre le graphène et les ondes électromagnétiques dans le domaine des micro-ondes. En fabriquant un guide d'ondes de graphène coplanaire à large bande, nous établissons que le graphène possède une résistance de large bande constante comprise entre 17 Hz et 110 GHz. Ceci est attribuable à l'inductivité cinétique et à l'effet pelliculaire négligeables jusqu'à 110 GHz. Nous décrivons l'impédance des contacts entre le graphène et les électrodes métalliques. Nos dispositifs démontrent que la capacitance de contact court-circuite la résistance de contact au-dessus de 2 GHz, permettant les mesures du graphène sans contact jusqu'à 110 GHz. Nous avons mesuré la conductivité magnétique du graphène à grande surface sous excitation de micro-ondes utilisant une géométrie de disque Corbino en transférant les films de graphène sur des embouts de câble coaxial polis. Notre installation permet l'utilisation de dispositifs de graphène actifs et passifs où les dispositifs actifs sont dopés par effet de champ avec une grille de silicium intrinsèque transparente aux micro-ondes. Nous avons extrait des mobilités à base de la conductivité magnétique autour de 1000 cm… en utilisant le model de Drude à une composante à haute densité. Une magnéto résistance atypique a également été observée. Nous avons créé, fabriqué et caractérisé un guide d'onde isolateur creux avec du graphène biaisé magnétiquement agissant comme élément non-réciproque par rotation de Faraday. Notre montage expérimentale permet la caractérisation sans contact de la conductivité, la mobilité et la densité de porteurs de charges du film de graphène. La rotation de Faraday a été mesuré jusqu'à 1.5 ce qui résulte en une isolation de 25dB. Nous démontrons que la performance de l'isolateur peut être améliorée en augmentant la mobilité dans le graphène. Étant donné que la direction de la rotation de Faraday dépend du signe du porteur de charge dominant dans le graphène, nous soumettons des données démontrant que la direction de l'isolation peut être modulée et changée en utilisant l'effet de champ implémenté dans le guide d'ondes creux avec une seule source de voltage à basse puissance. Notre travail suggère que d'autres dispositifs non-réciproques comme des circulateurs peuvent être implémentés de façon compacte avec du graphène.
Auton, Gregory. "High-mobility graphene nano-rectifiers and transistors for high frequency applications." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/highmobility-graphene-nanorectifiers-and-transistors-for-high-frequency-applications(1250a10d-e3c8-45f7-ba85-0d2e89f1bd04).html.
Full textTavakoli, Hanif. "A High Frequency Transformer Winding Model for FRA Applications." Licentiate thesis, Stockholm : Skolan för elektro- och systemteknik, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11178.
Full textForsberg, Urban. "CVD Growth of Silicon Carbide for High Frequency Applications." Doctoral thesis, Linköping : Univ, 2001. http://www.bibl.liu.se/liupubl/disp/disp2001/tek708s.pdf.
Full textBishop, Gary J. "High pulse repetition frequency XeCl laser and its applications." Thesis, University of Hull, 1990. http://hydra.hull.ac.uk/resources/hull:6917.
Full textRoss, Gordon J. "Detecting changes in high frequency data streams, with applications." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/12255.
Full textYang, Rachel S. (Rachel Shanting). "Low-loss inductor design for high-frequency power applications." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/123006.
Full textThesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2019
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 72-74).
Miniaturization of power electronics can improve the performance of many applications, such as renewable energy systems, data centers, and aerospace systems. Operation in the high frequency (HF) regime (3{ 30 MHz) has potential for miniaturizing power electronics, but designing small, efficient inductors at HF can be challenging. At these frequencies, losses due to skin and proximity effects are difficult to reduce, and gaps needed to keep B fields low in the core add fringing field loss. This thesis aims to improve the design of HF inductors. A low-loss inductor structure for HF applications and associated design guidelines that optimize for loss have been developed. The structure achieves low loss through quasi-distributed gaps and a new field shaping technique that achieves low winding loss through double-sided conduction. An example ~15 [mu]H inductor designed using the proposed guidelines achieved an experimental quality factor of 720 at 3MHz and 2A (peak) of ac current.
In some cases, litz wire may further improve the performance of the proposed structure. With litz wire, the example inductor achieved an improved quality factor of 980. The proposed structure also has great design and application flexibility. Core sets for this structure can be scaled by a factor-of-four in volume and still cover a large, continuous range of inductor requirements, e.g. power handling and inductances. A wide range of requirements can therefore be achieved with a small set of core pieces. The proposed inductor structure and design techniques thus have greater potential for commercial adoption to facilitate the design of low-loss HF inductors. The design techniques used in the proposed structure can also be extended to high-power radio-frequency (RF) applications, such as RF power amplifiers for industrial plasma generation. A modified version of the proposed structure, along with modified design guidelines, can achieve low loss in this operating space.
Simulations show that an example ~600 nH inductor achieves a quality factor of 1900 at 13:56MHz and 78A (peak). Therefore, the developed design techniques and inductor structures are suitable for small, highly-efficient inductors at HF, and can thereby help realize high-frequency miniaturization of power electronics.
by Rachel S. Yang.
M. Eng.
M.Eng. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
Patel, Ketan. "OXIDE BASED MAGNETIC NANOCRYSTALS FOR HIGH-FREQUENCY AND HIGH-ENERGY PRODUCT APPLICATIONS." Master's thesis, Temple University Libraries, 2017. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/464990.
Full textM.S.M.E.
Magnets play a major role in our rapidly developing world of technology. Electric motors and generators, transformers, data storage devices, MRI machines, cellphones, and NMR are some of the many applications for magnets. However, almost all the magnets currently being used have rare-earth heavy metals in them. Despite their high-energy product, the presence of rare-earth metals increases the cost significantly. Also, the processes involved in the mining of rare-earth metals are hazardous to the environment, and to all life forms. In the past few decades, oxide based magnets have gained a lot of attention as potential replacements for the rare-earth magnets. Oxide based magnetic nanocrystals are attracting a lot of attention as a potential replacement for rare-earth magnets. They are stable in ambient condition and their manufacturing cost is very low when compared to the rare-earth magnets. My work deals with the synthesis of core-shell magnetic structure for high frequency applications (Chapter 1) and the synthesis of high energy product magnetic nanocrystals (Chapter 2) and the synthesis of soft magnetic nanocrystals for high frequency measurement. NiZn ferrite, a soft oxide based magnet cannot be directly implied at high frequencies as they fail at the frequency which over the MHz range. On the other hand, BaZn ferrite is a Y-type magnets, which is robust at higher frequencies. Therefore, using the latter magnet as a protective shell for core material, made of former magnet, enables us to manufacture a cheap solution to the rare-earth magnets used in our cell phones and other devices that work on high frequency signals. On the other hand, successful coating of a very soft magnetic material on a hard-magnetic core increases the total energy product of the magnetic composite, which enhances its versatility.
Temple University--Theses
Nuttall, Daniel Robert. "Advanced high frequency switched-mode power supply techniques and applications." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/advanced-high-frequency-switchedmode-power-supply-techniques-and-applications(5792cb86-58e3-488b-b27e-559c18e55250).html.
Full textLópez, Domínguez Víctor. "Nanomagnetism and high frequency experiments. Basic science and technological applications." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/146177.
Full textLa interacción de nanopartículas magnéticas con radiación de microondas y sus aplicaciones en campos como la electrónica, la farmacia y la medicina son actualmente un campo de gran interés científico y tecnológico. En esta área son de gran importancia los efectos de tamaño de las nanopartículas magnéticas ya que modifican propiedades como la temperatura de bloqueo o de Curie ya que determinan su interacción con altas frecuencias. En esta tesis se muestran nuevos fenómenos como la reducción colosal de la temperatura de Curie en nanopartículas de CoFe2O4 debida a efectos de tamaño en nanopartículas menores de 3 nm (capitulo 1). Para estos tamaños se detectó una distorsión en la estructura cristalina modificando la interacción de intercambio entre los átomos que forman dichas nanopartículas. En consecuencia la temperatura de Curie, de 700 K para sustancia pura, se reduce hasta 10 K, siendo el primer sistema donde se observan una temperatura de bloqueo y de Curie similares entre ellas. Todas estas propiedades pueden ser estudiadas mediante la absorción de microondas que presentan las nanopartículas magnéticas (capitulo 2). De esta manera la caracterización de los perfiles de absorción entre 1 y 20 GHz, proporcionan de una manera rápida las propiedades básicas de dichos sistemas y su dinámica magnética, así como la posibilidad de nuevas aplicaciones tecnológicas en electrónica y medicina. Los efectos de tamaño también pueden ser combinados con la modificación superficial de nanopartículas de oro mediante la unión de diferentes moléculas a la superficie de las nanopartículas (capitulo 3); también investigadas en esta tesis. La aparición de una señal magnética en estos sistemas es debida a la interacción de la molécula enlazada con la superficie de la nanopartícula. Por último en este trabajo se exponen las diferentes aplicaciones de la radiación de teraherzio (capitulo 4), comprendida entre 0.3 y 3 THz, en ciencias de materiales, biolog_á y farmacia. El principal interés que presenta esta radiación reside en que es una radiación no invasiva, no ionizante, y no destructiva. Como aplicación principal se estudió la permeación de medicamentos de uso tópico a través de membranas artificiales y piel. Para este caso se estudió las variaciones dimensionales de la capa que contiene la formulación tópica sobre las membranas artificiales y la piel. De esta manera, se pudo obtener la transferencia de masa de la formulación a la membrana y se pudo caracterizar el proceso de permeación. Esta técnica representa un método no invasivo y limpio frente a otras técnicas actuales como el skin stripping.
Teirikangas, M. (Merja). "Advanced 0–3 ceramic polymer composites for high frequency applications." Doctoral thesis, Oulun yliopisto, 2011. http://urn.fi/urn:isbn:9789514296185.
Full textTiivistelmä Väitöstyön tavoitteena oli tutkia ruiskuvalettavien 0–3 –liitännäisten keraami-polymeerikomposiittien ominaisuuksia erityisesti niiden GHz-taajuusalueen dielektristen ja magneettisten ominaisuuksien kannalta. Työ on jaettu kolmeen osaan. Ensimmäisessä osassa on tutkittu kaksikomponenttisia keraami-polymeerikomposiitteja, joissa täytemateriaali on joko dielektristä tai magneettista materiaalia. Komposiittien ominaisuuksia on analysoitu jo olemassa olevien seosmallinnuskaavojen avulla. Komposiittien hyödyntämistä erilaisten sovellusten, kuten antennien, minityrisoinnissa on myös käsitelty. Toinen osa käsittelee kolmikomponenttisia komposiitteja, joissa lisäaineena on käytetty pieniä määriä nanomateriaaleja (hopea- ja piipartikkelit sekä alumiinioksidikuitu) tarkoituksena parantaa komposiitin dielektrisiä. Kolmannessa osassa on tutkittu periodisia ja monikerroksisia keraami- polymeerikomposiittirakenteita rakenteita. Kaksikomponenttisten keraami-polymeerikomposiittien tapauksessa suurin permittiivisyyden arvo 15 dielektristen häviöiden ollessa 0.008 (mittaustaajuus 1 GHz) saatiin komposiitille, jossa dielektristä täytemateriaalia (Barium Strontium Titanaatti, BST) oli 37 tilavuus-% termoplastisessa polymeerimatriisissa (ER140). Korkein saavutettu permeabiliteetin arvo 1.8 magneettisten häviöiden ollessa 0.077 (mittaustaajuus 1 GHz) saatiin komposiitille, jossa magneettista täyteainetta (hexaferriitti, Co2Z) oli 43 tilavuus-% ER182 -matriisissa. Tämä täyteaine mahdollistaa nykyistä jopa 77 % pienempien antennielementtien kehittämisen. Tukimuksessa todettiin 2–6 tilavuus-% nanomateriaalin lisäyksen BST-ER140 -komposiitteihin kasvattavan permittiivisyyttä merkittävästi juurikaan vaikuttamatta dielektrisiin häviöihin. Erityisesti 2 tilavuus-% hopeananopartikkeleiden lisäys BST-ER140 -komposiitteihin kasvatti permittiivisyyttä 52 % dielektristen häviöiden (tan δε = 0.004) kasvamatta. Työssä on myös tutkittu periodisesti (vertikaali ja horisontaali) koostettuja dielektrisiä komposiittirakenteita, jossa eri kerroksissa on erilaiset dielektriset ominaisuudet sekä monikerrosrakenteita, joissa vuorottelevat dielektriset ja magneettiset kerrokset. Mittaukset osoittivat, että monimateriaaliset monikerrosrakenteet ovat hyviä kandidaatteja komponentteihin, jotka vaativat pieniä dielektrisiä ja magneettisiä häviöitä
Regimbal, Nicolas. "Study of fractional frequency synthesizers for high data rate applications." Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14292/document.
Full textThis dissertation deals with frequency synthesis and more specifically with the fractional frequency divider, one of the most critical blocks in radio frequency systems. A new fractional division method is presented along with two possible embodiments. It is based on a random dithering of the phase error. The divider output spectrum is cleaned from any fractional spurious tone. The spurious tones energy is uniformly spread on the whole spectrum, without noise shaping. The proposed solution can be implemented in frequency synthesizers like Phase Locked Loops (PLL). As no noise shaping is applied, the PLL bandwidth can be optimized. In this context, the possibility of high data-rate direct modulation is studied. Finally, solutions for the optimization of the resulting system are inspected
Chinthakindi, Anil Kumar. "Fabrication and modeling of electrostatic actuators for high frequency applications." Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/11170.
Full textLi, Kezheng. "Germanium bipolar transistor design and technology for high frequency applications." Thesis, Queen's University Belfast, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.579763.
Full textJi, Chao. "High performance resonant pulsed power supply for radio frequency applications." Thesis, University of Nottingham, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.594395.
Full textKablan, Abdalla. "The use of fuzzy logic applications for high frequency trading." Thesis, University of Essex, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.542339.
Full textBar, Galit 1970. "High-frequency time domain electron paramagnetic resonance : methods and applications." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/17826.
Full textVita.
Includes bibliographical references.
There are numerous advantages to high frequency (high field) electron paramagnetic resonance (EPR) spectroscopy. Two of the most important are improved sensitivity and the improved resolution of field dependent interactions. In addition, there are many attractive features to time domain spectroscopy. Pulsed EPR allows for the design of experiments, which can specifically be used to study structure and dynamics of paramagnetic species and provide utmost resolution by separating interactions from each other. The combination of pulsed techniques and high frequencies is not only complimentary to continuous wave (CW) low frequency EPR but it also greatly increases the accessible information on paramagnetic species. High frequency, time domain EPR is still in its infancy. Spectrometers at W-band ([approximately] 95 GHz) are now available commercially but to date very few spectrometers operating at higher frequencies have been described. The spectrometer developed in the Francis Bitter Magnet Laboratory operates at a microwave (MW) frequency of 139.5 GHz corresponding to [approximately] 5 T magnetic field. The applications presented in this thesis illustrate the potential of high frequency, time domain EPR spectroscopy at 139.5 GHz in obtaining structural and mechanistic insights of several paramagnetic systems. Well resolved EPR spectra observed at 139.5 GHz of the stable tyrosine radical in ribonucleotide reductase (RNR) revealed the existence of a hydrogen bond in RNR from yeast, chapter 1. The bond length and orientation were determined from the nuclear frequencies of the proton, detected by orientation selective electron nuclear double resonance (ENDOR).
(cont.) The advantage of the time domain detection scheme is demonstrated in chapters 4, 5 and 6. A stimulated echo sequence is used to separate different organic radicals associated with the reduction chemistry and inhibition mechanisms of RNR. Using the dispersion in relaxation rates at high temperature ([approximately] 60 K) it is possible to filter the multi component spectrum. The assignment of new radicals is possible at high field, 5 T, due to the high resolution in g anisotropy. The findings support earlier proposals for the mechanism of nucleotide reduction and inhibition of this very important enzyme. To study photoexcited triplet molecules a light source was coupled to the high frequency spectrometer and the pulsed mode detection scheme was used to acquire EPR spectra. The new technique is demonstrated on several model systems. In addition to the basic advantages described above, high frequency EPR opens new frontiers for high spin systems, S >[or equal to] 1, with large spin-spin interaction. Because of the inverse field dependency of the zero field splitting, such systems may be totally EPR-silent at normal EPR frequencies. However their EPR spectra are accessible at high frequencies due to the reduction of linewidth. The Mn(II), S = 5/2, in superoxide dismutase (SOD) is a good example for such system.
by Galit Bar.
Ph.D.
Li, Yifan. "Point process based high frequency volatility estimation : theory and applications." Thesis, Lancaster University, 2018. http://eprints.lancs.ac.uk/127786/.
Full textGrowden, Tyler A. "III-V Tunneling Based Quantum Devices for High Frequency Applications." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1469199253.
Full textLim, Ying Ying. "Printing conductive traces to enable high frequency wearable electronics applications." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/17880.
Full textFarzanehfard, Hosein. "Wideband characterization of aluminum nitride substrates and high power-high frequency thick film applications." Diss., Virginia Tech, 1992. http://hdl.handle.net/10919/39788.
Full textPh. D.
Cheng, Jung-hui 1960. "Steady-state and dynamic analysis of high-order resonant converters for high-frequency applications." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/282337.
Full textSoufizadeh, Balaneji Nasim. "A New Generation of Particle-Based Radio Frequency (RF) Switches for Portable and High-Frequency Applications." Thesis, North Dakota State University, 2019. https://hdl.handle.net/10365/31148.
Full textBelcher, Robert W. "Extremely High Frequency (EHF) Low Probability of Intercept (LPI) communication applications." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA226653.
Full textThesis Advisor(s): Schwendtner, Thomas A. Second Reader: Davidson, K. L. "March 1990." Description based on title screen as viewed on August 25, 2009. DTIC Descriptor(s): Interception probabilities, communication and radio systems, communications networks, spectra, command and control systems, extremely high frequency, naval operations, tactical warfare, low rate, theses, scenarios, line of sight, military applications. Author(s) subject terms: Millimeter wave, EHF, Extremely High Frequency, LPI, Low Probability of Intercept. Includes bibliographical references (p. 68-70). Also available print.
O'Toole, Vincent. "A novel high frequency power supply for use in welding applications." Thesis, University of Liverpool, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293140.
Full textHu, Kan-Nian. "Polarizing agents for high-frequency Dynamic Nuclear Polarization : development and applications." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/37887.
Full textVita.
Includes bibliographical references (p. 269-273).
Dynamic Nuclear Polarization (DNP) is utilized to enhance NMR signal intensities in systems including metals, ceramics, polymers and biological solids. The enhancement results from polarization transfers from unpaired electrons, usually carried by a polarizing agent such as TEMPO (2,2,6,6-tetramethylpiperydin-l-oxyl), to the target nuclei. In this thesis, polarizing agents were developed for efficient polarization mechanisms at 5 Tesla. DNP using biradicals yielded improvements of proton enhancement by about fourfold compared to an identical amount of monomeric TEMPO as used previously. The polarizing mechanism involved was the cross effect (CE), which relies on three-spin processes involving two electrons and one nucleus. Optimization of the CE requires the appropriate electron-electron interaction and the correct EPR frequency separation matching the nuclear Larmor frequency. Due to the relatively short inter-radical distance in interesting biradicals, multi-frequency EPR lineshape analyses are suitable to characterize, the distance and relative g-tensor orientations between electrons, revealing spectral parameters that explain the improvement of DNP efficiency. Alternatively, radical mixtures of TEMPO and Trityl, methyl tris(8-carboxy-2,2,6,6-tetramethyl-benzo[ 1 ,2-d:4,5-d']bis( 1 ,3)dithiol-4-yl, improve the probability of the correct EPR frequency separation compared to TEMPO by itself.
(cont.) A 1:1 radical mixture produced a combined EPR spectrum with the required frequency separation and gave an improvement of the DNP enhancement by about threefold relative to TEMPO alone. In addition, a quantum mechanical theory of the CE was developed to provide sound explanations of the improved polarizing mechanism using the above polarizing agents. The soluble biradical-TOTAPOL, yielding proton enhancements of 160-290-was developed and applied to a wide range of aqueous systems from amyloid peptide nanocrystals to liquid samples. Polarizing nanocrystals relies on nuclear spin diffusion that transfers enhanced nuclear polarization from solvent into crystals that are isolated from paramagnetic species. This requires efficient polarizing agents that produce and maintain a high level of nuclear polarization surrounding the nanocrystals. In a second application, efficient polarizing agents that reduce the required radical concentration are important for temperature-jump DNP experiments involving a cycle of freezing, polarization, melting and observation of the liquid-state NMR spectrum of samples of interest. During melting, preservation of the nuclear polarization benefits from reduced paramagnetic relaxation at low radical concentrations.
by Kan-Nian Hu.
Ph.D.
Benedick, Andrew John. "Applications and noise properties of high repetition rate : TiSapphire frequency combs." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/66001.
Full textCataloged from PDF version of thesis. Vita.
Includes bibliographical references (p. 179-186).
Femtosecond mode-locked lasers are a unique laser technology due to their broad optical bandwidth and potential for linking the optical and radio frequency domains when these lasers are configured as frequency combs. Ti:Sapphire based mode-locked lasers offer considerable advantages over other laser systems by generating both the broadest optical spectrum and highest fundamental pulse repetition rates directly from the laser cavity. Recent advances in laser diode technology have reduced the cost of pump lasers for Ti:Sapphire based frequency combs considerably, and the recent demonstration of direct diode pumping of a narrowband mode-locked Ti:Sapphire laser suggests that Ti:Sapphire frequency combs may finally be ready to make the transition from an indispensible research tool to a wider set of industrial applications. In this thesis, several applications and fundamental properties of Ti:Sapphire based mode-locked lasers are investigated. To enable more widespread use of Ti:Sapphire based frequency combs, a frequency comb based on an octave spanning 1 GHz Ti:Sapphire laser is demonstrated. The I GHz Ti:Sapphire laser is referenced to a methane stabilized HeNe laser, resulting in a frequency comb with a fractional frequency stability of its optical spectrum of 2x1 0-14 on a 20 second timescale. A recently identified frequency comb application is the calibration of astronomical spectrographs to enable detection of Earth-like planets which are orbiting Sun-like stars. In support of this application, a second frequency comb system was constructed which ultimately was characterized by a 51 GHz pulse repetition rate and 12 nm bandwidth centered at 410 nm. This "astro-comb" system was deployed to the Fred Lawrence Whipple Observatory where preliminary results indicate a 40-fold increase in the spectrograph stability due to calibration by the astro-comb. Finally, the stability of the optical pulse train emitted from femtosecond mode-locked lasers is expected to exhibit the lowest phase noise of any oscillator, with theoretical predictions of phase noise levels below -190 dBc for offset frequencies exceeding 1 kHz. A comparison between the pulse trains of two nearly identical mode-locked lasers resulted in a measured timing error of less than 13 attoseconds measured over the entire Nyquist bandwidth.
by Andrew John Benedick.
Ph.D.
Makwana, Mehul. "Theoretical extensions and applications of high frequency homogenisation to periodic media." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/28236.
Full textSchmid, Robert L. "High-frequency silicon-germanium reconfigurable circuits for radar, communication, and radiometry applications." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/54838.
Full textSeo, Sanghyun. "GaN-based heterostructure field effect transistors and MMICs for high frequency applications." Aachen Shaker, 2009. http://d-nb.info/999595059/04.
Full textAguirre, Morales Jorge Daniel. "Characterization and modeling of graphene-based transistors towards high frequency circuit applications." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0235/document.
Full textThis work presents an evaluation of the performances of graphene-based Field-Effect Transistors (GFETs) through electrical compact model simulation for high-frequency applications. Graphene-based transistors are one of the novel technologies and promising candidates for future high performance applications in the beyond CMOS roadmap. In that context, this thesis presents a comprehensive evaluation of graphene FETs at both device and circuit level through development of accurate compact models for GFETs, reliability analysis by studying critical degradation mechanisms of GFETs and design of GFET-based circuit architectures.In this thesis, an accurate physics-based large-signal compact model for dual-gate monolayer graphene FET is presented. This work also extends the model capabilities to RF simulation by including an accurate description of the gate capacitances and the electro-magnetic environment. The accuracy of the developed compact model is assessed by comparison with a numerical model and with measurements from different GFET technologies.In continuation, an accurate large-signal model for dual-gate bilayer GFETs is presented. As a key modeling feature, the opening and modulation of an energy bandgap through gate biasing is included to the model. The versatility and applicability of the monolayer and bilayer GFET compact models are assessed by studying GFETs with structural alterations.The compact model capabilities are further extended by including aging laws describing the charge trapping and the interface state generation responsible for bias-stress induced degradation.Lastly, the developed large-signal compact model has been used along with EM simulations at circuit level for further assessment of its capabilities in the prediction of the performances of three circuit architectures: a triple-mode amplifier, an amplifier circuit and a balun circuit architecture
Roberts, David C. (David Christopher). "Design, modeling, fabrication and testing of a piezoelectric microvalve for high pressure, high frequency hydraulic applications." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/8332.
Full textIncludes bibliographical references.
A piezoelectrically-driven hydraulic amplification microvalve for use in high specific power hydraulic pumping applications was designed, fabricated, and experimentally characterized. High frequency, high force actuation capabilities were enabled through the incorporation of one or more bulk piezoelectric material elements beneath a micromachined annular tethered-piston structure. An hydraulic amplification mechanism was employed to amplify the limited stroke of this piezoelectrically-driven piston structure to a significantly larger motion (40-50x) of a micromachined valve membrane with attached valve cap. This valve cap was actuated through its stroke to open and close against a fluid orifice. These design features enabled the valve device to simultaneously meet a set of high frequency (1-10kHz), high pressure(0.1-IMPa), and large stroke (15-40,um) requirements that had not previously been satisfied by other microvalves presented in the literature. This research was carried out through a series of modeling, design, fabrication, assembly, and experimental testing tasks. Linear and non-linear modeling tools characterizing the structural deformations of the active valve sub-systems were developed. These tools enabled accurate prediction of real-time stresses along the micromachined valve membrane structure during deflection into its non-linear large-deflection regime. A systematic design procedure was developed to generate an active valve geometry to satisfy membrane stress limitations and valve power consumption requirements set forth by external hydraulic system performance goals.
(cont.) Fabrication challenges, such as deep-reactive ion etching (DRIE) of the drive element and valve membrane structures, wafer-level silicon-to-silicon fusion bonding and silicon-to-glass anodic bonding operations, preparation and integration of piezoelectric material elements within the micromachined tethered piston structure, die-level assembly and bonding of silicon and glass dies, and filling of degassed fluid within the hydraulic amplification chamber were overcome. The active valve structural behavior and flow regulation capabilities were evaluated over a range of applied piezoelectric voltages, actuation frequencies, and differential pressures across the valve. For applied piezoelectric voltages up to 500Vpp at lkHz, the valve devices demonstrated amplification ratios of drive element deflection to valve cap deflection of 40-50x. These amplification ratios correlated within 5 - 10% of the model expectations. Flow regulation experiments proved that a peak average flow rate through the device of 0.21mL/s under a lkHz sinusoidal drive voltage of 500Vpp, with valve opening of 17pm, against a differential pressure of 260kPa could be obtained. Tests revealed that fluid-structural interactions between the valve cap and membrane components and flow instabilities (due to transition between the laminar and turbulent flow regimes through the valve orifice) limited the valve performance capabilities.
by David C. Roberts.
Ph.D.
Li, Cong. "High Frequency High Boost Ratio Dc-dc Converters with Wide Bandgap Devices for PV System Applications." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1411858489.
Full textHaug, Stephan. "Exponential COGARCH and other continuous time models with applications to high frequency data /." [S.l.] : [s.n.], 2007. http://mediatum2.ub.tum.de/doc/620244/document.pdf.
Full textPasadas, Cantos Francisco. "Modelling of field-effect transistors based on 2D materials targeting high-frequency applications." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/405314.
Full textNew technologies are necessary for the unprecedented expansion of connectivity and communications in the modern technological society. The specific needs of wireless communication systems in 5G and beyond, as well as devices for the future deployment of the Internet of Things has caused that the International Technology Roadmap for Semiconductors, which is the strategic planning document of the semiconductor industry, considered since 2011, graphene and related materials (GRMs) as promising candidates for the future of electronics. Graphene, a one-atom-thick of carbon, is considered a promising material for high-frequency applications due to its intrinsic superior carrier mobility and very high saturation velocity. These exceptional carrier transport properties suggest that GRM based field-effect transistors can potentially outperform other technologies. This thesis presents a body of work on the modelling, performance prediction and simulation of GRM based field-effect transistors and circuits. The main goal of this work is to provide models and tools to ease the following issues: (i) gaining technological control of single layer and bilayer graphene devices and, more generally, devices based on 2D materials, (ii) assessment of RF performance and microwave stability, (iii) benchmarking against other existing technologies, (iv) providing guidance for device and circuit design, (v) simulation of circuits formed by GRM based transistors. In doing so, a key contribution of this thesis is the development of a small-signal model suited to 2D-material based field-effect transistors (2D-FETs) that guarantees charge conservation. It is also provided a parameter extraction methodology that includes both the contact and access resistances, which are of upmost importance when dealing with low dimensional FETs. Taking it as a basis, an investigation of the GFET RF performance scalability is provided, together with an analysis of the device stability. The presented small-signal model is potentially very useful for fast prototyping, which is of relevance when dealing with the first stages of any new technology. To complete the modelling task, an intrinsic physics-based large-signal compact model of graphene field-effect transistors (GFETs) has been developed, ready to be used in conventional electronic design automation tools. That is considered to be a big step towards the design of complex monolithic millimetre-wave integrated circuits (MMICs). Most of the demonstrated circuits based on GRMs so far are not integrated circuits (ICs), so requiring external circuitries for operation. At mm-wave frequencies, broadband circuits can practically only be realized in IC technology. The compact model presented in this thesis is the starting point towards the design of complex MMICs based on graphene. It has been benchmarked against high-performance and ambipolar electronics’ circuits such as a high-frequency voltage amplifier, a high-performance frequency doubler, a radio-frequency subharmonic mixer and a multiplier phase detector. The final part of the thesis is devoted to the bilayer graphene based FET. Bilayer graphene is a promising material for RF transistors because its energy bandgap might result in a better current saturation than the single layer graphene. Because the great deal of interest in this technology, especially for flexible applications, gaining control of it requires the formulation of appropriate models. A numerical large-signal model of bilayer graphene field-effect transistors has been realized, which allows for (i) understanding the electronic properties of bilayer graphene, in particular the tunable bandgap, (ii) evaluating the impact of the bandgap opening in the RF performance, (iii) benchmarking against other existing technologies, and (iv) providing guidance for device design. The model has been verified against measurement data reported, including DC electrical behaviour and RF figures of merit.
Lou, Fan. "Mismatch-insensitive N-path multirate SC Sigma-Delta Modulator for high-frequency applications." Thesis, University of Macau, 2002. http://umaclib3.umac.mo/record=b1445818.
Full textWei, Fangxing. "Submicron CMOS building blocks for high-speed frequency synthesis and clock recovery applications." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq22130.pdf.
Full textAntonakakis, Tryfon. "Theoretical extensions and applications of high frequency homogenization on photonics, phononics and platonics." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/23657.
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