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1
Stevens, M. J. "Digital control of high frequency pulse-width modulated inverters". Thesis, University of Bristol, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373297.
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Ward, Gillian Anne. "Design of a multi-kilowatt, high frequency, DC-DC converter". Thesis, University of Birmingham, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274596.
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3
Williams, Richard. "High frequency multi-element transformers for switched-mode power supplies". Thesis, University of Bristol, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283625.
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Skulason, 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.
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In this thesis, we have experimentally probed the microwave frequency electrodynamics of large area graphene, focussing on contactless measurements of graphene to extract material properties and implementation of non-reciprocal microwave devices. Our goal is to exploit interaction of graphene with electromagnetic waves in the microwave domain.By fabricating wideband graphene coplanar waveguides, we show that graphene has a constant wideband resistance from 17 Hz to 110 GHz due to negligible kinetic inductance and negligible skin effect up to 110 GHz. We characterize contact impedance between graphene and metal electrodes and our devices show that contact capacitance shorts the contact resistance above ~ 2 GHz, allowing for contactless measurements of graphene up to 110 GHz. We measured the magnetoconductance of large-area graphene under microwave excitation by employing Corbino disk geometry via the transfer of graphene films onto polished coaxial flanges. Our experimental setup allows for both passive and active graphene devices where the active devices are doped by field effect with an intrinsic silicon gate electrode transparent to microwaves. Magnetoconductive mobilities of ~ 1,000 cm2/Vs were extracted from a single component Drude model observed at high carrier density. An anomalous microwave magnetoresistance was also observed. We designed, fabricated and characterized a hollow waveguide isolator with a magnetically biased graphene acting as the non-reciprocal element via Faraday rotation. Our experimental setup allows for contactless characterization of conductivity, mobility and charge carrier density of the graphene film. Faraday rotation was measured up to 1.5° which resulted in isolation of 25 dB. We show that performance of the isolator can be improved by increasing carrier mobility in graphene. As the direction of Faraday rotation is contingent on majority charge carrier type in graphene, we give evidence that the isolation direction can be modulated and switched via field effect graphene device implemented in the hollow waveguide using a single low-power voltage source. We demonstrate the first voltage-tunable isolator with a maximum isolation of 47 dB and voltage-tunable isolation up to 26 dB. Our work suggests that other non-reciprocal devices such as circulators can be implemented compactly with graphene.Dans 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.
5
Lotfi, Ashraf W. "The electrodynamics of high frequency magnetics in power electronics /". This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-06062008-171908/.
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Frake, James Christopher. "Investigations of mesoscopic device physics using high frequency electronic techniques". Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.707903.
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Kudrya, V. G. y D. A. Voronenko. "Designing Nanotechnology Matching Devices". Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35357.
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The work describes the features of simulation of the ultrahigh-frequency electromagnetic interaction, which forms an internal solenoid status of monolithic integrated circuits. As an example, is the study of matching devices, which are made in the form of the band-pass lines. The proposed method of modeling, to determine the dependence of the finite frequency and temporal characteristics of the cascading schemes amplifiers. Thus, the proposed method of modeling physical processes appear not only domestic but also external display spatially distributed nano-and micro-strip technology structures.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35357
8
Lotfi, Ashraf Wagih. "The electrodynamics of high frequency magnetics in power electronics". Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/38504.
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The electromagnetic behavior of magnetic devices used in power electronics circuitry, is studied in order to predict their performance within a context of desirable circuit parameters. Past efforts have focused on simplifications widely used in electric machinery applications. Due to the greatly increased operating frequencies of today's circuits (in the upper kHz and lower MHz region), the operation and design of magnetic components greatly differs from those of 60 Hz machinery. A set of models based on assumptions that are unique to the these devices used in power electronics are put forth. The entire approach is based on deriving models from solutions of the field equations, rather than using older, less accurate circuit analogies. More importantly, models are needed for accurate design and optimization processes of complete power electronic systems, in which the magnetic components form a small part. Solutions are sought without using the popular simplifications at very low and very high frequencies, since they are not accurate at intermediate frequencies encountered in power electronics. The conductors used in transformers and inductors are modelled in these high frequency regions.Ph. D.
9
Le, Minh-Nhat Ba. "ADVANCED THERMOSONIC WIRE BONDING USING HIGH FREQUENCY ULTRASONIC POWER: OPTIMIZATION, BONDABILITY, AND RELIABILITY". DigitalCommons@CalPoly, 2009. https://digitalcommons.calpoly.edu/theses/177.
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Gold wire bonding typically uses 60 KHz ultrasonic frequency. Studies have been reported that increasing ultrasonic frequency from 60KHz to 120KHz can decrease bonding time, lower bonding temperature, and/or improve the bondability of Au metalized organic substrates. This thesis presents a systematic study of the effects of 120 KHz ultrasonic frequency on the reliability of fine pitch gold wire bonding. Two wire sizes, 25.4 and 17.8 μm in diameter (1.0 and 0.7 mil, respectively) were used. The gold wires were bonded to metalized pads over organic substrates with five different metallization. The studies were carried out using a thermosonic ball bonder that is able to easily switch from ultrasonic frequency from 60 KHz to 120 KHz by changing the ultrasonic transducer and the ultrasonic generator. Bonding parameters were optimized through design of experiment methodology for four different cases: 60 KHz with 25.4 μm wire, 60 KHz with 17.8 μm wire, 120 KHz with 25.4 μm wire, and 120 KHz with 17.8 μm wire. The integrity of wire bonds was evaluated by the wire pull and the ball bond shear tests. With the optimized bonding parameters, over 2,250 bonds were made for each frequency and wire size. The samples were then divided into three groups. The first group was subjected to temperature cycling from -55°C to +125°C with one hour per cycle for up to 1000 cycles. The second group was subject to thermal aging at 125°C for up to 1000 hours. The third group was subject to humidity at 85°C/85% relative humidity (RH) for up to 1000 hours. The bond integrity was evaluated through the wire pull and the ball shear tests immediately after bonding, and after each 150, 300, 500, and 1000 hours time interval in the reliability tests. The pull and shear data are then analyzed to compare the wire bond performance between different ultrasonic frequencies.
10
Gradzki, Pawel Miroslaw. "Core loss characterization and design optimization of high-frequency power ferrite devices in power electronics applications". Diss., This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-06062008-165934/.
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Masuda, Michael Curtis Meyer. "Investigation of Degradation Effects Due to Gate Stress in GaN-on-Si High Electron Mobility Transistors Through Analysis of Low Frequency Noise". DigitalCommons@CalPoly, 2014. https://digitalcommons.calpoly.edu/theses/1169.
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Gallium Nitride (GaN) high electron mobility transistors (HEMT) have superior performance characteristics compared to Silicon (Si) and Gallium Arsenide (GaAs) based transistors. GaN is a wide bandgap semiconductor which allows it to operate at higher breakdown voltages and power. Unlike traditional semiconductor devices, the GaN HEMT channel region is undoped and relies on the piezoelectric effect created at the GaN and Aluminum Gallium Nitride (AlGaN) heterojunction to create a conduction channel in the form of a quantum well known as the two dimensional electron gas (2DEG). Because the GaN HEMTs are undoped, these devices have higher electron mobility crucial for high frequency operation. However, over time and use these devices degrade in a manner that is not well understood. This research utilizes low frequency noise (LFN) as a method for analyzing changes and degradation mechanisms in GaN-on-Si devices due to gate stress.
LFN is a useful tool for probing different regions of the device that cannot be measured through direct means. LFN generation in GaN HEMTs is based on the carrier fluctuation theory of 1/f noise generation which states fluctuations in the number of charge carriers results in conductance fluctuations that produce a Lorentzian noise spectrum. The summing Lorentzian noise spectra from multiple traps leads to 1/f and random telegraph signal (RTS) noise. The primary cause of carrier fluctuations are electron traps near the 2DEG and in the AlGaN bulk. These traps occur naturally due to dislocations and impurities in the manufacturing process, but new traps can be generated by the inverse-piezoelectric effect during gate stress.
This thesis introduces noise and presents a circuit to bias the devices and measure gate and drain LFN simultaneously. Three measurements are performed before and after gate DC stress at three different temperatures: DC characterization, capacitance-voltage (C-V) measurements, and LFN measurements. The DC characteristics show an increase in gate leakage after stress caused by an increase in traps after degradation consistent with trap assisted tunneling. However, the leakage current on the drain and source side differ before and after stress leading to the conclusion that the source side of the gate is more sensitive to gate stress. Gate leakage current on the drain side is also sensitive to temperature due to thermionic trap assisted tunneling. Hooge parameter calculations agree with previous research. The LFN results show an increase in gate and drain noise power, SIg(f) and SId(f), in accordance with increased gate leakage current under cutoff bias. RTS noise is also observed to increase in frequency with increased temperature. Activation energies for RTS noise are extracted and qualitatively linked to trap depth based on the McWhorter trap model.
12
Wang, Tong. "Enhanced Field Emission Studies on Nioboim Surfaces Relevant to High Field Superconducting Radio-Frequency Devices". Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/29284.
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Enhanced field emission (EFE) presents the main impediment to higher acceleration gradients in superconducting niobium (Nb) radiofrequency cavities for particle accelerators. The strength, number and sources of EFE sites strongly depend on surface preparation and handling.
The main objective of this thesis project is to systematically investigate the sources of EFE from Nb, to evaluate the best available surface preparation techniques with respect to resulting field emission, and to establish an optimized process to minimize or eliminate EFE.
To achieve these goals, a scanning field emission microscope (SFEM) was designed and built as an extension to an existing commercial scanning electron microscope (SEM). In the SFEM chamber of ultra high vacuum, a sample is moved laterally in a raster pattern under a high voltage anode tip for EFE detection and localization. The sample is then transferred under vacuum to the SEM chamber equipped with an energy-dispersive x-ray spectrometer for individual emitting site characterization. Compared to other systems built for similar purposes, this apparatus has low cost and maintenance, high operational flexibility, considerably bigger scan area, as well as reliable performance.
EFE sources from planar Nb have been studied after various surface preparation, including chemical etching and electropolishing, combined with ultrasonic or high-pressure water rinse. Emitters have been identified, analyzed and the preparation process has been examined and improved based on EFE results. As a result, field-emission-free or near field-emission-free surfaces at ~140 MV/m have been consistently achieved with the above techniques. Characterization on the remaining emitters leads to the conclusion that no evidence of intrinsic emitters, i.e., no fundamental electric field limit induced by EFE, has been observed up to ~140 MV/m. Chemically etched and electropolished Nb are compared and no significant difference is observed up to ~140 MV/m.
To address concerns on the effect of natural air drying process on EFE, a comparative study was conducted on Nb and the results showed insignificant difference under the experimental conditions.
Nb thin films deposited on Cu present a possible alternative to bulk Nb in superconducting cavities. The EFE performance of a preliminary energetically deposited Nb thin film sample are presented.Ph. D.
13
Benali, Abdelilah. "Development of semi-classical and quantum tools for the high-frequency simulation of nanoscale electron devices". Doctoral thesis, Universitat Autònoma de Barcelona, 2013. http://hdl.handle.net/10803/129125.
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La electrónica envuelve muchos aspectos de nuestra vida cotidiana. El progreso de nuestra
sociedad actual, en última instancia, está relacionado con el progreso de la electrónica.
Tal progreso exige que las nuevas generaciones de dispositivos sean cada vez mas pequeñas
y mas rapidas. Por lo tanto , las herramientas de simulación necesarias para poder entender
el comportamiento de los dispositivos electrónicos emergentes, y luego de mejorarlos , tiene
que ser reinventada para cada nueva generación de dispositivos .
El ”International Technology Roadmap for Semiconductors” predice que en diez años los
dispositivos electrónicos tendrán menos de 10 nanómetros de longitud de canal y que trabajarán a frecuencias de THz . La comunidad cientifica ha hecho una importante esfuerzo
en proporcionar herramientas de simulación fiables para estudiar el comportamiento DC de
estos dispositivos. Algunas de las técnicas de simulació comunes par sistemas clásicos y
cuánticos se menciona en el primer captulo. Sin embargo, un esfuerzo similar para la simulaci
ón cuántica de comportamiento AC de tales dispositivos esta todavía en las primeras
etapas de la eleboración.
Para los dispositivos de nanoescala , a alta frecuencia , las principales dificultades que
tienen que ser considerarse para caracterizar el comportamiento de AC de estos dispositivos
es el papel de la corriente de desplazamiento (que implica una aproximación adecuada para
el problema cuático de muchos cuerpos ) y constatación que la corriente AC implica que
el sistemas cuántico se medirán de forma continua . En esta tesis se ofrece una solución
aproximada a mediante el uso de trayectorias cuánticas (trayectorias Bohmianas). Como se
observa en el segundo capítulo las trayectorias de Bohm tienen ventajas computacionales
cuando tratamos con muchos problemas de muchas partículas o la medición continua .
En el capítulo tres , el cálculo práctico de las corrientes de partículas de desplazamiento
se discuten con el teorema de Ramo - Shockley - Pellegrini. Hemos presentado un extensin
cuántica del teorema utilizando trayectorias Bohmianas. También se discute en detalle la
aplicación del teorema para del desarrollo del simulador cuántico el BITLLES ( Bohmiana
Transporte para obrar recíprocamente no equilibrio estructuras electrónicas ) discutido en
el apéndice C. Las expresiones de la corriente total se pueden utilizar ya sea para soluciones
clásica de Monte Carlo de la ecuación de Botzmann con trayectorias clásicas o solución de
la ecuación Schrödinger de muchas partículas con trayectorias Bohmianas.
Por último , el uso de las herramientas desarrolladas en esta tesis se usan , en el capítulo
cuatro, para estudiar la dependencia de la corriente y el ruido en la geometría y las condiciones
de contorno electrostática de nanotransistors . Además , hemos presentado una estrategia
original para mejorar el frecuencia corte de dispositivos emergentes balísticos de
múltiples puerta.
Esta tesis es un paso en la dirección de proporcionar un simulador quántico para AC y
ruido a la industria electrónica y a la comunidad científica.nica envuelve muchos aspectos de nuestra vida cotidiana. El progreso de nuestra
sociedad actual, en última instancia, está relacionado con el progreso de la electrónica.
Tal progreso exige que las nuevas generaciones de dispositivos sean cada vez mas pequeñas
y mas rapidas. Por lo tanto , las herramientas de simulación necesarias para poder entender
el comportamiento de los dispositivos electrónicos emergentes, y luego de mejorarlos , tiene
que ser reinventada para cada nueva generación de dispositivos .
El ”International Technology Roadmap for Semiconductors” predice que en diez años los
dispositivos electrónicos tendrán menos de 10 nanómetros de longitud de canal y que trabajar
án a frecuencias de THz . La comunidad cientifica ha hecho una importante esfuerzo
en proporcionar herramientas de simulación fiables para estudiar el comportamiento DC de
estos dispositivos. Algunas de las técnicas de simulació comunes par sistemas clásicos y
cuánticos se menciona en el primer captulo. Sin embargo, un esfuerzo similar para la simulaci
ón cuántica de comportamiento AC de tales dispositivos esta todavía en las primeras
etapas de la eleboración.
Para los dispositivos de nanoescala , a alta frecuencia , las principales dificultades que
tienen que ser considerarse para caracterizar el comportamiento de AC de estos dispositivos
es el papel de la corriente de desplazamiento (que implica una aproximación adecuada para
el problema cuático de muchos cuerpos ) y constatación que la corriente AC implica que
el sistemas cuántico se medirán de forma continua . En esta tesis se ofrece una solución
aproximada a mediante el uso de trayectorias cuánticas (trayectorias Bohmianas). Como se
observa en el segundo capítulo las trayectorias de Bohm tienen ventajas computacionales
cuando tratamos con muchos problemas de muchas partículas o la medición continua .
En el capítulo tres , el cálculo práctico de las corrientes de partículas de desplazamiento
se discuten con el teorema de Ramo - Shockley - Pellegrini. Hemos presentado un extensin
cuántica del teorema utilizando trayectorias Bohmianas. También se discute en detalle la
aplicación del teorema para del desarrollo del simulador cuántico el BITLLES ( Bohmiana
Transporte para obrar recíprocamente no equilibrio estructuras electrónicas ) discutido en
el apéndice C. Las expresiones de la corriente total se pueden utilizar ya sea para soluciones
clásica de Monte Carlo de la ecuación de Botzmann con trayectorias clásicas o solución de
la ecuación Schr¨odinger de muchas partículas con trayectorias Bohmianas.
Por último , el uso de las herramientas desarrolladas en esta tesis se usan , en el capítulo
cuatro, para estudiar la dependencia de la corriente y el ruido en la geometría y las condiciones
de contorno electrostática de nanotransistors . Además , hemos presentado una estrategia
original para mejorar el frecuencia corte de dispositivos emergentes balísticos de
múltiples puerta.
Esta tesis es un paso en la dirección de proporcionar un simulador quántico para AC y
ruido a la industria electrónica y a la comunidad científica.Electronics surrounds many aspects of our everyday life. The progress of our actual society is somehow ultimately linked to the progress of electronics. Such progress demands smaller and faster devices. Therefore, the simulations tools needed to be able, to understand the behavior of emerging electron devices and to improve them, have to be reinvented for each new generation of devices. The International Technology Roadmap for Semiconductors predicts that, in ten years, electron devices will have less than 10 nanometers of channel length and they will work at THz frequencies. The scientific community has done an important effort to provide reliable simulations tools for studying the DC behavior of state-of-the-art nanoscale devices. Some of the common classical and quantum simulation techniques are mentioned in the first chapter. However, a similar effort for the the quantum simulation of the AC performance of such nano metric and THz devices is still missing. For nanoscale devices, at high frequency, the main difficulties that have to be taken into account are the role of the displacement current (which imply a proper approximation for the many-body problem) and the assumption that the total quantum current needs to be continuously measured. This thesis provides an approximate solution to these problems through the use of quantum (Bohmian) trajectories. As seen in the second chapter, such Bohmian trajectories have advantages, from the computational point of view when we deal with the many body problem or the continuous measurement. In chapter three, the practical computation of the particle and displacement currents are discussed using the so called Ramo-Shockley-Pellegrini theorem. We have presented a quantum extension of the theorem using Bohmian (trajectories). We also discuss in detail the implementation of the theorem in the BITLLES (Bohmian Interacting Transport for non- equiLibrium eLEctronic Structures) simulator discussed in the appendix C. The expressions of the total current can be used either for classical Monte Carlo solutions of the Botzmann equation with classical trajectories or for the many-particle Schr¨odinger equation with Bohmian trajectories. Finally, using the tools developed in the previous chapters of this thesis, in chapter four, we have studied the dependence of the current and the noise on the geometry and the electrostatic boundary conditions of nanotransistors. In addition, we have presented and original strategy to improve the cut off frequency of emerging multi-gate ballistic devices. These numerical studies have been carried out by means of the BITLLES simulator for classical and quantum scenarios. This thesis is a step in the direction of providing a reliable dynamic quantum simulator to the industry and the scientific community.
14
Ghosh, Malinky Dai Foster. "A novel ROM compression technique and a high speed sigma-delta modulator design for direct digital synthesizer". Auburn, Ala., 2006. http://hdl.handle.net/10415/1312.
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15
Karisan, Yasir. "Full-wave Electromagnetic Modeling of Electronic Device Parasitics for Terahertz Applications". The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1419019102.
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Mays, Kenneth W. "A 40 GHz Power Amplifier Using a Low Cost High Volume 0.15 um Optical Lithography pHEMT Process". PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/552.
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The demand for higher frequency applications is largely driven by bandwidth. The evolution of circuits in the microwave and millimeter frequency ranges always demands higher performance and lower cost as the technology and specification requirements evolve. Thus the development of new processes addressing higher frequencies and bandwidth requirements is essential to the growth of any semiconductor company participating in these markets. There exist processes which can perform in the higher frequency design space from a technical perspective. However, a cost effective solution must complement the technical merits for deployment. Thus a new 0.15 um optical lithography pHEMT process was developed at TriQuint Semiconductor to address this market segment. A 40 GHz power amplifier has been designed to quantify and showcase the capabilities of this new process by leveraging the existing processing knowledge and the implementation of high frequency scalable models. The three stage power amplifier was designed using the TOM4 scalable depletion mode FET model. The TriQuint TQP15 Design Kit also implements microstrip transmission line models that can be used for evaluating the interconnect lines and matching networks. The process also features substrate vias and the thin film resistor and MIM capacitor models which utilize the capabilities of the BCB process flow. During the design stage we extensively used Agilent ADS program for circuit and EM simulation in order to optimize the final design. Special attention was paid to proper sizing of devices, developing matching circuits, optimizing transmission lines and power combining. The final design exhibits good performance in the 40 GHz range using the new TQP15 process. The measured results show a gain of greater than 13 dB under 3 volt drain voltage and a linear output power of greater than 28 dBm at 40 GHz. The 40 GHz power amplifier demonstrates that the new process has successfully leveraged an existing manufacturing infrastructure and has achieved repeatability, high volume manufacturing, and low cost in the millimeter frequency range.
17
Perrin, Rémi. "Characterization and design of high-switching speed capability of GaN power devices in a 3-phase inverter". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI001/document.
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Le projet industriel français MEGaN vise le développement de module de puissance à base de compostant HEMT en GaN. Une des application industrielle concerne l’aéronautique avec une forte contrainte en isolation galvanique (>100 kV/s) et en température ambiante (200°C). Le travail de thèse a été concentré sur une brique module de puissance (bras d’onduleur 650 V 30 A). L’objectif est d’atteindre un prototype de facteur de forme peu épais, 30 cm2 et embarquant l’ensemble des fonctions driver, alimentation de driver, la capacité de bus et capteur de courant phase. Cet objectif implique un fort rendement énergétique, et le respect de l’isolation galvanique alors que la contrainte en surface est forte. Le manuscrit, outre l’état de l’art relatif au module de puissance et notamment celui à base de transistor GaN HEMT, aborde une solution d’isolation de signaux de commande à base de micro-transformateur. Des prototypes de micro-transformateur ont été caractérisés et vieillis pendant 3000 H pour évaluer la robustesse de la solution. Les travaux ont contribué à la caractérisation de plusieurs composants GaN afin de mûrir des modèles pour la simulation circuit de topologie de convertisseur. Au sein du travail collaboratif MEGaN, notre contribution ne concernait pas la conception du circuit intégré (driver de grille), tout en ayant participé à la validation des spécifications, mais une stratégie d’alimentation du driver de grille. Une première proposition d’alimentation isolée pour le driver de grille a privilégié l’utilisation de composants GaN basse-tension. La topologie Flyback résonante avec clamp permet de tirer le meilleur parti de ces composants GaN mais pose la contrainte du transformateur de puissance. Plusieurs technologies pour la réalisation du transformateur ont été validées expérimentalement et notamment une proposition originale enfouissement du composant magnétique au sein d’un substrat polymère haute-température. En particulier, un procédé de fabrication peu onéreux permet d’obtenir un dispositif fiable (1000 H de cyclage entre - 55 ; + 200°C), avec un rendement intrinsèque de 88 % pour 2 W transférés. La capacité parasite d’isolation est réduite par rapport aux prototypes précédent. Deux prototypes d’alimentations à forte intégration utilisent soit les transistors GaN basse tension (2.4 MHz, 2 W, 74 %, 6 cm2), soit un circuit intégré dédié en technologie CMOS SOI, conçu pour l’application (1.2 MHz, 2 W, 77 %, 8.5 cm2). Le manuscrit propose par la suite une solution intégrable de mesure de courant de phase du bras de pont, basé sur une magnétorésistance. La comparaison expérimentale vis à vis d’une solution à résistance de shunt. Enfin, deux prototypes de convertisseur sont décrits, dont une a pu faire l’objet d’une validation expérimentale démontrant des pertes en commutation réduitesThe french industrial project MEGaN targets the development of power module based on GaN HEMT transistors. One of the industrial applications is the aeronautics field with a high-constraint on the galvanic isolation (>100 kV/s) and ambient temperature (200°C). The intent of this work is the power module block (3 phases inverter 650 V 30 A). The goal is to obtain a small footprint module, 30 cm2, with necessary functions such as gate driver, gate driver power supply, bulk capacitor and current phase sensor. This goal implies high efficiency as well as respect of the constraint of galvanic isolation with an optimized volume. This dissertation, besides the state of the art of power modules and especially the GaN HEMT ones, addressed a control signal isolation solution based on coreless transformers. Different prototypes based on coreless transformers were characterized and verified over 3000 hours in order to evaluate their robustness. The different studies realized the characterization of the different market available GaN HEMTs in order to mature a circuit simulation model for various converter topologies. In the collaborative work of the project, our contribution did not focus on the gate driver chip design even if experimental evaluation work was made, but a gate driver power supply strategy. The first gate driver isolated power supply design proposition focused on the low-voltage GaN HEMT conversion. The active-clamp Flyback topology allows to have the best trade-off between the GaN transistors and the isolation constraint of the transformer. Different transformer topolgies were experimentally performed and a novel PCB embedded transformer process was proposed with high-temperature capability. A lamination process was proposed for its cost-efficiency and for the reliability of the prototype (1000 H cycling test between - 55; + 200°C), with 88 % intrinsic efficiency. However, the transformer isolation capacitance was drastically reduced compared to the previous prototypes. 2 high-integrated gate driver power supply prototypes were designed with: GaN transistors (2.4 MHz, 2 W, 74 %, 6 cm2), and with a CMOS SOI dedicated chip (1.2 MHz, 2 W, 77 %, 8.5 cm2). In the last chapter, this dissertation presents an easily integrated solution for a phase current sensor based on the magnetoresistance component. The comparison between shunt resistor and magnetoresistance is experimentally performed. Finally, two inverter prototypes are presented, with one multi-level gate driver dedicated for GaN HEMT showing small switching loss performance
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Neophytou, Regas Ioanni. "Modelling of radio frequency heating systems". Thesis, University of Cambridge, 1998. https://www.repository.cam.ac.uk/handle/1810/272305.
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Meier, Sven Damian. "High-frequency electromagnetic emissions from mechanical switching devices". Thesis, University of Strathclyde, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436097.
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Xia, Zhanbo. "Materials and Device Engineering for High Performance β-Ga2O3-based Electronics". The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587688595358557.
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Meng, Ling Guang. "Frequency domain methods for turbogenerator and power system transient studies". Thesis, University of Newcastle Upon Tyne, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308982.
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Radhakrishna, Ujwal. "Modeling gallium-nitride based high electron Mobility transistors : linking device physics to high voltage and high frequency circuit design". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/105951.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 285-291).
Gallium-Nitride-based high electron mobility transistor (HEMTs) technology is increasingly finding space in high voltage (HV) and high frequency (HF) circuit application domains. The superior breakdown electric field, high electron mobility, and high temperature performance of GaN HEMTs are the key factors for its use as HV switches in converters and active components of RF-power amplifiers. Designing circuits in both application regimes requires accurate compact device models that are grounded in physics and can describe the non-linear terminal characteristics. Currently available compact models for HEMTs are empirical and hence are lacking in physical description of the device, which becomes a handicap in understanding key device-circuit interactions and in accurate estimation of device behavior in circuits. This thesis seeks to develop a physics-based compact model for GaN HEMTs from first principles which can be used as a design tool for technology optimization to identify device-performance bottlenecks on one hand and as a tool for circuit design to investigate the impact of behavioral nuances of the device on circuit performance, on the other. Part of this thesis consists of demonstrations of the capabilities of the model to accurately predict device characteristics such as terminal DC- and pulsed-currents, charges, small-signal S-parameters, large-signal switching characteristics, load-pull, source-pull and power-sweep, inter-modulation-distortion and noise-figure of both HV- and RF-devices. The thesis also aims to tie device-physics concepts of carrier transport and charge distribution in GaN HEMTs to circuit-design through circuit-level evaluation. In the HV-application regime benchmarking is conducted against switching characteristics of a GaN DC-DC converter to understand the impact of device capacitances, field plates, temperature and charge-trapping on switching slew rates. In the RF-application regime validation is done against the large-signal characteristics of GaN-power amplifiers to study the output-power, efficiency and compression characteristics as function of class-of-operation. Noise-figure of low-noise amplifiers is tested to estimate the contributions of device-level noise sources, and validation against switching frequency and phase-noise characteristics of voltage-controlled oscillators is done to evaluate the noise performance of GaN HEMT technology. Evaluation of model-accuracy in determining the conversion-efficiency of RF-converters and linearity metrics of saturated non-linear amplifiers is carried out. The key contribution of this work is to provide a tool in the form of a physics-based compact model to device-technology-engineers and circuit-designers, who can use it to evaluate the potential strengths and weaknesses of the emerging GaN technology.
by Ujwal Radhakrishna.
Ph. D.
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Abou-Fakher, Yehia. "Implementing and simulating low frequency inverters using high frequency transformers and devices". Thesis, University of Bath, 1997. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362147.
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Poddar, Ravi. "Accurate, high speed predictive modeling of passive devices". Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/14905.
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Skutt, Glenn R. "High-Frequency Dimensional Effects in Ferrite-Core Magnetic Devices". Diss., Virginia Tech, 1996. http://hdl.handle.net/10919/30596.
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MnZn ferrites are widely used in power electronics applications where the switching frequency is in the range of several tens of kilohertz to a megahertz. In this range of frequencies the combination of relatively high permeability and relatively low conductivity found in MnZn ferrite helps to minimize the size of magnetic devices while maintaining high efficiency. The continuing improvement in semiconductor switches and circuit topologies has led to use of high-frequency switching circuits at ever increasing power levels. The magnetic devices for these high-power, high-frequency circuits require magnetic CORES that are significantly larger than standard ferrite-core devices used at lower power levels. Often such large ferrite cores must be custom designed, and at present this custom design is based on available material information without regard for the physical size of the structure.
This thesis examines the issues encountered in the use of larger MnZn ferrite cores for high-frequency, high-power applications. The two main issues of concern are the increased power dissipation due to induced currents in the structure and the change in inductance that results as the flux within the core is redistributed at higher frequencies. In order to model these problems using either numerical or analytical methods requires a reliable and complete set of material information. A significant portion of this work is devoted to methods for acquiring such material information since such information is not generally available from the manufacturers. Once the material constants required for the analysis are determined, they are used in both closed-form and numerical model to illustrate that large ferrite cores suffer significant increases in loss and significant decreases in inductance for frequencies as low as several hundred kilohertz. The separate impacts of the electrical and magnetic losses in the core are illustrated through the use of linear finite element analyses of several example core structures. The device impedances calculated using the FEA tools show fair agreement with measurement. An analysis of gapped structures and segmented cross-sections shows that these design options can reduce the severity of the dimensional problems for some designs.Ph. D.
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Jury, Jason Charles. "High-frequency phenomena in magnetic recording and inductive devices /". May be available electronically:, 2007. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Siebert, Wolfgang Peter. "Alternative electronic packaging concepts for high frequency electronics". Doctoral thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-223.
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Wang, Hongfang. "Investigation of Power Semiconductor Devices for High Frequency High Density Power Converters". Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/27517.
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The next generation of power converters not only must meet the characteristics demanded by the load, but also has to meet some specific requirements like limited space and high ambient temperature etc. This needs the power converter to achieve high power density and high temperature operation. It is usually required that the active power devices operate at higher switching frequencies to shrink the passive components volume.
The power semiconductor devices for high frequency high density power converter applications have been investigated. Firstly, the methodology is developed to evaluate the power semiconductor devices for high power density applications. The power density figure of merit (PDFOM) for power MOSFET and IGBT are derived from the junction temperature rise, power loss and package points of view. The device matrices are generated for device comparison and selection to show how to use the PDFOM. A calculation example is given to validate the PDFOM. Several semiconductor material figures of merit are also proposed. The wide bandgap materials based power devices benefits for power density are explored compared to the silicon material power devices.
Secondly, the high temperature operation characteristics of power semiconductor devices have been presented that benefit the power density. The electrical characteristics and thermal stabilities are tested and analyzed, which include the avalanche breakdown voltage, leakage current variation with junction temperature rise. To study the thermal stability of power device, the closed loop thermal system and stability criteria are developed and analyzed. From the developed thermal stability criterion, the maximum switching frequency can be derived for the converter system design. The developed thermal system analysis approach can be extended to other Si devices or wide bandgap devices. To fully and safely utilize the power devices the junction temperature prediction approach is developed and implemented in the system test, which considers the parasitic components inside the power MOSFET module when the power MOSFET module switches at hundreds of kHz. Also the thermal stability for pulse power application characteristics is studied further to predict how the high junction temperature operation affects the power density improvement.
Thirdly, to develop high frequency high power devices for high power high density converter design, the basic approaches are paralleling low current rating power MOSFETs or series low voltage rating IGBTs to achieve high frequency high power output, because power MOSFETs and low voltage IGBTs can operate at high switching frequency and have better thermal handling capability. However the current sharing issues caused by transconductance, threshold voltage and miller capacitance mismatch during conduction and switching transient states may generate higher power losses, which need to be analyzed further. A current sharing control approach from the gate side is developed. The experimental results indicate that the power MOSFETs can be paralleled with proper gate driver design and accordingly the switching losses are reduced to some extent, which is very useful for the switching loss dominated high power density converter design.
The gate driving design is also important for the power MOSFET module with parallel dice inside thus increased input capacitance. This results in the higher gate driver power loss when the traditional resistive gate driver is implemented. Therefore the advanced self-power resonant gate driver is investigated and implemented. The low gate driver loss results in the development of the self-power unit that takes the power from the power bus. The overall volume of the gate driver can be minimized thus the power density is improved.
Next, power semiconductor device series-connection operation is often used in the high power density converter to meet the high voltage output such as high power density boost converter. The static and dynamic voltage balancing between series-connected IGBTs is achieved using a hybrid approach of an active clamp circuit and an active gate control. A Scalable Power Semiconductor Switch (SPSS) based on series-IGBTs is developed with built-in power supply and a single optical control terminal. An integrated package with a common baseplate is used to achieve a better thermal characteristic. These design features allow the SPSS unit to function as a single optically controlled three-terminal switching device for users. Experimental evaluation of the prototype SPSS shows it fully achieved the design objectives. The SPSS is a useful power switch concept for building high power density, high switching frequency and high voltage functions that are beyond the capability of individual power devices.
As conclusions, in this dissertation, the above-mentioned issues and approaches to develop high density power converter from power semiconductor devices standpoint are explored, particularly with regards to high frequency high temperature operation. To realize such power switches the related current sharing, voltage balance and gate driving techniques are developed. The power density potential improvements are investigated based on the real high density power converter design. The power semiconductor devices effects on power density are investigated from the power device figure of merit, high frequency high temperature operation and device parallel operation points of view.Ph. D.
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Arjona, Lopez Marco Antonio. "Steady state and frequency domain lumped model numerical characterisation of solid rotor synchronous generators". Thesis, Imperial College London, 1996. http://hdl.handle.net/10044/1/7548.
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Leung, Chiu Hon. "The output frequency spectrum of a thyristor phase-controlled cycloconverter using digital control techniques". Thesis, University of Plymouth, 1985. http://hdl.handle.net/10026.1/2261.
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The principle of operation dictates that the output of a cycloconverter contains some harmonics. For drive applications, the harmonics at best increase losses in the motor and may well cause instability. Various methods of analysing the output waveform have been considered. A Fortran 77 program employing a modified Fourier series, making use of the fact that the input waveforms are sinusoidal, was used to compute the individual harmonic amplitudes. A six pulse three phase to single phase cycloconverter was built and a Z-80 microprocessor was used for the control of firing angles. Phase locked loops were used for timing, and their effect upon the output with changing input frequency and voltage were established. The experimental waveforms are analysed by a FFT spectrum analyser. The flexibility of the control circuit enables the following investigations not easily carry out using traditional analog control circuit. The phase relationship between the cosine timing and reference wave in the cosinusoidal control method was shown to affect the output waveform and hence the harmonic content. There is no clear optimum value of phase and the T.H.D. up to 500Hz remains virtually constant. However, the changes of individual harmonic amplitudes is quite significant. In practice it may not be possible to keep the value of phase constant but it should be considered when comparing control strategies. Another investigation involves the changing of the last firing angle in a half cycle. It shows that the value of firing angles produced by the cosinusoidal control method is desirable. Operation at theoretical maximum output frequency was also demonstrated.
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Marais, Johannes Izak Frederik. "A permittivity measurement system for high frequency laboratories". Thesis, Link to the online version, 2006. http://hdl.handle.net/10019/580.
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Agar, Joshua Carl. "Highly conductive stretchable electrically conductive composites for electronic and radio frequency devices". Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/44875.
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The electronics industry is shifting its emphasis from reducing transistor size and operational frequency to increasing device integration, reducing form factor and increasing the interface of electronics with their surroundings. This new emphasis has created increased demands on the electronic package. To accomplish the goals to increase device integration and interfaces will undoubtedly require new materials with increased functionality both electrically and mechanically.
This thesis focuses on developing new interconnect and printable conductive materials capable of providing power, ground and signal transmission with enhanced electrical performance and mechanical flexibility and robustness. More specifically, we develop: 1.) A new understanding of the conduction mechanism in electrically conductive composites (ECC). 2.) Develop highly conductive stretchable silicone ECC (S-ECC) via in-situ nanoparticle formation and sintering. 3.) Fabricate and test stretchable radio frequency devices based on S-ECC. 4.) Develop techniques and processes necessary to fabricate a stretchable package for stretchable electronic and radio frequency devices.
In this thesis we provide convincing evidence that conduction in ECC occurs predominantly through secondary charge transport mechanism (tunneling, hopping). Furthermore, we develop a stretchable silicone-based ECC which, through the incorporation of a special additive, can form and sinter nanoparticles on the surface of the metallic conductive fillers. This sintering process decreases the contact resistance and enhances conductivity of the composite. The conductive composite developed has the best reported conductivity, stretchability and reliability. Using this S-ECC we fabricate a stretchable microstrip line with good performance up to 6 GHz and a stretchable antenna with good return loss and bandwidth.
The work presented provides a foundation to create high performance stretchable electronic packages and radio frequency devices for curvilinear spaces. Future development of these technologies will enable the fabrication of ultra-low stress large area interconnects, reconfigurable antennas and other electronic and RF devices where the ability to flex and stretch provides additional functionality impossible using conventional rigid electronics.
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Lundvall, Alex y Vincent Sollie. "Quantifying Middle Frequency Transient Currents in Power Consuming Devices". Thesis, Uppsala universitet, Institutionen för elektroteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-448949.
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The complexity of electrical systems present in vehicles is continuously rising and the number of interconnected electrical devices is growing during the strive for optimization and reaching higher efficiency levels. Actuation of said devices have the possibility of injecting voltage and current harmonics into the system, thus negatively affecting neighbouring devices. A measurement method for detecting the transient currents originating from such devices was therefore desirable. Focus was placed on current transients with frequency components within the range 1 kHz to 1 MHz. The report presents theory regarding current sensing techniques, where sensors based on the Rogowski coil were chosen for further implementation. Signal analysis theory included choice of sampling frequency and the FFT approach. Different data acquisition hardware were considered for usage with the current sensors, and evaluated both in field and a laboratory environment. Compiled application notes for the end-user of the measurement method are presented. Laboratory tests showed that Rogowski sensors were capable of measuring the transient currents with the desired spectral resolution. Caution should however be taken when measuring and interpreting low frequency components due to the droop effect. Among the evaluated Rogowski sensors, the sensor type 30LFB was found to be best fitted for measuring current transients originating from electrical loads in a vehicle. Different power cable set-ups can act on the system with low-pass characteristic. Field tests showed that the energy demand of an electrical unit is not solely supplied by the battery but also neighbouring devices. Most prominently were a 40 kHz component that could be seen propagating from the electronic clutch actuator to other loads. However, the majority of the currents’ frequency components with considerable amplitudes were located outside the delimited spectrum. It was concluded that sampling hardware have the possibility of injecting the quantified waveform with frequency components that are related to the sampling frequency.
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Growden, 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.
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Pang, Lisa Yee San. "Thin film diamond : electronic devices for high temperature, high power and high radiation applications". Thesis, University College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313317.
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Hinchliffe, Stephen. "Solid-state high-frequency electric process heating power supplies". Thesis, Loughborough University, 1989. https://dspace.lboro.ac.uk/2134/32518.
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A detailed critical review has been made of both solid state power devices and circuit topologies with emphasis on their application to high frequency electric process heating power supplies operating between 3and 30 MHz. A number of prototype units have been designed and constructed and their suitability for high frequency induction heating and dielectric heating applications investigated. Desirable qualities being robustness, tolerance to load mismatch, ease of design, simplicity and cost of constituent components as compared with present day valve equipment The experience gained in these investigations has resulted in the choice of the power MOSFET as the most appropriate device and Class E amplifier as being the most applicable circuit topology for the generation of RF power for high frequency electric process heating applications. A practical and theoretical study has been made of the limitations of the power MOSFET as a high frequency switching device. The effect of source feedback on the switching speed of T03 packaged devices has been investigated by the addition of a second source terminal in a specially modified T03 package. Novel drive circuits have been developed enabling high frequency switching of both power and RF MOSFETs. These have been employed in inverters operating at 3.3 MHz at power levels up to 600 W and at frequencies between 7 and 27 MHz at power levels over 100 W, with conversion efficiencies of up to 95%.
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Vasudeva, Vikas. "Characterization of MEMS devices on the basis of their frequency response function (FRF)". abstract and full text PDF (free order & download UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1447635.
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Whitman, Daniel Joseph. "Electromagnetic Fields, Power Losses, and Resistance of High-Frequency Magnetic Devices". Wright State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=wright1268951694.
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Oliver, Trevor N. "Surface acoustic wave devices with low loss and high frequency operation". Thesis, Aston University, 1989. http://publications.aston.ac.uk/8083/.
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This thesis describes an industrial research project carried out in collaboration with STC Components, Harlow, Essex. Technical and market trends in the use of surface acoustic wave (SAW) devices are reviewed. As a result, three areas not previously addressed by STC were identified: lower insertion loss designs, higher operating frequencies and improved temperature dependent stability. A review of the temperature performance of alternative lower insertion loss designs,shows that greater use could be made of the on-site quartz growing plant. Data is presented for quartz cuts in the ST-AT range. This data is used to modify the temperature performance of a SAW filter. Several recently identified quartz orientations have been tested. These are SST, LST and X33. Problems associated with each cut are described and devices demonstrated. LST quartz, although sensitive to accuracy of cut, is shown to have an improved temperature coefficient over the normal ST orientation. Results show that its use is restricted due to insertion loss variations with temperature. Effects associated with split-finger transducers on LST-quartz are described. Two low-loss options are studied, coupled resonator filters for very narrow bandwidth applications and single phase unidirectional transducers (SPUDT) for fractional bandwidths up to about 1%. Both designs can be implemented with one quarter wavelength transducer geometries at operating frequencies up to 1GHz. The SPUDT design utilised an existing impulse response model to provide analysis of ladder or rung transducers. A coupled resonator filter at 400MHz is demonstrated with a matched insertion loss of less than 3.5dB and bandwidth of 0.05%. A SPUDT device is designed as a re-timing filter for timing extraction in a long haul PCM transmission system. Filters operating at 565MHz are demonstrated with insertion losses of less than 6dB. This basic SPUDT design is extended to a maximally distributed version and demonstrated at 450MHz with 9.8dB insertion loss.
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CRIPPA, ALESSANDRO. "High frequency physics and broadband instrumentation in CMOS silicon quantum devices". Doctoral thesis, Università degli Studi di Milano-Bicocca, 2016. http://hdl.handle.net/10281/101823.
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The increasing interest in Si-based nanostructures for quantum information purposes is motivated by the advantages offered by the physical properties of the material and by the maturity of the industrial CMOS technology which ensures a real chance of scalability.
In such wide framework this thesis has investigated coherence-related effects of single electrons confined in silicon impurity or quantum dot in presence of oscillating electric fields. High frequency excitations in the MHz – GHz range on the one hand are demonstrated to be detrimental for coherent electron transfers; on the other hand they represent a tool for non-invasive and scalable charge detection through reflectometry.
The research activity has also concerned the development and assembly of a new setup for broadband manipulation and current sensing of nanoscaled MOSFETs at cryogenic temperatures.
Quantum transport measurements at 4 K in a single-gate FET evidence a hitherto unobserved selection rule on valley quantum numbers of the electrons. Here the 6-fold valley degeneracy typical of bulk Si is lifted by the confinement and electric field: the source-drain conduction is mediated by the energy levels of a single P atom that selects the valley state of the electron under tunneling.
Analogously to Coulomb blockade for charges and Pauli blockade for spins, this valley blockade determines the transport suppression by the orthogonality of valley-orbital degrees in the reservoirs and at the impurity site. The conservation of the electron valley index is further confirmed by the observation of spin-valley Kondo transitions at the neutral charge state of the atom.
The quantum transport is then driven out of equilibrium by an external field at several GHz frequencies and powers. The spin coherent fluctuations sustaining the Kondo effect are quenched by strong ac fields because of the spin-flips induced by electron-photon couplings. By contrast, the electron valley parity is not altered and the valley blockade phenomenology is fully preserved at several powers.
Interestingly, very small excitations of ~ 100 MHz are exploitable to measure physical mechanisms of transport at the nanoscale through phase sensitive detection by radio frequency reflectometry. By means of a new dual-port reflectometric apparatus several aspects of the ultra-low temperature transport of a nanodevice are investigated. The multiplexing scheme exploiting the double-gate geometry of the sample allows clearer and more complete measurement of the charge stability diagrams than standardly used one-port setups. The dispersive detection of spin-dependent transitions makes gate-based reflectometry a promising yet barely explored technique combining high sensitivity and large bandwidth. Transport data are critically compared with reflectometry.
Finally, the development and characterization at 4 K of a cryogenic modular setup for electrical measurements in multigate devices is reported. Degradation of ns voltage signals for electrical manipulation is minimized and custom cryogenic electronics allows low-noise current sensing. The versatile approach adopted for such platform can be replicated in more complicate systems like cryostats.
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Badenhorst, J. "Metrology and modelling of high frequency probes". Thesis, Link to the online version, 2008. http://hdl.handle.net/10019/808.
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Kren, David Edward. "High carbon-doped base HBTs : growth and processing engineering". Thesis, King's College London (University of London), 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274478.
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Miran, Seyed Mehdi. "Switches for pulsed-power conditioning in high energy applications". Thesis, Loughborough University, 1997. https://dspace.lboro.ac.uk/2134/10616.
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This dissertation presents theoretical and experimental results from a research program that was aimed at finding practical ways of transferring energy to various loads, mainly from an inductive energy store fluxed by a primary store such as a capacitor bank. The main obj ecti ves of the work were to investigate and develop high power opening and closing switches, together with the transfer circuits needed to generate the fast (less than lOOns duration) high energy, pulses required in many applications. The study was to include a feasibility study of the use of the Plasma Erosion Opening Switch (PEOS) in such a system. To produce the large fast pulses required, an opening switch is required that: * Carry a current of the order of several kA during the inductor storage time. It should also be able to interrupt this current and to withstand the high voltage it will experience as the current is subsequently transferred to a load. * Conduct for as long as possible (up to one quarter period of the current waveform), to maximise the inductively stored energy which can be transferred to xhe load when the switch opens. * Open to an impedance that is large compared to the load impedance . This ensures that most of the inductively stored energy is transferred to the load. Open sufficiently rapidly to produce the required sharp pulse of voltage. In pulsed-power applications, energy is usually supplied from slow and relatively inexpensive power sources such as a capacitor bank, or an explosive flux-compression generator, which deliver large quantities of energy in the lO-lOO time range. Although no single switch is currently available which has such a long conduction time, together with a nanosecond opening time, the PEOS is a potential candidate. To overcome its short conduction time, while still obtaining an opening time of less than lOOns, the PEOS is used together with an additional slower stage or stages of switching. The key to this method is that each successive switching stage produces a considerably increased voltage. Various different types of switch were investigated and these are described in the thesis. Particular consideration is paid to the performance of the PEOS, as the final conditioning stage. Exploding foils are also investigated, together with a novel Automatic Exploding Foil Change-Over Switch, since an exploding foil opening switch is needed to condition the output of the capacitor bank before the PEOS. The initial resistance of the PEOS is very low, and the change-over switch is required to ensure that the current transfer takes place when the voltage across the fuse approaches its peak value. An important part of the investigation was to develop a mathematical model of the PEOS, as a part of the power condi tioning circuit, in order to simulate the system for different load conditions. The thesis explains the design, operation and performance characteristics of the various pulsed-power components, such as capacitor banks, closing and opening switches, pulse transformer, the vacuum system required for a PEOS, and high voltage and current measurement techniques.
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Larsson, Anders. "High frequency distortion in power grids due to electronic equipment". Licentiate thesis, Luleå : Luleå tekniska universitet/Tillämpad fysik, maskin- och materialteknik/Energiteknik, 2006. http://epubl.ltu.se/1402-1757/2006/63/LTU-LIC-0663-SE.pdf.
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Tao, Fengfeng. "Advanced High-Frequency Electronic Ballasting Techniques for Gas Discharge Lamps". Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/25978.
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Small size, light weight, high efficacy, longer lifetime and controllable output are the main advantages of high-frequency electronic ballasts for gas discharge lamps. However, power line quality and electromagnetic interference (EMI) issues arise when a simple peak rectifying circuit is used. To suppress harmonic currents and improve power factor, input-current-shaping (ICS) or power-factor-correction (PFC) techniques are necessary.
This dissertation addresses advanced high-frequency electronic ballasting techniques by using a single-stage PFC approach. The proposed techniques include single-stage boost-derived PFC electronic ballasts with voltage-divider-rectifier front ends, single-stage PFC electronic ballasts with wide range dimming controls, single-stage charge-pump PFC electronic ballasts with lamp voltage feedback, and self-oscillating single-stage PFC electronic ballasts.
Single-stage boost-derived PFC electronic ballasts with voltage-divider-rectifier front ends are developed to solve the problem imposed by the high boost conversion ratio required by commonly used boost-derived PFC electronic ballast. Two circuit implementations are proposed, analyzed and verified by experimental results.
Due to the interaction between the PFC stage and the inverter stage, extremely high bus-voltage stress may exist during dimming operation. To reduce the bus voltage and achieve a wide-range dimming control, a novel PFC electronic ballast with asymmetrical duty-ratio control is proposed. Experimental results show that wide stable dimming operation is achieved with constant switching frequency.
Charge-pump (CP) PFC techniques utilize a high-frequency current source (CS) or voltage source (VS) or both to charge and discharge the so-called charge-pump capacitor in order to achieve PFC. The bulky DCM boost inductor is eliminated so that this family of PFC circuits has the potential for low cost and small size. A family of CPPFC electronic ballasts is investigated. A novel VSCS-CPPFC electronic ballast with lamp-voltage feedback is proposed to reduce the bus-voltage stress. This family of CPPFC electronic ballasts are implemented and evaluated, and verified by experimental results.
To further reduce the cost and size, a self-oscillating technique is applied to the CPPFC electronic ballast. Novel winding voltage modulation and current injection concepts are proposed to modulate the switching frequency. Experimental results show that the self-oscillating CS-CPPFC electronic ballast with current injection offers a more cost-effective solution for non-dimming electronic ballast applications.Ph. D.
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Monkhouse, Peter. "Design and analysis of a high performance brushless DC drive". Thesis, University of Sheffield, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389485.
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Wang, Cai Johnson R. Wayne. "High temperature high power SiC devices packaging processes and materials development". Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Spring/doctoral/WANG_CAI_24.pdf.
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Chen, Yupeng. "FINITE ELEMENT METHOD MODELING OF ADVANCED ELECTRONIC DEVICES". Doctoral diss., University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3115.
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In this dissertation, we use finite element method together with other numerical techniques to study advanced electron devices. We study the radiation properties in electron waveguide structure with multi-step discontinuities and soft wall lateral confinement. Radiation mechanism and conditions are examined by numerical simulation of dispersion relations and transport properties. The study of geometry variations shows its significant impact on the radiation intensity and direction. In particular, the periodic corrugation structure exhibits strong directional radiation. This interesting feature may be useful to design a nano-scale transmitter, a communication device for future nano-scale system. Non-quasi-static effects in AC characteristics of carbon nanotube field-effect transistors are examined by solving a full time-dependent, open-boundary Schrödinger equation. The non-quasi-static characteristics, such as the finite channel charging time, and the dependence of small signal transconductance and gate capacitance on the frequency, are explored. The validity of the widely used quasi-static approximation is examined. The results show that the quasi-static approximation overestimates the transconductance and gate capacitance at high frequencies, but gives a more accurate value for the intrinsic cut-off frequency over a wide range of bias conditions. The influence of metal interconnect resistance on the performance of vertical and lateral power MOSFETs is studied. Vertical MOSFETs in a D2PAK and DirectFET package, and lateral MOSFETs in power IC and flip chip are investigated as the case studies. The impact of various layout patterns and material properties on RDS(on) will provide useful guidelines for practical vertical and lateral power MOSFETs design.Ph.D.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering
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Carné, i. Fructuoso Sergi. "Electronic identification of goats: comparison of different types of radio-frequency and visual devices". Doctoral thesis, Universitat Autònoma de Barcelona, 2010. http://hdl.handle.net/10803/5714.
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L'objectiu d'aquesta tesi ha estat avaluar diferents dispositius de identificació del bestiar cabrum, recentment contemplades a la legislació europea. S'han portat a terme 4 experiments per tal d'avaluar els següents dispositius: cròtals plàstics i de ràdio freqüència (RFID), bols ruminals, i identificadors a les extremitats (injectables i braçalets). A l'Exp. 1 es van emprar 97 cabrits de raça Murciano-Granadina per estudiar l'aplicació i capacitat de lectura (CL) de cròtals visuals (V1: tip-tag; V2: oficial), cròtals de RFID (E1: bandera-botó; E2: botó), mini-bols (B1: 13,8 g; B2: 20 g), i injectables a l'extremitat anterior (T1: 15 mm; T2: 12 mm); les mares (n = 29) es van identificar amb bols de mida estàndard (B3: 75 g). Al cap d'un any, la CL de B3, E1 i E2 va ser del 100%. Les CL més baixes es van donar amb B1 (71,4%) i V1 (82,9%). En conclusió, només els cròtals de RFID tipus botó van permetre la adequada ID de cabrides de reposició de raça lletera.
A l'Exp. 2, es van emprar 295 cabres adultes i segalles de races Alpina, Angora, Boer i Spanish, explotades en condicions semi-extensives. Es va testar la retenció de 3 tipus de bols (B1: 20 g, n = 95; B2: 75 g, n = 100; B3: 82 g, n = 100) i 1 cròtal visual. Es va avaluar l'efecte del maneig alimentari en possibles pèrdues inicials (mes 1) mitjançant mesures del pH ruminal. No es van produir pèrdues inicials de bols, tot i que el pH diferí segons raça i maneig (6,32- 6,73). A l'any, la retenció de bols (98,1%) va ser superior a la de cròtals (91,7%). La menor retenció es va obtenir amb el B1 (96,3%), mentre que va ser de 97,8% per al B3 i de 100% per al B2. En conclusió, els bols de mida estàndard van oferir una retenció adequada a llarg termini per a cabrum en condicions semi-extensives.
A l'Exp. 3, 220 cabres de raça Murciano-Granadina es van identificar amb cròtals visuals (VE) i de RFID (EE, n = 47), bols ruminals (RB: 75 g), i identificadors a l'extremitat (LT) amb 2 tipus de transponedors tipus botó (ET1, n = 90; ET2, n = 130). Es va avaluar la CL durant 12 mesos. D'acord amb el perímetre de canya, es descartà l'ús de LT en cabrides i només s'utilitzà en cabres adultes. A l'any, no es van produir pèrdues de LT però l'1,5% van ésser retirats per causar coixeses. Les CL de RB, EE, VE, ET1 i ET2 van ser de 96.5, 95.7, 97, 93.9 i 98.3%, respectivament. En conclusió, els braçalets resultaren un mètode vàlid per a la ID de cabrum adult.
A l'Exp. 4, 2.482 bols ruminals pertanyents a 19 tipus diferents es van utilitzar per establir un model de regressió de la retenció de bols en cabrum. Els bols variaren en longitud (37-84 mm), diàmetre (9-22 mm), pes (W, 5-111 g), volum (V, 2,5-26 mL) i gravetat específica (SG, 1-5,5). Es va poder establir un model logístic de retenció de bols (R2 = 0,98), prenent W i V com a covariables. Els W i SG estimats per a bols mini (5 mL), mitjans (15 mL) i estàndards (22 mL) per a una retenció del 99,95% van ser de 42.9, 73.0, i 94.1 g, i de 8.58, 4.87, and 4.28, respectivament. L'augment de W i SG permetria reduir el V. Els materials ràdio-translúcids actuals permetrien obtenir bols de mida mitjana adequats per a cabrum.
En conclusió, en les nostres condicions, els cròtals visuals i els injectables a l'extremitat no s'aconsellen per ID oficial. Els cròtals electrònics botó mostraren resultats variables segons el tipus, i els braçalets són un mètode vàlid solsament en cabres adultes. D'acord amb el model de retenció de bols ruminals, es poden obtenir dispositius de mida mitjana adequats per a cabrum, mentre que els bols mini estan desaconsellats.
This thesis aimed to evaluate different visual and radio frequency identification (RFID) devices for goats. As current European regulations lay down the official use of visual and RFID ear tags, rumen boluses, and marks on the pastern (injects and RFID leg bands), these devices were tested in 4 experiments.
In Exp. 1, application and long-term readability of visual ear tags (V1: tip-tag; V2: official), mini-boluses (B1: 13.8 g; and B2: 20.0 g), RFID ear tags (E1: flag-button; E2: double button), and injects on the fore-hind pastern (T1: 15 mm; T2: 12 mm) in replacement Murciano-Granadina dairy goat kids (n = 97) were tested; standard-sized boluses (B3: 75 g) were evaluated as control devices in their mothers (n = 29). At 1 yr of age, readability of B3, E1 and E2 was 100%. Lower readabilities corresponded to B1 (71.4%) and V1 (82.9%). At 3 yr of age, only E1 was 100% readable. In conclusion, button RFID ear tags offered the best results for dairy goat ID at early ages.
In Exp. 2, a total of 295 adult and yearling goats from Alpine, Angora, Boer, and Spanish breeds managed under semi-extensive conditions, were used. Management system and breed effects on the retention of 3 bolus types (B1: 20 g, n = 95; B2: 75 g, n = 100; and B3: 82 g, n = 100) and 1 visual ear tag were investigated. No early losses (1 mo) occurred, although ruminal pH varied by breed and feeding management (6.32 to 6.73). At 1 yr, bolus retention (98.1%) was greater than ear tag (91.7%). Lowest bolus retention was for B1 (96.3%), whereas it was 97.8% for B3, and 100% for B2. Ear tag retention varied between breeds (82.9 to 98.6%). In conclusion, standard-sized boluses offered suitable long-term retention for goats under semi-extensive conditions.
In Exp. 3, adult Murciano-Granadina goats (n = 220) were identified with visual ear tags (VE), rumen boluses (RB: 75 g), RFID ear tags (EE, n = 47), and leg tags (LT) with 2 types of button transponders (ET1, n = 90; ET2, n = 130). According to shank circumference, LT for kid ID was discarded and only adult does were used. At 1 yr, no losses of LT occurred, although 1.5% were removed due to limping; readability of RB, EE, VE, ET1, and ET2 was 96.5, 95.7, 97, 93.9, and 98.3%, respectively. In conclusion, adequately designed leg tags are a valid ID method for adult dairy goats.
In Exp. 4, 2,482 RFID rumen boluses from 19 bolus types were used to construct a regression model of bolus retention in goats. Bolus features varied in length (37 to 84 mm), o.d. (9 to 22 mm), weight (W, 5 to 111 g), volume (V, 2.5 to 26 mL), and specific gravity (SG, 1 to 5.5). A logit regression model with W and V as covariates was constructed (R2 = 0.98). Estimated W and SG to produce mini- (5 mL), medium- (15 mL) and standard-sized (22 mL) boluses for a retention rate of 99.95% were 42.9, 73.0, and 94.1 g, and 8.58, 4.87, and 4.28, respectively. Increasing bolus W and SG allowed V to be reduced. Suitable medium-sized boluses for goats can be produced with radio translucent materials currently available.
In conclusion, under our conditions, visual ear tags and injects in the pastern were not recommended for official ID. Button electronic ear tags showed variable results according to type, and electronic leg tags were a valid method only for adult goats. According to the bolus retention model obtained, medium-sized boluses may be effectively produced for goat ID, but mini boluses are not recommended.
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Jansson, Vincent, David Bergman y Niklas Hermansson. "High Frequency Transformer : Implementation of prototype". Thesis, Uppsala universitet, Elektricitetslära, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-387307.
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Since its invention in 1885 by Otto Bláthy, Miksa Déri and KárolyZipernowsky, transformers have become an important cornerstone of theelectrical infrastructure we have today. They are found mostprominently in any machinery or device that requires a differentlevel of voltage or current than a general grid can supply, such ascomputers, motors or even cars. In the case of this project, thetransformer was originally intended to be connected to a resonatingH-bridge which supplies the primary coil with high frequency voltagepulses to be converted into a higher voltage transferred to arectifier unit. Because of the level of frequency supplied, thetransformer was required to be constructed with a different type ofcore and cable for the winding. When it became clear that the cablecouldn't be supplied in time, the focus shifted towards constructinga prototype instead. The prototype was designed to generate a certainamount of leakage inductance while subjected to a short circuit test.After a couple of attempts, the group managed to construct atransformer whose leakage inductance was well within range of thespecifications. The finished transformer prototype was delivered andthe group had thus successfully constructed what is to be used as atemplate for further transformers of the same type.A special thanks to ScandiNova Systems AB for initiating this projectand giving us the opportunity to participate, and to Per Nilsson, PerBenkowski and Klas Elmqvist for mentoring us along the way.