Dissertations / Theses on the topic 'High Frequency Applications'
To see the other types of publications on this topic, follow the link: High Frequency Applications.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'High Frequency Applications.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
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 textAbstract:
The main contribution of this project was to investigate power electronics technology in designing and developing high frequency high power converters for industrial applications. Therefore, the research was conducted at two levels; first at system level which mainly encapsulated the circuit topology and control scheme and second at application level which involves with real-world applications. Pursuing these objectives, varied topologies have been developed and proposed within this research. The main aim was to resolving solid-state switches limited power rating and operating speed while increasing the system flexibility considering the application characteristics. The developed new power converter configurations were applied to pulsed power and high power ultrasound applications for experimental validation.
2
Lee, 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 text
3
bi, 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 textAbstract:
In digital signal processing field, for recovering the signal without distortion, Shannon sampling theory must be fulfilled in the traditional signal sampling. However, in some practical applications, it is becoming an obstacle because of the dramatic increase of the costs due to increased volume of the storage and transmission as a function of frequency for sampling. Therefore, how to reduce the number of the sampling in analog to digital conversion (ADC) for wideband and how to compress the large data effectively has been becoming major subject for study. Recently, a novel technique, so-called “compressed sampling”, abbreviated as CS, has been proposed to solve the problem. This method will capture and represent compressible signals at a sampling rate significantly lower than the Nyquist rate. This paper not only surveys the theory of compressed sampling, but also simulates the CS with the software Matlab. The error between the recovered signal and original signal for simulation is around -200dB. The attempts were made to apply CS. The error between the recovered signal and original one for experiment is around -40 dB which means the CS is realized in a certain extent. Furthermore, some related applications and the suggestions of the further work are discussed.
4
Despotopoulos, Solon. "SiGe HFETs for analogue high frequency applications." Thesis, Imperial College London, 2003. http://hdl.handle.net/10044/1/8727.
Full text
5
Köroğlu, Mustafa Hadi. "High frequency integrated filters for wireless applications." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/14458.
Full text
6
Massicotte, 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 textAbstract:
The advent of large-scale graphene grown by chemical vapor deposition (CVD) offers a viable route towards high-frequency (HF) graphene-based analogue electronics. A significant challenge, however, is to synthesize and fabricate HF graphene-based devices with high carrier mobility. Here, we report our efforts to understand and control the CVD growth mechanism of graphene on copper, to characterize the synthesized film, and to fabricate graphene transistors and HF devices. In parallel, we describe the synthesis of large pristine dendritic graphene flakes that we name graphlocons. The electronic transport properties and magnetoresistance were assessed from 300 K to 100 mK and mobility up to 460 cm^2/Vs was obtained with a residual charge carrier density of 1.6x10^12 cm^-2. HF scattering parameters were measured from 0.04 to 20 GHz but they showed no dependence on temperature and magnetic field. This work provides a starting point for improving the structural and electronic properties of CVD graphene, and for exploring new phenomena in the GHz frequency range.L'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. .
7
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 text
8
Zhang, 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 text
9
Lin, Fang. "High-Q high-frequency CMOS bandpass filters for wireless applications." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/14869.
Full text
10
Escalante, Soberanis Mauricio Alberto. "High frequency data analysis for wind energy applications." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/54821.
Full textAbstract:
High frequency data (HFD) of three site studies in different geographic locations were analyzed to reproduce the power spectrum illustrated by Van der Hoven in 1957. His work represents the basis of wind energy standards such as averaging and variability in the frequency domain. The results presented in this thesis unveil discrepancies with Van der Hoven’s approach. A major eddy-energy peak is illustrated at a period of 2 days and a smaller eddy-energy peak contribution at frequencies higher than the region known as the spectrum gap. The variance in the microscale region was calculated by integrating the Power Spectral Density (PSD) over the corresponding range of frequencies. The economic value of this energy variance based on the turbulence kinetic energy of the wind data set is calculated. It is also concluded that, given the results of the study, HFD analysis in the frequency domain uncovers eddy-energy peaks that determine energy fluctuations in the short and long terms. An algorithm was developed to detect delay times in the turbulence kinetic energy (TKE) and the energy dissipation rate ε on a continuous basis (thereby identifying the highest cross-correlation coefficients between them). The Kolmogorov turbulence order is applied to calculate the energy dissipation rate ε through the identification of the inertial subrange. The time scale in the variations of both parameters was successfully calculated and it is close to the time the air takes to circulate between the surface and the top of the atmosphere’s mixed layer. High correlation coefficients are found in the three site studies from 4am to 8am, and from 8pm to 12pm. The cross-correlation function also determines delay time scales in the range of 10-20 minutes and approximately 2 hours. The energy dissipation rate can be calculated to characterize wind variability in a particular site that might affect the performance of a wind turbine. With these results, more information is generated that can be used in the wind turbine’s control system routines to improve its response under wind turbulence variations.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
11
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 textAbstract:
This thesis examines converter topologies suitable for Module Integrated Converters
(MICs) in grid interactive photovoltaic (PV) systems, and makes a contribution to
the development of the MIC topologies based on the two-inductor boost converter,
which has received less research interest than other well known converters.
The thesis provides a detailed analysis of the resonant two-inductor boost converter
in the MIC implementations with intermediate constant DC links. Under variable
frequency control, this converter is able to operate with a variable DC gain while
maintaining the resonant condition. A similar study is also provided for the resonant
two-inductor boost converter with the voltage clamp, which aims to increase the
output voltage range while reducing the switch voltage stress. An operating point
with minimized power loss can be also established under the fixed load condition.
Both the hard-switched and the soft-switched current fed two-inductor boost
converters are developed for the MIC implementations with unfolding stages. Nondissipative
snubbers and a resonant transition gate drive circuit are respectively
employed in the two converters to minimize the power loss.
The simulation study of a frequency-changer-based two-inductor boost converter is
also provided. This converter features a small non-polarised capacitor in a second
phase output to provide the power balance in single phase inverter applications.
Four magnetic integration solutions for the two-inductor boost converter have also
been presented and they are promising in reducing the converter size and power loss.
12
Boustedt, 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 text
13
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.
Full textAbstract:
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.
14
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 textAbstract:
Graphene has the highest mobility of any material at room temperature; this property has attracted a great deal of interest for applications in high frequency electronics, specifically transistors and diodes. To date, there has been little success using graphene for these purposes because it lacks the bandgap necessary to create an efficient device. This work aims to approach this problem from a different angle; using device architecture that potentially does not need a bandgap. This could allow graphene's excellent electrical properties to be exploited fully. The first example of this is the ballistic rectifier; a device that exploits the long mean free path of two dimensional electron gasses so that carriers can be treated like "billiard balls". Here we demonstrate two different four-terminal ballistic rectifiers that redirect carriers from the two input leads to one of the two output leads; the effect of this is to rectify an AC signal into a DC signal. An extremely high voltage responsivity of 23,000 V/W and a very low noise equivalent power of 0.64 pW/Hz1/2 are achieved from a low-frequency AC signal at room temperature. This same device has been tested at 220GHz and showed no signs of a cut-off frequency. Another rectifier tested here is the self-switching diode, a device that uses two side gates attached to its own source to locally gate its own conducting channel. This architecture demonstrates a modest peak responsivity of 690 V/W, a result of graphene's missing bandgap. A side-gated transistor with a modest on/off ratio of ~2.33 is also fabricated in order to better understand the limited capabilities of the graphene self-switching diode. Part of the novelty of this work is the introduction of a modified stamp transfer technique that allowed more flexibility creating hetero-structures. A dry etching recipe for hetero-structures is introduced that does not damage soft masks allowing for a new type of ultra-clean 1D contact. This new contact demonstrates considerably better contact resistance and reliability than previous generations; important for any high frequency application.
15
Tavakoli, 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 text
16
Forsberg, 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 text
17
Bishop, 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 textAbstract:
This thesis discusses the development, characterisation and evaluation of a compact, medium power, XeCl laser operating at pulse repetition frequencies (prf) >1kHz. The use of this laser to cut polymer films by ablative etching is also presented. The device uses a closed-cycle gas flow loop, constructed from stainless-steel for corrosive gas compatibility, and a total volume of 6 litres and a working pressure of 4 atmospheres. A magnetically coupled, tangential fan provides the gas flow and, with appropriate flow shaping into the 0.8 x 1.5 x 22.0cm⁻³ discharge region, produces a maximum flow velocity of 40m.s⁻¹. Electrical excitation is provided by a conventional, thyratron switched, capacitor discharge circuit, coupled with an internal, capacitively loaded, uv spark preionisation scheme, resulting in a rapid energy deposition into the discharge. Investigations of the effects of discharge perturbations on the maximum repetition rate capability of this laser, Indicate that repetition rates up to 1800Hz should be feasible. In operation, the laser has proven to be capable of 16W at 1kHz, and 22W at 700Hz, with a 10nF charging capacitor. Qualitative studies of the effect of resonator configuration on the beam profile, have shown that the use of folded cavities will produce more uniform beam profiles. Experiments have been carried out, using this laser, to cut thin polyethylene teraphthalate (PET) film at rates up to 1.3m.s⁻¹. The 8x15mm output beam from the laser, was brought to a 5.4mm long line-focus with a full width of 140µm. It is shown that the effective etch rate, and corresponding cutting efficiency, is markedly dependent on prf due, it Is thought, to cumulative heating.
18
Ross, Gordon J. "Detecting changes in high frequency data streams, with applications." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/12255.
Full textAbstract:
In recent years, problems relating to the analysis of data streams have become widespread. A data stream is a collection of time ordered observations x1, x2, ... generated from the random variables X1, X2, .... It is assumed that the observations are univariate and independent, and that they arrive in discrete time. Unlike traditional sequential analysis problems considered by statisticians, the size of a data stream is not assumed to be fixed, and new observations may be received over time. The rate at which these observations are received can be very high, perhaps several thousand every second. Therefore computational efficiency is very important, and methods used for analysis must be able to cope with potentially huge data sets. This paper is concerned with the task of detecting whether a data stream contains a change point, and extends traditional methods for sequential change detection to the streaming context. We focus on two different settings of the change point problem. The first is nonparametric change detection where, in contrast to most of the existing literature, we assume that nothing is known about either the pre- or post-change stream distribution. The task is then to detect a change from an unknown base distribution F0 to an unknown distribution F1. Further, we impose the constraint that change detection methods must have a bounded rate of false positives, which is important when it comes to assessing the significance of discovered change points. It is this constraint which makes the nonparametric problem difficult. We present several novel methods for this problem, and compare their performance via extensive experimental analysis. The second strand of our research is Bernoulli change detection, with application to streaming classification. In this setting, we assume a parametric form for the stream distribution, but one where both the pre- and post-change parameters are unknown. The task is again to detect changes, while having a control on the rate of false positives. After developing two different methods for tackling the pure Bernoulli change detection task, we then show how our approach can be deployed in streaming classification applications. Here, the goal is to classify objects into one of several categories. In the streaming case, the optimal classification rule can change over time, and classification techniques which are not able to adapt to these changes will suffer performance degradation. We show that by focusing only on the frequency of errors produced by the classifier, we can treat this as a Bernoulli change detection problem, and again perform extensive experimental analysis to show the value of our methods.
19
Yang, 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 textAbstract:
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: 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
20
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 textAbstract:
Mechanical EngineeringM.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
21
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 textAbstract:
This Thesis examines the operation and dynamic performance of a single-stage, single-switch power factor corrector, S4 PFC, with an integrated magnetic device, IM. Also detailed isthe development and analysis of a high power light emitting diode, HP LED, power factorcorrection converter and proposed voltage regulation band control approach.The S4 PFC consists of a cascaded discontinuous current mode, DCM, boost stage anda continuous current mode, CCM, forward converter. The S4 PFC achieves a high powerfactor, low input current harmonics and a regulated voltage output, utilising a singleMOSFET. A steady-state analysis of the S4 PFC with the IM is performed, identifying theoperating boundary conditions for the DCM power factor correction stage and the CCMoutput voltage regulation stage. Integrated magnetic analysis focuses on understanding theperformance, operation and generated flux paths within the IM core, ensuring the device doesnot affect the normal operation of the converter power stage. A design method for the S4 PFCwith IM component is developed along with a cost analysis of this approach. Analysis predictsthe performance of the S4 PFC and the IM, and the theoretical work is validated by MATLABand SABER simulations and measurements of a 180 W prototype converter.It is not only the development of new topological approaches that drives theadvancement of power electronic techniques. The recent emergence of HP LEDs has led to aflurry of new application areas for these devices. A DCM buck-boost converter performs thepower factor correction and energy storage, and a cascaded boundary conduction current modebuck converter regulates the current through the LED arrays. To match the useful operatinglifetime of the HP LEDs, electrolytic capacitors are not used in the PFC converter. Analysisexamines the operation and dynamic characteristics of a PFC converter with low capacitiveenergy storage capacity and its implications on the control method. A modified regulationband control approach is proposed to ensure a high power factor, low input current harmonicsand output voltage regulation of the PFC stage. Small signal analysis describes the dynamicperformance of the PFC converter, Circle Criterion is used to determine the loop stability.Theoretical work is validated by SABER and MATLAB simulations and measurements of a180 W prototype street luminaire.
22
López, 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 textAbstract:
The interaction between magnetic nanoparticles and high frequencies, such as microwaves or terahertz waves, is one of the most active field of research, with interesting applications in the screening of electromagnetic waves in electronic circuits, or medical applications such as the magnetic hyperthermia, or contrast in Nuclear Magnetic Imaging. Finite size effects are important in this field because they modify the basic properties of magnetic nanoparticles, for example, the blocking and the Curie temperature. In this thesis is shown new phenomena on nanomagnetism such as the colossal reduction of the Curie temperature in CoFe2O4 nanoparticles, the interaction between magnetic nanoparticles with microwave waves, the magnetic behavior of gold nanoparticles modified by different capping molecules, and new technological applications using terahertz radiation, such as the characterization of the drug diffusion into artificial membranes and human skin.
In the colossal reduction of the Curie temperature in CoFe2O4 nanoparticles due to size effects, it was observed a distortion in the crystallographic structure for these ferrite nanoparticles with mean diameter below 3 nm, and thus, the exchange interaction among the atoms that form the nanoparticles also varies. Consequently, the Curie temperature, which is round 700 K for bulk CoFe2O4, reduces until 10 K for nanoparticles with a size below 3 nm. That reduction was observed measuring the stable and metastable curves ZFC-FC, the isothermal magnetization in the temperature range between 2 and 300 K, and the ac-magnetic susceptibility in the frequency range belong 1 Hz to 1kHz. Furthermore, the magnetic relaxation curves at zero field showed a blocking temperature in the proximity of the reduced Curie temperature, it being the first time where the blocking temperature and the Curie temperature for a system of magnetic nanoparticles have a similar value. All these properties can be studied measuring the microwave absorption of the magnetic nanoparticles, between 1 and 20 GHz. Using this experimental technique, the basic properties and the magnetization dynamics of magnetic nanoparticles is characterized in a fast way, and in addition, it open new technological applications in electronics and medicine.
The surface modification as well as the magnetic properties of gold nanoparticles, using different capping molecules, have also been studied during this thesis. The type of bond at the surface of the nanoparticle stablished by the capping molecule generates a ferromagnetic shell that envelopes a diamagnetic core. This effect is due to the localization of surface charges in the proximity of the bond surface atom. In addition, it turns out that finire size effects in the gold nanoparticle affects to the size of the ferromagnetic domains, and hence, it is a crucial parameter that valance the interaction between the diamagnetic core and the ferromagnetic shell.
Finally, in this work it is exposed new technological applications performed by terahertz radiation, which is compressed between 0.3 and 3THz, for example in the study of layered materials, the creation of terahertz tagging using resonance phenomenon at these frequencies, the detection of biomolecules by their characteristic resonances, and the study of the dffusion of topic drugs into artificial membranes and abdominal human skin. The principle advantages that represent terahertz waves in front of other radiations are that they are non-ionizating, non-invasive, contactless and their spatial resolution. As principal application, it is presented how the permeation process of topic drugs can be studied by terahertz waves.This work was performed studying the time ight of the T-ray between the emitter/receptor and the drop that contains the topic formulation, previously pipetted onto an artificial membrane or human skin. Using this technique was possible to obtain a rate of mass transfer of the topic drug that fully characterized the permeation process. This technique can complement other currently techniques such as skin striping but it carry out by a non-invasive and contactless method.La 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.
23
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 textAbstract:
Abstract The main object of this thesis was to research injection mouldable 0–3 type ceramic polymer composites and their dielectric and magnetic properties in the GHz frequency region. The work has been divided into three sections. In the first section, two–phase ceramic polymer composites containing dielectric and magnetic fillers have been investigated and their characteristics analysed by reference to pre–existing mixing rules. The exploitation of these composites in miniaturizing devices, such as antennae, is presented and discussed. The second part describes three phase composites containing different nanosize additives (silver, silicon and alumina fibres) towards improving their dielectric properties. In the third part, some periodical and multilayer structures for ceramic polymer composite layers are proposed. In the case of two–phase ceramic polymer composites, with 37 vol.% of dielectric filler (Barium Strontium Titanate, BST) embedded into a thermoplastic polymer (ER140) matrix, the highest measured relative permittivity was 15 with a dielectric loss value of 0.008 at 1 GHz. With 43 vol.% of magnetic filler (hexaferrite, CO2Z) in ER182 matrix, the highest achieved relative permeability was 1.8 with a magnetic loss value of 0.077 at 1 GHz. Composites with Co2Z filler provide a 77% size reduction, and could thus be used advantageously in antennae. It was found that a 2–6 vol.% nanoaddition in BST–ER140 composites enhanced the relative permittivity drastically with only a minor effect on the dielectric losses. In particular, with only 2 vol.% addition of nanosize silver particles into the BST–ER140 composite, a 52% increase in the relative permittivity was obtained, with no significant change in the dielectric losses (tan δε = 0.004). Vertically and horizontally periodical dielectric composite structures comprising layers of different dielectric properties have been fabricated as well as multilayered structures containing dielectric and magnetic layers. The measurement results indicate that such multimaterial multilayer structures are good candidates for components with reduced dielectric and magnetic lossesTiivistelmä 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
24
Regimbal, Nicolas. "Study of fractional frequency synthesizers for high data rate applications." Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14292/document.
Full textAbstract:
Cette thèse traite de synthétiseurs de fréquence, et plus précisément de diviseurs de fréquence fractionnaires qui sont des blocs critiques en radiocommunications. Une nouvelle méthode pour la division de fréquence fractionnaire y est présentée : Elle est basée sur la répartition aléatoire de l'erreur de phase. Deux implémentations de cette méthode sont proposées. Le spectre du bruit de phase en sortie de diviseur est débarrassé de toute raie parasite. L'énergie habituellement contenue dans ces raies étant uniformément répartie sur l'ensemble du spectre, ce dernier adopte un profil plat. La solution proposée peut être implémentée dans des synthétiseurs de fréquence tels que les Boucles à Verrouillage de Phase (PLL). Puisque aucune mise en forme du bruit n'est appliquée par le diviseur, la bande passante de la PLL peut être optimisée. Dans ces conditions, la possibilité d'une modulation directe haut débit de la PLL résultante est étudiée. Pour finir, des solutions d'optimisation du système résultant sont étudiéesThis 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
25
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 text
26
Li, 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 textAbstract:
Germanium is a promising material for future high-performance semiconductor devices due to its superior carrier mobility compared to silicon. Work has been carried out with the aim of investigating the germanium as a semiconductor material for advanced bipolar transistors. A germanium compatible bipolar process has been developed and successfully demonstrated on bulk germanium substrates with a basic bipolar structure. Transistors with good output characteristics were achieved with an Early voltage of 55 V and common emitter current gain of 30. Novel Germanium-on-Sapphire (GeOS) was studied for further development of high-frequency application. GeOS substrates with a high quality single crystal germanium layer of thickness 8 urn were manufactured by direct wafer bonding and subsequent grinding and polishing. The germanium bipolar technology is then migrated to GeOS substrates and transistor output characteristics are reported for the first time. Investigation of poly-Ge emitter technology has been undertaken. A non-selective poly-Ge process at 400 QC has been developed by employing a silicon seed layer. This technology has been characterised by manufacture of a novel diode test structure with an n+ doped poly- Ge contact. A very shallow junction of 62 nm junction was successfully fabricated. Then the production of bipolar transistors on bulk germanium substrates through a self-aligned poly- Ge emitter bipolar process was established. These are the first bipolar transistors of this type to be manufactured and initial tests showed working transistors with a current gain of 50. Silvaco process and device simulation tools have been successfully adapted to model the processing steps in the germanium bipolar process flow and also to predict device performance. The issues that are overcome in this work not only apply to the germanium bipolar device, but also provide very useful information and experimental findings for material scientists and germanium-based process engineering.
27
Ji, 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 textAbstract:
In the past decade, there has been an increased demand to develop compact power supplies with high efficiency and high power density in order to revolutionise traditional approaches for high power radio frequency (RF) applications, such as long pulse modulators used for high energy physics acceleration experiments. Resonant technology has been considered to meet these challenges, due to its soft-switching characteristic at high operating frequency. The aim of this research project is to provide further knowledge in series resonant parallel loaded (SRPL) resonant converters for long pulse modulators, and to design advanced closed-loop control strategies for voltage pulse regulation. The proposed converter comprises three single phase SRPL resonant output stages, which guarantees a strong ability of overcoming the influence of tank unbalances and enables independent modulation procedures. A DQ modelling approach was utilized to analyse the converter. Based on it, a PI + repetitive control strategy was designed for voltage pulse regulation to obtain good dynamics and steady state performance. A combined frequency and phase shift modulation method was selected to control the converter so that soft-switching of semiconductor devices can be always achieved, even in the presence of large tank unbalances. Good correlation between simulation and experimental results has been demonstrated, which validates the converter circuit design, modelling approach, control strategy and modulation method
28
Kablan, 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 text
29
Bar, 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 textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2004.Vita.
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.
30
Li, Yifan. "Point process based high frequency volatility estimation : theory and applications." Thesis, Lancaster University, 2018. http://eprints.lancs.ac.uk/127786/.
Full textAbstract:
This thesis is a compilation of three main studies with the common theme: point process based high-frequency volatility estimation. The first chapter introduces a new class of high-frequency volatility estimators and examines its asymptotic properties. The second chapter studies the relative importance of market microstructure (MMS) variables on high-frequency volatility estimation. The third chapter proposes a Markov-switching model for high-frequency volatility estimation and provides intraday measures of information contents in the trading process using the proposed model. In the first chapter, we propose a novel class of volatility estimators named the Renewal Based Volatility (RBV) estimator, and derive its asymptotic properties. This class of estimators is motivated by the work of Engle and Russell (1998), Gerhard and Hautsch (2002), Andersen, Dobrev, and Schaumburg (2008), Tse and Yang (2012), Nolte, Taylor, and Zhao (2018), which use price durations to construct highfrequency volatility estimators. We show that our RBV estimator nests the volatility estimator using price duration, thus providing a theoretical framework to analyse its asymptotic properties. Our theoretical results support the simulation and empirical findings in Tse and Yang (2012) and Nolte, Taylor, and Zhao (2018) that: (1) both the non-parametric duration (NPD) based and the parametric duration (PD) based volatility estimators are more efficient than the Realized Volatility (RV) estimator; (2) a parametric design can greatly improve the efficiency of volatility estimation; (3) the PD estimator can provide accurate intraday volatility estimates. We provide simulation evidence for the performance of the NPD estimator and propose an exponentially smoothed version that can outperform noise-robust RV-type estimators under general market microstructure noise and jumps. In the second chapter, we augment the PD estimator by including MMS variables in the parametric model. Specifically, we use a lognormal version of the Autoregressive Conditional Duration (ACD) model by Engle and Russell (1998), and include trading volume, bid-ask spread, total quote depth, quote depth difference, number of trades, order imbalance and order flow in the ACD model. Moreover, we use a best subset regression (BSR) approach to rank and select the included MMS variables. Our empirical study based on high-frequency trade and quote data from 29 highly liquid securities and a market index ETF shows that, by benchmarking on a Realized Kernel measure, the inclusion of MMS covariates significantly improves the performance of volatility estimates on both daily and intraday levels. The BSR approach is very effective in selecting the most relevant MMS covariates for volatility estimation, and it suggests that contemporaneous number of trades and order flow are the most important variables for intraday volatility estimation. More importantly, intraday volatility estimates can be constructed from the ACD model even in the case when the RV-type estimators cannot be reliably constructed due to a lack of data. In the third chapter, we extend the Autoregressive Conditional Intensity (ACI) model (Russell, 1999) with a Markov-switching (MS) structure. We propose to use the Stochastic Approximation Expectation Maximization (SAEM) (Celeux and Diebolt, 1992) to estimate the MS-ACI model, and provide simulation evidence supporting the validity of the estimation procedure. We apply our MS-ACI model to high-frequency trade and quote data from 9 highly liquid securities and a market index ETF. Our empirical findings suggest that the MS-ACI model captures two distinct volume-volatility regimes in the high-frequency data: a dominant regime that spreads evenly throughout the trading day with strong correlation between cumulative trading volume and price duration, and a minor regime that concentrates at the beginning and end of a trading day with much weaker correlation between cumulative trading volume and price duration. We link this phenomenon to the firm-specific information arrival process into the market, and provide a measure of intraday information content of the transaction process.
31
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.
Full text
32
Lim, Ying Ying. "Printing conductive traces to enable high frequency wearable electronics applications." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/17880.
Full textAbstract:
With the emergence of the Internet of Things (IoT), wireless body area networks (WBANs) are becoming increasingly pervasive in everyday life. Most WBANs are currently working at the IEEE 802.15.4 Zigbee standard. However there are growing interests to investigate the performance of BANs operating at higher frequencies (e.g. millimetre-wave band), due to the advantages offered compared to those operating at lower microwave frequencies. This thesis aims to realise printed conductive traces on flexible substrates, targeted for high frequency wearable electronics applications. Specifically, investigations were performed in the areas pertaining to the surface modification of substrates and the electrical performance of printed interconnects. Firstly, a novel methodology was proposed to characterise the dielectric properties of a non-woven fabric (Tyvek) up to 20 GHz. This approach utilised electromagnetic (EM) simulation to improve the analytical equations based on transmission line structures, in order to improve the accuracy of the conductor loss values in the gigahertz range. To reduce the substrate roughness, an UV-curable insulator was used to form a planarisation layer on a non-porous substrate via inkjet printing. The results obtained demonstrated the importance of matching the surface energy of the substrate to the ink to minimise the ink de-wetting phenomenon, which was possible within the parameters of heating the platen. Furthermore, the substrate surface roughness was observed to affect the printed line width significantly, and a surface roughness factor was introduced in the equation of Smith et al. to predict the printed line width on a substrate with non-negligible surface roughness (Ra ≤ 1 μm). Silver ink de-wetting was observed when overprinting silver onto the UV-cured insulator, and studies were performed to investigate the conditions for achieving electrically conductive traces using commercial ink formulations, where the curing equipment may be non-optimal. In particular, different techniques were used to characterise the samples at different stages in order to evaluate the surface properties and printability, and to ascertain if measurable resistances could be predicted. Following the results obtained, it was demonstrated that measurable resistance could be obtained for samples cured under an ambient atmosphere, which was verified on Tyvek samples. Lastly, a methodology was proposed to model for the non-ideal characteristics of printed transmission lines to predict the high frequency electrical performance of those structures. The methodology was validated on transmission line structures of different lengths up to 30 GHz, where a good correlation was obtained between simulation and measurement results. Furthermore, the results obtained demonstrate the significance of the paste levelling effect on the extracted DC conductivity values, and the need for accurate DC conductivity values in the modelling of printed interconnects.
33
Farzanehfard, 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 textAbstract:
Ceramic substrates play an important role in thick film hybrid microelectronic circuits. Existing substrates such as alumina and beryllia do not meet satisfactorily the desired requirements. The newly developed aluminum nitride (AIN) substrate shows a great deal of promise and potentially embraces the best qualities of alumina and beryllia.
The objective of this dissertation is to study the electrical properties, thick film interaction, and environmental effects on AIN substrates, and also to examine the performance of this material for high power - high frequency hybrid thick film applications. In particular, wideband dielectric constant measurements of A1N and other ceramic substrates are performed, oxidization and humidity effects on surface properties of AIN are addressed, and short and long term aging effects on several circuit parameters are studied.
To evaluate the performance of AIN in high power and high frequency applications, two circuits; an impulse generator and a power converter, are realized, tested and compared with those on alumina substrates. The thick film circuits realized on AIN perform considerably better than those on alumina.Ph. D.
34
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 textAbstract:
Practical steady-state and dynamic design and analysis for high-order dc/dc resonant converters is presented. The analysis is mainly based on two types of the resonant converters, parallel-type and Class-D (a series-type), which are suitable for high-frequency applications. In the analysis of parallel resonant converters, the key step in the derivation of steady-state analytic equations for LLC-type parallel (LLC-PRC) and LLCC-type series-parallel resonant converter (LLCC-SPRC) is to reduce the order of their state-space models. In particular, the analytic equations for LLCC-SPRC can also be used to design and analyze the LC-PRC, LLC-PRC, and LCC-type series-parallel resonant converters. A simple design procedure along with design examples is given based on the derived analytic equations. Experimental LLC-PRC and LLCC-SPRC are implemented to verify the design results. In the analysis of the zero-voltage switch (ZVS) Class-D converter, both steady-state and dynamic analysis methods are presented. The analysis is based on the Class-D converter with a variable capacitance switch (VCS) for voltage regulation at constant frequency. A generalized DC model for steady-state and dynamic analysis of the converter is given. A simplified small-signal model is found from perturbing the DC model and can be used to predict the low-frequency dynamic control- and line-to-output transfer functions. To predict the high-frequency dynamics, two models are derived based on the amplitude and phase modulations from communication theory. Besides the steady-state and small-signal modeling, a strategy to achieve a stable loop gain for closed-loop operation is addressed. A compensation controller for closed-loop operation of the VCS is developed. All the calculated and design results of the dynamic responses are verified based on the experimental measurements from the prototype converter.
35
Soufizadeh, 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 textAbstract:
Reconfigurable and tunable designs which provide multi-functionality are highly desirable in wireless communication systems. Amongst different methodologies to design RF switching, a directly connected biasing circuitry is not required for Static Field Micro-Particle Components (SFM-PCs); therefore, not only power consumption is lowered but also these particle-based switches can be used in complex geometries. However, the traditional structure has low-frequency bandwidth for both ON and OFF states and fails to operate correctly when undergoing rotation, these result in difficulties in using them in portable higher band applications. To address these issues, here two new techniques to increase the frequency bandwidth of ON and OFF states were proposed. Furthermore, a novel 360-degree rotatable structure was developed. The efficacy of these structures were evaluated by embedding them into discontinuous microstrip transmission lines. Both HFSS simulations and measurements show the accuracy of the analysis and the efficacy of the proposed designs.
36
Belcher, 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 textAbstract:
Thesis (M.S. in Telecommunications Systems Management)--Naval Postgraduate School, March 1990.Thesis 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.
37
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 text
38
Hu, 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 textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2006.Vita.
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.
39
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 textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged 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.
40
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 textAbstract:
An asymptotic scheme is generated that captures the motion of waves within discrete, semi-discrete and continuous periodic media by creating continuum homogenised equations. Conventional homogenisation theory is a well-known classical method valid when the wavelength of any disturbance is long relative to the microstructure. Unfortunately many of the features of interest in real applications involve wave oscillations that are of high frequency and that have wavelength of the same, or similar, order to the microstructure; this requires a new version of homogenisation theory: High frequency homogenisation. This has already been introduced for periodic microstructured continua and extended to discrete systems. Herein we extend high frequency homogenisation further, to deal with localised defect states and non-orthogonal geometries for both discrete and continuous media. We also apply the asymptotic theory to new models, such as in-plane oscillations of the discrete vector system. In each of the studies presented herein, the homogenisation method is verified using numerical and/or analytical solutions.
41
Schmid, 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 textAbstract:
The objective of the proposed research is to create new reconfigurable RF and millimeter-wave circuit topologies that enable significant systems benefits. The market of RF systems has long evolved under a paradigm where once a system is built, performance cannot be changed. Companies have recognized that building flexibility into RF systems and providing mechanisms to reconfigure the RF performance can enable significant benefits, including: the ability support multiple modulation schemes and standards, the reduction of product size and overdesign, the ability to adapt to environmental conditions, the improvement in spectrum utilization, and the ability to calibrate, characterize, and monitor system performance. This work demonstrates X-band LNA designs with the ability to change the frequency of operation, improve linearity, and digitally control the tradeoff between performance and power dissipation. At W-band frequencies, a novel device configuration is developed, which significantly improves state-of-the-art silicon-based switch performance. The excellent switch performance is leveraged to address major issues in current millimeter-wave systems. A front-end built-in-self-test switch topology is developed to facilitate the characterization of millimeter-wave transceivers without expensive millimeter-wave equipment. A highly integrated Dicke radiometer is also created to enable sensitive measurements of thermal noise.
42
Seo, Sanghyun. "GaN-based heterostructure field effect transistors and MMICs for high frequency applications." Aachen Shaker, 2009. http://d-nb.info/999595059/04.
Full text
43
Aguirre, 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 textAbstract:
Ce travail présente une évaluation des performances des transistors à effet de champ à base de graphène (GFET) grâce à des simulations électriques des modèles compact dédiés à des applications à haute fréquence. Les transistors à base de graphène sont parmi les nouvelles technologies et sont des candidats prometteurs pour de futures applications à hautes performances dans le cadre du plan d’action « au-delà du transistor CMOS ». Dans ce contexte, cette thèse présente une évaluation complète des transistors à base de graphène tant au niveau du dispositif que du circuit grâce au développement de modèles compacts précis pour des GFETs, de l’analyse de la fiabilité, en étudiant les mécanismes critiques de dégradation des GFETs, et de la conception des architectures de circuits basés sur des GFETs.Dans cette thèse nous présentons, à l’aide de certaines notions bien particulières de la physique, un modèle compact grand signal des transistors FET à double grille à base de graphène monocouche. Ainsi, en y incluant une description précise des capacités de grille et de l’environnement électromagnétique (EM), ce travail étend également les aptitudes de ce modèle à la simulation RF. Sa précision est évaluée en le comparant à la fois avec un modèle numérique et avec des mesures de différentes technologies GFET. Par extension, un modèle grand signal pour les transistors FET à double grille à base de graphène bicouche est présenté. Ce modèle considère la modélisation de l’ouverture et de la modulation de la bande interdite (bandgap) dues à la polarisation de la grille. La polyvalence et l’applicabilité de ces modèles compacts des GFETs monocouches et bicouches ont été évalués en étudiant les GFETs avec des altérations structurelles.Les aptitudes du modèle compact sont encore étendues en incluant des lois de vieillissement qui décrivent le piégeage de charges et la génération d’états d’interface qui sont responsables de la dégradation induite par les contraintes de polarisation. Enfin, pour évaluer les aptitudes du modèle compact grand signal développé, il a été implémenté au niveau de différents circuits afin de prédire les performances par simulations. Les trois architectures de circuits utilisées étaient un amplificateur triple mode, un circuit amplificateur et une architecture de circuit « balun »This 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
44
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 textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002.Includes 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.
45
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 text
46
Haug, 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 text
47
Pasadas, 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 textAbstract:
Los sistemas de comunicación inalámbricos 5G, así como el futuro despliegue del “Internet of Things”, han hecho que el International Technology Roadmap for Semiconductors, documento estratégico que marca la hoja de ruta de la industria de los semiconductores, incluya desde 2011 al grafeno y los 2DMs relacionados (GRMs) como candidatos para la electrónica del futuro. Así, el grafeno es considerado actualmente una excelente opción debido a que presenta unas propiedades excepcionales en cuanto al transporte electrónico; y se prevé que los transistores de efecto de campo (FET) que basen su funcionamiento en GRMs (2D-FETs), podrán superar el rendimiento de otras tecnologías.
La presente tesis está dedicada al modelado de 2D-FETs. El objetivo principal es el desarrollo de modelos y herramientas que permitan (i) ganar control tecnológico de los dispositivos basados en grafeno y grafeno bicapa (BLG), (ii) predecir el rendimiento en radiofrecuencia y evaluar la estabilidad de dichos dispositivos, (iii) comparar el rendimiento con otras tecnologías existentes, (iv) servir de ayuda al diseño de circuitos y dispositivos y (v) simular circuitos basados en 2D-FETs.
Para ello, la presente tesis comprende el desarrollo de un modelo de pequeña señal adecuado para 2D-FETs que garantiza la conservación de la carga. Este modelo viene acompañado de una metodología de extracción de parámetros que incluye las resistencias de contacto y acceso, las cuales son de extrema importancia en FETs de baja dimensionalidad. Tomando tal modelo como base, se realiza el análisis de las prestaciones en radiofrecuencia, la evaluación de la estabilidad cuando dichos dispositivos actúan como amplificadores de potencia, y un estudio del escalado del GFET. Los modelos de pequeña señal, como el presentado en esta tesis, son muy útiles para posibilitar el desarrollo de prototipos de una forma rápida y sencilla, lo cual es de especial importancia para tecnologías que se encuentran en las primeras fases de desarrollo, como es el caso actual de la tecnología basada en 2DMs.
Como principal contribución de esta tesis se presenta el desarrollo de un modelo compacto intrínseco de gran señal y basado en la física para FETs de grafeno (GFETs). La importancia de dicho modelo reside en su facultad de poder ser incluido en herramientas software de diseño asistido. El esfuerzo de crear un modelo es un paso necesario para facilitar el diseño de circuitos integrados monolíticos (MMICs) complejos que operen a frecuencias de microondas. La mayoría de los circuitos basados en GRMs demostrados hasta el momento no son ICs, por lo que se requiere de circuitos externos para su funcionamiento. Sin embargo, el desarrollo de circuitos de banda ancha operando a frecuencias de microondas precisa de esta tecnología. El modelo presentado en esta tesis es un buen punto de partida para el futuro desarrollo del diseño asistido de MMICs basados en grafeno. Los resultados son comparados con medidas experimentales de diversos circuitos, como por ejemplo, un amplificador de tensión, un doblador de frecuencia, un mezclador subharmónico de radiofrecuencia; y un detector de fase.
Por otra parte, el BLG es también un material prometedor para transistores que operan en radiofrecuencia. Este material posee una banda prohibida que resulta en una mejor saturación de la corriente que en grafeno monocapa. Motivado por esta importante propiedad física, en esta tesis se lleva a cabo el desarrollo de un modelo numérico de gran señal para FETs basados en BLG, el cual permite lo siguiente: (i) entender las propiedades electrónicas del BLG y cómo estas pueden ser controladas por acción del campo eléctrico, (ii) evaluar el impacto de la banda prohibida en las prestaciones de radiofrecuencia, (iii) comparar dichas prestaciones con otras tecnologías, y (iv) proporcionar asistencia al diseño de dispositivos. De forma notable, el modelo ha sido verificado con datos experimentales obtenidos en la literatura científica.New 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.
48
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 text
49
Wei, 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 text
50
Antonakakis, 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.
Full textAbstract:
In the context of acoustics, single polarization electromagnetism and elastic plates we consider microstructured media that have an underlying periodic structure and we develop an asymptotic continuum model that captures the essential microstructural behaviour entirely in a macroscale setting. The asymptotics are based upon a two-scale approach and are valid even at high frequencies when the wavelength and microscale length are of the same order. The general theory is illustrated via one- and two-dimensional model problems that can have zero-frequency stop bands that preclude conventional averaging and homogenization theories. Localized defect modes created by material or shape variations are also modelled using the theory and compared to numerical simulations.