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Wang, Meng. "A Tesla-Blumlein PFL-Bipolar pulsed power generator." Thesis, Loughborough University, 2016. https://dspace.lboro.ac.uk/2134/22802.
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A Tesla-Blumlein PFL-Bipolar pulsed power generator, has been successfully designed, manufactured and demonstrated. The compact Tesla transformer that it employs has successfully charged capacitive loads to peak voltages up to 0.6 MV with an overall energy efficiency in excess of 90%. The Tesla driven Blumlein PFL generator is capable of producing a voltage impulse approaching 0.6 MV with a rise time close to 2 ns, generating a peak electrical power of up to 10 GW for 5 ns when connected to a 30 Ω resistive load. Potentially for medical application, a bipolar former has been designed and successfully implemented as an extension to the system and to enable the generation of a sinusoid-like voltage impulse with a peak-to-peak value reaching 650 kV and having a frequency bandwidth beyond 1 GHz. This thesis describes the application of various numerical techniques used to design a successful generator, such as filamentary modelling, electrostatic and transient (PSpice) circuit analysis, and Computer Simulation Technology (CST) simulation. All the major parameters of both the Tesla transformer, the Blumlein pulse forming line and the bipolar former were determined, enabling accurate modelling of the overall unit to be performed. The wide bandwidth and ultrafast embedded sensors used to monitor the dynamic characteristics of the overall system are also presented. Experimental results obtained during this major experimental programme are compared with theoretical predictions and the way ahead towards connecting to an antenna for medical application is considered.
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Grenier, Jason. "Design of a MOSFET-Based Pulsed Power Supply for Electroporation." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/844.
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The use of high-voltage pulsed electric fields in biotechnology and medicine has lead to new methods of cancer treatment, gene therapy, drug delivery, and non-thermal inactivation of microorganisms. Regardless of the application, the objective is to open pores in the cell membrane and hence either facilitate the delivery of foreign materials inside the cell or to kill the cell completely. Pulsed power supplies are needed for electroporation, which is the process of applying pulsed electric fields to biological cells to induce a temporary permeability in the cell membrane. The applications of pulsed electric fields are dependent on the output pulse shape and pulse parameters, both of which can be affected by the circuit parameters of the pulsed power supply and the conductivity of the media being treated. In this research, two Metal Oxide Field Effect Transistor (MOSFET)-based pulsed power supplies that are used for electroporation experiments were designed and built. The first used up to three MOSFETs in parallel to deliver high voltage pulses to highly conductive loads. To produce pulses with higher voltages, a second pulsed power supply using two MOSFETs connected in series was designed and built. The parallel and series MOSFET-based pulsed power supplies are capable of producing controllable square pulses with widths of a few hundred nanoseconds to dc and amplitudes up to 1500 V and 3000 V, respectively. The load in this study is a 1-mm electroporation cuvette filled with a buffer solution that is varied in conductivity from 0. 7 mS/m to 1000 mS/m. The results indicate that by controlling the circuit parameters such as the number of parallel MOSFETs, gate resistance, energy storage capacitance, and the parameters of the MOSFET driver gating pulses, the output pulse parameters can be made almost independent of the load conductivity.
Using the pulsed power supplies designed in this work, an investigation into electroporation-mediated delivery of a plasmid DNA molecule into the pathogenic bacterium E. coli O157:H7, was conducted. It was concluded that increasing the electric field strength and pulse amplitude resulted in an increase in the number of transformants. However, increasing the number of pulses had the effect of reducing the number of transformants. In all of the experiments the number of cells that were inactivated by the exposure to the pulsed electric field was measured.
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Kadja, Tchamie. "Chip Scale Tunable Nanosecond Pulsed Electric Field Generator for Electroporation." University of Dayton / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1556028923379642.
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Lindblom, Adam. "Inductive Pulse Generation." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6699.
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Bendixsen, Luis Sebastian Caballero. "The design and construction of a compact, high-current pulsed power generator based on multiple low impedance pulse forming lines and networks." Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526548.
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Motloung, Setumo Victor. "Intense pulsed neutron generation based on the principle of Plasma Immersion Ion Implantation (PI3) technique." Thesis, University of the Western Cape, 2006. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_9599_1182748458.
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The development of a deuterium-deuterium/ tritium-deuterium (D-D/ D-T) pulsed neutron generator based on the principle of the Plasma Immersion Ion Implantation (PI3) technique is presented, in terms of investigating development of a compact system to generate an ultra short burst of mono-energetic neutrons (of order 1010 per second) during a short period of time (<
20&mu
s) at repetition rates up to 1 kHz. The system will facilitate neutron detection techniques, such as neutron back-scattering, neutron radiography and time-of-flight activation analysis.
Aspects addressed in developing the system includes (a) characterizing the neutron spectra generated as a function of the target configuration/ design to ensure a sustained intense neutron flux for long periods of time, (b) the system was also characterised as a function of power supply operating conditions such as voltage, current, gas pressure and plasma density.
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Drexler, Petr. "METODY MĚŘENÍ ULTRAKRÁTKÝCH NEPERIODICKÝCH ELEKTROMAGNETICKÝCH IMPULSŮ." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2007. http://www.nusl.cz/ntk/nusl-233412.
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This thesis deals with the aspects of methods for pulsed high-level EM quantities measurement. Methods for current and voltage measurement in pulsed power generator and power measurement in pulse microwave generator are discussed. New approaches to single-shot measurement methods application are proposed. The theoretical analysis of suitable sensor designs is performed. The magneto-optic measurement method has been experimentally realized. On the basis of experimental results a fiber-optic current sensor has been designed and theoretically analyzed. For identification and measurement of the free-space electromagnetic pulse a combined calorimetric sensor has been designed and built.
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Rondani, Bruno. "Projeto, desenvolvimento e construção de um modulador de pulso estado-solido para transmissores pulsados de alta potencia." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/261786.
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Orientador: Jose Antenor PomilioDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
Made available in DSpace on 2018-08-06T14:09:31Z (GMT). No. of bitstreams: 1 Rondani_Bruno_M.pdf: 5870538 bytes, checksum: 69f2b2bd154400cd5b620b87a2c4fe8c (MD5) Previous issue date: 2005
Resumo: Descreve-se neste trabalho o desenvolvimento de uma topologia de modulador de pulso estado-sólido e a linha de retardo modular, para aplicação em transmissores pulsados de alta potência que utilizem válvulas de microondas magnetron empregadas comumente em radares de trajetografia, meteorologia e controle de tráfego aéreo. A pesquisa abrange o projeto, desenvolvimento e construção de um modulador de pulso destinado à modernização do transmissor do radar de trajetografia Bearn do Centro de Lançamentos de Foguetes da Barreira do Inferno, Natal -RN. O equipamento desenvolvido fornece pulsos de até 37,5kV e 60A em três modos de transmissão, a saber: monopulso longo, monopulso curto e bipulso. No modo monopulso longo, a largura de pulso é de 1,7µs e nos outros dois modos, 0,85µs. A taxa de repetição dos pulsos é de 585,5Hz. A unidade de modulação de pulso consiste de oito módulos de chaveamento em paralelo, conectados ao primário de um transformador de pulso de razão 1:50. Cada módulo contém dois trechos de linha de retardo e duas chaves estado-sólido e é capaz de gerar pulsos de até 790V e 390A nos diferentes modos de operação. A alimentação da linha de retardo é feita através de um circuito de carga composto por um indutor de alimentação e um circuito de Clipper. O indutor de alimentação faz com que a tensão de carga na linha seja dobrada em relação à tensão contínua presente na saída da fonte de alimentação de entrada, devido à ressonância série criada entre esse indutor e a capacitância total das linhas de retardo. O circuito de Clipper garante a regulação de tensão pulso a pulso e a proteção do modulador contra surto de sobre-corrente na carga e sobre-tensão nas linhas de retardo. Esta topologia foi desenvolvida para melhorar a confiabilidade e facilitar a manutenção dos transmissores de radar com a implementação do conceito de degradação suave (graceful degradation) do modulador de pulso
Abstract: This work describes the development of a modular line-type solid-state pulse modulator topology to be applied in magnetron pulsed power radar transmitters, commonly found on tracking, weather and air traffic management radars. This research includes the design, development and assembling of a pulsed modulator for the Barreira do Inferno Launching Center (CLBI, Natal-RN) Bearn tracking radar upgrade program. The equipment developed provides pulses of 37.5 KV and 60 A in three transmission modes: single long pulse, single short pulse and bipulse. In the single long pulse the pulse width is 1.7 µs and in the other modes 0.85 µs. The pulse repetition frequency is of 585.5Hz. The modulator unit is composed by eight switching modules connected in parallel with the primary windings of a 1:50 ratio pulse transformer. Each module has two pulse-forming network and two IGBT switches and it is capable of handling 790 V and 390 A in the three operational modes. An inductor and a Clipper circuit implement the pulse-forming network charging. The charging inductor allows charging the pulse-forming network with twice the supply voltage since there is a resonance with the total modulator capacitance. The Clipper circuit assures the pulse-to-pulse charging voltage regulation and protects the modulator against load over-current and over-voltage charging. This topology was developed to improve reliability and maintainability of radar transmitters by implementing the graceful degradation (soft failure mode) in the pulse modulator
Mestrado
Sistemas e Controle de Energia
Mestre em Engenharia Elétrica
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Ure, K. A. N. "The generation of short, tunable high power optical pulses." Thesis, University of Southampton, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383874.
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Takayanagi, Jun, Norihiko Nishizawa, Hiroyuki Nagai, Makoto Yoshida, and Toshio Goto. "Generation of high-power femtosecond pulse and octave-spanning ultrabroad supercontinuum using all-fiber system." IEEE, 2005. http://hdl.handle.net/2237/6770.
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Marsden, Kevin Matthew. "A Study of a Versatile Low Power CMOS Pulse Generator for Ultra Wideband Radios." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/9754.
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Ultra-Wideband (UWB) technologies are at the forefront of wireless communications, offering the possibility to provide extremely high data rate wireless solutions. In addition to high data rate applications, UWB technologies also offer an extremely low cost alternative for many low data rate systems. In this thesis, we describe the design of a CMOS pulse generator for impulse based UWB systems. The structure of our pulse generator is based on the topology of a single tap CMOS power amplifier. By increasing the number of taps on a CMOS power amplifier, it is possible to generate sub-nanosecond pulses with a desired shape. A power saving scheme that significantly reduces the power consumed at low data rates is also described. The versatility of our design lies in the ability to support dynamically varying output power levels and center frequencies. Our pulse generator design is extended to a rectified cosine generator, necessary for a multiband approach. The performance of our pulse generators is estimated through simulation with a target technology of TSMC 0.18 µm CMOS at a supply voltage of 1.8 V. The simulation results indicate that our pulse generator produces high fidelity Gaussian monocycle pulses with a pulse width of approximately 160 ps and a peak output power of more than 10 mW. We believe that our design of a CMOS pulse generator for UWB systems is a feasible option for many applications in which power and cost are most important.Master of Science
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Laurain, Alexandre, Declan Marah, Robert Rockmore, John G. McInerney, Jorg Hader, Perez Antje Ruiz, Stephan W. Koch, Wolfgang Stolz, and Jerome V. Moloney. "High power sub-200fs pulse generation from a colliding pulse modelocked VECSEL." SPIE-INT SOC OPTICAL ENGINEERING, 2017. http://hdl.handle.net/10150/625500.
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We present a passive and robust mode-locking scheme for a Vertical External Cavity Surface Emitting Laser (VECSEL). We placed the semiconductor gain medium and the semiconductor saturable absorber mirror (SESAM) strategically in a ring cavity to provide a stable colliding pulse operation. With this cavity geometry, the two counter propagating pulses synchronize on the SESAM to saturate the absorber together. This minimizes the energy lost and creates a transient carrier grating due to the interference of the two beams. The interaction of the two counter-propagating pulses in the SESAM is shown to extend the range of the modelocking regime and to enable higher output power when compared to the conventional VECSEL cavity geometry. In this configuration, we demonstrate a pulse duration of 195fs with an average power of 225mW per output beam at a repetition rate of 2.2GHz, giving a peak power of 460W per beam. The remarkable robustness of the modelocking regime is discussed and a rigorous pulse characterization is presented.
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Nikitichev, Daniil I. "High power ultra-short pulse quantum-dot lasers." Thesis, University of Dundee, 2012. https://discovery.dundee.ac.uk/en/studentTheses/b7cec111-5ed7-4020-9fad-794d817e8f61.
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In this thesis, novel multi-section laser diodes based on quantum-dot material are designed and investigated which exhibit a number of advantages such as low threshold current density; temperature-insensitivity and suppress carrier diffusion due to discrete nature of density of state of quantum-dots. The spectral versatility in the range of 1.1 µm – 1.3 µm wavelengths is demonstrated through novel mode-locking regimes such as dual-wavelength mode-locking, wavelength bistability and broad tunability. Moreover, broad pulse repetition rate tuning using an external cavity configuration is presented. A high peak power of 17.7 W was generated from the quantum-dot laser as a result of the tapered geometry of the gain section of the laser has led to successful application of such device for two-photon imaging. Dual-wavelength mode-locking is demonstrated via ground (?=1180 nm) and excited (?=1263 nm) spectral bands with optical pulses from both states simultaneously in the 5-layer quantum-dot two-section diode laser. The widest spectral separation of 83 nm between the modes was achieved in a dual-wavelength mode-locked non-vibronic laser. Power and wavelength bistability are achieved in a mode-locked multi-section laser which active region incorporates non-identical QD layers grown by molecular beam epitaxy. As a result the wavelength can be electronically controlled between 1245 nm and 1290 nm by applying different voltages to the saturable absorber. Mode-locked or continuous-wave regimes are observed for both wavelengths over a 260 mA – 330 mA current ranges with average power up to 28 mW and 31 mW, respectively. In mode-locked regime, a repetition rate of 10 GHz of optical pulses as short as 4 ps is observed. Noticeable hysteresis of average power for different bias conditions is also demonstrated. The wavelength and power bistability in QD lasers are potentially suitable for flip-flop memory application. In addition, a unique mode-locked regime at expense of the reverse bias with 50 nm wavelength tuning range from 1245 nm to 1290 nm is also presented. Broad repetition rate tunability is shown from quantum-dot external cavity mode-locked 1.27 µm laser. The repetition rate from record low of 191 MHz to 1 GHz from fundamental mode-locking was achieved. Harmonic mode-locking allows further to increase tuning up to 6.8 GHz (34th-order harmonic) from 200 MHz fundamental mode-locking. High peak power of 1.5 W can be generated directly from two-section 4 mm long laser with bent waveguide at angle of 7° at 1.14 GHz repetition rate without the use of any pulse compression and optical amplifier. Stable mode-locking with an average power up to 60 mW, corresponding to 25 pJ pulse energy is also obtained at a repetition frequency of 2.4 GHz. The minimum time-bandwidth product of 1.01 is obtained with the pulse duration of 8.4 ps. Novel tapered quantum-dot lasers with a gain-guided geometry operating in a passively mode-locked regime have been investigated, using structures that incorporated either 5 or 10 quantum dot layers. The peak power of 3.6 W is achieved with pulse duration of 3.2 ps. Furthermore, the record peak power of 17.7 W and transform limited pulses of 672 fs were achieved with optimized structure. The generation of picosecond pulses with high average power of up to 209 mW was demonstrated, corresponding to 14.2 pJ pulse energy. The improved optical parameters of the tapered laser enable to achieve nonlinear images of fluorescent beads. Thus it is for the first time that QD based compact monolithic device enables to image biological samples using two-photon microscopy imaging technique.
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Sali, Emiliano. "Broadband nonlinear processes for high-power ultra short pulse generation." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412572.
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Chen, Zhao S. M. Massachusetts Institute of Technology Department of Chemistry. "Generation of high power single-cycle and multiple-cycle terahertz pulses." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79269.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 131-141).
In this thesis, we present experimental methods and results of tabletop generation of high power single-cycle and frequency-tunable multiple-cycle terahertz (THz) pulses pumped with near-infrared ultrashort optical pulses at 1 kHz and 10 Hz repetition rates. Single-cycle THz pulses with sub-picosecond duration and more than 50 pJ pulse energy, and multiple-cycle THz pulses with picosecond duration and more than 10 pJ pulse energy, are achieved respectively. These THz outputs are very close approximations to Gaussian beams, and can be well collimated and focused into samples for time-resolved spectroscopic experiments. This may allow for explorations in coherent nonlinear spectroscopy in the THz region such as the photon echo and multidimensional spectroscopy, revealing novel phenomena in solids, liquids, gases, and complex materials.
by Zhao Chen.
S.M.
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Kim, Jong Wan. "Back to Back Active Power Filter for Multi-Generator Power Architecture with Reduced dc-link Capacitor." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/96638.
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Multi-pulse converters have been widely used for a multi-megawatt scale power generating system to comply with harmonic regulations. Among all types of multi-pulse converters, a 12-pulse converter is the most widely used due to the simple structure, which consists of a delta-delta and a delta-wye phase-shift transformer pair and it effectively mitigates undesirable harmonics from the nonlinear load.
In the early 2000s, a shunt type passive front-end for a shipboard power system was proposed. By shunting the two gensets with 30° phase angle difference, a single phase-shift transformer effectively eliminates 5th and 7th harmonics. It achieves a significant size and weight reduction compared to a 12-pulse converter while keep the comparable harmonic cancellation performance. Recently, a hybrid type front-end was proposed. On top of the passive front-end, 3 phase active power filter was added and an additional harmonic cancellation was achieved to further eliminate 11th and 13th harmonics. However, the performance of both the passive and hybrid type front-end are highly dependent on the size of the line reactor in ac mains.
A back to back active power filter is proposed in this dissertation to replace the phase-shift transformer in the multi-generator power architecture. The proposed front-end does not include phase-shift transformer and the size and the weight of the overall front-end can be significantly reduced. Due to the active harmonic compensation, the back to back front-end achieves better power quality and the line reactor dependency is improved. The number of required dc-link capacitors is reduced by half by introducing a back to back configuration and the capacitor size is reduced by adjusting the phase angle difference of genset to cancel out the most significant voltage harmonics in the shared dc-link bus.
The overview of the existing shunt type front-end is provided and the concept of back to back active power filter is validated by simulation and prototype hardware. The comparison between existing front-end and the proposed front-end is provided to highlight the superior performance of back to back active front-end. The dc-link bus current and voltage ripple analysis is provided to explain the dc-link ripple reduction mechanism.Doctor of Philosophy
The transportation electrification has gained more and more attention due to its smaller carbon dioxide emission, better fuel efficiency. The recent advances in power devices, microcontrollers, and transducers accelerate the electrification of transportation. This trend is shown in the propulsion system in marine transport as well and the electric propulsion system has been widely used to meet the strict environmental regulations. However, the non-linear circuit components such as capacitor and diode in the electric propulsion system draw non-linear current and significantly deteriorate power quality and lead to critical problems such as reduced life span of circuit components Accordingly, a front-end is required to improve power quality. Also, it is desired to have compact and lightweight front-end for installation flexibility and fuel efficiency improvement. In this dissertation, several front-ends using a phase-shift transformer are reviewed and a detailed analysis is provided to help understand the harmonic cancellation principle of the existing front-end through equivalent circuit analysis, quantitative analysis, and a phasor diagram representation. Based on the analysis of the existing front-ends and shipboard power architecture, lightweight and high-performance front-end is proposed and verified by simulation and prototype hardware. The performance, size comparison between existing front-end and the proposed front-end is provided to show the advantage of the proposed front-end.
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Leigh, Matthew. "HIGH POWER PULSED FIBER LASER SOURCES AND THEIR USE IN TERAHERTZ GENERATION ." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/193797.
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In this dissertation I report the development of high power pulsed fiber laser systems. These systems utilize phosphate glass fiber for active elements, instead of the industry-standard silica fiber. Because the phosphate glass allows for much higher doping of rare-earth ions than silica fibers, much shorter phosphate fibers can be used to achieve the same gain as longer silica fibers.This single-frequency laser technology was used to develop an all-fiber actively Q-switched fiber lasers. A short cavity is used to create large spacing between longitudinal modes. Using this method, we demonstrated the first all-fiber Q-switched fiber laser in the 1 micron region.In addition to creating high peak powers with Q-switched lasers, created even higher powers using fiber amplifier systems. High power fiber lasers typically produce spectral broadening through the nonlinear effects of stimulated Raman scattering, stimulated Brullion scattering, and self-phase modulation. The thresholds for these nonlinearities scale inversely with intensity and length. Thus, we used a short phosphate fiber gain stage to reduce the length, and a large core fiber final stage to reduce intensity. In this way we were able to generate high peak power pulses while avoiding visible nonlinearities, and keeping a narrow bandwidth.The immediate goal of developing these high power fiber laser systems was to generate narrowband terahertz radiation. Two different wavelengths were combined into the final amplifier stage at orthogonal polarizations. These were collimated and directed into a GaSe crystal, which has a very high figure of merit for THz generation. The two wavelengths combined in the crystal through the process of nonlinear difference frequency generation. This produced a narrowband beam of THz pulses, at higher powers than previous narrowband THz pulses produced by eyesafe fiber lasers.
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Fang, Qiang. "2 μm Pulsed Fiber Laser Sources and Their Application in Terahertz Generation." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/232475.
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In this dissertation, an all-fiber-based single frequency nanosecond pulsed laser system at ~ 1918.4 nm in master-oscillator-power-amplifier (MOPA) configuration is present. The nanosecond pulse seed is achieved by directly modulating a continuous wave (CW) single frequency fiber laser using a fast electro-optical modulator (EOM) driven by an arbitrary waveform generator (AWG). One piece of single mode, large core, polarization-maintaining (PM) highly thulium-doped (Tm-doped) germanate glass fiber (LC-TGF) is used to boost the pulse power and pulse energy of these modulated pulses in the final power amplifier. This laser system can work in both high power and high energy regime: in high power regime, to the best of our knowledge, the highest average power 16 W and peak power 78.1 kW are achieved for single frequency transform-limited ~2.0 ns pulses at 500 kHz and 100 kHz repetition rate, respectively: In high energy regime, nearly 1 mJ and half mJ pulse energy is obtained for ~15 ns pulses at 1 kHz repetition rate and 5 kHz repetition rate, respectively. Theoretical modeling of the large-core highly Tm-doped germanate glass double-cladding fiber amplifier (LC-TG-DC-FA) is also present for 2&mum nanosecond pulse amplification. A good agreement between the theoretical and experimental results is achieved. The model can simulate the evolution of pump power, signal energy, pulse shape and the amplified stimulated emission (ASE) in the amplifier. It can also be utilized to investigate the dependence of the stored energy in the LC-TGF on the pump power, seed energy and repetition rate, which can be used to design and optimize the LC-TG-DC-FA to achieve higher pulse energy and average power. Two channel of high energy nanosecond pulses (at 1918.4 nm and 1938 nm) are utilized to generate THz wave in a quasi-phase-matched (QPM) gallium arsenide (GaAs) based on difference frequency generation. THz wave with ~ 5.4μW average power and ~18 mW peak power has been achieved. Besides, one model is built to simulate a singly resonated THz parametric oscillator. The threshold, the dependence of output THz energy on pump energy has been investigated through this model. One pump enhanced THz parametric oscillator has been proposed. The enhancement factor of the nanosecond pulses in a bow-tie ring cavity has been calculated for different pulse duration, cavity length and the transmission of the coupler. And the laser resonances in the ring cavity have been observed by using a piezo to periodically adjust the cavity length. We also build an all-fiber thulium-doped wavelength tunable mode-locked laser operating near 2&mum. Reliable self-starting mode locking over a large tuning range (>50 nm) using fiber taper based carbon nanotube (FTCNT) saturable absorber (SA) is observed. Spectral tuning is achieved by stretching another fiber taper. To the best of our knowledge, this is the first demonstration of an all-fiber wavelength tunable mode-locked laser near 2&mum.
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Darling, Jamie. "High power pulsed RF generation by soliton type oscillation on nonlinear lumped element transmission lines." Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526556.
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Appelgren, Patrik. "Experiments with and modelling of explosively driven mangetic flux compression generators." Licentiate thesis, KTH, Rymd- och plasmafysik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9638.
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This thesis presents work performed on explosively driven magnetic flux compression generators. This kind of devices converts the chemically stored energy in a high explosive into electromagnetic energy in the form of a powerful current pulse. The high energy density of the high explosives makes flux compression generators attractive as compact power sources. In order to study these devices a generator was designed at FOI in the mid-90ies. Two generators remained unused and became available for this licentiate work. The thesis reports experiments with, and simulations of, the operation of the two remaining generators. The aim was to fully understand the performance of the generator design and be able to accurately simulate its behaviour. The generators were improved and fitted with various types of diagnostics to monitor the generator operation. Two experiments were performed of which the first generator was operated well below its current capability limits while the second was stressed far above its limits. Since the generator generates a rapidly increasing current, a current measurement is the most important diagnostic revealing the current amplification of the generator and its overall performance. Further it is important to measure the timing of various events in the generator. With a common time reference it is possible to combine data from different probes and extract interesting information which cannot be directly obtained with a single measurement. Two types of numerical simulations have been performed: Hydrodynamic simulations of the high explosive interaction with the armature were used to verify the measured armature dynamics. A zero-dimensional code was used to perform circuit simulations of the generator. The model takes into account the inductance reduction due to the compression of the generator as well as the change in conductivity due to heating of the conductors in the generators.QC 20101103
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Guo, Xuhan. "Generation of ultrashort optical pulses with high peak power by monolithic laser diodes." Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648571.
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Sedlock, Steve. "Design and analysis of an integrated pulse modulated S-band power amplifier in gallium nitride process." Thesis, Kansas State University, 2012. http://hdl.handle.net/2097/13697.
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Master of ScienceDepartment of Electrical and Computer Engineering
William B. Kuhn
The design of power amplifiers in any semi-conductor process is not a trivial exercise and it is often encountered that the simulated solution is significantly different than the results obtained. Oscillatory phenomena occurring either in-band or out of band and sometimes at subharmonic intervals can render a design useless. Other less apparent effects such as jumps, hysteresis and continuous spectrum, often referred to as chaos, can also invalidate a design. All of these problems might have been identified through a more rigorous approach to stability analysis. Designing for stability is probably the one area of amplifier design that receives the least amount of attention but incurs the most catastrophic of effects if it is not performed properly. Other parameters such as gain, power output, frequency response and even matching may have suitable mitigation paths. But the lack of stability in an amplifier has no mitigating path. In addition to the loss of the design there are the increased production cycle costs, costs involved with investigating and resolving the problem and the costs involved with schedule slips or delays resulting from it. The Linville or Rollett stability criteria that many microwave engineers follow and rely exclusively on is not sufficient by itself to ensure a stable and robust design. It will be shown that the belief that unconditional stability is obtained through an analysis of the scattering matrix S to determine if K>1 and [delta][supscript]s<1 can fail and other tools must be used to validate circuit stability. With the emphasis being placed on stability, a 1W pulse modulated S-band power amplifier is designed using a battery of analysis tools in addition to the standard Linville or Rollett criteria to rigorously confirm the stability of the circuit. Test measurements are then presented to confirm the stability of the design and illustrate the results. The research shown contributes to the state of the art by offering a detailed approach to stability design and then applying the techniques to the design of a 1W pulse modulated S-band power amplifier demonstrating the first with 20 nanosecond pulse width switching and single digit nanosecond rise and fall times at 1 Watt power levels.
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Wang, Haochuan [Verfasser], and Ferenc [Akademischer Betreuer] Krausz. "High-energy and high-power multi-octave pulse generation / Haochuan Wang ; Betreuer: Ferenc Krausz." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2020. http://d-nb.info/1223849872/34.
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Jin, Hanbing. "Particle-in-Cell Simulation of Electromagnetic Pulse Generated by High-power Laser-target Interaction." Thesis, KTH, Fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-231339.
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Dai, Min. "Control of power converters for distributed generation applications." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1124329850.
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Kaumanns, Reimund Martin [Verfasser], and Ferenc [Akademischer Betreuer] Krausz. "Generation of energetic femtosecond pulses at high average power / Reimund Martin Kaumanns ; Betreuer: Ferenc Krausz." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2020. http://d-nb.info/1206878312/34.
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Scurria, Giuseppe. "High power 2 μm fiber laser for mid-infrared supercontinuum generation in fluoride fibers." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0342.
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Le développement de sources optiques ayant une forte brillance et un large spectre est nécessaire pour différentes applications telles que les contremesures optroniques, les systèmes LIDAR et la spectroscopie. Ce travail de thèse est consacré à l'étude de la génération de supercontinuum de forte puissance dans le domaine spectral allant de 2 à 5 μm. Un laser à fibre dopé thulium, émettant à 2 μm, a été réalisé et caractérisé en régimes continu, déclenché et à verrouillage de modes déclenchés. En régime continu, une puissance de 45 W a été atteinte avec un rendement différentiel de 58%. L'intégration de deux embouts en quartz fondu, fusionnés aux extrémités de la fibre active, a permis une amélioration drastique du contrôle de la température et de la stabilité générale du système dans tous les régimes de fonctionnement précédemment mentionnés. En régime combiné, de verrouillage de modes déclenchés, la puissance moyenne maximale en sortie de laser était de 40 W à une fréquence de déclenchement de 150 kHz. Pour une puissance moyenne en sortie de 20 W et une fréquence de déclenchement de 50 kHz, l'impulsion verrouillée la plus énergétique avait une énergie de 88 μJ et une puissance crête estimée de 60 kW. Dans tous les régimes de fonctionnement mentionnés, le facteur de propagation du faisceau M2 était proche de la limite de diffraction avec une excellente valeur de 1,1. Le faisceau de ce laser fibré a été utilisé pour pomper des fibres optiques en fluorure pour la génération de supercontinuum dans le domaine spectral de 2 à 5 μm. Les travaux expérimentaux ont été focalisés sur les matériaux en fluorure que sont le ZBLAN et le fluorure d’indium (InF3). Avec la fibre en ZBLAN, plus de 10 W ont été générés sur l'ensemble du domaine spectral avec une limite supérieure de domaine spectrale allant jusqu'à 4,4 μm. L'efficacité de conversion du supercontinuum a été mesurée à 35%, 28%, 15% et 8% pour un faisceau généré de longueur d'onde supérieure à 2,15 μm, 2,65 μm, 3,1 μm et 3,5 μm, respectivement. Concernant la fibre en InF3, la réalisation d'un nouveau système d'injection (combinant une fibre ZBLAN large coeur et un coupleur commercial fibre à fibre) a permis d'atteindre une grande stabilité thermo-mécanique de la fibre pendant les expériences à haute puissance. La génération de supercontinuum dans cette fibre s'est concrétisée par un faisceau de sortie dont le spectre atteignait la longueur d'onde de 4,7 μm et une puissance de 7 W sur l'ensemble du domaine spectral. À notre connaissance, ceci est le premier faisceau supercontinuum, ayant une puissance de l'ordre de quelques watts, généré dans une fibre en InF3 pompée par un oscillateur uniqueHigh brightness and broad spectrum optical sources in the mid-infrared (mid-IR) are promising for different applications such as optronic countermeasures, LIDAR systems and spectroscopy. This thesis research work is dedicated to the investigation of high power supercontinuum generation in the 2-5 μm range. A thulium-doped fiber laser emitting at 2 μm has been built and characterized in continuous wave, Q-switching and Q-switched mode-locking regime. In continuous wave operation, as much as 45 W have been reached with a slope efficiency of 58%. The implementation of two fused-quartz end-caps fusion spliced at the extremities of the active-fiber improved the thermal management and the overall stability of the entire system in all mentioned regimes of operation, allowing for higher pump powers. In Q-switched mode-locking, the maximum average output power level was 40 W, for a Q-switch repetition rate of 150 kHz. At the average output power level of 20 W and 50 kHz of Q-switch repetition rate, the most energetic mode-locked pulse had an energy of 88 μJ and an estimated peak power of ~60 kW. In all the mentioned operation regimes, the measured beam parameter M2 of the fiber laser was 1.1, close to the diffraction limit. This laser has been used to pump fluoride optical fibers (ZBLAN and InF3) for supercontinuum generation in the 2-5 μm range. In ZBLAN, more than 10 W in all spectral bands have been obtained, with an output spectrum extending up to 4.4 μm. A conversion efficiency of 35%/28%/15%/8% has been measured for wavelengths longer than 2.15 μm/2.65 μm/3.1 μm/3.5 μm, respectively. For the InF3 fiber, a new design of an injection system, consisting of a large core diameter ZBLAN optical fiber and a commercial fiber-to-fiber coupler, allowed to enhance the thermo-mechanical stability of the fiber. The supercontinuum radiation generated in InF3 showed an output spectrum spanning up to around 4.7 μm with an output power level of 7 W in all spectral bands. To the best of our knowledge, this was the first Watt-level supercontinuum radiation in an InF3 fiber pumped by a singleoscillator
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Choi, Myoung-Taek. "ULTRASHORT, HIGH POWER, AND ULTRALOW NOISE MODE-LOCKED OPTICAL PULSE GENERATION USING QUANTUM-DOT SEMICONDUCTOR LASERS." Doctoral diss., University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3942.
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This dissertation explores various aspects and potential of optical pulse generation based on active, passive, and hybrid mode-locked quantum dot semiconductor lasers with target applications such as optical interconnect and high speed signal processing. Design guidelines are developed for the single mode operation with suppressed reflection from waveguide discontinuities. The device fabrication procedure is explained, followed by characteristics of FP laser, SOA, and monolithic two-section devices. Short pulse generation from an external cavity mode-locked QD two-section diode laser is studied. High quality, sub-picosecond (960 fs), high peak power (1.2 W) pulse trains are obtained. The sign and magnitude of pulse chirp were measured for the first time. The role of the self-phase modulation and the linewidth enhancement factor in QD mode-locked lasers is addressed. The noise performance of two-section mode-locked lasers and a SOA-based ring laser was investigated. Significant reduction of the timing jitter under hybrid mode-locked operation was achieved owing to more than one order of magnitude reduction of the linewidth in QD gain media. Ultralow phase noise performance (integrated timing jitter of a few fs at a 10 GHz repetition rate) was demonstrated from an actively mode-locked unidirectional ring laser. These results show that quantum dot mode-locked lasers are strong competitors to conventional semiconductor lasers in noise performance. Finally we demonstrated an opto-electronic oscillator (OEO) and coupled opto-electronic oscillators (COEO) which have the potential for both high purity microwave and low noise optical pulse generation. The phase noise of the COEO is measured by the photonic delay line frequency discriminator method. Based on this study we discuss the prospects of the COEO as a low noise optical pulse source.Ph.D.
Other
Optics and Photonics
Optics
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Rim, Geun-hie. "Variable speed constant frequency power conversion with permanent magnet synchronous and switched reluctance generators." Diss., Virginia Tech, 1992. http://hdl.handle.net/10919/40015.
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Rosado, Sebastian Pedro. "Voltage Stability and Control in Autonomous Electric Power Systems with Variable Frequency." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/29616.
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This work focuses on the safe and stable operation of an autonomous power system interconnecting an AC source with various types of power electronic loads. The stability of these systems is a challenge due to the inherent nonlinearity of the circuits involved. Traditionally, the stability analysis in this type of power systems has been approached by means of small-signal methodology derived from the Nyquist stability criterion. The small-signal analysis combined with physical insight and the adoption of safety margins is sufficient, in many cases, to achieve a stable operation with an acceptable system performance. Nonetheless, in many cases, the margins adopted result in conservative measures and consequent system over designs.
This work studies the system stability under large-perturbations by means of three different tools, namely parameter space mapping, energy functions, and time domain simulations. The developed parameters space mapping determines the region of the state and parameter space where the system operation is locally stable. In this way stability margins in terms of physical parameters can be established. Moreover, the boundaries of the identified stability region represent bifurcations of the system where typical nonlinear behavior appears. The second approach, based on the Lyapunov direct method, attempts to determine the region of attraction of an equilibrium point, defined by an operation condition. For this a Lyapunov function based on linear matrix inequalities was constructed and tested on a simplified autonomous system model. In Addition, the third approach simulates the system behavior on a computer using a detailed system model. The higher level of model detail allows identifying unstable behavior difficult to observe when simpler models are used.
Because the stability of the autonomous power system is strongly associated with the characteristics of the energy source, an improved voltage controller for the generator is also presented. The generator of an autonomous power system must provide a good performance under a wide variety of regimes. Under these conditions a model based controller is a good solution because it naturally adapts to the changing requirements. To this extent a controller based on the model of a variable frequency synchronous generator has been developed and tested. The results obtained show a considerable improvement performance when compared to previous practices.Ph. D.
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Woodburn, David. "Modeling and Simulation of All-electric Aircraft Power Generation and Actuation." Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/6037.
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Modern aircraft, military and commercial, rely extensively on hydraulic systems. However, there is great interest in the avionics community to replace hydraulic systems with electric systems. There are physical challenges to replacing hydraulic actuators with electromechanical actuators (EMAs), especially for flight control surface actuation. These include dynamic heat generation and power management.
Simulation is seen as a powerful tool in making the transition to all-electric aircraft by predicting the dynamic heat generated and the power flow in the EMA. Chapter 2 of this dissertation describes the nonlinear, lumped-element, integrated modeling of a permanent magnet (PM) motor used in an EMA. This model is capable of representing transient dynamics of an EMA, mechanically, electrically, and thermally.
Inductance is a primary parameter that links the electrical and mechanical domains and, therefore, is of critical importance to the modeling of the whole EMA. In the dynamic mode of operation of an EMA, the inductances are quite nonlinear. Chapter 3 details the careful analysis of the inductances from finite element software and the mathematical modeling of these inductances for use in the overall EMA model.
Chapter 4 covers the design and verification of a nonlinear, transient simulation model of a two-step synchronous generator with three-phase rectifiers. Simulation results are shown.Ph.D.
Doctorate
Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering
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Lee, Sang Min. "A CMOS analog pulse compressor with a low-power analog-to-digital converter for MIMO radar applications." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/42875.
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Multiple-input multiple-output (MIMO) radars, which utilize multiple transmitters and receivers to send and receive independent waveforms, have been actively investigated as a next generation radar technology inspired by MIMO techniques in communication theory. Complementary metal-oxide-semiconductor (CMOS) technology offers an opportunity for dramatic cost and size reduction for a MIMO array. However, the resulting formidable signal processing burden has not been addressed properly and remains a challenge. On the other hand, from a block-level point of view, an analog-to-digital converter (ADC) is required for mixed-signal processing to convert analog signals to digital signals, but an ADC occupies a significant portion of a system's budget. Therefore, improvement of an ADC will greatly enhance various trade-offs. This research presents an alternative and viable approach for a MIMO array from a system architecture point of view, and also develops circuit level improvement techniques for an ADC.
This dissertation presents a fully-integrated analog pulse compressor (APC) based on an analog matched filter in a mixed signal domain as a key block for the waveform diversity MIMO radar. The performance gain of the proposed system is mathematically presented, and the proposed system is successfully implemented and demonstrated from the block level to the system level using various waveforms. Various figures of merit are proposed to aid system evaluations. This dissertation also presents a low-power ADC based on an asynchronous sample-and-hold multiplying SAR (ASHMSAR) with an enhanced input range dynamic comparator as a key element of a future system. Overall, with the new ADC, a high level of system performance without severe penalty on power consumption is expected.
The research in this dissertation provides low-cost and low-power MIMO solutions for a future system by addressing both system issues and circuit issues comprehensively.
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Petraviciute-Lötscher, Lauryna [Verfasser], and Ferenc [Akademischer Betreuer] Krausz. "High-power ultrafast light : generation of 1 ps-to-70 fs, 5 mJ-to-mikroJ pulses and low-harmonic-generation at high repetition rate / Lauryna Petraviciute-Lötscher ; Betreuer: Ferenc Krausz." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2020. http://d-nb.info/1211957683/34.
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Vauché, Rémy. "Conception de générateurs d'impulsions ultra-large bande en technologie CMOS." Thesis, Aix-Marseille 1, 2011. http://www.theses.fr/2011AIX10098.
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La théorie de l'information développée par Claude Shannon (1916 - 2001) met en évidence le fait que pour accroître la capacité d'un canal de transmission, il est préférable d'élargir la bande de fréquences sur laquelle les informations sont émises plutôt que les puissances d'émissions. Cette constatation est le point de départ de nombreux travaux de recherche sur les communications Ultra-Large Bande (ULB) qui ont abouti en 2002 à la création aux Etats-Unis d'une bande fréquence dîtes ULB où aucun mode de communication n'est privilégié. C'est ainsi que 2 années plus tard ont débuté à l'IM2NP des travaux portant sur les communications ULB impulsionnelles, et notamment la conception d'amplificateur faible bruit, de détecteur d'énergie, mais également de générateurs d'impulsions qui est l'élément clé des émetteurs impulsionnels. Ces derniers constituent la base des travaux présentés dans le manuscrit qui se sont déroulés de 2008 à 2011. La nature discontinue des communications impulsionnelles a tout d'abord impliquée l'introduction de nouvelles figures de mérite permettant de mesurer les performances des générateurs d'impulsions. Ensuite, il est question de méthodes de conception permettant de dimensionner des structures fonctionnant aux fréquences en jeu mais également d'en réduire les consommations statiques principalement de fuite, et ce en vue de répondre aux contraintes de consommation des systèmes embarqués. Enfin sont développées 3 architectures de générateurs d'impulsions, chacune permettant de répondre à des contraintes différentes en termes de bande de fréquences, de consommation et de portéeThe information theory developed by Claude Shannon (1916 - 2001) highlights the fact that in order to increase the capacity of a transmission channel, it is preferable to extend the bandwidth used rather than the transmission power. This finding is the starting point of many papers on Ultra-Wideband (UWB) which led to the creation in the United States of UWB band since 2002 where no modulation is privileged. Two years later, many works on Impulsionnal Radio UWB (IR-UWB) communications began at IM2NP including the design of low noise amplifier, power detector, but also pulse generators which is the key element of IR-UWB emitters. These form basis of works presented in the manuscript that took place from 2008 to 2011. The discontinuous nature of communications impulse was first implied the introduction of new figures of merit for measuring performances of pulse generators. Then it deals with design techniques for sizing structures operating at frequencies involved, but also to reduce consumption and especially static leakage to reduce enough power consumption for embedded systems. Finally three architectures of pulse generators are developed, each one responding to different constraints in terms of frequency, consumption and range
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Resan, Bojan. "DISPERSION-MANAGED BREATHING-MODE SEMICONDUCTOR MODE-LOCKED RING LASER." Doctoral diss., University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2907.
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A novel dispersion-managed breathing-mode semiconductor mode-locked ring laser is developed. The "breathing-mode" designation derives from the fact that intracavity pulses are alternately stretched and compressed as they circulate around the ring resonator. The pulses are stretched before entering the semiconductor gain medium to minimize the detrimental strong integrating self-phase modulation and to enable efficient pulse amplification. Subsequently compressed pulses facilitate bleaching the semiconductor saturable absorber. The intracavity pulse compression ratio is higher than 50. Down chirping when compared to up chirping allows broader mode-locked spectra and shorter pulse generation owing to temporal and spectral semiconductor gain dynamics. Pulses as short as 185 fs, with a peak power of ~230 w, and a focused intensity of ~4.6 gw/cm2 are generated by linear down chirp compensation and characterized by shg-frog method. To our knowledge, this is the highest peak power and the shortest pulse generation from an electrically pumped all-semiconductor system. The very good agreement between the simulated and the measured results verifies our understanding and ability to control the physical mechanisms involved in the pulse shaping within the ring cavity. Application trends such as continuum generation via a photonic crystal fiber, two-photon fluorescence imaging, and ultrafast pulse source for pump-probe experiments are demonstrated.Ph.D.
Other
Optics and Photonics
Optics
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Baselt, Tobias, Christopher Taudt, Bryan Nelsen, Andrés Fabián Lasagni, and Peter Hartmann. "Development of a method to overcome the power threshold during supercontinuum generation based on an Yb-doped photonic crystal fiber." SPIE, 2017. https://tud.qucosa.de/id/qucosa%3A35385.
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Optical coherence tomography benefits from the high brightness and bandwidth, as well as the spatial coherence of supercontinuum (SC) sources. The increase of spectral power density (SPD) over conventional light sources leads to shorter measuring times and higher resolutions. For some applications, only a portion of the broad spectral range can be used. Therefore, an increase of the SPD in specific limited spectral regions would provide a clear advantage over spectral filtering. This study describes a method to increase the SPD of SC sources by amplifying the excitation wavelength inside of a nonlinear photonic crystal fiber (PCF). An ytterbium-doped PCF was manufactured by a nanopowder process and used in a fiber amplifier setup as the nonlinear fiber medium. The performance of the fiber was compared with a conventional PCF that possesses comparable parameters. Finally, the system as a whole was characterized in reference to common solid-state laser-based photonic SC light sources. An order-of-magnitude improvement of the power density was observed between the wavelengths from 1100 to 1350 nm.
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Hamilton, Hymiar. "An impact study of DC protection techniques for shipboard power systems." Master's thesis, Mississippi State : Mississippi State University, 2007. http://library.msstate.edu/etd/show.asp?etd=etd-07062007-144823.
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Jung, Jin Woo. "Modeling and control of fuel cell based distributed generation systems." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1116451881.
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Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xvi, 209 p.; also includes graphics. Includes bibliographical references (p. 202-209). Available online via OhioLINK's ETD Center
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Streek, André. "Lasermikrosintern." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-231058.
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Die Arbeit analysiert das Lasermikrosintern von Metallen in seiner Gesamtheit durch kalkulierbare Modelle und Formulierungen. Hierfür wird der Sintervorgang in relevante Prozessschritte untergliedert. Die darauf aufbauenden Berechnungen der Prozessparameter werden in Form analytischer Ansätze und durch numerische Simulation analysiert. Anfänglich werden die Modelle der Einzelschritte und deren Resultate werden auf Übereinstimmung mit den experimentellen Daten und Beobachtungen geprüft. Hierbei dienen die Modelle, Algorithmen und analytischen Beziehungen als nachhaltiges Instrumentarium für Analysen und Beschreibungen dieses und ähnlicher Prozesse.
Mithilfe der entwickelten Algorithmen werden die bisherigen Vorstellungen zum Prozessmechanismus verifiziert, korrigiert, ergänzt und offene Fragen zur Prozessmechanik beantwortet. Abschließend werden die mechanistischen Modelle der Einzelschritte zur Diskussion experimenteller Ergebnisse und beobachteter Prozessphänomene in Form einer Gesamtinterpretation der betreffenden Lasermikrosinterregime zusammengeführt.
Zunächst werden die Prozessbedingungen und Prozessbeschreibungen sowie die Modelle zur Strahlungsabsorption in Pulvern in Arbeiten fremder Autoren vorgestellt. Zur Beschreibung der Ursache und Wirkung laserinduzierter Plasmen, ein besonders beim Lasermikrosintern bedeutsames Phänomen, wird auf eigene frühere Arbeiten zurückgegriffen. Aus den besonderen Bedingungen des Lasermikrosinterns wird die formale Gliederung des Prozessverlaufs in drei separate Dissipationsphasen abgeleitet. Die drei relevanten Reaktionsphasen sind hierbei, die Absorption der Strahlung, die Wärmeausbreitung und Schmelzerzeugung sowie die Wärmeleitung im Pulverbett. Die ablaufenden Einzelmechanismen als Folge der gepulsten Laserstrahlung werden durch geeignete Näherungen beschrieben und berechnet. Die Resultate werden mit grundlegender Aussage mit experimentellen Beispielen verglichen und verifiziert. Die Betrachtung unterschiedlicher Regime des Lasermikrosinterns erfolgt, gestützt auf die Ergebnisse der Kalkulationen der energetisch-thermodynamischen Synthese. Es werden Aussagen zu den regimespezifischen Prozessmerkmalen getroffen und mit den Beobachtungen verglichen. Oder, es werden regimespezifische Beobachtungen mit Hilfe der im vorhergehenden Abschnitt entwickelten prozessanalytischen Werkzeuge interpretiert. Auswirkungen von Parametervariationen auf den Gesamtprozess werden im Hinblick auf das Optimierungspotential diskutiert.
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Dufernez, Bruno. "Étude et simulation numérique d'un cycloconvertisseur à commande entièrement numérique." Vandoeuvre-les-Nancy, INPL, 1992. http://www.theses.fr/1992INPL133N.
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Le travail présenté dans cette thèse a été réalisé au sein du groupe de recherches en électrotechnique et électronique de Nancy, en collaboration avec le centre de recherche en automatique de Nancy. Il s'agit d'une étude sur les cycloconvertisseurs et plus particulièrement sur la réalisation de la commande d'un cycloconvertisseur triphasé à 36 thyristors, entièrement numérique, sans courant de circulation et sans liaison de neutre. Cette commande numérique est basée sur un générateur d'impulsions de type allumeur à retard. L'étude a été réalisée principalement par simulation numérique. Le programme de simulation a été réalisé avec GASPE (générateur automatique de programme de simulation des procédés électromécaniques), en utilisant une méthode de modélisation permettant de prendre en compte toutes les topologies du convertisseur, en particulier les commutations avec empiétement. La comparaison entre les différentes stratégies de commande s'appuie sur l'observation des formes d'ondes et des taux d'harmoniques. L'ébauche d'une réalisation pratique d'un cycloconvertisseur monophasé, sans courant de circulation et entièrement numérique est aussi présentée
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Haloua, Abderrahmane. "Étude d’un protocole de communication asynchrone faible consommation à lien radio impulsionnel ultra-large bande : implémentation sur silicium des fonctions RF critiques." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0255.
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Au cours des dernières années, différents travaux de recherche ont été consacrés à l’étude et au développement des solutions de type réseau de capteurs sans fil. Ces travaux sont une réponse à l’augmentation du nombre d’objets connectés dans le monde avec le développement de l’internet des objets. La consommation d’énergie dans les réseaux de capteurs représente un des domaines les plus étudiés. Les communications dans les réseaux de capteurs représentent une part importante de leur consommation. Afin de réduire la consommation des communications dans les réseaux de capteurs, différents niveaux d’optimisation sont possibles. Dans ce contexte, différents travaux de recherches visant à réduire la consommation des émetteurs-récepteurs, grâce à des architectures innovantes, ont été menés à l’IM2NP. Beaucoup de ces travaux ont été consacrés aux radios impulsionnelles Ultra-Large Bande (ULB). En outre, les protocoles d’accès aux canaux de communications dans les réseaux de capteurs sont également importants quant à l’optimisation de leurs consommations. Les travaux de recherches proposés dans ce manuscrit, basés sur les travaux sur les radios impulsionnelles ULB réalisés au sein de l’IM2NP, proposent une optimisation de la consommation des réseaux de capteurs sur deux niveaux. Tout d’abord, un protocole asynchrone à base de radio de réveil d’accès au canal de communication adapté aux communications ULB est proposé ainsi que son étude énergétique. Suite à l'étude du protocole asynchrone proposé, la conception d’un récepteur de réveil semi-passif et d’un générateur d’impulsion ULB sous-GHz est abordée, et leurs performances en termes d’efficacité énergétique discutéesIn recent years, research has been devoted to the study and development of Wireless Sensor Network (WSN). These research are a response to the increase of the connected objet number in the world with development of smartphones and Internet of things (IoT). Energy consumption in sensor networks is one of the most studied areas. In fact, the optimization of the consumption of the elements making up the sensor networks allows a reduction in the costs associated with their installation, operation and maintenance. Communications in sensor networks represent an important part of their power consumption. In order to reduce the consumption of communications in sensor networks, different levels of optimization are possible. In this context, various IM2NP research projects aimed at reducing transceiver consumption through innovative design were carried out. Much of this work has been devoted to Impulsionnal Radio Ultra-Wide Band (IR-UWB). Moreover, MAC protocols used to manage the communication channel access in wireless sensor networks are also important in optimizing their consumption. The research work proposed in this manuscript, based on the work on impulse radios UWB carried out within the IM2NP, propose an optimization of the consumption of sensor networks on two levels. Firstly, an asynchronous MAC protocol based on radio wake-up radio suitable for UWB communications is proposed as well as its energy study. Following the study of the proposed asynchronous protocol, the design of a low power semi-passive wake-up receiver (WuRx) and a UWB sub-GHz impulse generator is presented and their performance in terms of energy efficiency discussed
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Novák, Pavel. "Konstrukční řešení modelu průtočné říční elektrárny." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-228356.
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This thesis deals with designing a small hydraulic power plant, where a swirl turbine is conected to a unique synchronous working, which will offer a reliable and easy installation of the hydraulic power plant. As a result a wider potential of energy could be produced from renewable resources. The use of a narrow rottor as a holder of the permanent magnets is the biggest difficulties of this design.
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Moonesan, Mohammad Saleh. "Design and Implementation of IGBT Based Power Supply for Food Treatment." Thesis, 2011. http://hdl.handle.net/10012/6298.
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Pulsed electric field (PEF) processing has been demonstrated to be an effective non-thermal pasteurization method for food-treatment applications. With this method, high voltage, short-duration pulses are applied to a chamber through which liquid food is passed. If the voltage applied and the corresponding electric field develops a potential higher than a critical trans-membrane potential, the pores expand, and the membrane of the living cell is ruptured. Due to the lower amount of energy consumed during a PEF process, the temperature of the liquid is kept much lower than as opposed to conventional pasteurization. The PEF method thus kills bacteria and other microorganisms while preserving the nutrition and taste of the liquid foods.
Although the parameter responsible for inactivation is the voltage applied, for any given voltage, the conductivity of the liquid defines a current through the liquid that causes the temperature to rise. Therefore, preventing excessive heating of the liquid requires the application of an efficient waveform. According to the literature, the most efficient waveform is a square wave since the entire energy applied would be used for the inactivation process. Although some power supplies are capable of generating such a waveform, the generation of an efficient waveform that satisfies all the requirements for producing a viable product for PEF applications is still a challenging problem.
In this research, a cascadable pulse generator, based on a Marx generator design, was designed and implemented in order to generate a pulsed waveform for the treatment of liquid food. IGBT switches were used to charge capacitors in parallel and to discharge them in series as a means of generating a high voltage at the output. The design was implemented and tested for two stages, generating up to 6 kV and 1.6 kA square pulses with a controllable pulse width from 1 µs to 10 µs. Up to 3 switches were connected in parallel to enhance the current capability of the system. Also investigated are ways to improve the transient time by enhancing the IGBT driver circuit. The effect of design parameters such as pulse width, voltage, and current on the temperature rise in the liquid was also studied. A variety of liquid foods with different conductivities were tested in order to confirm the functionality of the system.
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Wisher, Matthew Louis. "MegaGauss : a portable 40T magnetic field generator." Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-05-3498.
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Fusion neutrons from high energy density plasmas generated by pulsed laser irradiation of nanoscale atomic clusters have been explored in recent experiments at the University of Texas at Austin. A sufficiently strong (~200 T) magnetic field is expected to produce a magnetized, high temperature (10 keV) plasma with beta [approximately equal to] 1. Such a field along the laser axis may confine the plasma’s radial expansion, thus increasing fusion yield. As part of a multi-stage project to implement this experiment, a scaled (~40 T, ~500 KA) version of the final 200 T, 2.2 MA pulsed power device has been designed and built by Sandia National Laboratories and is now at UT-Austin. This apparatus, named MegaGauss, is meant to serve as a preparation tool for the 200 T system; as such, its current pulse was recorded for analysis, and is compared to a theoretical model to verify its response parameters (e.g. peak current, time to peak). Techniques and results of this comparison are discussed, followed by explanations of basic construction of the 40 T device and current sensing instrumentation. Discussion of MegaGauss is completed with a survey of notable failure modes, and a description of the often severe effects the miniature field-generating Helmholtz coil experiences due to the current pulse and magnetic field. Finally, a novel data archive scheme, structured around the familiar MDSplus archive system, is implemented in Labview and integrated into the main pulsed power control program. Specifically, methods for linking MDSplus’s robust functionality with Labview’s intuitive development environment are realized by means of a specialized software bridge between the two. These methods are used in software that allows MDSplus archives to be written and read exclusively through Labview.text
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Hung, Min-hsuan, and 洪敏軒. "PULSE POWER GENERATOR FOR CARBON NANOTUBE FIELD EMISSION LAMP." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/58979314041590546689.
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碩士大同大學
電機工程學系(所)
97
A flyback converter incorporating an energy recovery circuit is proposed to generate high voltage pulses for driving carbon nanotube field emission lamp (CNT-FEL). The employed energy recovery circuit will not only eliminate the arcing phenomenon caused by traditional DC driving, but also recover the excess energy to DC bus so as to improve the system efficiency. In this paper, we construct an equivalent model of the CNT-FEL to exhibit its electric characteristics. Moreover, the mathematical models of each operation mode are also derived. And then a complete design considerations and mathematical model are detailed. All the experimental results agree with the computer simulations to verify the theoretical predictions.
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Pande, Manish. "Voltage controlled pulse width modulation pattern generators for static power converters." Thesis, 1993. http://spectrum.library.concordia.ca/5537/1/MM90807.pdf.
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Chang, Kuan-Yuan, and 張冠元. "Generation of high-power ultrashort laser pulses from high-power and ultra-broadband supercontinuum." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/4a632j.
Full textAbstract:
碩士國立交通大學
光電系統研究所
107
In this study, we use supercontinuum to generate a high-power and ultrafast laser that has a center wavelength near 1.06 μm, which is different from that of the seed laser at 1.56 μm. To keep the system all-fiber, we use single-mode fibers of different cutoff wavelengths to construct a shortpass filter, instead of the commonly used reflective or transmissive filters in free space. As a result, laser pulses that have a center wavelength near 1.06 μm are filtered through. Then, we use a ytterbium-doped fiber amplifier to amplify the filtered pulses, scaling their average power up to watt-level. Through this approach, high-power, ultrashort laser pulses of respective center wavelengths at 1.56 μm and 1.06 μm that have wide industrial applications can be generated in one system. We also compare the results of noise-like pulses and well-defined pulses: Both kinds of pulses can reach 6 W of maximal average output power, having pulse widths about 11 ps. We find that the noise-like pulses maintain their temporal features better than the well-defined pulses through the processes of amplification, supercontinuum generation, filtering, and further amplification.
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Yu, Yatong. "Design and Development of IGBT-Based Pulse Voltage Generator for Insulation Testing." Thesis, 2009. http://hdl.handle.net/10012/4815.
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With the desire for energy conservation and lower costs, the application of pulse-width modulated (PWM) voltage source converter (VSC) drives has grown at an exponential rate. However, due to their high switching frequency and high dv/dt, increased dielectric stresses and thermal stresses are applied to the insulation system of the motors, which may lead to the failure of the insulation. In order to test the performance of the motor insulation under the above complex stress conditions, an IGBT-based pulse voltage generator which can produce high voltage square wave and PWM waveforms has been successfully developed in this research. The generator consists of IGBT switches and other wave shaping components. The special cascade connection circuit design enables the generator to produce the stable high voltage square wave and PWM waveforms. A microcontroller-based trigger signal generator is used to trigger the power electronic switches in the generator. In order to avoid false triggering from electromagnetic interference (EMI), optical fibre cables are used to connect the trigger signal generator to the switches which are located in a high electric potential area. The generator can produce square wave and PWM waveforms with a peak voltage up to 15 kV and with a switching frequency of 600 Hz to 6 kHz. The fundamental frequency of the PWM waveform is 20 Hz to 1200 Hz, the rise time is less than 200 ns, and the pulse width can be varied up to several milliseconds. A 4 kVrms form wound model stator coil was tested under different voltage waveforms: power frequency, exponential decay pulse, square wave, and sinusoidal pulse-width modulated (SPWM) waveform. Infrared images and the maximum temperature rise of the coil under different electrical stresses were recorded. The results show that both the square and SPWM voltage waveforms cause a significantly higher temperature rise than the power frequency and exponential decay pulse voltage waveforms. Since the actual VSCs generate transients similar to those of the square and PWM voltage waveforms, it is recommended that the stator coil insulation be analyzed using PWM voltage waveforms in order to simulate actual conditions.
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Li, Yue-Ying, and 李岳穎. "High-power Femtosecond Pulse Generation in a Chirped-Pulse Amplified Ytterbium-Doped Fiber Laser System." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/61637106219008095724.
Full textAbstract:
碩士國立清華大學
光電工程研究所
102
In this thesis, we demonstrated the chirped pulse amplification (CPA) of a high-power ytterbium-doped fiber amplifier at wavelength of 1064 nm without a stretcher. The all-normal dispersion (ANDi) passively mode-locked fiber laser is used to generate highly chirped seed pulse. Therefore, the pulse stretcher could be optional. The spectrum bandwidth of our ANDi fiber laser is 9 nm which can support 185-fs-width pulses. The actual output pulses width is 11.7 ps. In this case, it is equivalent to -60 times stretching of the seed pulses to reduce the peak power. After amplification, the output signal power can achieve ~1 W with pulse width of 20 picosecond (repetition rate ~ 15 MHz). The output power is basically limited by stimulated Raman scattering (SRS), which reduces the gain of the signal power. After compression by the gratings pair, the output peak power was shown to be 25 kW with a compression ratio ~ 25 (~900 fs). In the meantime, the power loss of the compressor is around 50%. Further, the compressed-pulse was frequency doubled by a type-I critically phase-matched (CPM) Lithium Triborate (LBO) crystal with optimal focal parameter of ξ~ 1.5. With 370 mW of fundamental light, we can generate 88 mW of green output (λ= 532 nm) with conversion efficiency of 23% which is much higher than that achieved with our picosecond laser system (10%). Power scaling is possible but requires introducing second amplification stage with larger mode-field-diameter active fiber or increasing the stretching ratio before the amplification.
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Wisher, Matthew Louis. "Pulsed magnetic field generation for experiments in high energy density plasmas." Thesis, 2014. http://hdl.handle.net/2152/25985.
Full textAbstract:
Experiments in high energy density (HED) plasma physics have become more accessible with the increasing availability of high-intensity pulsed lasers. Extending the experiment parameters to include magnetized HED plasmas requires a field source that can generate fields of order 100 tesla. This dissertation discusses the design and implementation of a pulsed field driver with a designed maximum of 2.2 MA from a 160 kJ capacitor bank. Faraday rotation measurement of 63 T for a 1.0 MA discharge supported Biot-Savart estimates for a single-turn coil with a 1 cm bore. After modification, the field driver generated up to 15 T to magnetize supernova-like spherical blast waves driven by the Texas Petawatt Laser. The presence of the high field suppressed blast wave expansion, and had the additional effect of revealing a cylindrical plasma along the laser axis.text