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1
CAMILHER, DALTON VILELA. "AUTOCALIBRATION OF FREQUENCY STANDARDS USING THE INTERNET." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2000. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=2015@1.
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MARINHA DO BRASILA calibração de padrões atômicos de tempo e freqüência, na forma atualmente realizada, apresenta o inconveniente de ter que se fazer o transporte do Padrão de Transferência até os laboratórios onde se encontram os padrões a serem calibrados. Isto se dá pelo fato destes laboratórios não possuírem uma maneira adequada para enviarem seus padrões ao Departamento do Serviço da Hora do Observatório Nacional (DSH/ON), órgão responsável perante o INMETRO na calibração em tempo e freqüência e detentor do Padrão Nacional. Propõe- se aqui a substituição do procedimento atual por um sistema de calibração automática via Internet, o que elimina a necessidade do deslocamento do Padrão de Transferência. Neste novo sistema de calibração, a referência passa a ser um receptor de GPS (Global Position Sistem), que assume o papel de Padrão de Transferência, ao qual o padrão a ser calibrado é ininterruptamente comparado. O acesso e armazenamento dos dados pelo DSH/ON é feito por meio de um programa que controla remotamente a calibração no laboratório via conexão pela Internet. O presente trabalho envolve uma comparação entre o sistema atual e o proposto aqui, todo o desenvolvimento e apresentação do programa computacional, a montagem de um sistema completo de simulação prática, inclusive com acesso remoto via Internet, a coleta e tratamento dos dados e a apresentação do procedimento utilizado para se chegar à incerteza de medição do sistema. Procura-se ressaltar a vantagem de um sistema de calibração automático, quanto à coleta dos dados, assim como a não dependência do transporte do Padrão de Transferência para a realização da calibração, evitando- se com isto a sua deterioração . Na conclusão deste trabalho a incerteza obtida é comparada com a do procedimento atualmente em prática e a partir desta comparação são feitas considerações quanto à implementação do novo sistema e ao uso do r eceptor de GPS como Padrão de Transferência.
The time and frequency calibration of atomic standards presents the inconvenience of the need of transportation of the Transfer Standard to the laboratories in which stay the standards to be calibrate. This happens because the laboratories do not possess a way to send its standards to the Departamento do Serviço da Hora do Observatório Nacional (DSH/ON), organ representative of INMETRO in Time and Frequency calibrations and detainer of the National Standard. This work intends the substitution of the procedure adopted today by a system of automatic calibration using Internet, eliminating the need of the displacement of the Transfer Standard. In this new procedure, the reference is t he Global Position Sistem (GPS) receiver, assuming the role of the Transfer Standard, to which the standard to be calibrate is compared continuosly. The access and storage of the data for the DSH/ON are made by means of a computer code that remotely controls the calibration through an Internet connection. The present work involves a comparison among both systems, the whole development and presentation of the computer code, the assembling of a complete system of practical simulation, the acquisition and data treatment and the presentation of the procedure used to obtain the measurement of the uncertainty. The advantage of an automatic calibration system, as well as of the collection of the data, is the fact that it not depending of the transportation of the Reference Standard for the accomplishment of the calibratio. As a conclusion of this work the obtained uncertainty is compared with the one in use today and based in this comparison we made considerations about the implementation of the new system and the use of the GPS receiver as Transfer Standard.
La calibración de padrones atómicos de tiempo y frecuencia, en la forma actualmente realizada, tiene el inconveniente de tener que realizar el transporte del Padrón de Transferencia hasta los laboratorios donde se encuentran los padrones que serán calibrados. Esto se debe al hecho de que estos laboratorios no poseen una manera adecuada para enviar sus padrones al Departamento de Servicio de la Hora del Observatorio Nacional (DSH/ON), óprgano responsable frente al INMETRO en la calibración en tiempo y frecuencia y detentor del Padrón Nacional. Se propone aqui la substituición del procedimiento actual por un sistema de calibración automática vía Internet, que elimina la necesidad del desplazamiento del Padrón de transferencia. En este nuevo sistema de calibración, la referencia pasa a ser un receptor de GPS (Global Position Sistem), que asume el papel de Padrón de Transferencia, al cual el padrón a ser calibrado es ininterruptamente comparado. El acceso y almacenamiento de los datos por el DSH/ON se realiza a través de un programa que controla remotamente la calibración en el laboratorio vía conexión por Internet. El presente trabajo compara el sistema actual con el aqui propuesto, todo el desarrollo y presenta el programa computacional, el montaje de un sistema completo de simulación práctica, incluso con acceso remoto víaa Internet, la recolección y tratamiento de datos y la presentación del procedimiento utilizado para llegar a los erros de medición del sistema. Se resalta la ventaja de un sistema de calibración automático, así como la no dependencia del transporte del Padrón de Transferencia para la realización de la calibración, evitando con esto su deterioración. En la conclusión de este trabajo se compara el error obtenido con el del procedimiento actualmente en práctica y a partir de esta comparación se realizan consideraciones respecto a la implementación del nuevo sistema y al uso del receptor de GPS como Padrón de Transferencia.
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PIZZOCARO, MARCO. "Realization and characterization of optical frequency standards." Doctoral thesis, Politecnico di Torino, 2013. http://hdl.handle.net/11583/2506152.
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During the Ph.D. Course I worked on the realization and the characterization of an ytterbium optical frequency standard. Since year 2000, it is possible using optical frequency comb to directly and reliably scale a frequency measurement in the optical domain to a measurement in the microwave domain. This possibility allows the realization of high
accuracy and high stability optical frequency standards, whose atomic quality factors are several orders of magnitude higher than the best microwave ones. Among others, the alkaline earth atoms are very promising and, once trapped in an optical lattice, are capable of a short term stability approaching 10−15 at 1 s.
A ytterbium optical clock is currently being developed in the laboratories of the Optics Division of Istituto Nazionale di Ricerca Metrologica (INRIM) The experiment aims to cool and trap ytterbium atoms in a two stage magneto-optical trap (MOT) (at 399 nm and 556 nm) and to probe them in an optical lattice with a ultrastable laser at 578 nm.
This thesis presents the realization of the required laser sources, the stabilization of the clock laser, the development of the cooling and trapping stages and the design of a new experimental setup.
The blue and green radiations for the two-stage MOT at 399 nm and 556 nm are obtained by second harmonic generation in non-linear crystals. The yellow clock laser at 578 nm is generated by sum of frequency in non-linear crystal. The clock laser is stabilized with the Pound-Drever-Hall technique on a high-finesse Fabry-Pérot cavity. The
temperature stabilization of the cavity is implemented with a novel Active Disturbance Rejection Control scheme. The frequency noise of the laser is characterized with a stability 3 × 10−15 at 1 s. Atoms are trapped in the blue magneto-optical trap at 399 nm and transferred in the green trap at 556 nm. A new experimental setup is designed, studying the vacuum chamber, the MOT coils and the atomic source.
I have been guest researcher at National Institute of Standards and Technology (NIST) for six months in 2011. I will describe development of NIST ytterbium optical clocks during my visit.
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Law, Eugene L. "TELEMETRY RF SIGNAL BANDWIDTH; DEFINITIONS AND STANDARDS." International Foundation for Telemetering, 1995. http://hdl.handle.net/10150/608400.
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International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, NevadaThis paper will present and compare several definitions of telemetry radio frequency (RF) signal bandwidth. Measured spectra for different signals will be presented. The bandwidths of these signals will then be determined and measurement methods will be discussed. This discussion will include the effects of spectrum analyzer resolution bandwidth, video bandwidth and detector type. Finally, a proposed spectral mask will be discussed. This spectral mask can be used to calculate the required attenuation for a given frequency offset from the center frequency. The required attenuation is a function of the the bit rate or maximum frequency of interest and the transmitter power. This spectral mask is proposed to be part of the next edition of the Telemetry Standards, Inter-Range Instrumentation Group (IRIG) Standard 106.
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Hella, Mona Mostafa. "CMOS radio frequency power amplifiers for short-range wireless standards /." The Ohio State University, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486399160107527.
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Smowton, P. M. "The frequency stabilisation of laser diodes for industrial applications." Thesis, Cardiff University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319933.
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BREGOLIN, FILIPPO. "Yb-171 optical frequency standards towards the redefinition of the second." Doctoral thesis, Politecnico di Torino, 2019. http://hdl.handle.net/11583/2754714.
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Langham, Conway David. "Cryogenic sapphire dielectric resonators as microwave frequency standards : development and performance." Thesis, University of Sussex, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364164.
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Smith, J. E. "The effects of rogueing on the frequency of atypical winter wheat plants." Thesis, University of Nottingham, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383798.
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Grishina, Vera. "Blue laser for precision spectroscopy : toward optical frequency standard referenced to laser cooled calcium atoms." University of Western Australia. School of Physics, 2008. http://theses.library.uwa.edu.au/adt-WU2009.0046.
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Optical frequency standards with the reference to a narrow electronic transition of a laser-cooled collection of neutral atomic particles are becoming essential tools of research in modern precision physics experiments. In the core of a building block of an optical frequency standard is the optical continuous wave laser that has a good spectral purity of the emitted light. Such a stable optical oscillator is highly desirable in high resolution spectroscopy, if it emits in a good quality beam at a short visible wavelength. This Master thesis explores efficient techniques for building such an optical frequency source intended for use in the cooling and trapping of Calcium atoms scheme. The strong dipole transition at the blue wavelength in the atomic Calcium is needed to reduce the kinetic energy of atoms by nearly six orders of magnitude. A further reduction in the thermal energy of the laser cooled atoms is required to locate with ultra-high precision the 400 Hz narrow clock transition of the stable 40Ca isotope. The experimental methods that achieve this and approach sub-microkelvin temperature of the laser cooled bosonic isotopes of alkaline earths are inspected. The blue laser with a uniform intensity distribution in the beam is useful to maintain the trapped number of cold atoms during these experiments. The spectroscopic properties of the relative transitions in Calcium atom are also reviewed following relevant publications in the area. The constructed blue laser can be used as a primary wavelength source in the lasers network for cooling and trapping of Calcium atoms. These experiments will constitute part of the project to build an optical atom clock referenced to 40Ca narrow linewidth transition. The blue laser is constructed by generating second harmonic in a Potassium Niobate crystal, which is temperature controlled to use a type-I noncritical phase-matching of the optical nonlinear process. The power of the intracavity-generated second harmonic depends on the resonance properties of the optical resonator where this nonlinear crystal is placed. The study is aimed at characterising the designed optical resonator and the experimental parameters that describe it. The formula is derived that relates the resonance power enhancement coefficient with finesse and the power coupling contrast of a passive optical cavity. The obtained relationship is verfied during the experiments. The produced efficiency of the intracavity second harmonic generation is approx. 0.0023 mWblue/(mWred)2. The research work also examines the noise characteristics of the infrared diode laser that is used as a pump source for the intracavity generated second harmonic and determines the spectroscopic precision of the produced blue light. The frequency locking experiment is analysed using the unbalanced scheme of the polarisation stabilisation technique. The designed optical buildup cavity became a part of the unbalanced frequency discriminator in such a scheme. The results demonstrate high gain of frequency noise suppression of the stabilised laser. The unbalanced arrangement of the H}ansch-Couillaud technique has been possible due to a very low amplitude noise of semiconductor lasers.
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Taylor, Paul. "Observation of an ultra-high Q resonance in a single ion of '1'7'2Yb'+." Thesis, University of London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337596.
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Srinivasan, Rangakrishnan. "Design and implementation of a frequency synthesizer for an IEEE 802.15.4/Zigbee transceiver." Texas A&M University, 2003. http://hdl.handle.net/1969.1/5898.
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The frequency synthesizer, which performs the main role of carrier generation
for the down-conversion/up-conversion operations, is a key building block in radio
transceiver front-ends. The design of a synthesizer for a 2.4 GHz IEEE 802.15.4/Zigbee
transceiver forms the core of this work. This thesis provides a step-by-step procedure for
the design of a frequency synthesizer in a transceiver environment, from the mapping of
standard-specifications to its integrated circuit implementation in a CMOS technology.
The results show that careful system level planning leads to high-performance
realizations of the synthesizer. A strategy of using different supply voltages to enhance
the performance of each building block is discussed. A section is presented on layout and
board level issues, especially for radio-frequency systems, and their effect on synthesizer
performance. The synthesizer consumes 15.5 mW and meets the specifications of the 2.4
GHz IEEE 802.15.4/Zigbee standard. It is capable of 5 GHz operation with a VCO
sensitivity of 135 MHz/V and a tuning range of 700 MHz. It can be seen that the adopted
methodology can be used for the design of high-performance frequency synthesizers for
any narrow-band wireless standard.
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Dawkins, Samuel T. "Sapphire room temperature optical frequency reference : design, construction and application." University of Western Australia. School of Physics, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0200.
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A pair of high-stability optical frequency references has been developed. The devices are based on room temperature Fabry-Perot cavities with mirrors spaced apart by a hollow single-crystal sapphire element. The sapphire element delivers mechanical sti ness that provides improved immunity to vibrational perturbations compared with the more common spacers made from ultra-low expansion glass. The system is housed in an vacuum chamber designed to provide isolation from environmental perturbations through the use of an active thermal control system, suspension legs and a unique beam alignment system. The dimensional stability of the Fabry-Perot was translated into a highly stable laser frequency by frequency locking a 1064nm Nd:YAG laser to the centre of a mode of the cavity. This frequency lock was implemented by the Pound-Drever-Hall scheme. By careful design, this control system was able to hold the frequency of the laser to within parts in 1016 of the frequency of the fundamental cavity mode. The minimum fractional frequency stability of the laser frequency was measured at 2.1x10[-]14 for integration times of 0.8 s, limited by the residual instability of the Fabry-Perot cavity. The experimental methods used to measure the performance of the system have also been considered in depth. For example, the most common way of characterizing the frequency stability of a frequency standard is the Allan variance. It is demonstrated that, without care, data taken with modern frequency counters can produce erroneous and distorted results when their output is supplied to this algorithm. The method to avoid or account for these errors is also presented. The Fabry-Perot cavity performance is limited on long timescales by residual temperature uctuations, which can be ameliorated in future by enhancing the design of the thermal control system. At short timescales, the system is limited by vibration-induced uctuations together with a white noise source, that is yet to be identi ed, but may relate to fundamental thermodynamic temperature uctuations of the sapphire spacer. This system was used to measure the stability of an optical signal synthesised from a cryogenic microwave sapphire oscillator using an wide-band optical frequency comb. This was the rst demonstration of a multiplication of an ultra-stable signal from the microwave frequency domain into the optical frequency domain, without loss of delity at the level of 2x10[-]14.
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Koryl, Margaret Nolan. "The formal evaluation of Indiana school superintendents : frequency, practices, and procedures." Virtual Press, 1996. http://liblink.bsu.edu/uhtbin/catkey/1036818.
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The primary purpose of this study was to examine the practice of formally evaluating Indiana school superintendents and to determine superintendent dispositions toward the process. More specifically, the following issues were analyzed: (a) the extent to which Indiana school superintendents were formally evaluated; (b) the extent to which job descriptions, district policy, or employment contracts were associated with formal evaluations; (c) superintendent opinions regarding criteria, purposes, and methods of evaluation; and (d) the extent to which selected demographic variables were associated with the practice of completing a formal evaluation.A descriptive survey research procedure was used in this study. The survey instrument was adapted from the one developed and used by Simpson (1994) in his study of South Carolina superintendents. Several modifications were made to adjust to current conditions in Indiana. The instrument was divided into two parts: current practices and procedures for formal evaluations and background information about the superintendent and school corporation. The population of this study was all 287 public school superintendents in Indiana. Data were collected in March and April of 1996. A total of 248 usable surveys was returned and analyzed.The findings indicated: (a) more than 78% of the superintendents were being formally evaluated; (b) more than 79% of the superintendents indicated the presence of a written job description, with over 59% of these superintendents indicating they were evaluated using the stated role expectations included in the job description; (c) more than 58% of the superintendents indicated their employment district had a written policy concerning superintendent evaluation; (d) more than 33% reported that a formal evaluation was a provision of their employment contract; (e) a checklist or rating scale was most frequently used in the evaluation process; (f) the most important criterion in evaluation was board and superintendent relations; (g) the primary purpose for superintendent evaluation was to identify areas needing improvement; and (h) the higher the superintendent's salary and the larger the school corporation, the more likely it was that the superintendent received a formal evaluation. In addition, the study offers recommendations for practice and for further research.Department of Education
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Lamilla, Rubio Erick Abraham 1985. "Transmitindo padrões de frequência atômicos por redes de fibras ópticas=Transmitting atomic frequency standards in optical fiber networks." [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/276939.
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Orientadores: Flavio Caldas Da Cruz, Luiz Eduardo Evangelista de AraujoDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin
Made available in DSpace on 2018-08-28T03:18:42Z (GMT). No. of bitstreams: 1 LamillaRubio_ErickAbraham_M.pdf: 5773132 bytes, checksum: 33effe596fdd1deb74be96f588fc6150 (MD5) Previous issue date: 2015
Resumo: Neste trabalho foi feito um estudo experimental da transmissão de padrões de frequência atómicos através de uma rede de fibra optica. Até onde sabemos este tipo de transmissão foi realizada pela primeira vez no Brasil. Utilizamos uma conexão de fibra óptica entre o Instituto de Física Gleb Wataghin (IFGW) e a Faculdade de Engenharia Elétrica e Computação (FEEC) da UNICAMP, correspondendo a uma distância de aproximadamente 2 km, e um comprimento total de fibra de 18 km. Frequências de RF derivadas de padrões de frequência de Rubídio e de um receptor GPS foram transmitidas e caracterizadas através de medidas de frequência, particularmente por gráficos de variância de Allan, e medidas da fase
Abstract: In this experimental work, transmission of an atomic frequency standard through an optical fiber network has been implemented for first time in Brazil, to the best of our knowledge. We have used a fiber link between the Institute of Physics (IFGW) and the Department of Electrical Engineering inside the campus of the University of Campinas (UNICAMP) corresponding to 18 km fiber link (2km between buildings). Radio frequencies derived from a Rubidium standard and a GPS (Global Position system) receiver has been transmitted and characterized via phase and frequency measurements, particularly trough Allan deviation plots and phase measurements
Mestrado
Física
Mestre em Física
2013/15492-2
FAPESP
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Trimble, William L. "High-resolution spectroscopy in ¹¹⁵In⁺ and prospects for an indium ion optical frequency reference /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/9661.
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Sharma, Abhinav. "ESTIMATING THE EFFECTS OF BLASTING VIBRATIONS ON THE HIGH-WALL STABILITY." UKnowledge, 2017. https://uknowledge.uky.edu/mng_etds/38.
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The stability of the high-walls is one of the major concerns for open pit mines. Among the various factors affecting the stability of high-walls, blast vibrations can be an important one. In general, worldwide the established respective government regulations and industry standards are used as guidance to determine the maximum recommended levels of the peak particle velocity and frequency from the blast to avoid any effects on the structures around the mining project. However, most of the regulations are meant for buildings or houses and do not concern high-walls.
This thesis investigates the response of high-walls under the effects of vibrations from mine blasting. In this research, the relationship between the high-wall response, the geometry of the slope, the frequency and the amplitude, of the ground vibration produced by blasting, is explored using numerical models in 3DEC. The numerical models were calibrated initially with data collected using seismographs installed in a surface mine operation and recording vibrations produced by an underground mine drill and blast operation. Once the calibration was accomplished, a parametric study was developed to explore the relationships between various parameters under study and its impact on the stability of high-walls.
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Kalogrias, Christos. "Performance analysis of the IEEE 802.11A WLAN standard optimum and sub-optimum receiver in frequency-selective, slowly fading Nakagami channels with AWGN and pulsed noise jamming." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Mar%5FKalogrias.pdf.
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Thesis (M.S. in Electrical Engineering and M.S. in Systems Engineering)--Naval Postgraduate School, March 2004.Thesis advisor(s): Clark Robertson. Includes bibliographical references (p. 143). Also available online.
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Junior, Jair De Martin. "Sistema de laser de diodo de cavidade estendida para padrões de frequência." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/18/18149/tde-29052014-144230/.
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Este trabalho tem como objetivo principal desenvolver uma nova fonte de laser de diodo compacta e robusta, além de um novo drive de controle para serem utilizados em padrões primário de tempo e frequência tipo chafariz de átomo de Césio e padrões compacto baseados em átomos frios. Um dos requisitos para utilização de laser de diodo em padrões primários de tempo e frequência é sua estabilidade em frequência e baixíssimo ruído espectral. Além disto, dada à aplicação embarcada, o laser deve ser extremamente robusto com relação às condições adversas: mecânicas, térmicas e elétricas. Tanto a parte optomecânica, quanto os controles eletrônicos do novo laser foram desenvolvidos neste trabalho. Vale salientar que tal sistema, em sua concepção, é de grande interesse para diversos outros tipos de aplicação, como espectroscopia de gases (LIDAR), referências em outras frequências e experimentos de física atômica e molecular, que possuem elevados níveis de exigência com relação a ruídos espectrais.This work has as main objective to develop a new source of diode laser compact and robust, beyond a new drive control for use in primary of time and frequency standards type cesium atom fountain and compact standards-based cold atoms. One of the requirements for the use of diode laser in primary of time and frequency standards are their stability in frequency and are very low spectral noise. Furthermore, given the embedded application, the laser must be extremely robust with respect to adverse conditions: mechanical, thermal and electrical. Both opto-mechanical part, as the electronic controls of the new laser were developed in this work. It is noteworthy that such a system, in its conception, is of great interest to many other types of applications such as spectroscopy of gases (LIDAR), references in other frequencies and experiments of atomic and molecular physics, which have high levels of demand with respect to spectral noise.
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Silander, Isak. "Cavity enhanced optical sensing." Doctoral thesis, Umeå universitet, Institutionen för fysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-110278.
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An optical cavity comprises a set of mirrors between which light can be reflected a number of times. The selectivity and stability of optical cavities make them extremely useful as frequency references or discriminators. With light coupled into the cavity, a sample placed inside a cavity will experience a significantly increased interaction length. Hence, they can be used also as amplifiers for sensing purposes. In the field of laser spectroscopy, some of the most sensitive techniques are therefore built upon optical cavities. In this work optical cavities are used to measure properties of gas samples, i.e. absorption, dispersion, and refractivity, with unprecedented precision. The most sensitive detection technique of all, Doppler-broadened noise-immune cavity enhanced optical heterodyne molecular spectrometry (Db NICE-OHMS), has in this work been developed to an ultra-sensitive spectroscopic technique with unprecedented detection sensitivity. By identifying limiting factors, realizing new experimental setups, and determining optimal detection conditions, the sensitivity of the technique has been improved several orders of magnitude, from 8 × 10-11 to 9 × 10-14 cm-1. The pressure interval in which NICE-OHMS can be applied has been extended by derivation and verification of dispersions equations for so-called Dicke narrowing and speed dependent broadening effects. The theoretical description of NICE-OHMS has been expanded through the development of a formalism that can be applied to the situations when the cavity absorption cannot be considered to be small, which has expanded the dynamic range of the technique. In order to enable analysis of a large number of molecules at their most sensitive transitions (mainly their fundamental CH vibrational transitions) NICE-OHMS instrumentation has also been developed for measurements in the mid-infrared (MIR) region. While it has been difficult to realize this in the past due to a lack of optical modulators in the MIR range, the system has been based on an optical parametric oscillator, which can be modulated in the near-infrared (NIR) range. As the index of refraction can be related to density, it is possible to retrieve gas density from measurements of the index of refraction. Two such instrumentations have been realized. The first one is based on a laser locked to a measurement cavity whose frequency is measured by compassion with an optical frequency comb. The second one is based on two lasers locked to a dual-cavity (i.e. one reference and one measurement cavity). By these methods changes in gas density down to 1 × 10-9 kg/m3 can be detected. All instrumentations presented in this work have pushed forward the limits of what previously has been considered measurable. The knowledge acquired will be of great use for future ultrasensitive cavity-based detection methods.
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Ahn, Hong Jo. "A frequency synthesizer for multi-standard wireless applications." Columbus, OH : Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1054488431.
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Thesis (Ph. D.)--Ohio State University, 2003.Title from first page of PDF file. Document formatted into pages; contains xix, 148 p.: ill. Includes abstract and vita. Advisor: Mohammed Ismail. Includes bibliographical references (p. 144-148).
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Podolan, Luděk. "Jednoúčelový stroj zajišťující lisování kanystrových nálevek." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2015. http://www.nusl.cz/ntk/nusl-221101.
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The aim of this diploma thesis is detail description of theory, design process and final realization of single-purpose machine for pressing canister funnels. Theoretical section of this work covers manufacturing standards of the electrical cabinets, options for the single-purpose machine control with focus on the programmable logic controller e.g. PLC, PLC control program concept with definition of the main alarm states and description of two types of electrical cabinet. Practical part contains description of the electrical cabinet, its block diagram, photo documentation of the wiring (chapter 4.), chosen PLC type, its advantages and detail program description using Ladder diagram notation, communication with operator realized with touch LCD panel, programming environment for this LCD panel and program realization process. Finalized machine description and its photo documentation in manufacturing process is covered in the end. This diploma thesis is based and extends previously successfully defended semester project.
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MILANI, GIANMARIA. "Realization of advanced 171Yb optical lattice frequency standard." Doctoral thesis, Politecnico di Torino, 2018. http://hdl.handle.net/11583/2706635.
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Atomic clocks constitute a fundamental tool for time and frequency metrology
and their application is widespread in many technological fields. In particular, the
International System of units (SI) defines the second on a microwave transition of
Caesium atoms. The realization is made by clocks reaching uncertainties of few
parts in 10^−16, making the second to be the quantity realized with the smallest
uncertainty in the SI. However, a new generation of atomic clocks, called optical
clocks, have already demonstrated to surpass Caesium standards both in accuracy
and stability.
The research performed during my PhD activity has been focused on the development
and characterization of Ytterbium (Yb) optical lattice clocks. These
systems operate with a large number of ultra-cold neutral atoms having a clock
transition in the visible region of the electromagnetic spectrum. The atomic sample
is trapped in an periodical optical potential called optical lattice that gives the
advantage to interrogate many quantum absorbers for an extended time, with small
perturbations, allowing to achieve an unprecedented stability and accuracy.
The main experimental work has been carried out in the laboratories of the
Istituto Nazionale di Ricerca Metrologica (INRIM) in Turin, where several atomic
clocks are present including the Italian primary frequency standard, the Caesium
fountain ITCsF2, and where an Yb optical lattice clock is currently being developed.
This thesis describes the functioning of the system along with the full characterization
of systematic effects, the complete uncertainty budget and its first absolute
frequency measurement against the primary frequency standard. The clock exhibited
an accuracy of 1.6 × 10^−16 and the comparison with the Cs fountain resulted
in a frequency of f171Yb = 518 295 836 590 863.59(31) Hz, limited by the fountain
uncertainty. This measurement is in agreement with the ytterbium frequency recommended
as a secondary representation of the second in the SI and constitutes
the first measurement of a Yb clock in Europe and the second one in the world
against a primary frequency standard.
Several upgrades have been applied after the absolute measurement. In particular,
the design and realization a system capable to frequency stabilize several lasers
on a single optical cavity is illustrated. This cavity has been implemented to lock
the lasers used to cool and trap the atomic sample at 399, 556 and 759nm using
the offset sideband locking technique, a modified version of the Pound–Drever–Hall
method that gives an extended frequency tunability. The system proved to be an
easy-to-use and reliable tool for the experimental activity showing a linewidth below
300 Hz at 556nm, which is the wavelength that requires the most stringent performance,
and a long term drift below 20 kHz per day at 759nm. That is suitable for
operating the lattice laser with a light shift uncertainty below 1 × 10−18.
During my PhD I have been guest researcher at the National Institute of Standards
and Technology (NIST) of Boulder, Colorado, for nine months in 2016. In
these laboratories two Yb optical lattice clocks are operative. I worked on the instability
measurement of a composite system exploiting the two clocks to suppress
the Dick effect, called zero-dead-time (ZDT) clock, which demonstrated a fractional
instability of 3 × 10−17 at 1s. The two clocks can also be operated to extend the
interrogation time obtaining a spectroscopic feature after 4 s of 120(20)mHz corresponding
to a quality factor Q > 4 × 10^15. I also worked on the characterization
of several systematic shifts that allowed to complete the uncertainty budget of the
clocks at 1.6 × 10^−18. In particular, I contributed to the characterization of lattice
light shifts considering the effect of atomic sample temperature and the identification
of a metrological regime called operational magic frequency where frequency
shifts are insensitive to changes in trap depth.
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Don, Wickramage Chathurika Pavithrani Kumari. "Information accountability in health information systems using process analytics." Thesis, Queensland University of Technology, 2020. https://eprints.qut.edu.au/205044/1/Chathurika_Don%20Wickramage_Thesis.pdf.
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The thesis presents ways of automatically detecting healthcare policy violations in Health Information Systems (HISs), as one part of an overall Information Accountability Framework, intended to hold system users answerable for their information use. The significance of this research is the demonstration of an auditing approach that includes healthcare log enrichment and methods of modelling healthcare policies and standards that can be used for checking policy compliance in the healthcare industry. It also paves the way for how process analytics can be used to hold people accountable for their information use in HISs.
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Eken, Yalcin Alper. "High frequency voltage controlled ring oscillators in standard CMOS." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/8064.
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Luo, Changling 1980. "Fluctuating wind power penetration as limited by frequency standard." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=83873.
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Fluctuating wind power is due to wind turbulence and is the part which should be filtered out leaving behind the more predictable mean wind power which can be traded in the hourly energy market. The power fluctuations cause the frequency of electric utility to deviate from the 60Hz standard. This thesis is concerned with estimating the maximum fluctuating wind power before the 1% deviation from the 60 Hz standard (required by some utilities) is exceeded. To keep the thesis manageable, the scope is narrowed to thermal power plants with governor speed control but no Automatic Governor Control (AGC). This thesis shows that each governor speed control system provides energy storage buffer to attenuate the wind power fluctuations and arrives at the estimate that the fluctuating wind power penetration is conservatively around 5% of the generation capacity of the utility grid. The methodologies used to reach this estimate are: (i) Transfer Function analysis of power plants; (ii) digital simulations using HYPERSIM. Through the research, an innovative method of predicting the frequency deviation in an electric grid with multiple power plants has been developed and validated by simulation.The thesis also shows that fluctuating wind power penetration can be higher when there are filtering also in the wind farms. Wind turbines, with small inertias, driving constant speed squirrel cage induction generators are found to provide poor filtering. On the other hand, the fluctuating wind power penetration limit is increased to 18% in the case of wind turbines, with large inertias, driving variable-speed doubly-fed induction generators (DFIG) with decoupled P-Q control to implement optimal wind power acquisition.
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Tang, Yiwu. "Adaptive phase locked loop in multi-standard frequency synthesizers /." The Ohio State University, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486401895208464.
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Eken, Yalçin Alper. "High frequency voltage controlled ring oscillators in standard CMOS." Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-06072004-131133/unrestricted/eken%5Fyalcin%5Fa%5F200405%5Fphd.pdf.
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Homklintian, Monthol [Verfasser], and Meinhard [Akademischer Betreuer] Schilling. "Frequency Dependence of Primary Capacitance Standard in Audio Frequency Range / Monthol Homklintian ; Betreuer: Meinhard Schilling." Braunschweig : Technische Universität Braunschweig, 2012. http://d-nb.info/1175823945/34.
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Cirineo, Tony, and Bob Troublefield. "STANDARD INTEROPERABLE DATALINK SYSTEM, ENGINEERING DEVELOPMENT MODEL." International Foundation for Telemetering, 1995. http://hdl.handle.net/10150/608398.
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International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, NevadaThis paper describes an Engineering Development Model (EDM) for the Standard Interoperable Datalink System (SIDS). This EDM represents an attempt to design and build a programmable system that can be used to test and evaluate various aspects of a modern digital datalink. First, an investigation was started of commercial wireless components and standards that could be used to construct the SIDS datalink. This investigation lead to the construction of an engineering developmental model. This model presently consists of wire wrap and prototype circuits that implement many aspects of a modern digital datalink.
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Gantenbein, Terry K. "Implementation of Multi-Frequency Modulation on an industry standard computer." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/27088.
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Approved for public release; distribution is unlimitedThis report discusses the theory, design, implementation and testing of a personal computer-based Multi-Frequency Modulation (MFM) packet communications system. Transmitter/receiver programs provide software drivers for D/A and A/D boards and perform symbol encoding, modulating, demodulating and decoding. The design and construction of a polarity coincidence correlator for receiver packet synchronization is presented. Experimental results show that the implemented MFM communication system conforms to theoretical analysis with acceptable bit error. Results also show the MFM can be uniquely adapted to a specific channel.
http://archive.org/details/implementationof00gant
Lieutenant, United States Navy
31
Tibbo, Maria S. "Optimization of a RF Single Ion Paul Trap for a 88Sr+ Ion Optical Clock Comparison." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/26254.
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As part of the ongoing world-wide effort in improving time and frequency references, a high accuracy optical frequency standard was developed using the electric quadrupole allowed clock transition at 445 THz (674 nm) in a trapped and laser cooled 88Sr+ion. An ion trap system of the endcap design has been recently evaluated with a fractional frequency uncertainty which surpasses the accuracy of the current realization of the SI second. This thesis seeks to further evaluate the limiting systematic shifts of the device by optimizing a second ion trap reference based on a rf Paul trap design, which was then compared with the endcap trap reference frequency. The comparison of the two ion traps' reference frequencies confirmed an overall offset of -0.36 pm 0.08 Hz at the 445 THz reference frequency corresponding to a fractional frequency offset of 8 x 10^-16.
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Kim, Hyungwook. "CMOS radio-frequency power amplifiers for multi-standard wireless communications." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/44786.
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The development of multi-standard wireless communication systems with low cost and high integration is continuously requested and accompanied by the explosive growth of the wireless communication market. Although CMOS technology can provide most building blocks in RF transceivers, the implementation of CMOS RF power amplifiers is still a challenging task. The objective of this research is to develop design techniques to implement fully-integrated multi-mode power amplifiers using CMOS technology.
In this dissertation, a load modulation technique with tunable matching networks and a pre-distortion technique in a multi-stage PA are proposed to support multi-communication standards with a single PA. A fully-integrated dual-mode GSM/EDGE PA was designed and implemented in a 0.18 um CMOS technology to achieve high output power for the GSM application and high linearity for the EDGE application. With the suggested power amplifier design techniques, fully-integrated PAs have been successfully demonstrated in GSM and EDGE applications.
In Addition to the proposed techniques, a body-switched cascode PA core is also proposed to utilize a single PA in multi-mode applications without hurting the performance. With the proposed techniques, a fully-integrated multi-mode PA has been implemented in a 0.18 um CMOS technology, and the power amplifier has been demonstrated successfully for GSM/EDGE/WCDMA applications.
In conclusion, the research in this dissertation provides CMOS RF power amplifier solutions for multiple standards in mobile wireless communications with low cost and high integration.
33
Singh, Rahul. "Design Techniques for Frequency Reconfigurability in Multi-Standard RF Transceivers." Research Showcase @ CMU, 2018. http://repository.cmu.edu/dissertations/1185.
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Compared to current single-standard radio solutions, multi-standard radio transceivers enable higher integration, backward compatibility and save power, area and cost. The primary bottleneck in their realization is the development of high-performance frequency-reconfigurable RF circuits. To that end, this research introduces several CMOS-integrated, transformer-based reconfigurable circuit techniques whose effectiveness is validated through measurements of designed transceiver front-end low-noise (LNA) and power amplifier (PA) prototypes. In the first part, the use of high figure-of-merit phase-change (PC) based RF switches in the reconfiguration of CMOS LNAs in the receiver front-end is proposed. The first reported demonstration of an integrated, PC-switch based, dual-band (3/5 GHz) reconfigurable CMOS LNA with transformer source degeneration and designed in a 0.13 μm process is presented. In the second part, a frequency-reconfigurable CMOS transformer combiner is introduced that can be reconfigured to have similar efficiencies at widely separated frequency bands. A 65-nm CMOS triple-band (2.5/3/3.5 GHz) PA employing the reconfigurable combiner was designed. In the final part of this work, the use of transformer coupled-resonators in mm-wave LNA designs for 28 GHz bands was investigated. To cover contiguous and/or widely-separated narrowband channels of the emerging 5G standards, a 65-nm CMOS 24.9-32.7 GHz wideband multi-mode LNA using one-port transformer coupled-resonators was designed. Finally, a 25.1-27.6 GHz tunable-narrowband digitally-calibrated merged LNA-vector modulator design employing transformer coupled-resonators is presented that proposes a compact, differential quadrature generation scheme for phased-array architectures.
34
Cha, Jeongwon. "A CMOS radio-frequency front-end for multi-standard wireless communications." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37250.
Full textAbstract:
The explosive growth of wireless communication market has led the development of low-cost, highly-integrated wireless communication systems. Even though most blocks in the front-end have successfully been integrated by using the CMOS technology, it is still a formidable challenge to integrate the entire front-end. Thus, the objective of this research is to demonstrate the feasibility of the integrated front-end by using improved circuit techniques as well as the improved process technologies. This dissertation proposes an improved control scheme to enhance the high-power handling capability of an antenna switch.
As a part of this research, an antenna switch controller for a GaAs antenna switch was first developed to enhance the performances of the GaAs antenna switch by using the boosted control voltage. To enhance the efficiency of the front-end, efficiency improvement techniques for the antenna switch controller has also been studied. With the suggested efficiency improvement techniques, a fully-integrated antenna switch was implemented using the SOI technology, and exceeding performances over many commercial products for watt-level high-power applications have been successfully demonstrated. As an effort to improve the efficiency of a power amplifier, a linear envelope detector was also implemented, and the results show that the envelope detector is suitable for dynamic biasing of the power amplifier. The research presented in this dissertation, thus, provides a low-cost and high-performance solution for highly-integrated RF front-end used in various wireless communication systems.
35
Stein, Björn [Verfasser]. "Contributions to a Yb+ single-ion optical frequency standard / Björn Stein." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover, 2010. http://d-nb.info/1005408955/34.
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RAYMUNDO, ELIZABETH VILCANAUPA. "DEVELOPMENT OF A METROLOGICAL STANDARD LASER FREQUENCY REFERENCE AT 532 NM." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2009. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=15143@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO
Este trabalho faz parte do projeto do desenvolvimento do primeiro padrão de referência metrológica de frequência em torno de 532 nm no Brasil, para a realização prática da definição do metro. A pesquisa foi desenvolvida no Laboratório de Interferometria (Laint) da Divisão de Metrologia Óptica do Inmetro, em convenio com o Programa de Pós-Graduação em Metrologia para Qualidade Industrial da PUC-Rio. No âmbito deste projeto, a realização de uma nova referência em comprimento/freqüência é feita mediante a estabilização de um laser comercial Nd:YAG emitindo uma radiação em torno de 532 nm. A estabilização é realizada numa componente hiperfina de uma transição do iodo molecular (127)I(2), segundo as recomendações do Comitê Internacional de Pesos e Medidas (CIPM- Comité International des Poids et Mesures). O vapor de iodo é contido numa célula externa de absorção resfriada à uma temperatura entre -10 °C e -15 °C. Neste trabalho são apresentadas as seguintes etapas do projeto: Montagem opto-mecânica do sistema e alinhamentos ópticos. Detecção e registro dos sinais de absorção com célula à temperatura ambiente correspondendo às transições do iodo em torno de 532 nm.Caracterização do laser Nd:YAG ou seja determinação da freqüência de emissão laser em função da temperatura TLC do cristal laser, utilizando para este fim um medidor de comprimento de onda (wavemeter). Medições preliminares do sistema de resfriamento e de regulação da temperatura da célula de iodo por meio de um dispositivo termoelétrico Peltier. O controle automático duma temperatura teste de -13°C é realizado via programação LabView.
This work is part of the project for development of the first metrology reference for frequency standard around 532 nm in Brazil for the practical realization of the definition of the meter. The study was conducted at the Laboratory Interferometry (Laint) Inmetro, through an agreement with the Posgraduation Program in Metrology for Quality Industrial, PUC-Rio. In the scope of this project, the realization of a new reference length/frequency is made by the stabilization of a commercial laser Nd:YAG emitting radiation around 532 nm. The stabilization is performed on a component of a hyperfine transition of molecular iodine (127)I(2), according to the recommendations of the International Committee of Weights and Measures (CIPM- Comité International des Poids et Mesures).The iodine vapor is contained in an external absorption cell cooled to a temperature between -10°C and -15°C. This work presents the following stages of the project: Opto-mechanical assembly of the system and optical alignments. Detection and recording of signals with absorption cell at room temperature corresponding to iodine transitions around 532 nm. Characterization of Nd: YAG laser that is determining the frequency of the laser emission as a function of laser crystal temperature TLC, using for this purpose a meter wavelength (wavemeter). Preliminary measurements of the cooling system and temperature regulation of the iodine cell by a Peltier thermoelectric device. The automatic control of a test temperature of -13°C is achieved via LabView programming.
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Kim, Hyung Joon. "Multi-standard radio transceiver architectures and radio frequency front-end design." Connect to this title online, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1110399471.
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Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xv, 128 p.; also includes graphics (some col.). Includes bibliographical references (p. 125-128). Available online via OhioLINK's ETD Center
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SECCO, MARCELLO. "Desenvolvimento de dispositivo movimentador automatizado de amostras com vista à aplicação em medidas de radioisótopos que possuem curto tempo de meia-vida." reponame:Repositório Institucional do IPEN, 2016. http://repositorio.ipen.br:8080/xmlui/handle/123456789/26619.
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Submitted by Marco Antonio Oliveira da Silva (maosilva@ipen.br) on 2016-08-26T12:45:07Z
No. of bitstreams: 0Made available in DSpace on 2016-08-26T12:45:07Z (GMT). No. of bitstreams: 0
Medidas de espectroscopia gama de alta resolução têm diversas aplicações. Aplicações envolvendo medidas de radioisótopos de meia-vida curta podem apresentar problemas de baixa precisão nas contagens quando a fonte radioativa está distante do detector e de perda de acurácia por efeitos de tempo morto e empilhamento de pulsos em situação de altas taxas de contagens. Um modo de minimizar esses problemas é alterando a posição da fonte radioativa durante o processo de medição, aproximando-a do detector conforme sua atividade diminui e assim maximizando o número de contagens medidas. Neste trabalho, foi desenvolvido o Movimentador de Amostras Radioativas Automatizado (MARA), um aparato de baixo custo, feito com materiais de baixo número atômico e leve, projetado e construído para auxiliar nas medidas de espectroscopia gama, capaz de controlar a distância entre a fonte e o detector, permitindo inclusive que ocorra alteração dessa distância durante o processo de medição. Por ser automatizado ele otimiza o tempo do operador, que tem total liberdade para criar suas rotinas de medidas no dispositivo, além de evitar que o mesmo tome uma parcela da dose radioativa. Foi também feita uma interface que permite controle do MARA e a programação do sistema de aquisição de dados. Foram realizados testes para otimização da operação do sistema MARA e foi verificada a segurança de operação do MARA, não apresentando nenhuma falha durante seus testes. Foi aplicado o teste de repetitividade, por meio de medições com uma fonte calibrada de 60Co, e verificou-se que o sistema de movimentação de prateleiras automatizado reproduziu os resultados do sistema estático com confiabilidade de 95%.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
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Chen, Xinhua. "Design of a highly-integrated frequency synthesizer for multi-standard mobile communications /." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17292.
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Girkin, J. M. "Development of a tellurium frequency standard for laser spectroscopy of atomic hydrogen." Thesis, University of Southampton, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382167.
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Johnson, Steven. "Narrow linewidth lasers for use with neutral strontium as a frequency standard." Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/4576/.
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The continual development of precise timing has always pushed technology forward, and the latest generation of clocks uses electronic transitions within cooled atoms as their frequency reference. For atoms where the clock transition is at an optical frequency an ultra stable laser is used to probe the transition; the construction and development of this laser for use with strontium is the subject of this thesis. The system consists of a laser, an optical cavity and the electronics to lock the laser to the optical cavity. The theoretical component of this thesis looked into the possible materials used to make the optical cavity from and how the optical cavity should be supported to minimize the frequency noise of the laser. A compact external cavity diode laser was constructed and shown to have a linewidth of 26 ±15 kHz. To lock and narrow the linewidth of this laser, two ultra stable optical cavity assemblies were constructed with vibration and thermal stabilisation enclosures. To characterise the laser stability a beat measurement was performed between the two stabilised lasers and a beat note linewidth of 1:37 ± 0:28 Hz was measured. The instability of the beat note was measured; an Allan deviation of 2 x10\(^-\)\(^1\)\(^4\) was obtained between averaging times of 0.2 s and 1 s.
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Garkusha, Sergey. "Analysis the Results of Frequency Planning in Mesh Networking Standard IEEE 802.11." Thesis, Modern Problems of Radio Engineering, Telecommunications and Computer Science. Proceedings of the international Conference TCSET’2012, 2012. http://dspace.uccu.org.ua/handle/123456789/870.
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The paper analyzes the influence of stations
territorial separation and technological characteristics of multiradio multichannel mesh networking upon the quality of of the allocation of channels problem solution
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Hill, Ian Robert. "Development of an apparatus for a strontium optical lattice optical frequency standard." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9822.
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Accurate time keeping is critical to the function and advancement of many human endeavours. Atomic clocks based on a microwave transition in atomic Cs have served as primary frequency standards to realise the SI second since their formal adoption in 1967. State-of-the-art, laser cooled, Cs fountains now routinely operate with fractional frequency uncertainties below the 10⁻¹⁵ level in laboratories throughout the world. Over the last decade, efforts to build frequency standards based on optical transitions have come to fruition and potential inaccuracies below the 10⁻¹⁷ level have been demonstrated. Such standards point to the future of time keeping and much development is being pursued to realise the potential of these 'next generation' optical clocks. One such approach, on which this work focusses, relies on a 'magic' wavelength optical lattice trap to provide (almost) Doppler- and recoil-free confinement of atoms during clock interrogation. At this 'magic' wavelength, light induced perturbation of the clock states is equal and so cancels precisely. This thesis describes the design and implementation of an optical lattice frequency standard apparatus based on 88Sr held in a 1D optical lattice. A review of the development of atomic frequency metrology is given from a historical viewpoint and the technology and limitations of current methods discussed. To tackle the blackbody radiation shift, which currently presents the greatest limitation to the Sr lattice clock, imposing at the 10⁻¹⁶ level, a scheme to measure the blackbody radiation shift coefficient at the 10⁻¹⁷ level is developed. Techniques to laser cool and trap atomic strontium are described and the implementation detailed. All laser systems required for clock operation are described including the design and implementation of extended-cavity diode lasers for precision spectroscopy. Details relevant to the eventual operation of the apparatus are discussed.
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Abd, Halim Hasliza. "Restricted Verb Phrase Collocations in Standard and Learner Malaysian English." Thesis, University of Canterbury. Linguistics, 2014. http://hdl.handle.net/10092/10362.
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The English used in Malaysia is one of the varieties of New Englishes and this variety has emerged due to the spread of English around the world (Platt, et al., 1983; Pillai, 2006). In the case of Malaysia, Malay is the national language and standard English exists to be the language of an elite (Bao, 2006), also as a language of interaction. Over years of playing its various roles as a language of interaction, there has emerged a variety of English that is distinctively Malaysian (Asmah, 1992). Baskaran (2002) points out that English is now adopted and adapted in the linguistic ecology of Malaysia, and all Malaysians should be proud of it with all its local ‘nuances and innuendos’. Malaysian English today is ‘a rich tapestry of a typical transplanted variety of English’. Malaysian English (ME) is one of the new varieties of English, with some distinct features include the localized vocabulary, pronunciation, grammar as well as pragmatic features (Pillai, 2006; Pillai and Fauziah, 2006, p.39). The present study has embarked on a specialised study of vocabulary. In particular, it examined the English collocations produced by non-native speaker English users in Malaysia. The study provided insight into the nature of the internal norms of English used in Malaysia to see how these English restricted collocations being used by this group of learners. The investigation focused on the learners’ productive knowledge of Verb-Noun collocations of their written English with the impact of exposure and frequency. Nesselhauf (2003) has the opinion that verb-noun combinations are the most frequently mistaken so they should perceive particular attention of learners.
Investigating collocation in English language learning is paramount as such study may inform us on the use of restricted collocations in English language teaching and learning in Malaysian context. The findings in Chapter 4 and 5 suggest that the frequency of the cloze verb does have an effect as predicted by Kuiper, Columbus and Schmitt (2009). This is so because frequency is a measure of likely exposure. The more frequent an item is in corpora, the more likely a learner is to be exposed to it. What is needed is a much more nuanced notion of exposure. The findings in Chapter 6 proves that the malformed collocations make sense could be a way of making the World English perspective relevant after all. A new testing approach is proposed; semantic plausibility metric, which is used as a tool for this study, can be useful used as a measure of vocabulary acquisition as well as looking at learners’ test taking strategies. The findings of the present research on Malaysian English collocations contribute new knowledge to the existing understanding and literature on the acquisition of collocations.
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Papageorgiou, Nikolaos A. "Development of RF front end prototype compliant with the 802.11a standard for wireless applications." Diss., Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04072004-180131/unrestricted/papageorgiou%5Fnikolaos%5Fa%5F200312%5Fms.pdf.
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Huang, Wenxiang. "A broadband RF CMOS frond-end for multi-standard wireless communication." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1170882877.
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Kao, Chi-Han. "Performance of IEEE 802.11a wireless LAN standard over frequency-selective, slow, ricean fading channels." Thesis, Monterey California. Naval Postgraduate School, 2002. http://hdl.handle.net/10945/5020.
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Approved for public release, distribution is unlimitedWith the rapidly growing demand for more reliable and higher data rate wireless communications, the Institute of the Electrical and Electronics Engineers (IEEE) 802.11 working group approved a standard for 5 GHz band, wireless local area networks (WLAN) in 1999. This standard, IEEE 802.11a, supports data rates from 6 up to 54 Mbps, and uses orthogonal frequency division multiplexing (OFDM) for transmission in indoor wireless environments. This thesis examines the performance of the IEEE 802.11a standard for different combinations of sub-carrier modulation type and code rate and determines the signal-to-noise ratio required to obtain a probability of bit error b P of 10-5. The channel is modeled as a frequency-selective, slow, Ricean fading channel with additive white Gaussian noise (AWGN). Contrary to expectations, for the combinations of sub-carrier modulation type and code rate utilized by the IEEE 802.11a standard, some of the higher data rate combinations outperform some of the lower data rate combinations. On the other hand, the results also show significant coding gain when applying convolutional coding with Viterbi decoding, and hence highlight the importance of forward error correction (FEC) coding to the performance of wireless communications systems.
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Kao, Chi-han. "Performance of IEEE 802.11a wireless LAN standard over frequency-selective, slow, ricean fading channels /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2002. http://library.nps.navy.mil/uhtbin/hyperion-image/02sep%5FKao.pdf.
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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, September 2002.Thesis advisor(s): R. Clark Robertson, Roberto Cristi. Includes bibliographical references (p. 93-94). Also available online.
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Muhammad, Wasim. "CMOS LNA Design for Multi-Standard Applications." Thesis, Linköping University, Department of Electrical Engineering, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-7841.
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This thesis discusses design of narrowband low noise amplifiers for multi¬standard applications. The target of this work is to design a low noise ampli¬fier(LNA) for DCS1800 and Bluetooth standard frequency bands. Various designs for narrowband multi-standard LNAs have been studied and a new design for tunable multi-standard LNA has been presented and designed using accumulation mode MOS varactors.
As this design includes on-chip spiral inductors, the design, modelling and layout of on-chip inductors have been discussed briefly. The tool used for this purpose is ASITIC.
Also ESD protection techniques for RF circuits and their effect on LNA per¬formance has been discussed.
Finally fully differential LNA has been designed in O.35um AMS thick metal CMOS process using Cadence SpectreRF. The design also includes ESD pro¬tection at the input of LNA.
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Sastrawan, Wayan Jarrah Scheeres. "Novel precision control techniques in a trapped Yb+ ion implementation." Thesis, The University of Sydney, 2015. http://hdl.handle.net/2123/13534.
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Precise control of quantum systems is vital to scientific and technological progress, including the realisation of quantum computation and simulation, record-breaking timekeeping and positioning applications. Control of quantum systems is hampered by the effects of random environmental or hardware noise, which leads to unknown deviations from the system's desired evolution. This thesis presents a set of interaction-focussed methods for improving precision control, tailored to the problems of quantum error suppression and stabilisation of oscillators, which share a common basic structure. These methods are based on a theoretical framework called the filter-transfer function formalism, which expresses the convolution of user-applied control and random noise in the language of spectral filtering. This powerful and accessible approach is experimentally verified in this thesis, and is used to formulate novel control techniques and improve on existing ones. This thesis experimentally demonstrates the effectiveness of novel composite pulse schemes for suppressing error in quantum bits. Furthermore, the thesis derives and demonstrates a novel predictive technique for stabilising oscillators by means of combining multiple frequency measurements against a quantum reference. The thesis therefore advances the theoretical understanding of a frequency-domain formalism for noise-affected quantum systems, on which basis it presents and demonstrates novel and improved techniques for mitigating the effects of such noise on the user's precision control over the system.