Dissertations / Theses on the topic 'Frequency estimator'
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Palmer, Joseph. "A HIGH-ACCURACY AND LOW-COMPLEXITY CARRIER-OFFSET-FREQUENCY ESTIMATOR." International Foundation for Telemetering, 2007. http://hdl.handle.net/10150/604513.
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ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, NevadaA single-tone frequency estimator for a non-uniformly sampled sinusoid is proposed. A nonuniformly sampled sinusoid may be generated from the received training sequences of a telemetry link. The frequency of the sinusoid matches the carrier-frequency-offset (CFO) of the received signal, and estimation of this quantity allows a receiver to compensate for the CFO. The performance bounds of this type of estimator have been investigated in the literature, though little work has been published on practical algorithms. The estimator proposed in this paper is a generalization of phase-increment estimators previously described in the literature. It exhibits a low computational complexity yet converges to theoretical bounds at high SNR. The paper argues that a periodic training sequence structure, combined with the new estimator, allows for a high-accuracy and lowcomplexity CFO compensator.
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Feldman, Jonathan Michael S. M. Massachusetts Institute of Technology. "The Augmented Geometrically Spaced Transform : applications of the single channel frequency estimator." Thesis, Massachusetts Institute of Technology, 2021. https://hdl.handle.net/1721.1/131006.
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Thesis: S.M., Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, February, 2021Cataloged from the official PDF version of thesis.
Includes bibliographical references (pages 99-103).
The Augmented Geometrically Spaced Transform (AGST) is an auditory model that is based on an inversion of the acoustic piano, where the piano produces music and the transform analyses it. In contrast with the standard spectrogram, which is a complex frequency vector versus time, the AGST is based around a matrix of frequencies, known as the AGST Frequency Matrix, where for every frequency in the matrix, a spectral envelope is computed using a Single Channel Frequency Estimator (SCFE). The core invention of the thesis is the algorithm for the SCFE, which computes spectral envelopes with maximally high definition in a computationally efficient manner. A bank of SCFEs is assembled into a constant Q transform, known as a Geometrically Spaced Transform (GST). The GST can be used to visualize harmonics inside of musical notes, or audio in general, in a constant Q fashion. It is then shown that the AGST is a good front-end model for computational pitch perception. For example, it can be used to solve an important problem in auditory perception, the case of the missing fundamental. The entire thesis is framed in the context of building artificially intelligent music systems, including synthetic listeners (machines that listen in the way that people do), and synthetic performers (machines that allow for interactive music performance).
by Jonathan Michael Feldman.
S.M.
S.M. Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences
3
Kitchen, John. "The effect of quadrature hybrid errors on a phase difference frequency estimator and methods for correction /." Title page, contents and summary only, 1991. http://web4.library.adelaide.edu.au/theses/09AS/09ask62.pdf.
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Cobb, Richard E. "Confidence bands, measurement noise, and multiple input - multiple output measurements using three-channel frequency response function estimator." Diss., Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/53675.
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A three-channel Frequency Response Function (FRF) estimator is discussed and statistical relations developed. Methods for estimating the variance of the FRF magnitude and levels of uncorrelated content in the test signals are developed. FRF magnitude variance estimates allow ’confidence bands’ to be placed on FRF magnitude estimates, giving an indication of the variability of the result. Uncorrelated content estimates indicate sources and magnitudes of noise in the measurement system. Both Monte Carlo simulations and experimental work are used to verify the statistical and uncorrelated content estimates. Relations to extend the three-channel FRF estimator to multiple input-multiple output measurements are developed and verified through simulations.Ph. D.
5
Bibinger, Markus. "Estimating the quadratic covariation from asynchronous noisy high-frequency observations." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, 2011. http://dx.doi.org/10.18452/16365.
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Ein nichtparametrisches Schätzverfahren für die quadratische Kovariation von hochfrequent nicht-synchron beobachteter Itô-Prozessen mit einem additiven Rauschen wird entwickelt. Für eine artverwandte Folge von statistischen Experimenten wird die lokal asymptotische Normalität (LAN) im Sinne von Le Cam bewiesen. Mit dieser lassen sich optimale Konvergenzraten und Effizienzschranken für asymptotische Varianzen ableiten. Der vorgestellte Schätzer wird auf Grundlage von zwei modernen Verfahren, für die Anwendung bei nicht-synchronen Beobachtungen zum einen, und einem additiven Rauschen zum anderen, entwickelt. Der Hayashi-Yoshida Schätzer wird in einer neuen Darstellung eingeführt, welche einen Synchronisierungsalgorithmus mit einschließt, der für die kombinierte Methode ausgelegt werden kann. Es wird eine stabiles zentrales Grenzwerttheorem bewiesen, wobei spezieller Wert auf die Analyse des Einflusses der Nicht-Synchronität auf die asymptotische Varianz gelegt wird. Nach diesen Vorbereitungen wird das kombinierte Schätzverfahren für den allgemeinsten Fall nicht-synchroner verrauschter Beobachtungen vorgestellt. Dieses beruht auf Subsampling- und Multiskalenmethoden, die auf Mykland, Zhang und Aït-Sahalia zurück gehen. Es vereint positive Eigenschaften der beiden Ursprünge. Das zentrale Resultat dieser Arbeit ist der Beweis, dass der Schätzfehler stabil in Verteilung gegen eine gemischte Normalverteilung konvergiert. Für die asymptotische Varianz wird ein konsistenter Schätzer angegeben. In einer Anwendungsstudie wird eine praktische Implementierung des Schätzverfahrens, die die Wahl von abhängigen Parametern beinhaltet, getestet und auf ihre Eigenschaften im Falle endlicher Stichprobenumfänge untersucht. Neuen fortgeschrittenen Entwicklungen auf dem Forschungsfeld von Seite anderer Autoren wird Rechnung getragen durch Vergleiche und diesbezügliche Kommentare.A nonparametric estimation approach for the quadratic covariation of Itô processes from high-frequency observations with an additive noise is developed. It is proved that a closely related sequence of statistical experiments is locally asymptotically normal (LAN) in the Le Cam sense. By virtue of this property optimal convergence rates and efficiency bounds for asymptotic variances of estimators can be concluded. The proposed nonparametric estimator is founded on a combination of two modern estimation methods devoted to an additive observation noise on the one hand and asynchronous observation schemes on the other hand. We reinvent this Hayashi-Yoshida estimator in a new illustration that can serve as a synchronization method which is possible to adapt for the combined approach. A stable central limit theorem is proved focusing especially on the impact of non-synchronicity on the asymptotic variance. With this preparations on hand, the generalized multiscale estimator for the noisy and asynchronous setting arises. This convenient method for the general model is based on subsampling and multiscale estimation techniques that have been established by Mykland, Zhang and Aït-Sahalia. It preserves valuable features of the synchronization methodology and the estimators to cope with noise perturbation. The central result of the thesis is that the estimation error of the generalized multiscale estimator converges with optimal rate stably in law to a centred mixed normal limiting distribution on fairly general regularity assumptions. For the asymptotic variance a consistent estimator based on time transformed histograms is given making the central limit theorem feasible. In an application study a practicable estimation algorithm including a choice of tuning parameters is tested for its features and finite sample size behaviour. We take account of recent advances on the research field by other authors in comparisons and notes.
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Park, Sujin. "Consistent estimator of ex-post covariation of discretely observed diffusion processes and its application to high frequency financial time series." Thesis, London School of Economics and Political Science (University of London), 2011. http://etheses.lse.ac.uk/182/.
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First chapter of my thesis reviews recent developments in the theory and practice of volatility measurement. We review the basic theoretical framework and describe the main approaches to volatility measurement in continuous time. In this literature the central parameter of interest is the integrated variance and its multivariate counterpart. We describe the measurement of these parameters under ideal circumstances and when the data are subject to measurement error, microstructure issues. We also describe some common applications of this literature. In the second chapter, we propose a new estimator of multivariate ex-post volatility that is robust to microstructure noise and asynchronous data timing. The method is based on Fourier domain techniques. The advantage of this method is that it does not require an explicit time alignment, unlike existing methods in the literature. We derive the large sample properties of our estimator under general assumptions allowing for the number of sample points for different assets to be of different order of magnitude. We show in extensive simulations that our method outperforms the time domain estimator especially when two assets are traded very asynchronously and with different liquidity. In the third chapter, we propose to model high frequency price series by a timedeformed L´evy process. The deformation function is modeled by a piecewise linear function of a physical time with a slope depending on the marks associated with intra-day transaction data. The performance of a quasi-MLE and an estimator based on a permutation-like statistic is examined in extensive simulations. We also consider estimating the deformation function nonparametrically by pulling together many time series. We show that financial returns spaced by equal elapse of estimated deformed time are homogenous. We propose an order execution strategy using the fitted deformation time
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Tjahyadi, Hendra, and hendramega@yahoo com. "Adaptive Multi Mode Vibration Control of Dynamically Loaded Flexible Structures." Flinders University. Engineering, 2006. http://catalogue.flinders.edu.au./local/adt/public/adt-SFU20070130.192707.
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In this thesis, three control methodologies are proposed for suppressing multi-mode vibration in flexible structures. Controllers developed using these methods are designed to (i) be able to cope with large and sudden changes in the system's parameters, (ii) be robust to unmodelled dynamics, and (iii) have a fast transient response. In addition, the controllers are designed to employ a minimum number of sensor-actuator pairs, and yet pose a minimum computational demand so as to allow real-time implementation.
A cantilever beam with magnetically clamped loads is designed and constructed as the research vehicle for evaluation of the proposed controllers. Using this set-up, sudden and large dynamic variations of the beam loading can be tested, and the corresponding changes in the plant's parameters can be observed. Modal testing reveals that the first three modes of the plant are the most significant and need to be suppressed. It is also identified that the first and third modes are spaced more than a decade apart in frequency. The latter characteristic increases the difficulty of effectively controlling all three modes simultaneously using one controller. To overcome this problem, the resonant control method is chosen as the basis for the control methodologies discussed in this thesis.
The key advantage of resonant control is that it can be tuned to provide specific attenuation only at and immediately close to the resonant frequency of concern. Consequently, it does not cause control spillover to other modes owing to unmodeled dynamics. Because of these properties, a resonant controller can be configured to form a parallel structure with the objective of targeting and cancelling multiple modes individually. This is possible regardless of the mode spacing. In addition, resonant control requires only a minimum number of collocated sensor-actuator pairs for multi-mode vibration cancellation. All these characteristics make resonant control a suitable candidate for multi-mode vibration cancellation of flexible structures.
Since a resonant controller provides negligible attenuation away from the natural frequencies that it has been specifically designed for, it is very sensitive to changes of a system's natural frequencies and becomes ineffective when these mode frequencies change. Hence, for the case of a dynamically loaded structure with consequent variations in mode frequencies, the resonant control method must be modified to allow tracking of system parameter changes. This consideration forms the theme of this thesis, which is to allow adaptive multi-mode vibration control of dynamically-loaded flexible structures. Three controller design methodologies based on the resonant control principle are consequently proposed and evaluated.
In the first approach, all possible loading conditions are assumed to be a priori known. Based on this assumption, a multi-model multi-mode resonant control (M4RC) method is proposed. The basis of the M4RC approach is that it comprises a bank of known loading models that are designed such that each model gives optimum attenuation for a particular loading condition. Conceptually, each model is implemented as a set of fixed-parameter controllers, one for each mode of concern. In reality, each mode controller is implemented as an adjustable resonant controller that is loaded with the fixed-model parameters of the corresponding mode. The M4RC method takes advantage of the highly frequency-sensitive nature of resonant control to allow simple and rapid selection of the optimum controller. Identification of the set of resonant frequencies is implemented using a bank of band-pass filters that correspond to the mode frequencies of the known models. At each time interval a supervisor scheme determines for each mode which model has the closest frequency to the observed vibration frequency and switches the corresponding model controller output to attenuate the mode. Selection is handled on a mode-by-mode basis, such that for each mode the closest model is selected. The proposed M4RC is relatively simple and less computationally complex compared to other multi-model methods reported in the literature. In particular, the M4RC uses a simple supervisor scheme and requires only a single controller per mode. Other multi-model methods use more complex supervision schemes and require one controller per model. The M4RC method is evaluated through both simulation and experimental studies. The results reveal that the proposed M4RC is very effective for controlling multi-mode vibration of a flexible structure with known loading conditions, but is ineffective for unmodeled loading conditions.
In the second approach, the assumption that all loading conditions are a priori known is relaxed. An adaptive multi-mode resonant control (ARC) method is proposed to control the flexible structure for all possible (including unknown) loading conditions. On-line estimation of the structure's natural frequencies is used to update the adaptive resonant controller's parameters. The estimation of the natural frequencies is achieved using a parallel set of second-order recursive least-squares estimators, each of which is designed for a specific mode of concern. To optimise the estimation accuracy for each mode frequency, a different sampling rate suitable for that mode is used for the corresponding estimator. Simulation and experiment results show that the proposed adaptive method can achieve better performance, as measured by attenuation level, over its fixed-parameter counterpart for a range of unmodeled dynamics. The results also reveal that, for the same sequences of known loading changes, the transient responses of the ARC are slower than those of the M4RC.
In the third approach, a hybrid multi-model and adaptive resonant control is utilized to improve the transient response of the ARC. The proposed multi-model multi-mode adaptive resonant control (M4ARC) method is designed as a combination of the M4RC and ARC methods. The basis of the proposed method is to use the M4RC fixed-parameter model scheme to deal with transient conditions while the ARC adaptive parameter estimator is still in a state of fluctuation. Then, once the estimator has reached the vicinity of its steady-state, the adaptive model is switched in place of the fixed model to achieve optimum control of the unforeseen loading condition. Whenever a loading change is experienced, the simple M4RC supervisor scheme is used to identify the closest model and to load the adjustable resonant controllers with the fixed parameters for that model. Meanwhile, the mode estimators developed for the ARC method are used to identify the exact plant parameters for the modes of concern. As soon as these parameters stop rapidly evolving and reach their steady-state, they are loaded into the respective adjustable controllers. The same process is repeated whenever a loading change occurs. Given the simplicity of the M4ARC method and its minimal computation demand, it is easily applicable for real-time implementation. Simulation and experiment results show that the proposed M4ARC outperforms both the ARC with respect to transient performance, and the M4RC with respect to unmodeled loading conditions.
The outcomes of this thesis provide a basis for further development of the theory and application of active control for flexible structures with unforeseen configuration variations. Moreover, the basis for the proposed multi-model adaptive control can be used in other areas of control (not limited to vibration cancellation) where fast dynamic reconfiguration of the controller is necessary to accommodate structural changes and fluctuating external disturbances.
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Gyongy, Istvan. "Phase/amplitude estimation for tuning and monitoring." Thesis, University of Oxford, 2008. http://ora.ox.ac.uk/objects/uuid:f398b986-e8a0-403a-9118-5edae6403e00.
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The benefits of good loop tuning in the process industries have long been recognized. Ensuring that controllers are kept well-configured despite changes in process dynamics can bring energy and material savings, improved product quality as well as reduced downtime. A number of loop tuning packages therefore exist that can, on demand, check the state of a loop and adjust the controller as necessary. These methods generally apply some form of upset to the process to identify the current plant dynamics, against which the controller can then be evaluated. A simple approach to the automatic tuning of PI controllers injects variable frequency sinewaves into the loop under normal plant operation. The method employs a phase-locked loop-based device called a phase-frequency/estimation and uses 'design-point' rules, where the aim is for the Nyquist locus of the loop to pass through a particular point on the complex plane. A number of advantages are offered by the scheme: it can carry out both 'one shot' tuning and continuous adaptation, the latter even with the test signal set to a lower amplitude than that of noise. A published article is included here that extends the approach to PID controllers, with simulations studies and real-life test showing the method to work consistently well for a for a wide range of typical process dynamics, the closed-loop having a response that compares well with that produced by standard tuning rules. The associated signal processing tools are tested by applying them to the transmitter of a Coriolis mass-flow meter. Schemes are devised for the tracking and control of the second mode of measurementtube oscillation alongside the so-called 'driven mode', at which the tubes are usually vibrated, leading to useful information being made available for measurement correction purposes. Once a loop has been tuned, it is important to assess it periodically and to detect any performance losses resulting from events such as changes in process or disturbance dynamics and equipment malfunction such as faulty sensors and actuators. Motivated by the effective behaviour of the controller tuners, a loop monitor developed here, also using probing sinewaves coupled with 'design-point' ideas. In this application, the effect on the process must be minimal, so the device must work with lower still SNRs. Thus it is practical to use a fixed-frequency probing signal, together with a different tool set for tracking it. An extensive mathematical framework is developed describing the statistical properties of the signal parameter estimates, and those of the indices derived from these estimates indicating the state of the loop. The result is specific practical guidelines for the application of the monitor (e.g. for the choices of test signal amplitude and test duration). Loop monitoring itself has traditionally been carried out by passive methods that calculate various performance indicators from routine operating data. Playing a central role amongst these metrics is the Harris Index (HI) and its variants, which compare the output variance to a 'minimum achievable' figure. A key advantage of the active monitor proposed here is that it is able not only to detect suboptimal control but also to suggest how the controller should be adjusted. Moreover, the monitor’s index provides a strong indication of changes in damping factor. Through simple adjustments to the algorithm (by raising the amplitude of the test signal or adding high frequency dither to the control signal), the method can be applied even in the presence of actuator non-linearity, allowing it to identify the cause of performance losses. This is confirmed by real-life trials on a non-linear flow rig.
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Curuk, Selva Muratoglu. "Highly Efficient New Methods Of Channel Estimation For Ofdm Systems." Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/2/12609290/index.pdf.
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In the first part, the topic of average channel capacity for Orthogonal Frequency Division Multiplexing (OFDM) under Rayleigh, Rician, Nakagami-m, Hoyt, Weibull and Lognormal fading is addressed. With the assumption that channel state information is known, we deal with a lower bound for the capacity and find closed computable forms for Rician fading without diversity and with Maximum Ratio Combining diversity at the receiver. Approximate expressions are also provided for the capacity lower bound in the case of high Signal to Noise Ratio.
This thesis presents two simplified Maximum A Posteriori (MAP) channel estimators to be used in OFDM systems under frequency selective slowly varying Rayleigh fading. Both estimators use parametric models, where the first model assumes exponential frequency domain correlation while the second model is based on the assumption of exponential power delay profile. Expressions for the mean square error of estimations are derived and the relation between the correlation of subchannel taps and error variance is investigated. Dependencies of the proposed estimators&rsquoperformances on the model parameter and noise variance estimation errors are analyzed. We also provide approximations on the estimators&rsquo
algorithms in order to make the estimators practical. Finally, we investigate SER performance of the simplified MAP estimator based on exponential power delay profile assumption used for OFDM systems with QPSK modulation. The results indicate that the proposed estimator performance is always better than that of the ML estimator, and as the subchannel correlation increases the performance comes closer to that of perfectly estimated channel case.
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Silva, Tiago Vieira da. "Algoritmos evolutivos como estimadores de frequência e fase de sinais elétricos: métodos multiobjetivos e paralelização em FPGAs." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/55/55134/tde-14012014-105606/.
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Este trabalho propõe o desenvolvimento de Algoritmos Evolutivos (AEs) para estimação dos parâmetros que modelam sinais elétricos (frequência, fase e amplitude) em tempo-real. A abordagem proposta deve ser robusta a ruídos e harmônicos em sinais distorcidos, por exemplo devido à presença de faltas na rede elétrica. AEs mostram vantagens para lidar com tais tipos de sinais. Por outro lado, esses algoritmos quando implementados em software não possibilitam respostas em tempo-real para uso da estimação como relé de frequência ou Unidade de Medição Fasorial. O desenvolvimento em FPGA apresentado nesse trabalho torna possível paralelizar o cálculo da estimação em hardware, viabilizando AEs para análise de sinal elétrico em tempo real. Além disso, mostra-se que AEs multiobjetivos podem extrair informações não evidentes das três fases do sistema e estimar os parâmetros adequadamente mesmo em casos em que as estimativas por fase divirjam entre si. Em outras palavras, as duas principais contribuições computacionais são: a paralelização do AE em hardware por meio de seu desenvolvimento em um circuito de FPGA otimizado a nível de operações lógicas básicas e a modelagem multiobjetiva do problema possibilitando análises dos sinais de cada fase, tanto independentemente quanto de forma agregada. Resultados experimentais mostram superioridade do método proposto em relação ao estimador baseado em transformada de Fourier para determinação de frequência e faseThis work proposes the development of Evolutionary Algorithms (EAs) for the estimation of the basic parameters from electrical signals (frequency, phase and amplitude) in real time. The proposed approach must be robust to noise and harmonics in signals distorted, for example, due to the presence of faults in the electrical network. EAs show advantages for dealing with these types of signals. On the other hand, these algorithms when implemented in software cant produce real-time responses in order to use their estimations as frequency relay or Phasor Measurement Unit. The approach developed on FPGA proposed in this work parallelizes in hardware the process of estimation, enabling analyses of electrical signals in real time. Furthermore, it is shown that multi-objective EAs can extract non-evident information from the three phases of the system and properly estimate parameters even when the phase estimates diverge from each other. This research proposes: the parallelization of an EA in hardware through its design on FPGA circuit optimized at level of basic logic operations and the modeling of the problem enabling multi-objective analyses of the signals from each phase in both independent and aggregate ways. Experimental results show the superiority of the proposed method compared to an estimator based on Fourier transform for determining frequency and phase
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Koski, Antti E. "Rapid frequency estimation." Worcester, Mass. : Worcester Polytechnic Institute, 2006. http://www.wpi.edu/Pubs/ETD/Available/etd-032806-165036/.
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Thesis (M.S.)--Worcester Polytechnic Institute.Keywords: DSS; ECM; SVD; Singular Value Decomposition; rapid frequency estimation; frequency estimation. Includes bibliographical references (leaves 174-177).
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Xu, Wen. "Méthodes d’analyse et de modélisation pertinentes pour la propagation des ondes à l’échelle méso dans des milieux hétérogènes." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLC044/document.
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Les travaux de la présente thèse portent sur l’estimation d'erreur a posteriori pour les solutions numériques par éléments finis de l'équation des ondes élastiques dans les milieux hétérogènes. Deux types d’estimation ont été développés. Le premier considère directement l’équation élastodynamique et conduit à un nouvel estimateur d'erreur a posteriori explicite en norme L∞ en temps. Les principales caractéristiques de cet estimateur explicite sont l'utilisation de la méthode de résidus et le développement de reconstructions en temps et en espace selon les différentes régularités exigées par les différents termes contribuant à l’obtention d’une borne supérieure. L’analyse numérique de cet estimateur dans le cas des maillages uniformes montre qu’il assure bien une borne supérieure mais avec une propriété asymptotique qui reste à améliorer. Le deuxième type d’estimateur d’erreur est développé dans le contexte de la propagation des ondes à haute fréquence dans des milieux hétérogènes à l’échelle mésoscopique. Il s’agit d’une nouvelle erreur en résidus basée sur l'équation de transfert radiatif, qui est obtenue par un développement asymptotique multi-échelle de l'équation d'onde en utilisant la transformation de Wigner en espace-temps. Les résidus sont exprimés en termes de densités énergétiques calculés dans l’espace des phases pour les solutions d’onde numériques transitoires par éléments finis. L’analyse numérique de cette erreur appliquée aux milieux homogènes et hétérogènes en 1D a permis de valider notre approche. Les champs d’application visés sont la propagation des ondes sismiques dans les milieux géophysiques ou la propagation des ondes ultrasonores dans les milieux polycristallinsThis thesis work deals with a posteriori error estimates for finite element solutions of the elastic wave equation in heterogeneous media. Two different a posteriori estimation approaches are developed. The first one, in a classical way, considers directly the elastodynamic equation and results in a new explicit error estimator in a non-natural L∞ norm in time. Its key features are the use of the residual method and the development of space and time reconstructions with respect to regularities required by different residual operators contributing to the proposed error bound. Numerical applications of the error bound with different mesh sizes show that it gives rise to a fully computable upper bound. However, its effectivity index and its asymptotic accuracy remain to be improved. The second error estimator is derived for high frequency wave propagation problem in heterogeneous media in the weak coupling regime. It is a new residual-type error based on the radiative transfer equation, which is derived by a multi-scale asymptotic expansion of the wave equation in terms of the spatio-temporal Wigner transforms of wave fields. The residual errors are in terms of angularly resolved energy quantities of numerical solutions of waves by finite element method. Numerical calculations of the defined errors in 1D homogeneous and heterogeneous media allow validating the proposed error estimation approach. The application field of this work is the numerical modelling of the seismic wave propagation in geophysical media or the ultrasonic wave propagation in polycrystalline materials
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Mai, Cuong. "Frequency Estimation Using Time-Frequency Based Methods." ScholarWorks@UNO, 2007. http://scholarworks.uno.edu/td/571.
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Any periodic signal can be decomposed into a sum of oscillating functions. Traditionally, cosine and sine segments have been used to represent a single period of the periodic signal (Fourier Series). In more general cases, each of these functions can be represented by a set of spectral parameters such as its amplitude, frequency, phase, and the variability of its instantaneous spectral components. The accuracy of these parameters depends on several processing variables such as resolution, noise level, and bias of the algorithm used. This thesis presents some background of existing frequency estimation techniques and proposes a new technique for estimating the instantaneous frequency of signals using short sinusoid-like basis functions. Furthermore, it also shows that the proposed algorithm can be implemented in a popular embedded DSPmicroprocessor for practical use. This algorithm can also be implemented using more complex features on more resourceful processing processors in order to improve estimation accuracy
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Gendron, Paul John. "A comparison of digital beacon receiver frequency estimators." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-09292009-020307/.
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Challakere, Nagaravind. "Carrier Frequency Offset Estimation for Orthogonal Frequency Division Multiplexing." DigitalCommons@USU, 2012. https://digitalcommons.usu.edu/etd/1423.
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This thesis presents a novel method to solve the problem of estimating the carrier frequency set in an Orthogonal Frequency Division Multiplexing (OFDM) system. The approach is based on the minimization of the probability of symbol error. Hence, this approach is called the Minimum Symbol Error Rate (MSER) approach. An existing approach based on Maximum Likelihood (ML) is chosen to benchmark the performance of the MSER-based algorithm. The MSER approach is computationally intensive. The thesis evaluates the approximations that can be made to the MSER-based objective function to make the computation tractable. A modified gradient function based on the MSER objective is developed which provides better performance characteristics than the ML-based estimator. The estimates produced by the MSER approach exhibit lower Mean Squared Error compared to the ML benchmark. The performance of MSER-based estimator is simulated with Quaternary Phase Shift Keying (QPSK) symbols, but the algorithm presented is applicable to all complex symbol constellations.
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Shatnawi, Heba Awad Addad. "Frequency estimation using subspace methods." Thesis, Wichita State University, 2009. http://hdl.handle.net/10057/2419.
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Complex frequency estimation problem plays a significant role in many engineering
applications. The estimation process was traditionally achieved by the Eigenvalue
Decomposition (EVD) of the spatial correlation matrix of observations. Frequency estimation
has fundamental significant and wide relevance for many reasons. First, any arbitrary signal may
be modeled as a sum of frequencies. Hence, any signal estimation problem may be expressed in
terms of frequency estimation problems. Second, many parameter estimation applications may
be mathematically expressed as a frequency estimation problem.
In this thesis an improved frequency estimation technique is presented based on the
unitary transformation, which was basically applied in the direction of arrival problem. The key
idea of the proposed technique is to convert the complex valued autocorrelation, cumulant, or the
direct data matrix in Hankel like shape into a real valued data matrix with the same dimension.
The resultant real valued matrix will be used to extract the noise and/or the signal subspace
instead of the original complex one. It is well known that real manipulations are easier and faster
than the complex ones.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Electrical and Computer Engineering
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Osesina, Olukayode Isaac, Yafan Zhang, and Shirisha Pagoti. "OFDM Carrier Frequency Offset Estimation." Thesis, Karlstad University, Division for Information Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-343.
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This thesis discusses and investigates the estimation of carrier offset frequency in
orthogonal frequency division multiplexing (OFDM) mobile systems. The investigation
starts by using Mobile WiMAX wireless communication specifications described
in IEEE 802.16e as the primary system setup. Under this setup orthogonal
frequency division multiple access (OFDMA) is used as a physical layer scheme; it
also involves the use of pilots in the OFDM symbol for channel estimation.
Although OFDM is resistant to multipath fading, it requires a high degree of synchronisation
to maintain sub-carrier orthogonality. Therefore the level of performance
of the system depends first on the accuracy in estimating the carrier frequency
offset and then the estimation of the channel. Maximum likelihood estimator
is used for estimating carrier frequency offset; its performance under different conditions
for example SNR, number of virtual carriers needed for estimation etc. are
simulated and compared with theoretical results. The optimality of IEEE 802.16e
specifications was also examined during the simulations and results analysis.
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Johansson, Hampus, and Nicklas Höglund. "Weight Estimation through Frequency Analysis." Thesis, Linköping University, Linköping University, Linköping University, Linköping University, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-19166.
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The weight of a heavy duty vehicle plays an important role when dealing with different control systems. Examples of control units in a truck that need this parameter are the ones used to control the brakes, the engine and the gearbox. An accurate estimation of the weight leads not only to a more fuel efficient and safer transport, but also assures the driver that current law limits are not exceeded. The weight can be estimated with pretty good accuracy if the truck is equipped with air suspension. In trucks that lack this type of suspension other methods are used to estimate the weight. At present these methods are inaccurate. In this thesis a new method where the weight is to be estimated through frequency analysis of the truck's driveline is developed and evaluated.
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Andersson, Tomas. "Selected topics in frequency estimation." Licentiate thesis, KTH, Signals, Sensors and Systems, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1586.
Full textAbstract:
Frequency estimation has been studied for a number of years.One reason for this is that the problem is easy to understand,but difficult to solve. Another reason, for sure, is the largenumber of applications that involves frequency estimation, e.gradar applications using frequency modulated continuous wave(FMCW) techniques where the distance to the target is embeddedin the frequency, resonance sensor system where the outputsignal is given as the frequency displacement from a nominalfrequency, in radio frequency identification systems (RFID)where frequency modulation is used in the communication link,etc. The requirement on the frequency estimator varies with theapplication but typical issues are: accuracy, processing speedor complexity, and ability to handle multiple signals. Many ofthe problems have been solved but there still exist severalopen questions.
The first part of this thesis addresses the problem offrequency estimation using low complexity algorithms. One wayof achieving such an algorithm is to use 1-bit quantizedsamples of the input signal. Frequency estimation using look-uptables has been studied and the properties of such an estimatorare presented. By analyzing the look-up tables using theHadamard transform a novel type of low-complexity frequencyestimators is proposed. They use operations such as binarymultiplication and addition of precalculated constants. Thisfact makes it suitable in applications where low complexity isa major issue. A hardware demonstrator using the table look-uptechnique has been build and a short description of it isincluded in the thesis.
Today, the interest of using digital signal processinginstead of analog processing is almost absolute. Accordingly,analog-to-digital converters (ADC) are used in order todigitalize the analog input before digital processing is takenplace. The ADC performance is measured according to the IEEEStandard 1241. The waveform fitting method included in thestandard has been studied in some detail. A criterion for modelselection has been derived using the parsimony principle.Further, an algorithm has been derived for estimation of theparameters of multiple sinusoids using the standardizedwave-fitting method, in combination with the expectationmaximization (EM) algorithm. The performance of the algorithmhas been studied and it is shown to produce statisticallyefficient estimates.
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Dickerson, Jeffrey Crawford. "Frequency domain secondary pulse estimation." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/36983.
Full textAbstract:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.Includes bibliographical references (leaves 44-45).
by Jeffrey Crawford Dickerson.
M.Eng.
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Lindfors, Martin. "Frequency Tracking for Speed Estimation." Licentiate thesis, Linköpings universitet, Reglerteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-149804.
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Estimating the frequency of a periodic signal, or tracking the time-varying frequency of an almost periodic signal, is an important problem that is well studied in literature. This thesis focuses on two subproblems where contributions can be made to the existing theory: frequency tracking methods and measurements containing outliers. Maximum-likelihood-based frequency estimation methods are studied, focusing on methods which can handle outliers in the measurements. Katkovnik’s frequency estimation method is generalized to real and harmonic signals, and a new method based on expectation-maximization is proposed. The methods are compared in a simulation study in which the measurements contain outliers. The proposed methods are compared with the standard periodogram method. Recursive Bayesian methods for frequency tracking are studied, focusing on the Rao-Blackwellized point mass filter (RBPMF). Two reformulations of the RBPMF aiming to reduce computational costs are proposed. Furthermore, the technique of variational approximate Rao-Blackwellization is proposed, which allows usage of a Student’s t distributed measurement noise model. This enables recursive frequency tracking methods to handle outliers using heavy-tailed noise models in Rao-Blackwellized filters such as the RBPMF. A simulation study illustrates the performance of the methods when outliers occur in the measurement noise. The framework above is applied to and studied in detail in two applications. The first application is on frequency tracking of engine sound. Microphone measurements are used to track the frequency of Doppler-shifted variants of the engine sound of a vehicle moving through an area. These estimates can be used to compute the speed of the vehicle. Periodogram-based methods and the RBPMF are evaluated on simulated and experimental data. The results indicate that the RBPMF has lower rmse than periodogram-based methods when tracking fast changes in the frequency. The second application relates to frequency tracking of wheel vibrations, where a car has been equipped with an accelerometer. The accelerometer measurements are used to track the frequency of the wheel axle vibrations, which relates to the wheel rotational speed. The velocity of the vehicle can then be estimated without any other sensors and without requiring integration of the accelerometer measurements. In situations with high signal-to-noise ratio (SNR), the methods perform well. To remedy situations when the methods perform poorly, an accelerometer input is introduced to the formulation. This input is used to predict changes in the frequency for short time intervals.Periodiska signaler förekommer ofta i praktiken. I många tillämpningar är det intressant att försöka skatta frekvensen av dessa periodiska signaler, eller vibrationer, genom mätningar av dem. Detta kallas för frekvensskattning eller frekvensföljning beroende på om frekvensen är konstant eller varierar över tid. Två tillämpningar studeras i denna licentiatavhandling. Målet i båda tillämpningarna är att skatta hastigheten på fordon. Den första tillämpningen handlar om att följa frekvensen av ett fordons motorljud, när fordonet kör genom ett område där mikrofoner har blivit utplacerade. Man kan skatta ett fordons hastighet från motorljudet, vars frekvens beror på Dopplereffekten. Denna avhandling undersöker förbättrad följning av denna frekvens, vilket förbättrar skattningen av hastigheten. Två olika sätt för frekvensföljning används. Ett sätt är att anta att frekvensen är konstant inom korta tidsintervall och räkna ut en skattning av frekvensen. Ett annat sätt är att använda en matematisk modell som tar hänsyn till att frekvensen varierar över tid, och försöka följa den. För detta syfte föreslås det Rao-Blackwelliserade punktmassefiltret. Det är en metod som utnyttjar strukturen i den matematiska modellen av problemet för att erhålla bra prestanda och lägre krav på beräkningskraft. Resultaten visar att den föreslagna metoden förbättrar träffsäkerheten på frekvensföljningen i vissa fall, vilket kan förbättra prestanda för hastighetsskattningen. Den andra tillämpningen handlar om att skatta ett fordons hastighet med enbart en accelerometer (mätare av acceleration) fastsatt i chassit. Hjulvibrationer kan mätas av denna accelerometer. Frekvenserna av dessa vibrationer ges av hjulaxelns rotationshastighet. Om hjulradien är känd eller skattad så kan man räkna ut fordonets hastighet, så att man inte behöver använda externa mätningar som gps eller hjulhastighetsmätningar. Accelerationsmätningarna är brusiga och innehåller outliers, vilka är mätvärden som ibland slumpmässigt kraftigt skiljer sig från det förväntade. Därför studeras metoder som är konstruerade för att hantera dessa. Det föreslås en approximation till Rao-Blackwellisering för att kunna hantera dessa outliers. Det föreslås också en ny frekvensskattningsmetod baserad på expectation-maximization, vilket är ytterligare en metod som utnyttjar strukturer i matematiska modeller. En simuleringsstudie visar att metoderna har lägre genomsnittligt skattningsfel än standardmetoder. På insamlad experimentell data visas att metoderna ofta fungerar, men att de behöver kompletteras med en ytterligare komponent för död räkning (prognosvärden) med accelerometer för att öka antalet testfall där de erhåller godtagbar prestanda.
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Avan, Muhammet. "Joint Frequency Offset And Channel Estimation." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/2/12610149/index.pdf.
Full textAbstract:
In this thesis study, joint frequency offset and channel estimation methods for
single-input single-output (SISO) systems are examined. The performance of
maximum likelihood estimate of the parameters are studied for different training
sequences. Conventionally training sequences are designed solely for the channel
estimation purpose. We present a numerical comparison of different training
sequences for the joint estimation problem. The performance comparisons are made
in terms of mean square estimation error (MSE) versus SNR and MSE versus the
total training energy metrics. A novel estimation scheme using complementary
sequences have been proposed and compared with existing schemes. The proposed
scheme presents a lower estimation error than the others in almost all numerical
simulations. The thesis also includes an extension for the joint channel-frequency
offset estimation problem to the multi-input multi-output systems and a brief
discussion for multiple frequency offset case is also given.
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Daley, Neil. "Problems in the estimation of frequency." Thesis, Goldsmiths College (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248955.
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Rainton, D. "Time-frequency spectral estimation of speech." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334249.
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Chen, Jian. "Accurate frequency estimation with phasor angles." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-12042009-020203/.
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Cai, Kun, and 蔡琨. "Bayesian carrier frequency offset estimation in orthogonal frequency division multiplexing systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B42841367.
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Cai, Kun. "Bayesian carrier frequency offset estimation in orthogonal frequency division multiplexing systems." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B42841367.
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Ledingham, Jamie Andrew. "The estimation of flood frequency curves by mapping from rainfall frequency curves." Thesis, University of Newcastle Upon Tyne, 2011. http://hdl.handle.net/10443/1320.
Full textAbstract:
Recent large flooding events have reinforced the need for prudent flood risk management. The July 2007 floods in Yorkshire and the Midlands and the November 2009 floods in the Lake District have highlighted the current vulnerability of key infrastructure and the built environment in the UK to flooding. This existing flood risk is coupled with concerns over the potential impacts of future climate change on flood regimes. Therefore, there is a need to develop tools and methodologies to assess the potential impact of likely climate change on flood risk. The link between large rainfall and flow events is first examined, as well as an assessment of the seasonality of these events. This reveals a distinct east-west split in the seasonal concentration of flooding. This work provides a basis for the development of a statistical modelling technique which estimates a catchment flood record on an event basis. The model uses estimates of the flood generating storm and the antecedent conditions to estimate a flow magnitude. The modelled flood record is then transformed into a flood frequency curve using an appropriate statistical method. Extensive testing of the model has assessed its robustness to the length of flood record used in fitting and its sensitivity to the input climate data. Several case studies using the UKCP weather generator show how the method works as well as providing an indication of how future climate changes may affect the flood frequency curve. The frequency curve mapping method developed here performs best on catchments whose flood regime is driven by rainfall. The use of a simple antecedent rainfall accounting method has been shown to perform as well as a quasi-physical soil moisture estimation method. The research undertaken offers several possibilities to develop understanding of flood frequency curves in catchments with short gauged records. This new methodology has the potential for further development and can be used to explore a wide range of future scenarios.
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Williams, N. G. "Frequency domain parameter identification and the statistical properties of frequency response estimates." Thesis, Loughborough University, 1993. https://dspace.lboro.ac.uk/2134/25141.
Full textAbstract:
Frequency domain techniques in systems theory have their origins in Heavyside's operational calculus (Heavyside, 1889). Such work was later developed by Foster and Campbell (1931), Brune (1931), Nyquist (1932), Black (1934), Darlington (1939) and subsequently Bode (1948). This interest in the frequency domain was due to its appeal to the intuition of the engineer. The dominance of frequency domain techniques was subsequently eroded from the late 1950s through the 1960s by the influence of the space programmes. The space systems being analysed were based on strong theoretical foundations with well-defined sets of differential equations. The analysis led to the development of the state-space methods which were able to cope with the multivariable problems and were amenable to numerical solution. As a result of these developments, control engineering was largely dominated by the state-space approach and the associated areas of LQG optimal control, Kaiman-Bucy filters, observability and controllability. Two factors led to a resurgence of interest amongst academics in the development of frequency domain techniques in the 1970s and 1980s. The first was the development of the Fast Fourier Transform (FFT) (Cooley & Tookey, 1965). This provided an efficient method of analysing the Fourier transforms of signals and allowed the development of spectral methods of obtaining frequency response estimates. The collection of data was greatly speeded up and this enabled frequency domain methods to be increasingly applied to on-line control problems. The second factor was that the developments in the time domain were never fully embraced by practicing engineers in traditional control environments.
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Caprio, James R., and Lennart Nystrom. "HIGH SPEED, WIDE BANDWIDTH SIGNAL DETECTION AND FREQUENCY ESTIMATION." International Foundation for Telemetering, 1986. http://hdl.handle.net/10150/615572.
Full textAbstract:
International Telemetering Conference Proceedings / October 13-16, 1986 / Riviera Hotel, Las Vegas, NevadaA digital frequency discriminator (DFD) of the delay-correlator type is described. The device is shown to have an instantaneous frequency measurement capability on very short pulses. The theoretical performance of the DFD in a noisy background is derived and shown to compare favorably with measured results.
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Chen, Wei Zhang Ruifeng. "Time- frequency- selective channel estimation of ofdm systems /." Philadelphia, Pa. : Drexel University, 2005. http://dspace.library.drexel.edu/handle/1860/616.
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Aboussouan, Patrick. "Frequency response estimation of manipulator dynamic parameters." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65927.
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Ahmad, Anita. "Dominant frequency estimation for atrial fibrillation studies." Thesis, University of Leicester, 2012. http://hdl.handle.net/2381/10309.
Full textAbstract:
This research work explores the feasibility of using frequency domain analysis in the study of arrhythmias. The research involves the application of spectrum analysis to obtain the dominant frequency (DF) of atrial electrograms (AE) at different sites in the atria. It is an alternative way of interpreting the chaotic electrical activity seen during AF and reveals critical sites to guide ablation. As longer ablation procedure time implies higher risk to the patient, DF estimation needs to be obtained as quickly as possible. Four techniques (FFT, Blackman-Tukey, Autoregressive and Multiple Signal Classification) were used to compare the computation times taken for spectrum estimation analysis. The FFT technique produces an accurate DF result with the shortest time. DF analysis was first used for ventricular fibrillation with data from the surface of the left ventricle (in animal studies). It was found that spectrograms show the DF drifting along time and with significant changes in power. This approach was then applied for bipolar AF signals (in human studies). The changes of the frequency along time were observed when the stimulation was given, either using high frequency stimulation or drug infusion. We have developed a novel technique for the removal of ventricular signals from virtual AE. The surface ECG is used to identify ventricular activity. A band pass filter (8 Hz to 20 Hz) followed by rectification and then a low pass filter (6 Hz) are used for QRS detection. QRST subtraction was performed using three different approaches: flat, linear and spline interpolation. QRST subtraction affects the power of the signals but not the DF. We also developed an adaptive power threshold tool to observe the distribution of the DFs with an adjustable power threshold setting. Using this tool the 3D maps can display the evolution of the DFs within a chosen threshold power bracket.
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Li, Cheng, and 李鋮. "Carrier frequency offset estimation for multicarrier communications." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B29725331.
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Zhang, Zhuo. "Sinusoidal frequency estimation with applications to ultrasound." Thesis, Cardiff University, 2005. http://orca.cf.ac.uk/56018/.
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This thesis comprises two parts. The first part deals with single carrier and multiple-carrier based frequency estimation. The second part is concerned with the application of ultrasound using the proposed estimators and introduces a novel efficient implementation of a subspace tracking technique. In the first part, the problem of single frequency estimation is initially examined, and a hybrid single tone estimator is proposed, comprising both coarse and refined estimates. The coarse estimate of the unknown frequency is obtained using the unweighted linear prediction method, and is used to remove the frequency dependence of the signal-to-noise ratio (SNR) threshold. The SNR threshold is then further reduced via a combination of using an aver aging filter and an outlier removal scheme. Finally, a refined frequency estimate is formed using a weighted phase average technique. The hybrid estimator outperforms other recently developed estimators and is found to be independent of the underlying frequency. A second topic considered in the first part of this thesis is multiple-carrier based frequency estimation. Based on this idea, three novel velocity estimators are proposed by exploiting the velocity dependence of the backscattered carriers using synthetic data, all three proposed estimators are found to exhibit the capability of mitigating the poor high velocity performance of the conventional correlation based techniques and thereby provide usable performance beyond the conventional Nyquist velocity limit. To evaluate these methods statistically, the Cramer-Rao lower bound for the velocity estimation is derived. In the second part, the fundamentals of ultrasound are briefly reviewed. An efficient subspace tracking technique is introduced as a way to implement clutter eigenfilters, greatly reducing the computation complexity as compared to conventional eigenfilters which are based on the evaluation of the block singular value decomposition technique. Finally, the hybrid estimator and the multiple-carrier based velocity estimators proposed in the first part of the thesis are examined with realistic radio frequency data, illustrating the usefulness of these methods in solving practical problems.
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Hwang, Irena T. (Irena Tammy). "Frequency domain model-based intracranial pressure estimation." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/77016.
Full textAbstract:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 73-75).
Elevation of intracranial pressure (ICP), the pressure of the fluid surrounding the brain, can require urgent medical attention. Current methods for determining ICP are invasive, require neurosurgical expertise, and can lead to infection. ICP measurement is therefore limited to the sickest patients, though many others could potentially benefit from availability of this vital sign. We present a frequency-domain approach to ICP estimation using a simple lumped, linear time-invariant model of cerebrovascular dynamics. Preliminary results from 28 records of patients with severe traumatic brain injury are presented and discussed. Suggestions for future work to improve the estimation algorithm are proposed.
by Irena T. Hwang.
M.Eng.
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Kanagasabapathy, Shri. "Distributed adaptive signal processing for frequency estimation." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/49783.
Full textAbstract:
It is widely recognised that future smart grids will heavily rely upon intelligent communication and signal processing as enabling technologies for their operation. Traditional tools for power system analysis, which have been built from a circuit theory perspective, are a good match for balanced system conditions. However, the unprecedented changes that are imposed by smart grid requirements, are pushing the limits of these old paradigms. To this end, we provide new signal processing perspectives to address some fundamental operations in power systems such as frequency estimation, regulation and fault detection. Firstly, motivated by our finding that any excursion from nominal power system conditions results in a degree of non-circularity in the measured variables, we cast the frequency estimation problem into a distributed estimation framework for noncircular complex random variables. Next, we derive the required next generation widely linear, frequency estimators which incorporate the so-called augmented data statistics and cater for the noncircularity and a widely linear nature of system functions. Uniquely, we also show that by virtue of augmented complex statistics, it is possible to treat frequency tracking and fault detection in a unified way. To address the ever shortening time-scales in future frequency regulation tasks, the developed distributed widely linear frequency estimators are equipped with the ability to compensate for the fewer available temporal voltage data by exploiting spatial diversity in wide area measurements. This contribution is further supported by new physically meaningful theoretical results on the statistical behavior of distributed adaptive filters. Our approach avoids the current restrictive assumptions routinely employed to simplify the analysis by making use of the collaborative learning strategies of distributed agents. The efficacy of the proposed distributed frequency estimators over standard strictly linear and stand-alone algorithms is illustrated in case studies over synthetic and real-world three-phase measurements. An overarching theme in this thesis is the elucidation of underlying commonalities between different methodologies employed in classical power engineering and signal processing. By revisiting fundamental power system ideas within the framework of augmented complex statistics, we provide a physically meaningful signal processing perspective of three-phase transforms and reveal their intimate connections with spatial discrete Fourier transform (DFT), optimal dimensionality reduction and frequency demodulation techniques. Moreover, under the widely linear framework, we also show that the two most widely used frequency estimators in the power grid are in fact special cases of frequency demodulation techniques. Finally, revisiting classic estimation problems in power engineering through the lens of non-circular complex estimation has made it possible to develop a new self-stabilising adaptive three-phase transformation which enables algorithms designed for balanced operating conditions to be straightforwardly implemented in a variety of real-world unbalanced operating conditions. This thesis therefore aims to help bridge the gap between signal processing and power communities by providing power system designers with advanced estimation algorithms and modern physically meaningful interpretations of key power engineering paradigms in order to match the dynamic and decentralised nature of the smart grid.
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Ilvedson, Corinne Rachel 1974. "Transfer function estimation using time-frequency analysis." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/50472.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1998.Includes bibliographical references (p. 135-136).
Given limited and noisy data, identifying the transfer function of a complex aerospace system may prove difficult. In order to obtain a clean transfer function estimate despite noisy data, a time-frequency analysis approach to system identification has been developed. The method is based on the observation that for a linear system, an input at a given frequency should result in a response at the same frequency, and a time localized frequency input should result in a response that is nearby in time to the input. Using these principles, the noise in the response can be separated from the physical dynamics. In addition, the impulse response of the system can be restricted to be causal and of limited duration, thereby reducing the number of degrees of freedom in the estimation problem. The estimation method consists of finding a rough estimate of the impulse response from the sampled input and output data. The impulse response estimate is then transformed to a two dimensional time-frequency mapping. The mapping provides a clear graphical method for distinguishing the noise from the system dynamics. The information believed to correspond to noise is discarded and a cleaner estimate of the impulse response is obtained from the remaining information. The new impulse response estimate is then used to obtain the transfer function estimate. The results indicate that the time-frequency transfer function estimation method can provide estimates that are often less noisy than those obtained from other methods such as the Empirical Transfer Function Estimate and Welch's Averaged Periodogram Method.
by Corinne Rachel Ilvedson.
S.M.
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Patwardhan, Rohit S. "Frequency Response and Coherence function estimation methods." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1592169805143687.
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Liao, Yizheng. "Phase and Frequency Estimation: High-Accuracy and Low- Complexity Techniques." Digital WPI, 2011. https://digitalcommons.wpi.edu/etd-theses/283.
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The estimation of the frequency and phase of a complex exponential in additive white Gaussian noise (AWGN) is a fundamental and well-studied problem in signal processing and communications. A variety of approaches to this problem, distinguished primarily by estimation accuracy, computational complexity, and processing latency, have been developed. One class of approaches is based on the Fast Fourier Transform (FFT) due to its connections with the maximum likelihood estimator (MLE) of frequency. This thesis compares several FFT-based approaches to the MLE in terms of their estimation accuracy and computational complexity. While FFT-based frequency estimation tends to be very accurate, the computational complexity of the FFT and the latency associated with performing these computations after the entire signal has been received can be prohibitive in some scenarios. Another class of approaches that addresses some of these shortcomings is based on linear regression of samples of the instantaneous phase of the observation. Linear- regression-based techniques have been shown to be very accurate at moderate to high signal to noise ratios and have the additional benefit of low computational complexity and low latency due to the fact that the processing can be performed as the samples arrive. These techniques, however, typically require the computation of four-quadrant arctangents, which must be approximated to retain low computational complexity. This thesis proposes a new frequency and phase estimator based on simple estimates of the zero-crossing times of the observation. An advantage of this approach is that it does not require arctangent calculations. Simulation results show that the zero-crossing frequency and phase estimator can provide high estimation accuracy, low computational complexity, and low processing latency, making it suitable for real-time applications. Accordingly, this thesis also presents a real-time implementation of the zero-crossing frequency and phase estimator in the context of a time-slotted round-trip carrier synchronization system for distributed beamforming. The experimental results show this approach can outperform a Phase Locked Loop (PLL) implementation of the same distributed beamforming system.
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Wong, Kar Lun (Clarence). "Space-time-frequency channel estimation for multiple-antenna orthogonal frequency division multiplexing systems." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100244.
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We propose a linear mean square error channel estimator that exploits the joint space-time-frequency (STF) correlations of the wireless fading channel for applications in multiple-antenna orthogonal frequency division multiplexing systems. Our work generalizes existing channel estimators to the full dimensions including transmit spatial, receive spatial, time, and frequency. This allows versatile applications of our STF channel estimator to any fading environment, ranging from spatially-uncorrelated slow-varying frequency-flat channels to spatially-correlated fast-varying frequency-selective channels.The proposed STF channel estimator reduces to a time-frequency (TF) channel estimator when no spatial correlations exist. In another perspective, the lower-dimension TF channel estimator can be viewed as an STF channel estimator with spatial correlation mismatch for space-time-frequency selective channels.
Computer simulations were performed to study the mean-square-error (MSE) behavior with different pilot parameters. We then evaluate the suitability of our STF channel estimator on a space-frequency block coded OFDM system. Bit error rate (BER) performance degradation, with respect to perfect coherent detection, is limited to less than 2 dB at a BER of 10-5 in the modified 3GPP fast-fading suburban macro environment. Modifications to the 3GPP channel involves reducing the base station angle spread to imitate a high transmit spatial correlation scenario to emphasize the benefit of exploiting spatial correlation in our STF channel estimator.
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Wiltshire, S. E. "Statistical techniques for regional flood-frequency analysis." Thesis, University of Newcastle Upon Tyne, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378267.
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Al, Hosani Mohamed. "Transient and Distributed Algorithms to Improve Islanding Detection Capability of Inverter Based Distributed Generation." Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/6235.
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Recently, a lot of research work has been dedicated toward enhancing performance, reliability and integrity of distributed energy resources that are integrated into distribution networks. The problem of islanding detection and islanding prevention (i.e. anti-islanding) has stimulated a lot of research due to its role in severely compromising the safety of working personnel and resulting in equipment damages. Various Islanding Detection Methods (IDMs) have been developed within the last ten years in anticipation of the tremendous increase in the penetration of Distributed Generation (DG) in distribution system. This work proposes new IDMs that rely on transient and distributed behaviors to improve integrity and performance of DGs while maintaining multi-DG islanding detection capability.
In this thesis, the following questions have been addressed: How to utilize the transient behavior arising from an islanding condition to improve detectability and robust performance of IDMs in a distributive manner? How to reduce the negative stability impact of the well-known Sandia Frequency Shift (SFS) IDM while maintaining its islanding detection capability? How to incorporate the perturbations provided by each of DGs in such a way that the negative interference of different IDMs is minimized without the need of any type of communication among the different DGs?
It is shown that the proposed techniques are local, scalable and robust against different loading conditions and topology changes. Also, the proposed techniques can successfully distinguish an islanding condition from other disturbances that may occur in power system networks. This work improves the efficiency, reliability and safety of integrated DGs, which presents a necessary advance toward making electric power grids a smart grid.Ph.D.
Doctorate
Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering
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Ruan, Matt (Ming), and mattruan@gmail com. "Timing and Frequency Synchronization in Practical OFDM Systems." The Australian National University. ANU College of Engineering & Computer Science, 2009. http://thesis.anu.edu.au./public/adt-ANU20100728.103929.
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Orthogonal frequency-division multiplexing (OFDM) has been adopted by many
broadband wireless communication systems for the simplicity of the receiver technique to support high data rates and user mobility. However, studies also show
that the advantage of OFDM over the single-carrier modulation schemes could be
substantially compromised by timing or frequency estimation errors at the receiver.
In this thesis we investigate the synchronization problem for practical OFDM systems using a system model generalized from the IEEE 802.11 and IEEE 802.16
standards.
For preamble based synchronization schemes, which are most common in the
downlink of wireless communication systems, we propose a novel timing acquisition algorithm which minimizes false alarm probability and indirectly improves correct detection probability. We then introduce a universal fractional carrier frequency offset (CFO) estimator that outperforms conventional methods at low signal to noise ratio with lower complexity. More accurate timing and frequency estimates can be obtained by our proposed frequency-domain algorithms incorporating channel knowledge. We derive four joint frequency, timing, and channel estimators with different approximations, and then propose a hybrid integer CFO estimation scheme to provide flexible performance and complexity tradeoffs. When the exact channel delay profile is unknown at the receiver, we present a successive timing estimation algorithm to solve the timing ambiguity. Both analytical and simulation results are presented to confirm the performance of the proposed methods in various realistic channel conditions.
The ranging based synchronization scheme is most commonly used in the uplink
of wireless communication systems. Here we propose a successive multiuser detection algorithm to mitigate multiple access interference and achieve better performance than that of conventional single-user based methods. A reduced-complexity version of the successive algorithm feasible for hardware real-time implementation is also presented in the thesis. To better understand the performance of a ranging detector from a system point of view, we develop a technique that can directly translate a detector�s missed detection probability into the maximum number of users that the method can support in one cell with a given number of ranging opportunities. The analytical results match the simulations reasonably well and show that the proposed successive algorithms allow a base station to serve more than double the number of users supported by the conventional methods.
Finally, we investigate inter-carrier interference which is caused by the timevarying
communication channels. We derive the bounds on the power of residual inter-carrier interference that cannot be mitigated by a frequency-domain equalizer with a given number of taps. We also propose a Turbo equalization scheme using the novel grouped Particle filter, which approaches the performance of the Maximum A Posterior algorithm with much lower complexity.
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Qasaymeh, Mahmoud Mohammad. "Blind carrier frequency offset estimation for multicarrier systems." Diss., Wichita State University, 2009. http://hdl.handle.net/10057/2379.
Full textAbstract:
A Multicarrier Communication (MCM) system such as an Orthogonal Frequency
Division Multiplexing OFDM or Discrete Multi Tone (DMT) system has been shown to be an
effective technique to combat multipath fading in wireless communications. OFDM is a
modulation scheme that allows digital data to be efficiently and reliably transmitted over a radio
channel, even in multipath environments. OFDM transmits data by using a large number of
narrow bandwidth carriers. These carriers are regularly spaced in frequency, forming a block of
spectrum. The frequency spacing and time synchronization of the carriers is chosen in such a
way that the carriers are orthogonal, meaning that they do not cause interference to each other. In
spite of the success and effectiveness of the OFDM systems, it suffers from two well known
draw backs: large Peak to Average Power Ratio (PAPR) and high sensitivity to Carrier
Frequency Offset (CFO). The presence of the CFO in the received carrier will lose orthogonality
among the carriers and because the CFO causes a reduction of desired signal amplitude in the
output decision variable and introduces Inter Carrier Interference (ICI). It then brings up an
increase of Bit Error Rate (BER). This makes the problem of estimating the CFO an attractive
and necessary research problem. In this dissertation blind estimation techniques will be proposed
to estimate the offset parameter.Thesis (Ph.D.)--Wichita State University, College of Engineering, Dept. of Electrical and Computer Engineering
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Azemi, Ghasem. "Mobile Velocity Estimation Using a Time-Frequency Approach." Queensland University of Technology, 2003. http://eprints.qut.edu.au/15807/.
Full textAbstract:
This thesis deals with the problem of estimating the velocity of a mobile station (MS)in a mobile communication system using the instantaneous frequency (IF) of the received signal at the MS antenna. This estimate is essential for satisfactory handover performance, effective dynamic channel assignment, and optimisation of adaptive multiple access wireless receivers. Conventional methods for estimating the MS velocity are based either on the statistics of the envelope or quadrature components of the received signal. In chapter 4 of the thesis, we show that their performance deteriorates in the presence of shadowing. Other velocity estimators have also been proposed which require prior estimation of the channel or the average received power. These are generally difficult to obtain due to the non-stationary nature of the received signal. An appropriate window which depends on the unknown MS velocity must first be applied in order to accurately estimate the required quantities. Using the statistics of the IF of the received signal at the MS antenna given in chapter 3, new velocity estimators are proposed in chapter 4 of this thesis. The proposed estimators are based on the moments, zero-crossing rate, and covariance of the received IF. Since the IF of the received signal is not affected by any amplitude distortion, the proposed IF-based estimators are robust to shadowing and propagation path-loss. The estimators for the MS velocity in a macro- and micro-cellular system are presented separately. A macro-cell system can be considered as a special case of a micro-cell in which there is no line-of-sight component at the receiver antenna. It follows that those estimators which are derived for micro-cells can be used in a macro-cell as well. In chapter 4, we analyse the performance of the proposed velocity estimators in the presence of additive noise, non-isotropic scattering, and shadowing. We also prove analytically that the proposed velocity estimators outperform the existing methods in the presence of shadowing and additive noise. The proposed IF-based estimators need prior estimation of both the IF of the received signal and Ricean K-factor. The IF estimation in a typical wireless environment, can be considered as a special case of a general problem of IF estimation in the presence of multiplicative and additive noise. In chapter 5, we show that current time-frequency approaches to this problem which are based on the peak of a time-frequency distribution (TFD) of the signal, fail because of the special shape of the power spectral density of the multiplicative noise in a wireless environment. To overcome this drawback, the use of the first-order moment of a TFD is studied in chapter 5. Theoretical analysis and simulations show that the IF estimator based on the first-order moment of a TFD exhibits negligible bias when the signal-to-additive noise ratio is more than 10 dB. The Ricean K-factor is not only necessary for velocity estimation in micro-cells, but also is a measure of the severity of fading and a good indicator of the channel quality. Two new methods for estimating the Ricean K-factor based on the first two moments of the envelope of the received signal, are proposed in chapter 6. Performance analysis presented in chapter 6, prove that the proposed K estimators are robust to non-isotropic scattering. Theoretical analysis and simulations which are presented in chapters 4 and 7 of this thesis, prove that the proposed velocity and K estimators outperform existing estimators in the presence of shadowing and additive noise.
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Olsson, Mattias. "Contributions to Frequency Offset and Time Delay Estimation." Licentiate thesis, Linköping : Linköping University, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-6436.
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McCord, Virgil Alexander Stuart. "Augmenting flood frequency estimates using flood-scarred trees." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185017.
Full textAbstract:
Flood-damaged trees along streams and rivers in 20 localities in Arizona, Colorado, New Mexico, and Utah were examined to assess the feasibility of reconstructing the frequency and magnitude of floods over the last several hundred years. Tree-ring dating of the flood damage produced evidence for 17 floods during the last 125 years, and for at least four floods prior to 1866. Most of the flood-scar dates from the historic period were found to coincide with the dates of major floods on the waterways from which they were collected, or from nearby streams. Flood damage to trees was found to be very abundant and accessible, with the most productive situation probably being that of seasonal streambeds in narrow deep canyons with relatively steep gradients. Amount of effort required to produce a flood chronology appears to be relatively small. Collections at most sites involved sampling from 1 to 5 trees, by extracting 3 to 6 increment cores from each visibly scarred tree, and 2 cores from undamaged trees to facilitate crossdating. At two sites larger collections were made, including 3 cross sections (V-cuts), which were very helpful in establishing dates of scars. For a given channel gradient, scars seem to develop only when the flood depth is above a particular threshold level. This threshold was defined by plotting scar height for scarred trees and flow depth for other floods not producing scars against the logarithm of channel slope. The scarred and unscarred individual points were separated into two well-defined fields, separated by a fairly straight line. Discriminant function analysis showed the separation to be highly significant, and classification of individual points as scarred or unscarred was usually correct. The implication of the scar threshold is that even in drainages with no gage or historical record at all, the presence or absence of flood scars on channelside trees would indicate the occurrence or nonoccurrence of floods of a certain depth over the lifetime of the trees. Basin analysis and field measurements of appropriate channel characteristics would allow this depth and the corresponding discharge to be calculated.
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Khan, Arshad Zaman. "Frequency estimation of pre-stressed and composite floors." Thesis, City University London, 1996. http://openaccess.city.ac.uk/7929/.
Full textAbstract:
The modern trends towards economy and the use of high strength materials have resulted in long spans and slender floors of low frequencies. These frequencies may be within the range of the first few harmonics of daily life human activities. Though the problem of resonance with walking vibrations, an activity most common on all floors, is unlikely, high amplitude or persistent vibrations due to these low-level excitations may cause alarm to building occupants. There may also be some problems with the most sensitive equipment. These uncomfortable vibrations are a serviceability limit state problem and can only be avoided by ensuring a high floor fundamental natural frequency and damping. There is a need, therefore, for a method to accurately predict the fundamental natural frequency and damping of these floors and to ensure that they are high enough to avoid any resonance or perceptibility problems. Available analytical formulae for the estimation of fundamental natural frequency are not directly applicable to actual floors due to various assumptions. The only method that may be reliably used for static or dynamic analyses is the finite element method because it can conveniently model the three dimensional nature of structures and account for the various boundary conditions and material properties. The research reported in this thesis consists of measuring fundamental natural frequencies and corresponding damping of a range of actual floors. The experimental frequencies have then been compared with those results which are based on the analytical formulae and finite element method. The analytical methods suitable for various categories of floors have been identified. A new linear-elastic single panel or beam finite element model, correlated with the experimental results, has been developed for the accurate estimation of the fundamental natural frequency of these floors. The correct boundary conditions for various categories of floors have been identified. The single-degree-of-freedom (SDOF) formula for the estimation of fundamental natural frequency using static deflections has been modified for the floors tested. This modified SDOF formula can be used for convenient hand calculations by the consultants and designers who want a quick estimation of fundamental natural frequency due to time and cost limitations. The formula may also be used to limit static deflections and, therefore, design loads for any choice of a minimum fundamental natural frequency. Also, new limits on span/depth ratios for flat slabs and span limits for double-T beam floors have been suggested. Similarly, minimum fundamental natural frequencies, damping ratios and maximum static deflections have been suggested for the floors tested. The single panel or beam model may also be used for various parametric studies, both for static and dynamic analyses.
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Foster, Collin David. "Spatial parameter estimation using measured frequency response functions." Thesis, University of Liverpool, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314556.
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