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Dissertations / Theses on the topic 'Doppler Signals'
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1
Colosimo, Joseph William. "Doppler channel emulation of high-bandwidth signals." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/85698.
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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (page 97).
The Airborne Networks Group at MIT Lincoln Laboratory has funded the construction of a channel emulator capable of applying, in real-time, environmental models to communications equipment in order to test the robustness of new wireless communications algorithms in development. Specific design goals for the new emulator included support for higher bandwidth capabilities than commercial channel emulators and the creation of a flexible framework for future implementation of more complex channel models. Following construction of the emulator's framework, a module capable of applying Doppler shifting to the input signal was created and tested using DVB-S2 satellite modems. Testing not only verified the functionality of the emulator but also showed that DVB-S2 modems are unequipped to handle the continuous spectral frequency shifts due to the Doppler effect. The emulator framework has considerable room for growth, both in terms of implementing new channel transformation models as well as the re-implementation of the emulator on custom hardware for emulation of channels with wider bandwidths, more complex noise sources, or platform-dependent spatial blockage effects.
by Joseph William Colosimo.
M. Eng.
2
Walther, Julia, Lars Kirsten, and Edmund Koch. "Optimal processing of Doppler signals in OCT." SPIE, 2015. https://tud.qucosa.de/id/qucosa%3A35190.
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Besides structural imaging, OCT can be used to estimate axial velocities of the sample resolved in depth by Dopplerprocessing. In Fourier domain OCT (FD-OCT), this is accomplished by measuring the phase difference (i.e. phase shift) between timely separated A-scans at the same depth. In most cases, these data are disturbed by noise caused by intrinsic noise of the OCT system, specified by the SNR, and decorrelation noise caused by the transversal movement of the optical beam relative to the sample. Since the first use of Doppler methods in OCT, many methods to reduce the phase shift noise by averaging have been presented. While all these methods use a fixed set of consecutive A-scans, the best method, exhibiting no bias and having the smallest standard deviation, was questionable. Recently, Doppler processing methods depending on the mentioned noise sources and delivering the most likely phase shift and thereby axial velocity became available. The relation of these methods to previously known methods like the Kasai estimator, maximum likelihood estimator (MLE) and joint spectral and time domain OCT (jSTdOCT) will be discussed.
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Mehmood, Asif. "Instantaneous frequency analysis of ultrasonic doppler vibrometery signals /." Full text available from ProQuest UM Digital Dissertations, 2008. http://0-proquest.umi.com.umiss.lib.olemiss.edu/pqdweb?index=0&did=1850482451&SrchMode=1&sid=2&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1277394744&clientId=22256.
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Thesis (Ph.D.)--University of Mississippi, 2008.Typescript. Vita. "May 2008." Dissertation director : Paul M. Goggans Includes bibliographical references (leaves 106-112). Also available online via ProQuest to authorized users.
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Eldred, Randy Michael. "Doppler processing of phase encoded underwater acoustic signals." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA241283.
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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, September 1990.Thesis Advisor(s): Miller, James H. Second Reader: Tummala, Murali. "September 1990." Description based on title screen as viewed on December 17, 2009. DTIC Identifier(s): Acoustic tomography, inverse problems, Fast Hadamard Transforms, theses. Author(s) subject terms: Acoustic tomography, Fast Hadamard Transform, maximal-length sequences, Doppler processing. Includes bibliographical references (p. 95-96). Also available in print.
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Malachias, Nickolaos. "Doppler shift and spread study for ionospherically propagated signals." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1994. http://handle.dtic.mil/100.2/ADA284610.
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Alzogaiby, Adel. "Using Micro-Doppler radar signals for human gait detection." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86652.
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Thesis (MScEng)--Stellenbosch University, 2014.ENGLISH ABSTRACT: This work entails the development and performance analysis of a human gait detection system based on radar micro-Doppler signals. The system consists of a tracking functionality and a target classifier. Target micro-Doppler signatures are extracted with Short-Time Fourier Transform (STFT) based spectrogram providing a high-resolution signatures with the radar that is used. A feature extraction mechanism is developed to extract six features from the signature and an artificial neural network (A-NN) based classifier is designed to carry out the classification process. The system is tested on real X-band radar data of human subjects performing six activities. Those activities are walking and speed walking, walking with hands in pockets, marching, running, walking with a weapon, and walking with arms swaying. The multiclass classifier was designed to discriminate between those activities. High classification accuracy of 96% is demonstrated.
AFRIKAANSE OPSOMMING: Hierdie werk behels die ontwikkeling, en analise van werksverrigting, van ’n menslike stapdetekor gebaseer op radar-mikrodoppleranalise. Die stelsel bestaan uit ’n teikenvolger en -klassifiseerder. Die mikrodoppler-kenmerke van ’n teiken word met behulp van die korttyd-Fourier-transform onttrek, en verskaf hoe-resolusie-kenmerke met die radar wat vir die implementering gebruik word. ’n Kenmerkontrekkingstelsel is ontwikkel om ses kenmerke vanuit die spektrogram te onttrek, en ’n kunsmatige neurale netwerk word as klassifiseerder gebruik. Die stelsel is met ’n X-band radar op werklike menslike beweging getoets, terwyl vrywilligers ses aktiwiteite uitgevoer het: loop, loop (hand in die sakke), marsjeer, hardloop, loop met ’n wapen, loop met arms wat swaai. Die multiklas-klassifiseerder is ontwerp om tussen hierdie aktiwiteite te onderskei. ’n Hoe klassifiseringsakkuraatheid van 96% word gedemonstreer.
7
Fan, Lingke. "Spectral and time-frequency analysis of ultrasonic Doppler signals." Thesis, University of Leicester, 1994. http://hdl.handle.net/2381/34342.
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Spectral analysis of Doppler signals plays a very important role in non-invasive measurements of blood velocity distributions. Among the various spectral analysis methods available, the fast Fourier transform (FFT) is regarded as a "traditional" spectral analysis tool and is widely used in commercial, clinical, experimental and research equipment. Some drawbacks of this method, however, have imposed limitations on its use in some clinical cases. A numbers of spectral and time-frequency analysis methods have been studied in this dissertation. These include the traditional FFT, the autoregressive (AR) method, the Wigner-Ville distribution (WVD), and the Choi-Williams distribution (CWD). The advantages and disadvantages of each method have been studied and summarised. Efforts have been made to improve the temporal and frequency resolution of the results. New analysis methods such as the WVD and CWD have been interpreted physically, and some of their new properties have been explored. The results have suggested that the heights of the peaks in the AR spectra of narrow-band signals are not necessarily proportional to signal power, and should be used with caution in the context of Doppler signal processing. The results have also shown that it is appropriate to use the WVD or CWD to analyse signals when high temporal resolution is required. In practice, it is easier for the operator to handle the WVD, which usually produces reasonably good results. The above methods have been applied in practice. Considerable software and hardware development has been carried out, and a number of analysers have been implemented for use under different practical conditions. These analysers were also used to compare experimentally the analysis methods mentioned above, and to confirm the results of theoretical analyses. Some of these analysers have found applications in clinical practice.
8
Jack, Susan Heather. "The investigation of underwater acoustic signals using Laser Doppler Anemometry." Thesis, University of Edinburgh, 2000. http://hdl.handle.net/1842/15088.
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Laser Doppler Anemometry (LDA) has been used to study underwater acoustic signals both from emitting hydrophones and underwater explosions. A dual-beam LDA arrangement was used to capture Doppler signals arising from light scattered from particles suspended at the point of interest in the flow. These Doppler signals are analysed using either Hilbert transforms or wavelets, both of which allow instantaneous frequency information to be obtained. When an acoustic signal propagates through a medium it creates refractive index variations within the medium. The apparent motion of the scattering particles, as observed by the detector, which give rise to the Doppler signal, is therefore made up of two components. Firstly, the particles oscillate due to the sound field and secondly, the interference fringes oscillate due to the refractive index variations. This is termed the acousto-optic effect. A theory has been developed to investigate the effect of these refractive index variations on the analysed Doppler signals of an LDA system. Analysis of experimental Doppler signals using the Hilbert transform technique shows close agreement with the theoretical predictions. LDA has also been used to investigate the acoustic signal emitted by an oscillating explosion bubble. This is generated by an underwater spark which creates a similar situation to an underwater explosion in which a shock wave and an oscillating bubble are produced. Analysis of the Doppler signal using wavelets provides information on the bubble period, radius, energy and particle velocity. Explosive materials have traditionally been used for investigation of underwater explosions but they have the disadvantage of obscuring the area with explosion debris thus making optical investigation difficult. It is shown in this work that the use of LDA and analysis of Doppler signals using wavelets is an accurate technique for the investigation of acoustic signals from underwater explosions. This allows investigation of the area close to the explosion centre where measurements have been difficult to achieve with traditional techniques.
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CIATTAGLIA, Gianluca. "Modern techniques to process micro-Doppler signals from mmWave Radars." Doctoral thesis, Università Politecnica delle Marche, 2022. http://hdl.handle.net/11566/295142.
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I sistemi radar mmWave stanno diventando molto comuni sui veicoli e le loro capacità, in termini di portata e velocità, li rendono adatti a un'altra classica applicazione radar classica, quella relativa all'effetto micro-Doppler. Dall'elaborazione dei segnali radar mmWave, l'effetto micro-Doppler può essere sfruttato, rendendo così possibile estrarre informazioni interessanti sui bersagli. Con l'enorme larghezza di banda e il breve tempo di trasmissione del segnale, l effetto micro-Doppler può essere utilizzato per diversi scopi come la vibrazione del bersaglio o la classificazione dei bersagli. Grazie anche al progresso delle tecniche di Machine Learning, la loro combinazione con elaborazione del segnale radar è un campo interessante da esplorare e può essere usato per fornire soluzioni a diversi problemi radar. L'effetto Micro-Doppler ha una lunga storia nei sistemi radar, un sacco di letteratura può essere trovata su questo argomento, ma la maggior parte di loro considera dispositivi non commerciali quindi è abbastanza lontano da un caso pratico. In questa dissertazione, diverse tecniche per elaborare i segnali micro-Doppler provenienti da radar automobilistici sarà presentato, con lo scopo di classificarli ed estrarre informazioni sulle vibrazioni dal bersaglio. Il contributo principale di questo lavoro è la proposta di nuove tecniche che possono essere applicato su un sensore commerciale e li rende adatti per il micro- Doppler.mmWave Radar systems are becoming very common on vehicles and their capabilities, in terms of range and velocity, make them suitable for another classical radar application, the one related to the micro-Doppler effect. From the processing of mmWave radar signals, the micro-Doppler effect can be exploited, making so possible to extract interesting information on the observed targets. With the huge bandwidth and the short signal transmission time, the micro-Doppler effect can be used for different purposes such as target vibration measurements or targets classification. Thanks also to the advance of Machine Learning techniques, their combination with radar signal processing is an interesting field to explore and can be used to provide solutions to different radar problems. The Micro-Doppler effect has a long story in Radar systems, a lot of literature can be found on this topic but most of them consider non-commercial devices so is quite away from a practical case. In this dissertation, different techniques to process the micro-Doppler signals coming from automotive radars will be presented, with the purpose of classifying them and extracting vibration information from the target. The main contribution of this work is the proposal of novel techniques that can be applied on a commercial sensor and makes them suitable for the micro- Doppler application.
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Wendling, Fabrice. "Simulation of doppler ultrasound signals for a laminar, pulsatile, nonuniform flow." Thesis, Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/16875.
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Kwan, Katherine S. Y. "An adaptive line enhancer for tracking doppler frequency-shifted narrowband signals." Thesis, University of Bath, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357242.
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Warner, Margaret. "Automated algorithms for detection of stroke distance from Doppler ultrasound signals." Thesis, University of Aberdeen, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327097.
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Землянський, Володимир Михайлович. "the two-wave ldv with cophased reception of the doppler signals." Thesis, Національний авіаційний університет, 2014. http://er.nau.edu.ua/handle/NAU/11708.
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Cullinane, M. "The study of cerebral emboli using transcranial doppler ultrasound : clinical and technical studies." Thesis, King's College London (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369127.
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Pistacchio, David J. "Source/receiver motion-induced Doppler influence on the bandwidth of sinusoidal signals." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Dec%5FPistacchio.pdf.
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Thesis (M.S. in Engineering Acoustics)--Naval Postgraduate School, December 2003.Thesis advisor(s): Kevin Smith, Roy Streit. Includes bibliographical references (p. 95-100). Also available online.
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Hassana, Ramesh Rakesh Kashyap. "Transform Domain Acquisition of Spread Spectrum Signals in a Low Signal to Noise Ratio Environment." Ohio University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1289579500.
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Routh, H. F. "Scattering of ultrasound by blood with reference to the analysis of doppler signals." Thesis, Bucks New University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380271.
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Bastos, Carlos Alberto da Costa. "A model for the simulation of Doppler ultrasound signals from pulsatile blood flow." Phd thesis, Instituições portuguesas -- -Universidade de Aveiro -- -Departamento de Electrónica e Telecomunicações, 1999. http://dited.bn.pt:80/6564.
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The Doppler ultrasonic blood flow detector estimates
non-invasively the velocity of blood in the circulatory system. It has been
extensively used in the last four decades for the detection of stenoses in the
circulation.The development of new signal processing techniques for the Doppler
signal requires test signals with known or measurable characteristics. This is
very difficult to achieve with Doppler signals obtained in vivo because of the
variability of blood flow between persons and with physiological state, for
example blood pressure. A model for generating simulated Doppler signals whose
characteristics are controllable and/or measurable is a useful tool because it
permits the test of new processing techniques under controlled conditions. It
permits also the study of the effect of various factors on the Doppler
spectrum. Usually these effects cannot be isolated with in vivo
measurements.During this work a model for the generation of simulated Doppler
ultrasound signals was developed. It comprised two sub-models one for blood
flow in the human lower limb and the other for generating simulated signals
from the blood velocity field and the instrument's characteristics.Blood flow
in the lower limb was modelled by an electric analogue for the lower limb
vascular tree. Each artery was modelled by a lossy transmission line and the
peripheral vascular beds by three-element Windkessel models. The
electric analogue circuit was implemented with the SPICE circuit simulator. To
simulate the inter-action of the blood cells with the ultrasonic field the
vessel was divided into small elemental volumes whose contributions were added
together to generate the simulated Doppler signal. The model assumed
irrotational laminar flow and some other simplifying approximations.The
characteristics of the signals generated by the model were similar to those
expected for the Doppler signal. The model was used to study the influence of
blood acceleration, sample volume size and data segment duration on the root
mean square (rms) width of the Doppler spectrum. A simple formula was derived
for estimating the Doppler rms spectral width from the individual contribution
of non-stationarity broadening, intrinsic broadening, window broadening and the
range of blood velocities passing through the sample volume.In addition closed
form expressions were derived for the Doppler power spectrum due solely to the
range of blood velocities passing through a Gaussian sample volumes placed in
irrotational laminar flow with a velocity profile obeying a simple power law.
Closed form expressions were also obtained for the root mean square spectral
width in the special case of a spherically symmetric Gaussian sample volume
placed in the centre of the vessel.O detector ultra-sónico de fluxo sanguíneo usa o efeito Doppler para estimar de forma não invasiva a velocidade do sangue na circulação. Tem sido bastante usado nas últimas quatro décadas para detectar a presença de estenoses.O desenvolvimento de novas técnicas de processamento do sinal Doppler necessita de sinais de teste cujas características sejam conhecidas ou possam ser medidas com precisão. Isto é difícil de obter com sinais Doppler medidos in vivo devido à elevada variação do fluxo sanguíneo de pessoa para pessoa e também com o estado fisiológico da pessoa no momento da medida, por exemplo a tensão arterial influencia significativamente o fluxo sanguíneo. Um modelo para gerar sinais Doppler simulados cujas características sejam controláveis e/ou mensuráveis é uma ferramenta bastante útil, pois permite que as novas técnicas de processamento do sinal Doppler sejam testadas em condições controladas. Permite, também, estudar o efeito de vários factores que afectam o espectro do sinal Doppler. Habitualmente o efeito individual dos vários factores não pode ser identificado quando são usados sinais medidos in vivo.Neste trabalho foi desenvolvido um modelo para gerar sinais Doppler ultra-sónicos simulados. O modelo contém dois sub-modelos, um para o fluxo sanguíneo nos membros inferiores de um ser humano e outro para gerar os sinais simulados a partir do campo de velocidades do sangue e das características do instrumento.O fluxo sanguíneo nos membros inferiores foi simulado com um análogo eléctrico para a rede vascular dos membros inferiores. Cada artéria foi simulada por uma linha de transmissão com perdas e as redes vasculares periféricas por um circuito Windkessel com três elementos. O circuito eléctrico foi implementado com o simulador de circuitos SPICE.Para simular a interacção entre os glóbulos vermelhos e o campo de ultra-sons o vaso sanguíneo foi dividido em pequenos volumes elementares. As contribuições dos volumes elementares foram todas somadas para gerar o sinal Doppler simulado. O modelo fez algumas aproximações como sejam, por exemplo, considerar o fluxo sanguíneo laminar e sem rotação.As características dos sinais gerados pelo modelo são bastante parecidas com as esperadas para o sinal Doppler real. O modelo desenvolvido foi usado para estudar a influência que a aceleração sanguínea, o tamanho do volume de amostragem e a duração da janela de amostragem têm na largura de banda eficaz do espectro do sinal Doppler. Foi deduzida uma fórmula que estima a largura de banda eficaz a partir das contribuições individuais do alargamento espectral devido à não estacionaridade, do alargamento espectral intrínseco, do alargamento espectral devido à duração da janela de amostragem e ainda da gama das velocidades que passam pelo volume de amostragem. Foram, ainda, deduzidas expressões em forma fechada para o espectro de potência do sinal Doppler devido unicamente à gama de velocidades que atravessam um volume de amostragem com forma Gaussiana colocado num perfil de velocidades com forma exponêncial. Foram, também, obtidas expressões para a largura de banda eficaz no caso especial do volume de amostragem Gaussiano ter simetria esférica e estar colocado no centro do vaso sanguíneo.
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Kharchakdjian, Raffi. "Modelling the structure of the tumour vasculature and its effect on Doppler ultrasound signals." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq58834.pdf.
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Hertzog, P. E., and G. D. Jordaan. "Wavelets and short time fourier transforms on ultrasonic doppler signals for pregnancy determination in sheep." Interim : Interdisciplinary Journal, Vol 5, Issue 1: Bloemfontein : Central University of Technology, Free State, 2006. http://hdl.handle.net/11462/414.
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Published ArticleThe reproductive status of animals is of utmost importance to the modern farmer. Decisions concerning the management of the flock are influenced by the knowledge of the percentage of animals that are pregnant at any specific time. The aim of the project was to gain knowledge for the development of an instrument that is affordable and with which a farmer can do pregnancy determination himself/herself, thereby enabling him/her to make the correct management decisions. Experimental data were obtained from pregnant Dorper ewes with the aid of a portable Doppler instrument. Using real data as input, simulations of Wavelet and Short Time Fourier Transforms (STF) were done in MathCAD. In the simulations known levels of noise were added to the Doppler signals. Satisfactory results were obtained from the simulations of Wavelet Transforms. In the simulation of the Wavelet Transforms, signals with a SNR of -6.5 dB were successfully identified. It can thus be concluded that Wavelet Transforms can be used successfully for the detection of the fetal heartbeat in noisy ultrasonic Doppler signals.
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Schlindwein, Fernando Soares. "Real-time digital processing of Doppler ultrasound signals and its application to blood flow measurement." Thesis, University of Leicester, 1990. http://hdl.handle.net/2381/34225.
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A system comprising of a personal microcomputer and a Digital Signal Processor board has been assembled and programmed for real-time spectral analysis of Doppler ultrasound signals. Three spectrum analysis techniques were implemented to run in real-time on the system: The fast Fourier transform (FFT), the autoregressive (AR) model, and the moving average (MA) model. The FFT and the AR techniques were investigated in some depth. The advantages of using such a system are that it is entirely programmable, cheap, reliable, and that the processed information can be stored on diskettes. The inputs to the system are the forward and reverse components of the Doppler ultrasonic signal, and the outputs are the sonogram, the frequency envelope, and the intensity weighted mean frequency curve, which are presented on the screen and can be saved to diskette. Five frequency ranges can be selected by the operator, from 1.28 kHz to 20.48 kHz, corresponding to sampling frequencies from 2.56 kHz to 40.96 kHz. Most commercial systems for real-time spectral analysis of Doppler ultrasonic signals implement the modified FFT-periodogram technique for power spectral density estimation (PSDE), which is computationally very efficient but has some shortcomings, especially for the analysis of relatively short records. With the AR model approach the spectra can be estimated from short segments, no antileakage window is necessary and the spectral resolution is better than for the FFT. A study of some methods for order selection used with the autoregressive model for the spectrum analysis of Doppler signals is reported and the use of a fixed order of around 12 is suggested for the AR model. The implementation of the AR PSDE approach in real-time, in a reasonably priced system, is a step towards the practical use of the so called 'modern techniques' for spectral analysis of Doppler ultrasonic signals, but further work has to be done on the validation of the technique in clinical usage.
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Koseli, Volkan. "Experimental And Theoretical Investigation Of Complex Flows By Ultrasound Doppler Velocimetry." Phd thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610727/index.pdf.
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Non-invasive and fast flow measurement techniques have had increasing importance
for the last decades. Scientists are looking for such quick techniques to be able to
monitor real velocities without disturbing flow itself. Ultrasound Doppler
velocimetry (UDV) being one of such techniques promising with advantages of
getting simultaneous velocity measurements from several points and of applicability
for opaque liquids as well. UDV is a technique which is still being developed for
new applications and analysis of complex flows.
In this study effect of sinusoidal oscillating, turbulent (random) and viscoelastic fluid
motions on UDV signals were investigated theoretically and experimentally.
Obtained mathematical relations for random and viscoelastic motions were utilized
to get statistics of flow and distribution of relaxation spectrum, respectively.
Analytical analysis and numerical simulation of sinusoidal oscillating flow depicted
that there is a critical value for the ratio of oscillation amplitude to oscillation
frequency for a specified set of measurement parameters of UDV. Above this critical
value UDV is not successful to determine mean flow velocity. Mathematical
relations between velocity probability density function (PDF) &ndashvelocity auto correlation function (ACF) and UDV signal spectrum were obtained in the analysis v of flow with random velocity. Comparison of velocity ACFs from direct velocity measurements and from raw in-phase (I) and quadrature (Q) signals through derived relation, revealed that time resolution of UDV technique is not enough for getting a good velocity ACF and thus turbulence spectrum. Using I and Q signals rather than measured velocities to get velocity ACF, increased the time resolution in the order of number of pulses used for getting one velocity value (Nprn). Velocity PDF obtained from UDV spectrum was compared with the one obtained from measured velocities with the assumption of Gaussian PDF. Both velocity PDFs were consistent. Also some parameters of pipe turbulence from literature were compared with the presented findings from velocity ACF obtained from I and Q signals through derived relation. Results showed good compatibility. In the last part of the study, complex viscosity of a linear viscoelastic fluid mathematically related to spectrum of UDV for a pipe flow with small-amplitude oscillating pressure field. Generalized Maxwell model was employed to express complex viscosity terms. Zero frequency (mean flow) component of UDV spectrum was used to obtain an equation for relaxation viscosities of generalized Maxwell model. Results have revealed that UDV technique can also be used to probe some of viscoelastic material functions. In conclusion, UDV is relatively new but a promising technique for the measurement and analysis of complex flows in a non-invasive manner.
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Long, Xuguang. "Application of time-frequency analysis to Doppler ultrasound blood flow signals for detection of small stenoses." Thesis, King's College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390610.
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Patz, Ralf. "Time-frequency analysis of Doppler ultrasound blood flow signals : an investigation into automated diagnosis of vascular disease." Thesis, University of South Wales, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289393.
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Leclerc, Hélène. "An in vitro study of the relationship between fluid mechanical phenomena and signals from a 12 MHz doppler ultrasound guidewire in a model of coronary artery stenosis." Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/16013.
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Shaban, Fahad. "Application of L1 reconstruction of sparse signals to ambiguity resolution in radar." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47637.
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The objective of the proposed research is to develop a new algorithm for range and Doppler ambiguity resolution in radar detection data using L1 minimization methods for sparse signals and to investigate the properties of such techniques. This novel approach to ambiguity resolution makes use of the sparse measurement structure of the post-detection data in multiple pulse repetition frequency radars and the resulting equivalence of the computationally intractable L0 minimization and the surrogate L1 minimization methods. The ambiguity resolution problem is cast as a linear system of equations which is then solved for the unique sparse solution in the absence of errors. It is shown that the new technique successfully resolves range and Doppler ambiguities and the recovery is exact in the ideal case of no errors in the system. The behavior of the technique is then investigated in the presence of real world data errors encountered in radar measurement and detection process. Examples of such errors include blind zone effects, collisions, false alarms and missed detections. It is shown that the mathematical model consisting of a linear system of equations developed for the ideal case can be adjusted to account for data errors. Empirical results show that the L1 minimization approach also works well in the presence of errors with minor extensions to the algorithm. Several examples are presented to demonstrate the successful implementation of the new technique for range and Doppler ambiguity resolution in pulse Doppler radars.
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Sallem, Soumaya. "Traitements de réception mono et multi-antennes de signaux rectilignes ou quasi-rectilignes en présence de multitrajets de propagation." Thesis, Evry, Institut national des télécommunications, 2012. http://www.theses.fr/2012TELE0054/document.
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Le récepteur SAIC/MAIC introduit récemment est capable de séparer jusqu'à 2N utilisateurs synchronisés avec N antennes pour les réseaux de radiocommunications utilisant des modulations rectilignes ou quasi-rectilignes. Un tel récepteur, opérationnel dans les téléphones GSM depuis 2006, exploite la non-circularité du second ordre des signaux et met en œuvre un filtre optimal linéaire au sens large (widely linéaire WL). Il s'est montré performant pour les utilisateurs synchrones en absence de résidu de porteuse (l'effet doppler par exemple), mais son comportement en présence d'utilisateurs asynchrones ayant des résidus de porteuse potentiellement non nuls, omniprésents dans de nombreuses applications radio, n'a pas encore fait l'objet d'études théoriques, ce qui ne permet pas d'en connaître les dégradations. Le but de la 1e partie de ce travail consiste à présenter une analyse des performances du SAIC/MAIC, implanté via une approche MMSE avec séquence d'apprentissage, en présence de deux utilisateurs non nécessairement synchronisés et ayant des dérives de fréquence. Pour simplifier, nous avons limité l'analyse théorique à quelques cas particuliers avec des modulations rectilignes. Ainsi des expressions analytiques simples et interprétables ont été données et analysées. Nous avons prouvé que les performances sont moins dégradées dans le cas d'une dérive sur l'utile qu'en présence d'une dérive sur le brouilleur. En outre, la dégradation augmente avec la désynchronisation des deux signaux. Afin de préciser le domaine de validité des approximations analytiques, des illustrations numériques ont été réalisées en prenant comme paramètres ceux du standard GSM dans le but d'appliquer cette étude à ce standard et aux réseaux cellulaires. L'extension de l'analyse aux modulations quasi-rectilignes a nécessité la mise en œuvre d'un filtrage spatio-temporel. Nous avons ainsi étudié l'impact de la taille du filtre spatio-temporel sur les performances du MMSE SAIC/MAIC pour des modulations quasi-rectilignes (MSK et GMSK) en présence de résidus de porteuse. L'étude révèle qu'avec des résidus de porteuse standards, ce récepteur reste relativement robuste et ne nécessite pas de compensation. La 2e partie de ce travail considère des canaux sélectifs en fréquence et consiste à développer un SIMO MLSE pour un signal utile à modulation linéaire quelconque en présence de bruit additif gaussien centré stationnaire coloré temporellement et spatialement et potentiellement non circulaire, en partant d'un problème général de détection d'une forme d'onde. Nous avons démontré que le SIMO MLSE est constitué d'un filtre WL, d'un échantillonneur au rythme symbole et d'une minimisation récursive d'une métrique qui peut se mettre en oeuvre par l'algorithme de Viterbi. Le cas des modulations quasi rectilignes a aussi été considéré. Dans ce cadre, nous avons démontré que le SIMO MLSE a la même structure moyennant un prétraitement de dérotation. Tous ces filtres WL sont interprétés comme des filtres WL adaptés multidimensionnels (WL MMF) au sens où ils maximisent le rapport SNR sur le symbole courant en sortie. Nous avons ensuite étendu la structure du MLSE développée au cas d'un bruit gaussien non circulaire mais cyclostationnaire, de manière à se rapprocher des applications cellulaires. Nous appelons ce nouveau récepteur "pseudo-MLSE" car sa structure a été imposée. En conjecturant que les performances en probabilité d'erreur par symbole sont directement reliées au SNR sur le symbole courant, des expressions générales de celui-ci ont été données pour des MLSE et pseudo-MLSE dans le cadre d'interférences stationnaires et cyclostationnaires potentiellement non circulaires. Des formules interprétables de ces SNR ont été données dans des cas particuliers et des simulations numériques ont été présentées pour montrer les gains en performance des récepteurs introduits par rapport aux MLSE classiques dérivés sous hypothèse de bruit stationnaire circulaireThe SAIC/MAIC (Single/Multiple Antenna Interference Cancellation) receiver, recently introduced, is able to separate up to 2N synchronous users with N antennas for the radiocommunications networks using rectilinear or quasi-rectilinear modulations. A such receiver, operational in GSM handsets since 2006, exploits the second order non-circularity of signals and gives rise to an optimal widely linear (WL) filter. This receiver has been shown to be powerful for synchronous users without any frequency offsets (for example Doppler shift), but its behaviour in the presence of asynchronous users having potentially non zero carrier residues, omnipresent in many radio applications, has not yet been the subject of theoretical studies, which doesn't allow us to know their damage. For this reason, the purpose of the first part of this work is to present an analysis of SAIC/MAIC receiver performances, implemented via an MMSE approach with training sequence, with two users not necessarily synchronized with frequency shifts. To simplify the analytical developments, we limited the theoretical analysis to some particular cases with rectilinear modulations. Hence, simple and interpretable analytical expressions were given and analyzed. We proved in particular that the performance is less degraded in the case of a shift on the useful than in the presence of a drift on the jammer. Furthermore, the degradation increases with desynchronization of the two signals. To precise the range of validity of analytical approximations, numerical illustrations were made using as parameters those of the GSM standard in order to apply this study to this standard in particular and cellular networks in general. Extending the analysis to quasi-rectilinear modulations had required the implementation of a spatio-temporal filtering. We have studied the impact of the size of the spatio-temporal filter on the performance of MMSE SAIC/MAIC receiver for quasi-rectilinear modulations (GMSK and MSK) in the presence of residual frequencies. The study reveals that with standard carrier residues, this receiver remains relatively robust and doesn't require a compensation. The second part of this work considers frequency-selective channels and is developing a SIMO MLSE receiver for a useful signal with any linear modulation in the presence of an additive Gaussian centered stationary temporally and spatially colored and potentially non-circular noise, starting from a general problem of detection of a waveform. We have shown that SIMO MLSE receiver consists of a WL filter, a sampler at the symbol rate and a recursive minimization of a metric that can be solved by the Viterbi algorithm. The case of quasi-rectilinear modulations is also considered. Within this framework, we had proved that the SIMO MLSE receiver has the same structure through a postreatment derotation. All these filters are interpreted as WL multidimensional matched filters (WL MMF) in the sense that they maximize the SNR of the current symbol at output. Then, we extended the MLSE receiver structure developed in case of a noncircular gaussian noise but this time cyclostationary, so as to approximate radio cellular applications. We call this new receiver "pseudo-MLSE" because its structure was imposed. By conjecturing that the performances by per symbol error probability are directly related to the SNR of the current symbol, general expressions of this SNR are given for MLSE and pseudo MLSE receivers with stationary and cyclostationary potentially noncircular interferences. Interpretable formulas of these SNR were given in special cases and numerical simulations were presented to show performance gains of the receivers we have introduced relative to conventional MLSE receivers derived under the assumption of circular stationary noise
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Bouras, Bouhafs. "Traitement du signal adapté aux signaux GPS." Valenciennes, 1994. https://ged.uphf.fr/nuxeo/site/esupversions/357ad253-2be4-452d-ad4e-eb2a9e8ef7b6.
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Parmi les systèmes de radionavigation existants, GPS est sans doute le plus complet et le plus précis. Il est conçu pour fournir des mesures précises des trois coordonnées d'un navigateur partout dans le monde, et de corriger son horloge dans un repère référentiel. Compare aux autres systèmes de navigation, il fait appel à des traitements du signal plus sophistiques, et qui font des récepteurs GPS plus complexes que d'autres. Notre objectif est de rendre ces récepteurs compétitifs en termes de cout et d'utilisation sans compromettre leurs hautes performances. Dans notre travail sur une unité de traitement GPS, prototype réalisé dans notre laboratoire, de très bonnes performances étaient obtenues sur un signal GPS simule. Des signaux fortement noyés dans le bruit (avec un rapport signal a bruit inferieur a 23 dB) et affectes par le doppler, étaient traites avec succès et la reconnaissance des codes correspondants était établie. Parmi les aspects les plus importants du système réalisé, la haute immunité au bruit des signaux d'asservissement, permettait une opération stable en présence d'un bruit intense, permettant l'acquisition des données de navigation dans de bonnes conditions
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Meynard, Adrien. "Stationnarités brisées : approches à l'analyse et à la synthèse." Thesis, Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0475.
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La non-stationnarité est caractéristique des phénomènes physiques transitoires. Par exemple, elle peut être engendrée par la variation de vitesse d'un moteur lors d'une accélération. De même, du fait de l'effet Doppler, un son stationnaire émis par une source en mouvement sera perçu comme étant non stationnaire par un observateur fixe. Ces exemples nous conduisent à considérer une classe de non-stationnarité formée des signaux stationnaires dont la stationnarité a été brisée par une opérateur de déformation physiquement pertinent. Après avoir décrit les modèles de déformation considérés (chapitre 1), nous présentons différentes méthodes permettant d'étendre l'analyse et la synthèse spectrale à de tels signaux. L'estimation spectrale des signaux revient à déterminer le spectre du processus stationnaire sous-jacent et la déformation ayant brisé sa stationnarité. Ainsi, dans le chapitre 2, nous nous intéressons à l'analyse de signaux localement déformés pour lesquels la déformation subie s'exprime simplement comme un déplacement des coefficients d'ondelettes dans le plan temps-échelle. Nous tirons profit de cet propriété pour proposer l'algorithme d'estimation du spectre instantané JEFAS. Dans le chapitre 3, nous étendons cette analyse spectrale aux signaux multi-capteurs pour lesquels l'opérateur de déformation prend une forme matricielle. Il s'agit d'un problème de séparation de sources doublement non stationnaire. Dans le chapitre 4, nous proposons un approche à la synthèse pour étudier des signaux localement déformés. Enfin, dans le chapitre 5, nous construisons une représentation temps-fréquence adaptée à l'étude des signaux localement harmoniquesNonstationarity characterizes transient physical phenomena. For example, it may be caused by a speed variation of an accelerating engine. Similarly, because of the Doppler effect, a stationary sound emitted by a moving source is perceived as being nonstationary by a motionless observer. These examples lead us to consider a class of nonstationary signals formed from stationary signals whose stationarity has been broken by a physically relevant deformation operator. After describing the considered deformation models (chapter 1), we present different methods that extend the spectral analysis and synthesis to such signals. The spectral estimation amounts to determining simultaneously the spectrum of the underlying stationary process and the deformation breaking its stationarity. To this end, we consider representations of the signal in which this deformation is characterized by a simple operation. Thus, in chapter 2, we are interested in the analysis of locally deformed signals. The deformation describing these signals is simply expressed as a displacement of the wavelet coefficients in the time-scale domain. We take advantage of this property to develop a method for the estimation of these displacements. Then, we propose an instantaneous spectrum estimation algorithm, named JEFAS. In chapter 3, we extend this spectral analysis to multi-sensor signals where the deformation operator takes a matrix form. This is a doubly nonstationary blind source separation problem. In chapter 4, we propose a synthesis approach to study locally deformed signals. Finally, in chapter 5, we construct a time-frequency representation adapted to the description of locally harmonic signals
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Pawelka, Robert H. "Digitized Doppler Signal Processor." International Foundation for Telemetering, 1989. http://hdl.handle.net/10150/614677.
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International Telemetering Conference Proceedings / October 30-November 02, 1989 / Town & Country Hotel & Convention Center, San Diego, CaliforniaAt the present time there is a requirement for developing an airborne approach for processing radar doppler video data into digital PCM format compatible with current IRIG standards. Techniques for digitizing the doppler video presently exist, but have limitations due to the fact that the data is processed and represented in the time domain. These limitations can be mainly attributed to the high bit rates required for quantizing the dynamic nature of the doppler signal. Therefore, an alternate approach was selected by which the video doppler data is converted and represented in the frequency domain. The time to frequency domain conversion is accomplished with a digital Part Fourier Transform (FFT) implemented in conjunction with a quadrature translator. This method will provide a means by which the doppler signal can be represented as a quasi-static spectrum. The advantage in this application is that only the spectral data which contains relevant engineering information will be processed. The resultant system will thereby minimize the transmission bit rate and maximize the dynamic range for the purpose of signal analysis. The paper will describe the implementation and work performed on the digitized doppler signal processor along with the potential application in PCM systems requiring spectral signal analysis.
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Ferreira, Esteves Paulo Alexandre. "Techniques d'acquisition à haute sensibilité des signaux GNSS." Thesis, Toulouse, ISAE, 2014. http://www.theses.fr/2014ESAE0016/document.
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Les systèmes de navigation par satellite (GNSS) font partie de notre quotidien. On peut présentement les trouver dans un ensemble d’applications. Avec les nouveaux besoins, des nouveaux enjeux sont aussi apparus : le traitement du signal dans les environnements urbains est extrêmement complexe. Dans cette thèse, le traitement des signaux GNSS à faible puissance est abordé, en particulier dans la première phase du traitement, nommé acquisition de signal. Le premier axe de rechercheporte sur l’analyse et la compensation de l’effet Doppler dans l’acquisition. Le décalage Doppler perçu par l’utilisateur est un des paramètres principaux pour la configuration du module d’acquisition. Dans cette étude, des solutions sont proposées pour trouver le meilleur compromis sensibilité-complexité propre à l’acquisition. En deuxième axe, la caractérisation des détecteurs différentiels est abordée, en particulier la quantification de sa sensibilité. Pour l’acquisition des signaux faibles, après une première phase d’intégration cohérente, il faut passer par une intégration «postcohérente» (noncohérente ou différentielle.) L’analyse exécutée ici permet de meilleur identifier le meilleur choix entre les deux possibilités. Le troisième axe de recherche est consacré à la méthode de Détection Collective (CD), une innovation qui fait l’acquisition simultanée de tous les signaux visible par le récepteur. Plusieurs analyses sont réalisées incluant l’amélioration de la procédure de recherche de la CD, et l’hybridisation avec l’acquisition standard. Enfin on effectuel’analyse de la CD dans un contexte multi-constellation, en utilisant simultanément des vrais signaux GPS et GalileoSatellite navigation (GNSS) is a constant in our days. The number of applications that depend on it is already remarkable and is constantly increasing. With new applications, new challenges have also risen: much of the new demand for signals comes from urban areas where GNSS signal processing is highly complex. In this thesis the issue of weak GNSS signal processing is addressed, in particular at the first phase of the receiver processing, known as signal acquisition. The first axe of research pursued deals with the analysis and compensation of the Doppler effect in acquisition. The Doppler shift that is experienced by a user is one of the main design drivers for the acquisitionmodule and solutions are proposed to improve the sensitivity-complexity trade-off typical of the acquisition process. The second axe of research deals with the characterization of differential GNSS detectors. After a first step of coherent integration, transition to post coherent (noncoherent or differential) integration is required for acquiring weak signals. The quantification of the sensitivity of differential detectors was not found in literature and is the objective of this part of the research. Finally, the third axe of research is devoted to multi-constellation Collective Detection (CD). CD is an innovative approach for the simultaneous processing of all signals in view. Severalissues related to CD are addressed, including the improvement of the CD search process and the hybridization with standard acquisition. Finally, the application of this methodology in the context of a multi-constellation receiver is also addressed, by processing simultaneously real GPS and Galileo signals
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Gassier, Ghislain. "Contributions au Radar Passif sur Signaux d'Opportunité de Type Télévision Numérique Terrestre." Thesis, Toulon, 2016. http://www.theses.fr/2016TOUL0007/document.
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L’étude traite de la détection de cibles mobiles dans un contexte de radar passif bistatique utilisant les émetteursde télévision numérique TNT (DVB-T) comme émetteurs d’opportunité. Outre leur présence généralisée sur leterritoire, l’intérêt de ces émissions réside dans leur relative largeur de bande permettant une bonne précisiond’estimation. Le principal inconvénient de ce type d’approche réside dans l’éblouissement par le signal en trajetdirect, des échos de très faible intensité des cibles d’intérêt. Après un rappel du principe du radar bistatique etde la norme OFDM utilisée par les signaux TNT, une première étude donne une construction originale du signalde référence dans le cas multi-capteurs : le signal de référence est construit par un traitement d’antenne de typeCAPON où le balayage des paramètres optimaux est remplacé par la connaissance de signaux pilotes inséré dansles symboles OFDM. Ensuite le rapport se focalise sur l’estimation d’un filtre de canal multitrajet à partir dela connaissance de la modulation OFDM utilisée. Ce filtre, d’abord étudié comme réjecteur de fouillis originalavant détection par la fonction d’ambiguïté, donne des résultats semblables aux méthodes classiques de réjectionde fouillis standard. Étendu à toutes les fréquences Doppler, son module au carré est utilisé comme un nouveaudétecteur présentant un très faible niveau de clutter, surpassant ainsi la fonction d’ambiguïté. Une interprétationen terme de traitement d’antennes du nouveau détecteur ouvre la voie à des variantes haute-résolution de celui-ci.La validité du nouveau détecteur est illustrée par des résultats sur données réellesThe study focuses on moving target detection from passive bistatic radar with DVB-T transmitters used asopportunity transmitters. In addition to their widespread geographical coverage, they allow a good estimationaccuracy due to their quite large bandpass. Nevertheless the continuous powerful direct path masks the verylow intensity echoes of targets of interest. The passive bistatic radar principle and the CP-OFDM standardused by DVB-T are briefly reminded, then, a new first study of reference signal retrieving in multiple sensorsconfiguration is given : the reference signal is built using a Capon receptor where the parameters scan is replacedby the knowledge of pilot signals inserted in the OFDM symbols. Next, the report addresses the multipath channelestimate by using the OFDM signal structure. This channel is firstly studied for clutter rejection before detectionfrom the cross ambiguity function (CAF). We obtain similar results than those of the classical rejection methods.This channel is extended to the whole Doppler shift, and its squared modulus acts as a new low clutter detectorthat outperforms classical CAF. A virtual beamforming interpretation of the channel estimation opens a new pathtowards high resolution array processing. Results given on real data illustrate the validity of this new channeldetector (CHAD)
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Maršík, Lukáš. "Algoritmy zpracování signálu v FPGA." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2010. http://www.nusl.cz/ntk/nusl-237152.
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This master's thesis describes ways of signal processing via digital devices. Major field of interest is an analysis of Doppler radar response and then mining of informations about detected object (e.g. speed, movement direction, length, ...). There was realized too little research, that's why borrowing some procedures from different branches not too much related to the IT is necessary. In case of using very complex methods that are easy to parallel, hardware implementation on the FPGA is supposed. With transceiver there is created a very powerful on-line system able to process most of tasks real-time. Then processed and transformed data are sent to the output so visualization and display can be made.
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Raszka, Aleš. "Klasifikace vozidel s použitím radaru." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2017. http://www.nusl.cz/ntk/nusl-363896.
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This Master thesis deals with usage of radar signal for vehicle classification. The thesis uses radar modules with continuous wave based on Doppler effect. Radar signal is processed by a series of signal processing method finished by Fourier transform. Data produced by FFT is used to create SVM and AdaBoost classifier which can be used to classify vehicles into groups.
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Keenan, Desmond Barry. "Enhanced signal processing of pulsed doppler ultrasound." Thesis, University of Ulster, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342411.
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Cirineo, Tony. "Doppler Video Signal Conditioning, Theory of Operation." International Foundation for Telemetering, 1996. http://hdl.handle.net/10150/611417.
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International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, CaliforniaThis paper describes some of the signal conditioning and processing circuits that were developed to reconstruct the doppler video signal from a radar receiver under test. The reconstructed doppler video signal is then digitized and put into a telemetry frame for transmission to a ground receiving station.
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Girault, Jean-Marc. "Apport des techniques du traitement du signal à l'analyse et détection de signaux emboliques." Tours, 1999. http://www.theses.fr/1999TOUR4024.
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Depuis quelques années, la surveillance de pathologies vasculaires suscite un intérêt grandissant en raison notamment du nombre important d'accidents vasculaires cérébraux recensés. De nos jours, les algorithmes implémentés dans les appareils du commerce (tcd), bien qu'adaptés à la détection d'emboles (caillot de sang), ne permettent pas une détection correcte des micro-emboles. Aussi nous nous proposons de développer, dans ce travail, des outils capables de détecter de façon fiable les signaux micro-emboliques. Dans ce travail nous proposons deux estimateurs temporels de fréquence instantanée du signal doppler pour mesurer par exemple le degré de sténose artérielle : l'un base sur la mesure de la longueur euclidienne permet une estimation rapide mais sommaire, l'autre fondee sur un modele paramétrique évolutif récursif permet quant à lui une estimation précise. Dans la seconde partie de ce travail, en assimilant un micro-embole a un globule rouge de grande taille, nous transposons les connaissances relatives aux signaux doppler sanguins a celles relatives aux signaux micro-emboliques. Nous proposons deux méthodes de détection de ruptures de modèles : l'une est fondée sur un test de blancheur, l'autre est basée sur la dérivée de paramètres. Après avoir défini une mesure du degré de fiabilité, nous validons les méthodes de détection proposées a partir de signaux simules et de signaux in vitro et in vivo. Enfin nous montrons que les performances des détecteurs paramétriques sont de loin les meilleurs en termes de probabilités de fausse alarme et de non-détection. Ces résultats prometteurs nous laissent penser que ces détecteurs paramétriques, implémentes sur des appareils du commerce, devraient permettre de mettre en évidence des micro-emboles de très faibles tailles et des phénomènes actuellement difficiles a identifier tels que les agrégats.
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Erk, Patrick P. (Patrick Peter). "Digital signal processing techniques for laser-doppler anemometry." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/43026.
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Biard, Mathieu. "Analyse du signal Doppler et instrumentation : étude et caractérisation d'emboles." Université de Tours. UFR de médecine, 2005. http://www.theses.fr/2005TOUR3309.
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Keeton, Paul Ivan John. "Modern digital signal processing techniques applied to Doppler ultrasound." Thesis, University of Leicester, 1997. http://hdl.handle.net/2381/30188.
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Doppler ultrasound is used clinically to detect stenosis in the carotid artery. The presence of stenosis may be identified by disturbed flow patterns distal to the stenosis which cause spectral broadening in the spectrum of the Doppler signal around peak systole. This thesis investigates the ability of the short-time Fourier transform (STFT) and the autoregressive (AR) spectral estimators to perform time-frequency analysis of the non-stationary Doppler signal. Quantitative analysis of the degree of spectral broadening was measured using the spectral broadening index (SBI). A real-time system was developed using a modern DSP board combined with an IBM PC-compatible computer to analyse the Doppler signal in real-time using the STFT and AR algorithms. The spectral estimators were compared using simulated Doppler spectra contaminated with noise over a range of signal-to-noise ratios (SNRs) and also real clinical Doppler signals recorded from both healthy subjects and patients with varying degrees of stenosis. The SBI was calculated using the mean and maximum frequency envelopes which were extracted from the STFT and AR sonograms using a threshold at -6 dB of the maximum component of each individual spectrum. The results of the analysis shows a strong correlation between the indices calculated using the FFT and AR algorithms. A qualitative improvement in both the appearance of the AR sonograms and the shape of the individual AR spectra was noticeable, however, the estimation of SBI for short data frames is not significantly improved using AR. The final section of this thesis describes the wavelet transform (WT) and illustrates its application to Doppler ultrasound with two examples. Firstly, it is shown how wavelets can be used as an alternative to the STFT for the extraction of the time-frequency distribution of Doppler ultrasound signals. Secondly, wavelet-based adaptive filtering is implemented for the extraction of maximum blood velocity envelopes in the post processing of Doppler signals.
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Bailey, Eric Stanton. "Sparse Frequency Laser Radar Signal Modeling and Doppler Processing." University of Dayton / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1271937372.
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Halimi, Abderrahim. "De l'altimétrie conventionnelle à l'altimétrie SAR/Doppler." Phd thesis, Institut National Polytechnique de Toulouse - INPT, 2013. http://tel.archives-ouvertes.fr/tel-00951973.
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Depuis plus de vingt ans, les altimètres classiques comme Topex, Poseidon-2 ou Poséidon-3, ont fourni des formes d'onde qui sont utilisées pour estimer de nombreux paramètres tels que la distance entre le satellite et la scène observée, la hauteur des vagues et la vitesse du vent. L'amélioration de la qualité des paramètres altimétriques a nécessité le développement de plusieurs modèles d'échos et d'algorithmes d'estimation paramétrique. Par ailleurs, un grand effort est récemment dédié au traitement des échos côtiers afin d'analyser les mesures altimétriques le plus près possible des côtes. Cette thèse s'intéresse à la résolution de ces deux problèmes, à savoir, le traitement des formes d'onde côtières et l'amélioration de la qualité des paramètres océaniques estimés. La première partie de l'étude traite le problème des formes d'onde côtières en proposant un nouveau modèle altimétrique tenant compte de la présence éventuelle d'un pic sur l'écho altimétrique. Dans la seconde partie de notre travail, nous nous sommes intéressés à l'étude de l'altimétrie SAR/Doppler. Cette nouvelle technologie vise à réduire le bruit de mesure et à augmenter la résolution le long de la trace par rapport à l'altimétrie conventionnelle. Deux modèles altimétriques ont été développés afin d'estimer les paramètres associés aux échos SAR/Doppler. Ces modèles montrent une nette amélioration de la qualité des paramètres estimés par rapport à l'altimétrie conventionnelle.
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El, Saleous Nazmi. "Étude et réalisation d'un traitement de signal pour cinémomètre Doppler." Lille 1, 1990. http://www.theses.fr/1990LIL10164.
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Nous avons réalisé le traitement du signal d'un cinémomètre à effet doppler permettant d'obtenir la vitesse, le sens de marche et la distance parcourue par des véhicules terrestres. Notre travail a surtout été orienté vers les applications ferroviaires dans le cadre du projet ASTREE de la SNCF. Dans une première partie, nous présentons les aspects particuliers de l'effet doppler obtenu par rétrodiffusion, les relations mathématiques nous permettant d'obtenir les différentes grandeurs recherchées et les limites physiques du procédé. Dans une deuxième partie, nous détaillons, tant sur le plan matériel que logiciel le dispositif de traitement de signal associé à la tête hyperfréquence produisant l'information doppler. Dans une troisième partie, nous présentons les résultats de deux campagnes d'essais dont l'une, de 2400 km, est effectuée dans la voiture d'essais ARIANE, attelée à un convoi régulier sur la ligne Paris-Le Havre.
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Thouvenin, Indira. "Analyse spectrale adaptative du signal doppler en vélocimétrie sanguine ultrasonore." Paris 6, 1989. http://www.theses.fr/1989PA066364.
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L'analyse spectrale du signal doppler est effectuee generalement par transformee de fourier rapide. Ce procede est insuffisant tant sur le plan de la resolution frequentielle que sur celui de la variance de l'estimation. C'est pourquoi nous avons developpe une nouvelle methode d'analyse spectrale parametrique fondee sur une modelisation autoregressive par un filtre d'ordre eleve. L'estimation des parametres du modele est obtenue par minimisation d'un critere des moindre carres regularises. Nous conservons, contrairement aux auteurs qui s'interessent a ce genre de methodes, l'infirmation sur le sens de l'ecoulement sanguin en traitant directement le signal doppler demodule (forme i et q). L'imperatif du calcul en ligne nous a conduit a utiliser un filtre de kalman rapide. L'ajustement de l'a priori sur les donnees se fait par maximum de vraisemblance. Sur un signal test, notre methode est superieure a la transformee de fourier pour des fenetres courtes (1,6 ms), et equivalente sur des fenetres moyennes (12,8 ms) en ce qui concerne la definition et la variance de l'estimation. L'interet de notre methode est son fonctionnement en temps reel ce qui doit permettre de l'inserer dans un systeme de velocimetrie doppler courant. Les premiers resultats obtenus in vitro, puis in vivo montrent qu'elle peut apporter une aide au diagnostique medical.
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Venter, Christian Jacobus. "Software-defined pulse-doppler radar signal processing on graphics processors." Diss., University of Pretoria, 2014. http://hdl.handle.net/2263/43276.
Full textAbstract:
Modern pulse-Doppler radars use digital receivers with high speed ADCs and sophisticated radar signal
processors that necessitate high data rates, computationally intensive processing, and strict latency
requirements. Data-independent processing is performed as the first stage and requires the highest
data and computational rates of between 1 Gigaops to 1 Teraops, traditionally reserved for specialized
circuits that typically employ restrictive fixed-point arithmetic. The first stage generally requires FIR
filters, correlation, Fourier transforms, and matrix-vector algebra on multi-dimensional data, which
provides a range of demanding and interesting computational challenges, and that present ample opportunities
for parallel processing. Modern many-core GPUs provide general-purpose computation
on the GPU (GPGPU) for high-performance computing applications through fully programmable
pipelines, high memory bandwidths of up to hundreds of Gigabytes per second and high floatingpoint
computational performance of up to several Teraflops on a single chip. The massively-parallel
GPU architecture is well-suited for intrinsically parallel applications that require high dynamic range,
such as radar signal processing. However, numerous factors have to be considered in order to realize
the massive performance potential through a conventionally unfamiliar stream-programming
paradigm. Explicit control is also granted over a deep memory hierarchy and parallelism at various
granularities within an optimization space that is considered non-linear in many respects. The aim of this research is to address and characterize the challenges and intricacies of using modern
GPUs with GPGPU capabilities for the computationally demanding software-defined pulse-Doppler
radar signal processing application. A single receiver-element, coherent pulse-Doppler system with
a two-dimensional data storage model was assumed, due to widespread use and the interesting challenges
and opportunities that it provides for parallel implementation on the GPU architecture. The
NVIDIA Tesla C1060 GPU and CUDA were selected as a suitable GPGPU platform for the implementation
using single-precision floating-point arithmetic. A set of microbenchmarks was first
developed to isolate and highlight fundamental traits and relevant features of the GPU architecture, in
order to determine their impact in the radar application context. The common digital pulse compression
(DPC), corner turning (CT), Doppler filtering (DF), envelope (ENV) and constant false-alarm
rate (CFAR) processing functions were then implemented and optimized for the GPU architecture.
Multiple algorithmic variants were implemented, where appropriate, to evaluate the efficiency of different
algorithmic structures on the GPU architecture. These functions were then integrated to form
a radar signal processing chain, which allowed for further holistic optimization under realistic conditions.
An experimental framework and simple analytical framework was developed and utilized for
analyzing low-level kernel performance and high-level system performance for individual functions
and the processing chain.
The microbenchmark results highlighted the severity of uncoalesced device memory access as well as
the importance of high arithmetic intensity to achieve high computational throughput, and an asymmetry
in performance for primitive math operations. Further, the microbenchmark results showed
that memory transfer performance for small buffers or effectively small radar bursts is fundamentally
poor, but also that memory transfer can be efficiently overlapped with computation, reducing the impact
of slow transfers in general. For the DPC and DF functions, the FFT-based variants using the
CUFFT library proved optimal. For the CT function, the use of shared memory is vital to achieve fully
coalesced transfers, and the lesser-known, but potentially highly detrimental, partition camping effect
needs to be addressed. For the CFAR function, the segmentation into separate processing stages for
rows and columns proved the most vital overall optimization. The ENV function along with several
simple GPU helper-kernels with low arithmetic intensity such as padding, scaling, and the window
function were found to be bandwidth-limited, as expected, and hence performs comparably to a pure
copy kernel. Based on the findings, pulse-Doppler radar signal processing on GPUs is highly feasible
for medium to large burst sizes, provided that the main performance contributors and detractors for
the target GPU architecture is well understood and adhered to.Dissertation (MEng)--University of Pretoria, 2014.
lk2014
Electrical, Electronic and Computer Engineering
MEng
Unrestricted
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Geladakis, Dimitrios N. "Comparison of the step frequency radar with the conventional constant frequency radars." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1996. http://handle.dtic.mil/100.2/ADA328272.
Full textAbstract:
Thesis (M.S. in Electrical Engineering) Naval Postgraduate School, December 1996."December 1996." Thesis advisor(s): Gurnam S. Gill. Includes bibliographical references (p. 45). Also available online.
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Murphy, Charuwan. "Signal processing of Doppler ultrasound for the measurement of blood flow." Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386872.
Full text
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O’Cull, Douglas. "Applications of a Telemetry Signal Simulator." International Foundation for Telemetering, 1996. http://hdl.handle.net/10150/607636.
Full textAbstract:
International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, CaliforniaThis paper will discuss the use of a specialized telemetry signal simulator for pre-mission verification of a telemetry receiving system. This will include how to configure tests that will determine system performance under “real time” conditions such as multipath fading and Doppler shifting. The paper will analyze a telemetry receiving system and define tests for each part of the system. This will include tests for verification of the antenna system. Also included, will be tests for verification of the receiver/combiner system. The paper will further discuss how adding PCM simulation capabilities to the signal simulator will allow testing of frame synchronizers and decomutation equipment.
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Hallermeyer, Alexandre. "Traitement du Signal d’un LIDAR Doppler scannant dédié à la surveillance aéroportuaire." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLC007/document.
Full textAbstract:
Un algorithme permettant d’estimer précisément les paramètres des tourbillons de sillage (positions et circulations) en utilisant les données spectrales fournies par un LIDAR a été développé. Il s’articule en 3 grandes étapes : La première permet de détecter la présence de tourbillon et d’en faire une localisation grossière grâce à la méthode des enveloppes de vitesses. La seconde étape a pour but d’affiner l’estimation des positions des tourbillons en utilisant une optimisation du critère des moindres carrés. Cette étape permet également de faire une première estimation de la circulation des tourbillons. La troisième et dernière étape se concentre sur l’estimation des circulations des tourbillons en maximisant le critère de vraisemblance. Les estimations sont de plus en plus fines et se concentrent au fur et à mesure sur les paramètres les plus critiques. La mise au point de cet algorithme a nécessité d’utiliser plusieurs modèles (LIDAR, tourbillons de sillage, atmosphère) et de formuler un certain nombre d’hypothèses et approximations simplificatrices afin d’atteindre un coût calculatoire raisonnable. L’algorithme proposé a ensuite fait l’objet d’une évaluation de performances, l’intérêt étant porté sur la robustesse par rapport aux différents bruits altérant la mesure, en particulier celui lié à la turbulence atmosphérique et par rapport aux erreurs de modèle. Cette évaluation a été menée à la fois sur des données simulées à l’aide de modèles paramétriques simplifiés, et sur des données de simulations aux grandes échelles.Les paramètres instrumentaux du LIDAR constituent de potentiels degrés de liberté pour améliorer les performances de l’estimateur, en particulier pour les grandeurs les plus critiques, c’est-à-dire les valeurs de circulation. Le calcul des performances de l’estimateur nécessitant un coût de calcul non négligeable, il se prête mal à des fins d’optimisation. C’est pourquoi une étude de l’influence des paramètres du LIDAR sur la Borne de Cramér-Rao (BCR) a été menée. Cette étude a permis de mieux comprendre l’influence des paramètres instrumentaux et d’aboutir à une configuration optimale pour la BCRAn algorithm was developed to estimate precisely wake vortices parameters (positions and circulations) using spectral data provided by a LIDAR. It is articulated in 3 main stages: The first one allows to detect the presence of vortices and to make a rough localization thanks to the method of the velocity envelopes. The second step is to refine the estimation of vortex positions using an optimization of the least squares criterion. This step also permits to make an first estimation of the vortices circulation. The third and final step focuses on estimating vortex circulations by maximizing the likelihood criterion. Estimates are becoming finer and more focused on the most critical parameters. The development of this algorithm required the use of several models (LIDAR, wake vortices, atmosphere) and to formulate a number of simplifying assumptions in order to reach a reasonable computational cost. The proposed algorithm was then subjected to a performance evaluation, the interest being focused on the robustness with respect to the different noises altering the measurement, particularly the one related to the atmospheric turbulence, and with respect to the model errors. This evaluation was carried out both on simulated data using simplified parametric models, and on Large Eddy Simulations.The instrumental parameters of LIDAR are potential degrees of freedom to improve the performance of the estimator, in particular for the most critical quantities, that is to say the circulation values. The calculation of the performance of the estimator requiring a significant computational cost, it lends itself poorly for optimization purposes. This is why a study of the influence of the LIDAR parameters on the Cramér-Rao Bound (CRB) was carried out. This study allowed to understand the influence of the instrumental parameters and to reach an optimal configuration for the CRB
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Galtier, Frédéric. "Contribution a l'estimation frequentielle de signaux en anemometrie laser doppler." Toulouse 3, 1997. http://www.theses.fr/1997TOU30199.
Full textAbstract:
Un anemoclinometre doppler embarque peut fournir des mesures fiables et precises de la vitesse d'un avion et servir a apprehender le domaine de vol. Dans un tel systeme, deux faisceaux laser interferent au voisinage de l'avion. On cree ainsi un volume de mesure constitue de franges de lumiere claires et obscures equidistantes. Un aerosol le traversant reflechira ou non de la lumiere en accord avec l'alternance des franges. Le courant delivre par un photodetecteur consiste en une sinusoide a enveloppe gaussienne. L'enveloppe et la phase transportent toutes deux l'information vitesse. L'amplitude est representative de la particule. Au chapitre 1, en etudiant le systeme optique, on definit le modele original du signal a traiter. On montre les particularites du probleme. La seconde partie etudie la precision ultime des estimations possible avec un tel modele. On presente les bornes de rao-cramer sur les parametres estimes. Des formules approximees des bornes approfondissent l'influence des parametres. On developpe et presente alors l'estimateur par maximum de vraisemblance ainsi que sa version simplifiee. Le chapitre 3 s'occupe d'un estimateur de frequence fonde sur la phase de la correlation. Bien que plus simple que le mle, son analyse theorique en demontre l'efficacite statistique. On envisage egalement diverses autres techniques d'estimation spectrale plus classiques mais moins performantes. Notre but final est de reussir a deceler la presence effective d'une particule dans le volume de mesure afin d'en mesurer la vitesse. La quatrieme partie propose une methode de detection/estimation du signal utile. On en verifie les performances et analyse les avantages par rapport a d'autres techniques sous-optimales. Enfin, on valide les differentes methodes par leurs applications a des signaux reels issus d'un essai en vol. On detaille leurs performances en s'attachant a la precision de mesure atteinte et a la possibilite d'implantation en temps-reel.