Tesi sul tema "Signal to noise ratio"
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1
Pauluzzi, David Renato. "Signal-to-noise ratio and signal-to-impairment ratio estimation in AWGN and wireless channels". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq22377.pdf.
Testo completo
2
Hamid, Syamsul Bahrin Abdul. "Enhancing signal to noise ratio for electrostatic transducers". Thesis, University of Strathclyde, 2013. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=24250.
Testo completoAbstract (sommario):
This Thesis describes the design, manufacture and evaluation of a Fluidically Amplified Ultrasonic Transducer (FLAUT) for an air-coupled application. The transducer utilises a pipe as an amplification mechanism to increase the output pressure; and as a dissipation mechanism to reduce inherent noise within the transducer. The new transducer design introduces the concept of matched thin plate, cavity and pipe, of which the individual geometry enhances one another. Design methodologies, which consist of analytical modelling and Finite Element (FE) Modelling, have been implemented. The analytical modelling identifies the required geometry for the FLAUT based on the desired operating resonant frequency; while FE then verifies the vibrational characteristics of the design. Through the application of FE modelling and practical analysis, FLAUT devices have been designed, developed and compared with experiment. The sensitivity analysis is utilised to realise a design and manufacturing tolerance requirements. The devices were manufactured in the operating range of 25 kHz to 85 kHz. Air-coupled pulse-echo insertion loss was found to be 61.3 dB, an improvement of 9.1 dB over the conventional cavity only design. Results from the proof of concept prototype indicate that the output of the FLAUT is maximised when the pipe radius is designed to be as large as practically possible while maintaining the matched resonant frequencies. This correlates well with theory both in term of sensitivity and noise. Furthermore, the pressure output of a FLAUT array is maximised by arranging the cell spacing to be as close as practically possible. Thus, the cells were spaced at multiples of 2.25 to the cavity radius – to reduce the risk of cell damage. An analytical method to simulate, and a technique to measure the inherent noise using a specially designed hybrid isolation vessel has been developed. From the measurement, the FLAUT noise is found to be 5.8 W, an improvement of 2.7 dB compared to the conventional cavity only design.
3
Armstrong, Juliane. "Random inter stimulus interval increases signal-to-noise ratio". Digital Commons @ East Tennessee State University, 2012. https://dc.etsu.edu/honors/29.
Testo completoAbstract (sommario):
Incremental improvements are continuously being made to P300-Speller BCI paradigms. Accurate classification depends on a high signal-to-noise ratio (SNR) between the target and nontarget items. Fixed presentation rates produce a large flash-evoked response that persists throughout the recording epoch, which can potentially undermine the classification of P300-responses. By introducing a random interstimulus interval (ISI) to a previously improved P300-Speller paradigm (i.e., Checkerboard Paradigm; CBP) we expect to reduce the deleterious flash-evoked responses and increase the P300 classification SNR. Data were recorded from 32 EEG locations (right mastoid referenced) from 13 subjects using the CBP with two conditions. In the Random ISI (RI) condition, ISI varied between 0 ms and 187.5 ms and averaged 93.75 ms. In the Fixed ISI (SI) condition, ISI remained static at 93.75 ms. In both conditions, participants were instructed to spell out 72 characters using an 8x9 matrix of alphanumeric characters by silently counting each target flash. The first 36 characters served as ‘calibration’ data for a stepwise linear discriminant analysis (SWLDA; 0 - 800 ms poststimulus epochs). This SWLDA classifier was then used to provide online feedback for an additional 36 character selections. Absolute amplitude of target and nontarget responses were summed across the recording epoch for each subject and averaged between Pz and Cz (maximum). Target averages were then divided by nontarget averages to create a SNR measure and compared between RI and FI conditions. The RI manipulation produced a significantly (p = .04) larger SNR (M = 5.85) than the FI condition (M =4.07).Further analysis of the averaged waveforms revealed a significantly (p = .05) greater positive peak at Cz (253 ms peak latency) for the RI condition. Classification performance measures for RI and FI conditions were high for accuracy (84 and 85%, respectively; NS) and bitrate (21 and 23 bits/min, respectively; NS). Together these results suggest that while randomizing ISI can yield higher SNR, response classification is not affected. It is possible that SWLDA is a useful classification method, in general; however, these data suggest that it does not capitalize on the additional information gained from the increase in SNR. Alternative classification techniques that can take advantage of specific subcomponents of the response may be able to utilize this additional information to improve BCI speed and accuracy.
4
Cheng, Lui. "Improvement of signal-to-noise ratio in uterine EMG recordings". Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969.1/1548.
Testo completoAbstract (sommario):
The objective of this study is to remove or, at least, reduce the noise in uterine EMG recordings, which at their present noise level render the data unusable. Predicting when true labor will start and recognizing when labor actually starts are important for both normal and complex pregnancies. For normal pregnancy, the prognosis of labor is important for reducing unnecessary hospital costs. About 10% of the four million babies born each year in the United States are born prematurely. At $1,500 a day for neonatal intensive care, this comprises national health care expenses of well over $5 billion. Spectral analysis, filter design, and 1/3 octave analysis were applied to analyze the uterine EMG recordings. Signal-to-noise ratio was increased with IIR Butterworth bandstop filter. The spectral band between 0.25 and 0.4 Hz shows matching of the Toco belt via spectral analysis. Nevertheless, 1/3 octave analysis gives the highest correct detection percentage compare with frequency analysis and filter design.
5
Cheraghi, Parisa. "Fast and accurate spectrum sensing low signal noise ratio environment". Thesis, University of Surrey, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.581799.
Testo completoAbstract (sommario):
Opportunistic Spectrum Access (OSA) [1] promises tremendous gain in improving spectral efficiency. The main objective of OSA is to offer the ability of identifying and exploiting the under-utilised spectrum in an instantaneous manner in a wireless device, without any user intrusion. Hence, the initial requirement of any OSA device is the ability to perform spectrum sensing. Local narrow-band spectrum sensing has been quite well investigated in the literature. However, it is realised that existing schemes can hardly meet the requirements of a fast and accurate spectrum sensing particulariy in very low signal-to-noise-ratio (SNR) range without introducing high complexity to the system. Furthermore, increase in the spectrum utilisation calls for spectrum sensing techniques that adopt an architecture to simultaneously search over multiple frequency sub-bands at a time. However, the literature of sub-band spectrum sensing is rather limited at this time. The main contributions of this thesis is two-fold: First a clusterd-based differential energy detection for local sensing of multi- carrier based system is proposed. The proposed approach can form fast and reliable decision of spectrum availability even in very low SNR environment. The underlying initiative of the proposed scheme is applying order statistics on the clustered differential Energy Spectral Density (ESD) in order to exploit the channel frequency diversity inherent in high data-rate communications. Second contribution is three-fold: 1) re-defining the objective of the sub- band level spectrum sensing device to a model estimator, 2) deriving the optimal model selection estimator for sub-band level spectrum sensing for fixed and variable number of users along with a sub-optimal solution based on Bayesian statistical modelling and 3) proposing a practical model selection estimator with relaxed sample size constraint and limited system knowledge for sub-band spectrum sensing applications in Orthogonal Frequency-Division Multiple Access (OFDMA) systems. The result obtained showed that through exploitation of the channel frequency selectivity the performance of the stat-of-the-art spectrum sensing techniques can be significantly improved. Furthermore, by modelling the sub-band level spectrum sensing through model estimation allows for new spectrum sensing approach. It was proved both analytically and through simulations that the proposed approach have significantly extended to state-of-the-art spectrum sensing. Key words: Differential, energy detection, low signal-to- noise ratio (SNR), multi- carrier, opportunistic spectrum access, spectrum sensing.
6
Koul, Ashish 1979. "Use of intermicrophone correlation in estimating signal to noise ratio". Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29672.
Testo completoAbstract (sommario):
Thesis (M.Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.Includes bibliographical references (leaf 42).
This thesis presents the design, analysis, and simulation of a system that uses the correlation coefficient of audio inputs gathered at two spatially separate microphones to determine the signal to noise ratio in the environment. This work is motivated by past research in microphone array hearing aids, where accurate estimates of SNR were shown to improve performance. Signal to noise ratio is defined as the ratio of energy in the direct component (audio sources originating in front of a broadside array) to energy in the interference component (sources originating from the sides of the array). The design presented is a simple hypothesis testing mechanism for determining whether the SNR exceeds a fixed level. In the analysis, behavior of the system is studied theoretically under varying conditions of reverberation in the environment, and processing parameters are determined to optimize system performance. Finally, simulations test the true performance of the system to verify the validity of the theoretical analysis.
by Ashish Koul.
M.Eng.and S.B.
7
Liu, Janet (Janet Kay) 1976. "Determining signal-to-noise ratio in a burst coherent demodulator". Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/80142.
Testo completoAbstract (sommario):
Thesis (S.B. and M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.Includes bibliographical references (leaves 59-60).
by Janet Liu.
S.B.and M.Eng.
8
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.
Testo completo
9
Aldokhail, Abdullah M. "Automated Signal to Noise Ratio Analysis for Magnetic Resonance Imaging Using a Noise Distribution Model". University of Toledo Health Science Campus / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=mco1469557255.
Testo completo
10
Lie, Chin Cheong Patrick. "Iterative algorithms for fast, signal-to-noise ratio insensitive image restoration". Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63767.
Testo completo
11
Siddhichai, Supakorn. "Algorithms and structures for noise robust blind image deconvolution". Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248791.
Testo completo
12
Haboosheh, Ronette. "Diagnostic auditory brainstem response analysis : evaluation of signal-to-noise ratio criteria using signal detection theory". Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/31575.
Testo completoAbstract (sommario):
This study evaluated an online measure of signal-to-noise ratio (SNR) as a response-detection tool for threshold auditory brainstem response (ABR) testing. Threshold-ABR data were analysed for 98 infants and young children tested at BC Children's Hospital, and results were validated on an additional 10 patients. Using signal detection theory, it was possible to assess test performance for the SNR measure, with expert-clinician judgement as the gold standard. In addition, a range of SNR criteria were assessed in terms of sensitivity (the ability to accurately identify a response) and specificity (the ability to accurately reject waveforms that do not contain a response). The effect of residual noise (RN) exclusion criteria on SNR test performance, sensitivity, and specificity was also investigated. Waveforms to 500-, 2000-, and 4000-Hz air-conducted brief-tone stimuli were included in this study. Overall, SNR was found to have a test performance of A=.91, with improved performance (A=.93) when high residual-noise waveforms (RN>0.08 μV) were excluded. When low-RN data were separated by frequency, test performance for each frequency was A=.94. Results suggest that the optimal SNR criterion is slightly lower for 500-Hz recordings than for 2000- or 4000-Hz recordings. However, when high-RN recordings were excluded, a SNR criterion of 0.98 achieved a minimum specificity of 95% for each stimulus frequency, with sensitivity values ranging from 64%(for 500 Hz) to 79% (for 4000 Hz). Findings confirm the hypotheses that SNR accurately distinguishes response-present from response-absent waveform, and that quiet recordings are more easily interpreted than noisy recordings using SNR. Guidelines are provided for the clinical use of SNR as an objective response-detection tool.Medicine, Faculty of
Audiology and Speech Sciences, School of
Graduate
13
Fan, Yun-Hui. "A stereo audio coder with a nearly constant signal-to-noise ratio". Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/14788.
Testo completo
14
Anzaloni, Alessandro. "Frame Synchronization in Digital Burst Telecommand at Low Signal to Noise Ratio". International Foundation for Telemetering, 1989. http://hdl.handle.net/10150/614676.
Testo completoAbstract (sommario):
International Telemetering Conference Proceedings / October 30-November 02, 1989 / Town & Country Hotel & Convention Center, San Diego, CaliforniaFrame synchronization was extensively studied usually supposing that the bit pattern to acquire frame synchronization was imbedded in sequences of random bits. In this paper, the determination of a bit pattern for frame synchronization in digital burst telecommand at low signal to noise ratio is investigated, considering the a priori knowledgement of a bit pattern for bit synchronization and the format of the frame. The a priori knowledgement of a bit pattern for bit synchronization is used to find a bit sequence that minimize the false probability to acquire frame synchronization. A simple strategy using the aperture technique is stablished. An engineering model is used to find experimentally the mean probability of true synchronization after one burst. This initial research to find a bit pattern for frame synchronization presented good results.
15
Anzaloni, Alessandro, e de Almeida José Carlos Juliano. "FRAME SYNCHRONIZATION IN DIGITAL BURST TELECOMMAND AT LOW SIGNAL TO NOISE RATIO". International Foundation for Telemetering, 1989. http://hdl.handle.net/10150/615211.
Testo completoAbstract (sommario):
International Telemetering Conference Proceedings / October 30-November 02, 1989 / Town & Country Hotel & Convention Center, San Diego, CaliforniaFrame synchronization was extensively studied usually supposing that the bit pattern to acquire frame synchronization was imbeded in sequences of random bits. In this paper, the determination of a bit pattern for frame synchronization in digital burst telecommand at low signal to noise ratio is investigated, considering the a priori knowledgement of a bit pattern for bit synchronization and the format of the frame. The a priori knowledgement of a bit pattern for bit synchronization is used to find a bit sequence that minimize the false probability to acquire frame synchronization. A simple strategy using the aperture technique is stablished. An egineering model is used to find experimentally the mean probability of true synchronization after one burst. This initial research to find a bit pattern for frame synchronization presented good results.
16
Crotty, Maureen. "Signal to Noise Ratio Effects on Aperture Synthesis for Digital Holographic Ladar". University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1355245759.
Testo completo
17
Hurley, Sean M. "Signal-to-noise ratio gains and synchronization requirements of a distributed radar network". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2006. http://library.nps.navy.mil/uhtbin/hyperion/06Jun%5FHurley.pdf.
Testo completoAbstract (sommario):
Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, June 2006.Thesis Advisor(s): Murali Tummala, Phillip E. Pace. "June 2006." Includes bibliographical references (p. 59-60). Also available in print.
18
Nayak, Aravind Ratnakar. "Iterative Timing Recovery for Magnetic Recording Channels with Low Signal-to-Noise Ratio". Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5018.
Testo completoAbstract (sommario):
Digital communication systems invariably employ an underlying analog communication channel. At the transmitter, data is modulated to obtain an analog waveform which is input to the channel. At the receiver, the output of the channel needs to be mapped back into the discrete domain. To this effect, the continuous-time received waveform is sampled at instants chosen by the timing recovery block. Therefore, timing recovery is an essential component of digital communication systems.
A widely used timing recovery method is based on a phase-locked loop (PLL), which updates its timing estimates based on a decision-directed device. Timing recovery performance is a strong function of the reliability of decisions, and hence, of the channel signal-to-noise ratio (SNR). Iteratively decodable error-control codes (ECCs) like turbo codes and LDPC codes allow operation at SNRs lower than ever before, thus exacerbating timing recovery.
We propose iterative timing recovery, where the timing recovery block, the equalizer and the ECC decoder exchange information, giving the timing recovery block access to decisions that are much more reliable than the instantaneous ones. This provides significant SNR gains at a marginal complexity penalty over a conventional turbo equalizer where the equalizer and the ECC decoder exchange information. We also derive the Cramer-Rao bound, which is a lower bound on the estimation error variance of any timing estimator, and propose timing recovery methods that outperform the conventional PLL and achieve the Cramer-Rao bound in some cases.
At low SNR, timing recovery suffers from cycle slips, where the receiver drops or adds one or more symbols, and consequently, almost always the ECC decoder fails to decode. Iterative timing recovery has the ability to corrects cycle slips. To reduce the number of iterations, we propose cycle slip detection and correction methods. With iterative timing recovery, the PLL with cycle slip detection and correction recovers most of the SNR loss of the conventional receiver that separates timing recovery and turbo equalization.
19
Kakade, Rohan. "Improved resolution and signal-to-noise ratio performance of a confocal fluorescence microscope". Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/33699/.
Testo completoAbstract (sommario):
A culmination of theory, techniques and devices stemming from a wide variety of sources and disciplines, optical microscopy presents vast possibilities for visualisation of small structures. One of the most fundamental yet significant optical microscopy techniques is Confocal Fluorescence Microscopy (CFM). CFM is studied here by analysing its performance with respect to the two most important metrics - Signal-to-noise ratio and 3D optical resolution. Several authors have commented on the inherent inefficiency of imaging systems such as CFM to utilise the available light when providing resolution beyond the well-known diffraction limit, primarily due to the precise mechanisms that help realise the resolution gain in the first place. In CFM, the detection pinhole is the key mechanism that helps realise up to 1.4 times resolution improvement over conventional wide-field microscopy techniques by trading off SNR. First, an investigation of the inherent SNR-resolution trade-off in a CFM system is studied; the impact of the detection pinhole geometry on the performance of a CFM is examined by means of an effective trade-off curve. Using alternative pinhole geometries in conjunction with new detection schemes, it is next shown how performance gains are realised in both the lateral and axial directions. Examined next is a recently developed detection scheme called subtractive imaging; wherein a special annular pinhole is used to divide the confocal point spread function signal into two detectors. By using fast point detectors in place of CCD arrays, it is shown how using numerical optimisation yields an optimum “differential pinhole” to achieve considerable 3D resolution gains over conventional (circular pinhole based) CFM systems. By examining the trade-off curves it is also shown that the proposed design is able to offer simultaneous and maximum performance gains up to a considerably high SNR in comparison to conventional (circular pinhole) based CFM systems. Lastly, the work will propose the use of a deconvolution technique and an alternative detection scheme to demonstrate substantially higher improvements in the quality of images acquired by a CFM system. Image reconstruction is a tried and tested image post processing strategy to realise super resolution. An image reconstruction technique, based on an expectation maximisation maximum likelihood (EM-ML) algorithm is used in conjunction with array detectors to demonstrate enhanced resolution and noise performance of a CFM system. The point scan method used here renders the algorithm slow with long run times. To mitigate this, structured illumination is used to show how similar resolution gains in the array detector based CFM systems could be realised but in a much shorter time.
20
Tsuda, Hirofumi. "Study on Communication System From the Perspective of Improving Signal-to-Noise Ratio". Kyoto University, 2019. http://hdl.handle.net/2433/242440.
Testo completo
21
Miller, Matthew P. "Strategies to increase the signal to noise ratio in three-dimensional positron emission tomography". Thesis, University of Surrey, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322456.
Testo completoAbstract (sommario):
Positron Emission Tomography (PET) is an imaging technique that uses biologically relevant molecules labelled with positron emitting radioisotopes to measure regional tissue function in living organisms. To maximise the detection efficiency, data are acquired in 3D, that is, all possible detector combinations in a scanner without inter-ring shielding (septa). The gain in sensitivity afforded by 3D PET is offset by the increase in random coincidences, scattered coincidences and deadtime. These problems must be overcome for the gain in sensitivity to be fully realised. The aim of this research project was to investigate strategies to increase the signal to noise ratio of the 3D PET data. Additional side shielding, both in neuro and body scanning, has been implemented and assessed. Large gains were achieved using the neuro shields in experimental and clinical studies. The potential of the body shields was tested in experimental and in-vivo studies which showed that they were scan dependent. For example, no gain was found for a cardiac blood flow (H2 IS0) study. A model-based scatter correction was assessed by companng compartment ratios within the 'Utah' phantom with radioactivity outside the field of view, with and without neuroshielding. Recovered ratios were within 6% of their actual values. The integration time was reduced in an effort to decrease the system deadtime. A peak increase of 150/0 in noise equivalent count rate was measured for a uniform cylinder inside the field of view. A random coincidence variance reduction technique was implemented and assessed to reduce the noise contained in the delayed window random coincidence estimate. The algorithm was evaluated using phantoms and tested on clinical data. A mean 16% reduction in coefficient of variation was measured for a C15O torso study.
22
Walsh, Norman J. "Bandwidth and signal-to-noise ratio enhancement of the NPS Transient Electromagnetic Scattering Laboratory". Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/25710.
Testo completo
23
Mookherjea, Shayan 1977. "Optical distribution networks : signal-to-noise ratio optimization and distributed erbium-doped fiber amplifiers". Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/9087.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2000.Includes bibliographical references (leaves [149]-151) and index.
Two important issues related to the use of remotely-pumped erbium-doped fiber amplifiers in optical distribution networks are analyzed. We investigate the optimal allocation of gain and loss among the stages of a lumped amplifier chain, using the concepts of a Nash solution and Pareto optimality. The propagation of optical channels along an erbium-doped fiber is derived from basic physical considerations, and compared with the well-known Desurvire model. We demonstrate a simple method of constructing bus distribution networks, but this approach is particularly sensitive to the numerical values of the parameters. A second approach is then discussed, extending the analysis of Sun et al. from ab-initio principles to model the effect of detectors (users) along a distribution network. Theoretical closed-form results indicate that the number of optical receivers that can be supported using this scheme is at least two orders of magnitude higher than without optical amplification. Finally, we analyze the effect of dynamic perturbations in the power that is extracted at the receivers. Though our focus is on bus networks, we also discuss tree distribution networks as extensions of the basic models. Our results have implications on the architecture of optical distribution networks.
by Shayan Mookherjea.
S.M.
24
Bokulic, Robert S. "SIGNAL-TO-NOISE RATIO PERFORMANCE OF THE SAWTOOTH PHASE DETECTOR WHEN DEMODULATING PM SUBCARRIERS". International Foundation for Telemetering, 1986. http://hdl.handle.net/10150/615560.
Testo completoAbstract (sommario):
International Telemetering Conference Proceedings / October 13-16, 1986 / Riviera Hotel, Las Vegas, NevadaThe noise performance of the sawtooth phase detector when demodulating a sinusoidal subcarrier plus direct data modulation is studied. At predetection signal-to-noise ratio (SNR) levels of about 10 dB or more, significant improvements in the postdetection SNR of the subcarrier can be obtained using the sawtooth detector rather than a linear multiplier. Below predetection SNR levels of about 10 dB, significant improvements can still be obtained; however, a threshold occurs and the performance degrades until leveling off at 3.2 dB worse than that of a linear multiplier. The predetection SNR level where the sawtooth detector performance becomes worse than that of a linear multiplier depends upon the subcarrier and direct data modulation indices. Performance curves are given between predetection SNR levels of -20 dB and +20 dB for various values of subcarrier modulation index and direct data modulation index.
25
Grant, Andrew G. "The performance of orthogonal frequency division multiplexing in a high noise, low signal-to-noise ratio environment with cochannel interference /". Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Dec%5FGrant.pdf.
Testo completo
26
Grant, Andrew G. "Performance of orthogonal frequency division multiplexing in a high noise, low signal-to-noise ratio environment with co-channel interference". Thesis, Monterey, California. Naval Postgraduate School, 2005. http://hdl.handle.net/10945/1782.
Testo completoAbstract (sommario):
Orthogonal Frequency Division Multiplexing (OFDM) is fast becoming the signal modulation technique of choice for many commercial and military wireless applications. Its resilience to cochannel interference and bandwidth efficiency make it ideal for many different applications. With its increasing popularity among disparate facets of society, it becomes likelier that enemy militaries and/or nonmilitary combatants will utilize the technique or a system that uses the technique. In light of this development, the need to develop techniques and algorithms to enable detection becomes apparent. This thesis will attempt to develop a model for OFDM and measure its performance in a multipath, outdoor environment with low signal-to-noise ratio, high noise and cochannel interference. Because of the unpredictability of the outdoor environment and the proliferation of various OFDM standards, the simulation will utilize only one algorithm for modeling outdoor environments and the IEEE 802.11a standard.
27
Sciré, Scappuzzo Francesca. "Phase multipath estimation for global positioning system (GPS) using signal-to-noise-ratio (SNR) data". Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/45487.
Testo completoAbstract (sommario):
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1997.Includes bibliographical references (p. 83-87).
by Francesca Scrié Scappuzzo.
M.S.
28
Burmeister, Brian. "Cue estimation for vowel perception prediction in low signal-to-noise ratios". Diss., Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-05132009-151828/.
Testo completo
29
Abdullah, Mohammad Faiz Liew. "Techniques for signal to noise ratio adaptation in infared optical wireless for optimisation of receiver performance". Thesis, University of Warwick, 2006. http://wrap.warwick.ac.uk/2450/.
Testo completoAbstract (sommario):
The challenge of creating a new environment of links for wireless infrared and optical local area networks (LANs) is driving new innovations in the design of optical transceivers. This thesis is concerned with a systematic approach to the design of receivers for indoor optical wireless communication. In particular, it is concerned with how to offer bandwidth adjustment capability in a receiver according to the dynamic service quality of the incoming signals. Another part of the discussion of the thesis is how one can properly choose the front-end preamplifier and biasing circuitry for the photodetector. Also, comparison is made between different types of amplifier, and the methods of bandwidth enhancement. The designs of six different techniques of integrating transimpedance amplifiers, with photodetectors to adapt an adjustable bandwidth control receiver are discussed. The proposed topologies provide an adjustable range of bandwidths for different frequency ranges, typically between 52Hz to 115MHz. The composite technique designs were used to incorporate into a system with an automatic gain control to study its effect, on an optical wireless receiver which had bandwidth adjustment and automatic gain adjustment. Theoretical analysis of noise performance for all the designed circuits is also presented. The theory and design of obstacles of indoor optical wireless receiver delivery, in addition to techniques for mitigating these effects, are discussed. This shows that infrared is a viable alternative to ratio for certain applications.
30
Watkins, Gregory Douglas. "Speech Intelligibility Prediction for Cochlear Implant Recipients: An investigation of the Output Signal to Noise Ratio". Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/22909.
Testo completoAbstract (sommario):
Cochlear implants (CI) can achieve excellent hearing outcomes for people with severe or profound hearing loss. However, outcomes vary significantly, and hearing in noise is challenging. Evaluation of new sound processing ideas with recipient testing is a lengthy process. A metric which reliably predicted CI speech intelligibility would allow more sound processing ideas and parameter sets to be evaluated. Prediction for normal hearing people has been extensively investigated but CIs have received little attention. In this thesis, it was hypothesised that an extended Output Signal to Noise Ratio (OSNR) metric would be a reliable predictor of individual CI speech intelligibility. A series of retrospective CI experiments found i. OSNR was sensitive to changes in a range of test parameters, including Input Signal to Noise Ratio (ISNR), presentation level, noise type, and processing algorithms. ii. OSNR predicted mean speech scores for a group of recipients at least as accurately as other tested metrics. Being calculated at the sound processor output OSNR predicted scores in scenarios where other metrics could not. iii. A novel method, combining OSNR and test scores from a reference condition, predicted psychometric functions for individual CI recipients relatively accurately in many other conditions. Small differences in performance between test and reference conditions were accurately predicted. OSNR was not accurate in the presence of aggressive spectral masking. The feasibility of combining OSNR and Output Speech Power as an accurate predictor in this scenario was demonstrated. The author is not aware of any published works which predict psychometric functions for individual CI recipients listening to speech processed by novel algorithms, using scores from a separate, reference condition. Overall, there was considerable support for the hypothesis that OSNR was an accurate predictor. OSNR shows promise as a metric with research and clinical applications.
31
Constable, Christopher. "Investigation of the Effects of Image Signal-to-Noise Ratio on TSPO PET Quantification of Neuroinflammation". Thesis, The University of Sydney, 2013. http://hdl.handle.net/2123/9341.
Testo completoAbstract (sommario):
Neuroinflammation may be imaged using positron emission tomography (PET) and the tracer [11C]-PK11195. Accurate and precise quantification of 18 kilodalton Translocator Protein (TSPO) binding parameters in the brain has proven difficult with this tracer, due to an unfavourable combination of low target concentration in tissue, low brain uptake of the tracer and relatively high non-specific binding, all of which leads to higher levels of relative image noise. To address these limitations, research into new radioligands for the TSPO, with higher brain uptake and lower non-specific binding relative to [11C]-PK11195, is being conducted world-wide. However, factors other than radioligand properties are known to influence signal-to-noise ratio in quantitative PET studies, including the scanner sensitivity, image reconstruction algorithms and data analysis methodology. The aim of this thesis was to investigate and validate computational tools for predicting image noise in dynamic TSPO PET studies, and to employ those tools to investigate the factors that affect image SNR and reliability of TSPO quantification in the human brain. The feasibility of performing multiple (n≥40) independent Monte Carlo simulations for each dynamic [11C]-PK11195 frame- with realistic modelling of the radioactivity source, attenuation and PET tomograph geometries- was investigated. A Beowulf-type high performance computer cluster, constructed from commodity components, was found to be well suited to this task. Timing tests on a single desktop computer system indicated that a computer cluster capable of simulating an hour-long dynamic [11C]-PK11195 PET scan, with 40 independent repeats, and with a total simulation time of less than 6 weeks, could be constructed for less than 10,000 Australian dollars. A computer cluster containing 44 computing cores was therefore assembled, and a peak simulation rate of 2.84x105 photon pairs per second was achieved using the GEANT4 Application for Tomographic Emission (GATE) Monte Carlo simulation software. A simulated PET tomograph was developed in GATE that closely modelled the performance characteristics of several real-world clinical PET systems in terms of spatial resolution, sensitivity, scatter fraction and counting rate performance. The simulated PET system was validated using adaptations of the National Electrical Manufacturers Association (NEMA) quality assurance procedures within GATE. Image noise in dynamic TSPO PET scans was estimated by performing n=40 independent Monte Carlo simulations of an hour-long [11C]-PK11195 scan, and of an hour- long dynamic scan for a hypothetical TSPO ligand with double the brain activity concentration of [11C]-PK11195. From these data an analytical noise model was developed that allowed image noise to be predicted for any combination of brain tissue activity concentration and scan duration. The noise model was validated for the purpose of determining the precision of kinetic parameter estimates for TSPO PET. An investigation was made into the effects of activity concentration in tissue, radionuclide half-life, injected dose and compartmental model complexity on the reproducibility of kinetic parameters. Injecting 555 MBq of carbon-11 labelled TSPO tracer produced similar binding parameter precision to 185 MBq of fluorine-18, and a moderate (20%) reduction in precision was observed for the reduced carbon-11 dose of 370 MBq. Results indicated that a factor of 2 increase in frame count level (relative to [11C]-PK11195, and due for example to higher ligand uptake, injected dose or absolute scanner sensitivity) is required to obtain reliable binding parameter estimates for small regions of interest when fitting a two-tissue compartment, four-parameter compartmental model. However, compartmental model complexity had a similarly large effect, with the reduction of model complexity from the two-tissue compartment, four-parameter to a one-tissue compartment, two-parameter model producing a 78% reduction in coefficient of variation of the binding parameter estimates at each tissue activity level and region size studied. In summary, this thesis describes the development and validation of Monte Carlo methods for estimating image noise in dynamic TSPO PET scans, and analytical methods for predicting relative image noise for a wide range of tissue activity concentration and acquisition durations. The findings of this research suggest that a broader consideration of the kinetic properties of novel TSPO radioligands, with a view to selection of ligands that are potentially amenable to analysis with a simple one-tissue compartment model, is at least as important as efforts directed towards reducing image noise, such as higher brain uptake, in the search for the next generation of TSPO PET tracers.
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Gallupe, Gary. "FM, PM and NPR Calculations". International Foundation for Telemetering, 1993. http://hdl.handle.net/10150/608853.
Testo completoAbstract (sommario):
International Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, NevadaSystem performance can be ascertained via a number of parameters; one of which is Signal-to-Noise ratio (SNR). SNR is the ratio of the value of the signal to the value of the noise. It is generally expressed in decibels and usually a function of the system bandwidth. Another measure of performance is the Noise-Power ratio (NPR). NPR is the ratio of the noise level within a specific measurement channel when noise is applied to all channels, to the level that is measured within the specific channel with noise applied to all of the channels but not the specific channel.
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Dandu, Sai Venkata Satya Siva Kumar, e Sujit Kadimisetti. "2D SPECTRAL SUBTRACTION FOR NOISE SUPPRESSION IN FINGERPRINT IMAGES". Thesis, Blekinge Tekniska Högskola, Institutionen för tillämpad signalbehandling, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-13848.
Testo completoAbstract (sommario):
Human fingerprints are rich in details called the minutiae, which can be used as identification marks for fingerprint verification. To get the details, the fingerprint capturing techniques are to be improved. Since when we the fingerprint is captured, the noise from outside adds to it. The goal of this thesis is to remove the noise present in the fingerprint image. To achieve a good quality fingerprint image, this noise has to be removed or suppressed and here it is done by using an algorithm or technique called ’Spectral Subtraction’, where the algorithm is based on subtraction of estimated noise spectrum from noisy signal spectrum. The performance of the algorithm is assessed by comparing the original fingerprint image and image obtained after spectral subtraction several parameters like PSNR, SSIM and also for different fingerprints on the database. Finally, performance matching was done using NIST matching software, and the obtained results were presented in the form of Receiver Operating Characteristics (ROC)graphs, using MATLAB, and the experimental results were presented.
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Bhattad, Kapil. "Joint source channel coding for non-ergodic channels: the distortion signal-to-noise ratio (SNR) exponent perspective". Texas A&M University, 2008. http://hdl.handle.net/1969.1/85928.
Testo completoAbstract (sommario):
We study the problem of communicating a discrete time analog source over
a channel such that the resulting distortion is minimized. For ergodic channels,
Shannon showed that separate source and channel coding is optimal. In this work we
study this problem for non-ergodic channels.
Although not much can be said about the general problem of transmitting any
analog sources over any non-ergodic channels with any distortion metric, for many
practical problems like video broadcast and voice transmission, we can gain insights
by studying the transmission of a Gaussian source over a wireless channel with mean
square error as the distortion measure. Motivated by different applications, we consider three different non-ergodic channel models - (1) Additive white Gaussian noise
(AWGN) channel whose signal-to-noise ratio (SNR) is unknown at the transmitter; (2)
Rayleigh fading multiple-input multiple-output MIMO channel whose SNR is known
at the transmitter; and (3) Rayleigh fading MIMO channel whose SNR is unknown
at the transmitter.
The traditional approach to study these problems has been to fix certain SNRs
of interest and study the corresponding achievable distortion regions. However, the
problems formulated this way have not been solved even for simple setups like 2
SNRs for the AWGN channel. We are interested in performance over a wide range
of SNR and hence we use the distortion SNR exponent metric to study this problem.
Distortion SNR exponent is defined as the rate of decay of distortion with SNR in the high SNR limit.
We study several layered transmissions schemes where the source is first compressed in layers and then the layers are transmitted using channel codes that provide
variable error protection. Results show that in several cases such layered transmission
schemes are optimal in terms of the distortion SNR exponent. Specifically, if the band-
width expansion (number of channel uses per source sample) is b, we show that the
optimal distortion SNR exponent for the AWGN channel is b and it is achievable using
a superposition based layered scheme. For the L-block Rayleigh fading M x N MIMO
channel the optimal exponent is characterized for b < (|N - M|+1)= min(M;N) and
b > MNL2. This corresponds to the entire range of b when min(M;N) = 1 and
L = 1. The results also show that the exponents obtained using layered schemes
which are a small subclass of joint source channel coding (JSCC) schemes are, surprisingly, as good as and better in some cases than achievable exponent of all other
JSCC schemes reported so far.
35
McDonald, Mark. "Hyperpolarized ¹²§9Xe nuclear magnetic resonance at 1.89 T and 85 G, a signal-to-noise ratio comparison". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ57787.pdf.
Testo completo
36
McDonald, Mark (Mark Christopher) Carleton University Dissertation Physics. "Hyperpolarized 129Xe nuclear magnetic resonance at 1.89 T and 85 G: a signal-to-noise ratio comparison". Ottawa, 2001.
Cerca il testo completo
37
Cooper, Ian Philip. "Coherence as a Measure of Body-Wave Signal to Noise Ratio in the Northeastern United States and Southeastern Canada:". Thesis, Boston College, 2021. http://hdl.handle.net/2345/bc-ir:109210.
Testo completoAbstract (sommario):
Thesis advisor: John E. EbelDetermination of the source parameters of a local earthquake from full seismic waveforms requires seismograms with clear body-wave signals from the earthquake source. Coherence of the earthquake body-wave seismograms recorded at two different receivers can be used to estimate the signal-to-noise ratio (SNR) of the body-wave energy radiated by the source. In this study, the coherence of earthquake body waves recorded in the Northeastern United States and Southeastern Canada (NEUSSEC) is measured as a function of frequency, interstation distance, and ambient SNR, and then used as an estimate of body-wave SNR. Seismograms from the CN, IU, LD, N4, NE, TA, and US arrays were used to measure coherence between stations with a mean separation of 70 km. Seismograms from the Acton Littleton Seismic Array (ALSA) were used to measure coherence at 5 km mean station separation. Coherence is measured at frequencies between 0.05-10 Hz for Pn and Sn phases from NEUSSEC earthquakes with magnitudes (M) between 0.0 and 4.7 at epicentral distances between 180-1800 km as well as at frequencies between 0.05-10 Hz for the first arrivals of P and S waves from earthquakes M>6 at distances >2500 km. The teleseismic P waves display values of coherence greater than 0.9 out to interstation distances of 1500 km at frequencies <0.8 Hz, but as frequency increases, the interstation distance at which coherence falls below 0.9 decreases. Teleseismic S and regional Pn and Sn waves display coherence values around 0.5, suggesting the amplitudes of the body-waves are smaller than those of the noise, which likely is the result of converted and reflected or refracted P waves and/or smaller signal amplitudes. These coherence values are compared to the coherence values of ambient noise. For any two P, S, Pn or Sn waveforms recorded in the NEUSSEC at 3-5 Hz there is a 50% or greater chance of those two waveforms containing coherent energy that is not ambient noise; these frequencies are where this percent chance is greatest for all seismic phases. At frequencies between 3-5 Hz the effects of scattering are most pronounced on the coherence values of regional seismic phases, suggesting that most scattering in the crust of the NEUSSEC takes place at these frequencies. Teleseismic seismic phases do not include as much scattered energy as the regional seismic phases at 3-5 Hz, and must therefore encounter fewer scattering heterogeneities along their travel path than the regional seismic phases
Thesis (MS) — Boston College, 2021
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Earth and Environmental Sciences
38
Wang, Chunsheng. "Numerical study of RF magnetic field, specific absorption rate and signal to noise ratio in high field MRI". Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B36887560.
Testo completo
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Kanekama, Yori. "Effects of speechreading and signal-to-noise ratio on understanding mainstream American English by American and Indian adults". Diss., Wichita State University, 2009. http://hdl.handle.net/10057/2369.
Testo completoAbstract (sommario):
The purpose of this study was to measure effects of speechreading and signal-to-noise
ratio (SNR) on understanding mainstream American English (MAE) heard by 30 Indian adults
compared to 30 American adults. Participants listened to a recording of a female speaker of MAE
saying 10 lists of 10 different Everyday Speech Sentences per list. Participants heard sentences
from a TV loudspeaker at a conversational speech level while a four-talker babble played
through two surrounding loudspeakers at a +6, 0, -6, -12, or -18 dB SNR. Participants heard and
watched a different list of sentences at each SNR (i.e., through the Auditory-Visual modality) and
only heard a different list of sentences at each SNR (i.e., through an Auditory modality). After
listening to each sentence, participants wrote verbatim what they thought the speaker said. Each
participant’s speechreading performance at each SNR was computed as the difference in words
correctly heard through Auditory-Visual versus Auditory modalities. Consistent with most
previous research, American participants benefitted significantly more from speechreading at
poorer SNRs than at favorable SNRs. The novel finding of this study, however, was that Indian
participants benefitted less from speechreading than American participants at poorer SNRs, but
benefitted more from speechreading than American participants at favorable SNRs. Linguistic
(and, possibly, nonlinguistic) variables may have accounted for these findings; including an
increased need for Indian participants to integrate more auditory cues with visual cues to benefit
from speechreading, presumably because they only spoke English as a second language. These
findings have theoretical implications for understanding the role of auditory-visual integration on
cross-language perception of speech, and practical implications for understanding how much
speechreading helps people understand a second language in noisy environments.Thesis (Ph.D.)--Wichita State University, College of Health Professions, Dept. of Communication Sciences and Disorders
40
Hsu, Ken. "Stochastic analysis of lateral resolution and signal-to-noise ratio in fluorescence microscopy : application to structured illumination microscopy". Thesis, University of Nottingham, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.555413.
Testo completoAbstract (sommario):
This thesis investigates ways for assessing the practical lateral resolution performance of imaging systems and explores the trade-off between lateral resolution and signal-to-noise ratio (SNR) in high resolution systems. Several authors have commented on the seemingly inherent inefficiency in which imaging systems use the available light when providing resolution enhancement beyond the Abbe limit, often due to the precise mechanism that enabled the resolution enhancement in the first place. Two methods for assessing the lateral resolution and noise performance of microscope systems were developed in this project: a probabilistic analysis based on two-point resolution which has the novelty of being able to deal with synthetic images and the stochastic transfer function (STF) which looks into the effect of noise in the Fourier domain. Results can be determined semi-analytically or by using Monte- Carlo simulations. These methods were applied to several microscope systems such as conventional widefield fluorescence microscopy (WFM) and structured illumination microscopy (SIM) and used to compare their noise performance. These techniques were also used to compare several post-reconstruction processing algorithms for SIM, showing the strengths and weaknesses of each strategy. SIM encodes high spatial frequency information into a senes of images and uses a reconstruction algorithm to yield a high resolution unage. Without further processing, the STF showed that SIM generates noise that is three times greater than that associated with a conventional fluorescence microscope and based on the two-point resolution analysis, the SIM SNR performance in 2D was only comparable with WFM, even though SIM has twice the theoretical bandwidth. However, the reconstruction processing of SIM introduces many redundancies in the form of overlapping spatial frequency orders which can be exploited to improve the SNR further. The STF showed a transition spatial frequency below which the WFM system outperforms SIM and it was shown that a simple WFM-SIM hybrid algorithm based on this observation can indeed significantly improve the SIM result. Common strategies which provide more complete treatments include the Wiener filter and the weighted- average approach. Based on the assumption of uncorrelated noise and a pre-defined goal transfer function, it was shown that the weighted-average method gives the minimum resultant variance statistically. For SIM, this condition is only met when the maximum fringe spatial frequency allowed by the illumination optics is used and the level of noise correlation increases with decreasing illumination grating frequency. The development of a general standardised metric which includes noise considerations can allow more realistic performance assessments of imaging systems and facilitate comparisons. Along with other considerations, such analysis can help practitioners select the most appropriate system for the intended tasks. Understanding the strength and weakness of existing systems will reveal areas of possible enhancements and also help with the development of new techniques.
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Wang, Chunsheng, e 汪春生. "Numerical study of RF magnetic field, specific absorption rate and signal to noise ratio in high field MRI". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B36887560.
Testo completo
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Sartor, Mark Alan 1960. "Characterization and modeling of microchannel plate intensified charge coupled device signal to noise ratio variations with image size". Thesis, The University of Arizona, 1992. http://hdl.handle.net/10150/278136.
Testo completoAbstract (sommario):
It is a common misconception to consider the intensified charge coupled device (ICCD) to be simply a finite element detector. In reality, one must consider the ICCD as an optical system in and of itself, complete with its own throughput and point spread function. Only in this light can an accurate model for the ICCD performance be developed. Variations in signal to noise ratio (SNR) with image size can have broad implications in the design and modeling of ICCD based systems. Results from an experiment devised to measure the variation of SNR performance with input image size for selected Generation 2 microchannel plate (MCP) ICCD's are presented. Also presented is a generalized theoretical model for ICCD SNR performance for small images.
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Gupta, Amit. "Signal-to-noise-plus-interference ratio estimation and statistics for direct sequence spread spectrum code division multiple access communications". Ohio : Ohio University, 2004. http://www.ohiolink.edu/etd/view.cgi?ohiou1176321495.
Testo completo
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Farquharson, Maree Louise. "Estimating the parameters of polynomial phase signals". Thesis, Queensland University of Technology, 2006. https://eprints.qut.edu.au/16312/1/Maree_Farquharson_Thesis.pdf.
Testo completoAbstract (sommario):
Nonstationary signals are common in many environments such as radar, sonar, bioengineering and power systems. The nonstationary nature of the signals found in these environments means that classicalspectralanalysis techniques are notappropriate for estimating the parameters of these signals. Therefore it is important to develop techniques that can accommodate nonstationary signals. This thesis seeks to achieve this by firstly, modelling each component of the signal as having a polynomial phase and by secondly, developing techniques for estimating the parameters of these components.
Several approaches can be used for estimating the parameters of polynomial phase signals, eachwithvarying degrees ofsuccess.Criteria to consider in potential estimation algorithms are
(i) the signal-to-noise (SNR) ratio threshold of the algorithm, (ii) the amount of computation required for running the algorithm, and (iii) the closeness of the resulting estimates' mean-square errors to the minimum theoretical bound. These criteria will be used to compare the new techniques developed in this thesis with existing techniques.
The literature on polynomial phase signal estimation highlights the recurring trade-off between the accuracy of the estimates and the amount of computation required. For example, the Maximum Likelihood (ML) method provides near-optimal estimates above threshold, but also incurs a heavy computational cost for higher order phase signals. On the other hand, multi-linear techniques such as the high-order ambiguity function (HAF) method require little computation, but have a significantly higher SNR threshold than the ML method.
Of the existing techniques, the cubic phase (CP) function method is a promising technique because it provides an attractive SNR threshold and computational complexity trade-off. For this reason, the analysis techniques developed in this thesis will be derived from the CP function.
A limitation of the CP function is its inability to accurately process phase orders greater than three. Therefore, the first novel contribution to this thesis develops a broadened class of discrete-time higher order phase (HP)functions to address this limitation.This broadened class is achieved by providing a multi-linear extension of the CP function. Monte Carlo simulations are performed to demonstrate the statistical advantage of the HP functions compared to the HAFs. A first order statistical analysis of the HP functions is presented. This analysis verifies the simulation results.
The next novel contribution is a technique called the lower SNR cubic phase function (LCPF)method. It is an extension of the CP function, with the extension enabling performance at lower signal-to-noise ratios (SNRs). The improvement of the SNR threshold's performance is achieved by coherently integrating the CP function over a compact interval in the two-dimensional CP function space. The computation of the new algorithm is quite moderate, especially when compared to the ML method. Above threshold, the LCPF method's parameter estimates are asymptotically efficient. Monte Carlo simulation results are presented and a threshold analysis of the algorithm closely predicts the thresholds observed in these results.
The next original contribution to this research involves extending the LCPF method so that it is able to process multicomponent cubic phase signals and higher order phase signals. The LCPF method is extended to higher orders by applying a windowing technique as opposed to adjusting the order of the kernel as implemented in the HP function method. To demonstrate the extension of the LCPF method for processing higher order phase signals and multicomponent cubic phase signals, some Monte Carlo simulations are presented.
Finally, these estimation techniques are applied to real-worldscenarios in the fields of Power Systems Analysis, Neuroethology and Speech Analysis.
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Farquharson, Maree Louise. "Estimating the parameters of polynomial phase signals". Queensland University of Technology, 2006. http://eprints.qut.edu.au/16312/.
Testo completoAbstract (sommario):
Nonstationary signals are common in many environments such as radar, sonar, bioengineering and power systems. The nonstationary nature of the signals found in these environments means that classicalspectralanalysis techniques are notappropriate for estimating the parameters of these signals. Therefore it is important to develop techniques that can accommodate nonstationary signals. This thesis seeks to achieve this by firstly, modelling each component of the signal as having a polynomial phase and by secondly, developing techniques for estimating the parameters of these components. Several approaches can be used for estimating the parameters of polynomial phase signals, eachwithvarying degrees ofsuccess.Criteria to consider in potential estimation algorithms are (i) the signal-to-noise (SNR) ratio threshold of the algorithm, (ii) the amount of computation required for running the algorithm, and (iii) the closeness of the resulting estimates' mean-square errors to the minimum theoretical bound. These criteria will be used to compare the new techniques developed in this thesis with existing techniques. The literature on polynomial phase signal estimation highlights the recurring trade-off between the accuracy of the estimates and the amount of computation required. For example, the Maximum Likelihood (ML) method provides near-optimal estimates above threshold, but also incurs a heavy computational cost for higher order phase signals. On the other hand, multi-linear techniques such as the high-order ambiguity function (HAF) method require little computation, but have a significantly higher SNR threshold than the ML method. Of the existing techniques, the cubic phase (CP) function method is a promising technique because it provides an attractive SNR threshold and computational complexity trade-off. For this reason, the analysis techniques developed in this thesis will be derived from the CP function. A limitation of the CP function is its inability to accurately process phase orders greater than three. Therefore, the first novel contribution to this thesis develops a broadened class of discrete-time higher order phase (HP)functions to address this limitation.This broadened class is achieved by providing a multi-linear extension of the CP function. Monte Carlo simulations are performed to demonstrate the statistical advantage of the HP functions compared to the HAFs. A first order statistical analysis of the HP functions is presented. This analysis verifies the simulation results. The next novel contribution is a technique called the lower SNR cubic phase function (LCPF)method. It is an extension of the CP function, with the extension enabling performance at lower signal-to-noise ratios (SNRs). The improvement of the SNR threshold's performance is achieved by coherently integrating the CP function over a compact interval in the two-dimensional CP function space. The computation of the new algorithm is quite moderate, especially when compared to the ML method. Above threshold, the LCPF method's parameter estimates are asymptotically efficient. Monte Carlo simulation results are presented and a threshold analysis of the algorithm closely predicts the thresholds observed in these results. The next original contribution to this research involves extending the LCPF method so that it is able to process multicomponent cubic phase signals and higher order phase signals. The LCPF method is extended to higher orders by applying a windowing technique as opposed to adjusting the order of the kernel as implemented in the HP function method. To demonstrate the extension of the LCPF method for processing higher order phase signals and multicomponent cubic phase signals, some Monte Carlo simulations are presented. Finally, these estimation techniques are applied to real-worldscenarios in the fields of Power Systems Analysis, Neuroethology and Speech Analysis.
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Hughes, Colan Evan. "New techniques in NMR spectroscopy". Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297524.
Testo completo
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Sörnmo, Maria, e Julia Lind. "Fixerade elektroders betydelse för mängden uppkomna artefakter vid 24-timmars långtids-elektrokardiografi-registrering". Thesis, Hälsohögskolan, Högskolan i Jönköping, HHJ, Avd. för naturvetenskap och biomedicin, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-30484.
Testo completoAbstract (sommario):
Artefakter försvårar analys av långtids-elektrokardiografi-registrering (LTER) och resulterar i en försämrad diagnostisk säkerhet. Minimering av mängden artefakter spelar således en väsentlig roll för ställandet av rätt diagnos. Syftet med denna studie var att jämföra om mängden artefakter, som uppkom vid 24-timmars LTER på patienter, skiljde sig åt med och utan fixering av elektroderna. Populationen bestod av trettio patienter som var inbokade för 24-timmars LTER vid Länssjukhuset Ryhov i Jönköping. Patienterna delades in i två grupper med femton patienter i varje grupp. På grund av fyra externa bortfall bestod det slutgiltiga urvalet av tretton studiedeltagare i vardera gruppen. I grupp A användes ett tubnät för att hålla kablarna på plats och i grupp B fixerades varje elektrod och kabel med Mefix. Grupperna jämfördes sedan avseende mängden artefakter som uppkom under registreringsperioden. För att analysera om det förelåg någon signifikant skillnad i artefaktuppkomst mellan grupperna användes Wilcoxons rangsummetest. Rangsummorna för respektive grupp beräknades och jämfördes med ett kritiskt intervallvärde. Rangsummorna låg inom intervallet för det kritiska värdet, varpå nollhypotesen ej kan förkastas. Följaktligen förelåg ingen signifikant skillnad i mängden uppkomna artefakter mellan grupperna. På grund av ett litet urval samt brister i undersökningsförfarandet kunde dock inga grundade statistiska slutsatser konkluderas.Artefacts complicate the analysis of long-term electrocardiography-registration (LTER) and result in a worsened diagnostic accuracy. Thus, minimization of the amount of artefacts plays a vital role in the making of a correct diagnosis. The aim of this study was to compare if the amount of artefacts that occurred during 24-hour LTER on patients, differed with and without electrode fixation. Thirty patients who underwent a 24-hour LTER, at Länssjukhuset Ryhov in Jönköping, were included in the study and divided into two groups. In group A; a tubular net bandage was used to keep the electrocardiography (ECG) cables in place. In group B, the electrodes and ECG cables were fixated with Mefix. A comparison was made, between the groups, regarding the amount of artefacts that occurred during the registration period. To analyze if there was a significant difference between the groups, Wilcoxon rank sum test was applied. The result proved to be within the range limits of the critical value, which implies that the null hypothesis cannot be rejected. Hence, there was no significant difference regarding the amount of artefacts that occurred. However, because of a small sample volume and shortfalls in the study procedure, no founded statistical conclusions could be drawn.
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Nallamilli, Sai Chandra Sekhar Reddy, e Nihanth Kandi. "Detection of Human Emotion from Noise Speech". Thesis, Blekinge Tekniska Högskola, Institutionen för tillämpad signalbehandling, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-19610.
Testo completoAbstract (sommario):
Detection of a human emotion from human speech is always a challenging task. Factors like intonation, pitch, and loudness of signal vary from different human voice. So, it's important to know the exact pitch, intonation and loudness of a speech for making it a challenging task for detection. Some voices exhibit high background noise which will affect the amplitude or pitch of the signal. So, knowing the detailed properties of a speech to detect emotion is mandatory. Detection of emotion in humans from speech signals is a recent research field. One of the scenarios where this field has been applied is in situations where the human integrity and security are at risk In this project we are proposing a set of features based on the decomposition signals from discrete wavelet transform to characterize different types of negative emotions such as anger, happy, sad, and desperation. The features are measured in three different conditions: (1) the original speech signals, (2) the signals that are contaminated with noise or are affected by the presence of a phone channel, and (3) the signals that are obtained after processing using an algorithm for Speech Enhancement Transform. According to the results, when the speech enhancement is applied, the detection of emotion in speech is increased and compared to results obtained when the speech signal is highly contaminated with noise. Our objective is to use Artificial neural network because the brain is the most efficient and best machine to recognize speech. The brain is built with some neural network. At the same time, Artificial neural networks are clearly advanced with respect to several features, such as their nonlinearity and high classification capability. If we use Artificial neural networks to evolve the machine or computer that it can detect the emotion. Here we are using feedforward neural network which is suitable for classification process and using sigmoid function as activation function. The detection of human emotion from speech is achieved by training the neural network with features extracted from the speech. To achieve this, we need proper features from the speech. So, we must remove background noise in the speech. We can remove background noise by using filters. wavelet transform is the filtering technique used to remove the background noise and enhance the required features in the speech.
49
Godtmann, Susanne. "Iterative synchronization at low signal-to-noise ratios for wireless communications". Aachen : Shaker, 2009. http://d-nb.info/993288391/04.
Testo completo
50
Tomashevskyi, Roman, Yevhen Vikarii e Zinaida Dotsenko. "System for Recording Evoked Potentials in Liquid Biological Matrix". Thesis, IPM NASU, 2017. http://repository.kpi.kharkov.ua/handle/KhPI-Press/34109.
Testo completoAbstract (sommario):
The article deals with the development and investigation of a system for recording, amplifying and processing weak evoked potentials in liquid biological matrix. The main attention is paid to the study of the parameters of this system.