Global ETD Search

11	Quantization Effects Analysis on Phase Noise and Implementation of ALL Digital Phase Locked-Loop Shen, Jue January 2011 (has links) With the advancement of CMOS process and fabrication, it has been a trend to maximize digital design while minimize analog correspondents in mixed-signal system designs. So is the case for PLL. PLL has always been a traditional mixed-signal system limited by analog part performance. Around 2000, there emerged ADPLL of which all the blocks besides oscillator are implemented in digital circuits. There have been successful examples in application of Bluetooth, and it is moving to improve results for application of WiMax and ad-hoc frequency hopping communication link. Based on the theoretic and measurement results of existing materials, ADPLL has shown advantages such as fast time-to-market, low area, low cost and better system integration; but it also showed disadvantages in frequency resolution and phase noise, etc. Also this new topic still opens questions in many researching points important to PLL such as tracking behavior and quantization effect. In this thesis, a non-linear phase domain model for all digital phase-locked loop (ADPLL) was established and validated. Based on that, we analyzed that ADPLL phase noise prediction derived from traditional linear quantization model became inaccurate in non-linear cases because its probability density of quantization error did not meet the premise assumption of linear model. The phenomena of bandwidth expansion and in-band phase noise decreasing peculiar to integer-N ADPLL were demonstrated and explained by matlab and verilog behavior level simulation test bench. The expression of threshold quantization step was defined and derived as the method to distinguish whether an integer-N ADPLL was in non-linear cases or not, and the results conformed to those of matlab simulation. A simplified approximation model for non-linear integer-N ADPLL with noise sources was established to predict in-band phase noise, and the trends of the results conformed to those of matlab simulation. Other basic analysis serving for the conclusions above covered: ADPLL loop dynamics, traditional linear theory and its quantitative limitations and numerical analysis of random number. Finally, a present measurement setup was demonstrated and the results were analyzed for future work.
12	Airport noise in South Africa – Prediction models and their effect on land-use planning Goldschagg, Paul 12 1900 (has links) Thesis (DPhil (Geography and Environmental Studies))—University of Stellenbosch, 2007. / The use of average energy aircraft noise contours as the sole means for guiding aircraft noise-based planning around airports is being questioned increasingly. A growing proportion of residents who live in neighbourhoods adjacent to airports are dissatisfied with the averaging procedure that is employed. In their experience of exposure to aircraft noise, particularly in the evening and at night when they are at home, the average energy aircraft noise descriptors are misleading. In order to effectively analyse the socio-spatial interaction of annoyance at and interference by aircraft noise, an alternative approach has been suggested – a supplemental noise perspective. Conventional approaches to aircraft noise land use planning based on average energy noise descriptors run the risk of being ineffectual, or even counterproductive, because they do not consider the central aspects of disturbance, namely the loudness of an event and the number of times events are heard. Consequently, an alternative measure to ameliorate the limitations of average energy noise contours is needed by which airport neighbours, the aviation industry and town planners can better understand the nature of the problem. Although supplemental noise analysis is not new, this study applies it to a South African international airport (OR Tambo) for the first time. The airport’s operations are typical of many busy airports close to large urban areas, serving domestic, regional and international routes. Reportedly, there have been few complaints about noise emanating from the airport, but when they are made they are usually about evening and night-time aircraft noise events. In the context of South Africa as a developing society in transition, where growth of urban settlements continues apace, average energy aircraft noise information must be enhanced by providing supplemental noise information. This study investigated the broad issue of land use planning around airports by employing two aircraft noise prediction models, namely the Integrated Noise Model and the Transparent Noise Information Package, to establish the various potential effects and consequences of night-time aircraft noise in noise zones demarcated according to supplemental aircraft noise information. The effects and consequences examined include annoyance, disturbance of sleep, telephone conversations, watching television and work or study, and the likelihood that people will move away to escape night-time aircraft noise. The perceptions of residents living in neighbourhoods around the airport were surveyed and the responses analysed according to noise zones classified as supplemental noise information. The results show that the airport’s neighbours are annoyed by aircraft noise and that aircraft noise interferes with normal household activities. This annoyance and interference decreases with increasing distance from the airport. Furthermore, reported annoyance and interference is greater in those areas where higher numbers of noise events are encountered, even at relatively low noise levels of 60 LAmax – something not evident from average energy noise contours. This finding strengthens the argument that it is insufficient to provide only average energy aircraft noise information when studying the impact of aircraft noise. To understand the situation more fully, supplemental noise information is essential. The study concludes with a framework constructed to apply supplemental aircraft noise information to the abatement and mitigation measures normally used to deal with aircraft noise. Airport noise Aircraft noise Aircraft noise annoyance/interference Aircraft noise descriptors Average energy noise contours Integrated Noise Model Johannesburg International Airport Land use planning Noise abatement/mitigation Noise zones
13	Characterization of Flow Induced Noise Received by an Array Placed at Stagnation Point of an Underwater Axisymmetric Body Krishna Kumar, G V January 2017 (has links) (PDF) Given the interest on underwater axisymmetric cylindrical bodies for the development of high-speed underwater weapons, characterization of the boundary layer flow-induced noise received by a Sound NAvigation and Ranging (SONAR) is very important to improve sonar detection ranges. The debate on generating mechanisms of the flow induced noise received at the stagnation point is still on as there is no experimental evidence conclusively suggesting whether it is a near-field or far-field phenomenon, thereby introducing an element of uncertainty in the prediction models. Further, the models developed thus far were based on low Reynolds numbers involving flows in water tunnels and buoyant vehicles. Therefore, the main focus of the thesis is to measure the flow induced noise using a sonar fitted at the most forward stagnation point of an underwater axisymmetric body as realistically as possible and predict the same theoretically for identifying a suitable flow noise model for future use by designers. In order to meet the stated goal, two exclusive experiments were conducted at sea using an underwater autonomous high-speed axisymmetric vehicle fitted with a planar hydrophone array (8X8) in its nose cone which measured the flow noise signature. Two different sets of existing models are used in characterizing the flow noise received by the array, while the first set comprises of models developed based on the Turbulent Boundary Layer induced noise and other is based on the transition zone radiated noise model. Through this study, it was found that the transition zone radiated noise model is in close agreement with the measured data. High Speed Underwater Weapons Hydrodynamic Noise Sea Flow Noise Measurement Transition Zone Induced Noise Boumdary Layer Noise SONARs (Sound NAvigation and Ranging) Sound NAvigation and Ranging (SONAR) Transition Zone Radiated Noise Model Mechanical Engineering
14	Model based pulse shaping for detection of gamma rays Ödmark, Fredrik January 2017 (has links) To analyse drill samples in a mine, a scanner that uses a gamma ray detector can be used. The scanner can analyse the drill sample to quickly see the elements present in the sample without destroying it. To improve the performance of the scanner, the electric signal from the detector needs to be less noisy, and different pulse shaping methods, filters and smoothers can be used on the sampled data to achieve an improved performance. In this master thesis, the electric noise model of the electronics around the detector was modeled, and analysed. Different pulse shaping method, filters and smoothers was also tested to see which method gave the best performance in FWHM sense. The Full Width at Half Maximum (FWHM) is the energy resolution of a detector, and is defined as the full width of a photopeak at the half maximum. The noise model of the schematic for the preamplifier was made by hand with support from MATLAB. The resulting noise model was compared between MATLAB and LTspice, and the conclusion is that the JFET is the main contributor of the significant noise, contributing to 98 % of the total noise at 10 GHz. The adopted filters and pulse shaping method are, matched filter, custom filter, CR-RC shaping, mean filter, median filter and clustering. The results from the tests indicated that custom filter with a FWHM of 1.96 keV and CR-RC with a FWHM of 1.67 keV shaping were more accurate than the matched filter with the FWHM of 5.1 keV. But the results also showed that it is important to take into account the waveform variance, due to inherent properties in the detector, with this consideration the FWHM of CR-RC shaper was improved from 2.29 keV to 1.67 keV. The clustering method was the most promising method but due to time constraints this method was never fully tested and no FWHM value was achieved. pulse shaping FWHM CR-RC electric noise model analyse drill samples gamma ray detector matched filter custom filter clustering Annan elektroteknik och elektronik Signal Processing Signalbehandling
15	Grandes d´eviations de matrices aléatoires et équation de Fokker-Planck libre / Large deviations of random matrices and free Fokker-Planck equation Groux, Benjamin 09 December 2016 (has links) Cette thèse s'inscrit dans le domaine des probabilités et des statistiques, et plus précisément des matrices aléatoires. Dans la première partie, on étudie les grandes déviations de la mesure spectrale de matrices de covariance $XX^$, où $X$ est une matrice aléatoire rectangulaire à coefficients i.i.d. ayant une queue de probabilité en $exp(-at^{alpha})$, $alpha in ]0,2[$. On établit un principe de grandes déviations analogue à celui de Bordenave et Caputo, de vitesse $n^{1+alpha/2}$ et de fonction de taux explicite faisant intervenir la convolution libre rectangulaire. La démonstration repose sur un résultat de quantification de la liberté asymptotique dans le modèle information-plus-bruit. La seconde partie de cette thèse est consacrée à l'étude du comportement en temps long de la solution de l'équation de Fokker-Planck libre en présence du potentiel quartique $V(x) = frac14 x^4 + frac{c}{2} x^2$ avec $c ge -2$. On montre que quand $t to +infty$, la solution $mu_t$ de cette équation aux dérivées partielles converge en distance de Wasserstein vers la mesure d'équilibre associée au potentiel $V$. Ce résultat fournit un premier exemple de convergence en temps long de la solution de l'équation des milieux granulaires en présence d'un potentiel non convexe et d'une interaction logarithmique. Sa démonstration utilise notamment des techniques de probabilités libres. / This thesis lies within the field of probability and statistics, and more precisely of random matrix theory. In the first part, we study the large deviations of the spectral measure of covariance matrices XX, where X is a rectangular random matrix with i.i.d. coefficients having a probability tail like $exp(-at^{alpha})$, $alpha in (0,2)$. We establish a large deviation principle similar to Bordenave and Caputo's one, with speed $n^{1+alpha/2}$ and explicit rate function involving rectangular free convolution. The proof relies on a quantification result of asymptotic freeness in the information-plus-noise model. The second part of this thesis is devoted to the study of the long-time behaviour of the solution to free Fokker-Planck equation in the setting of the quartic potential $V(x) = frac14 x^4 + frac{c}{2} x^2$ with $c ge -2$. We prove that when $t to +infty$, the solution $mu_t$ to this partial differential equation converge in Wasserstein distance towards the equilibrium measure associated to the potential $V$. This result provides a first example of long-time convergence for the solution of granular media equation with a non-convex potential and a logarithmic interaction. Its proof involves in particular free probability techniques. Matrices aléatoires Grandes déviations Modèle information-Plus-Bruit Probabilités libres Equation de Fokker-Planck Convergence en temps long Relation de subordination Équation des milieux granulaires, Mesure d’équilibre Random matrices Large deviations Information-Plus-Noise model Free probability Fokker-Planck equation Long-Time convergence Subordination property Granular media equation Equilibrium measure 512.7
16	Error Sensor Placement for Active Control of an Axial Cooling Fan Shafer, Benjamin M. 24 October 2007 (has links) (PDF) Recent experimental achievements in active noise control (ANC) for cooling fans have used near-field error sensors whose locations are determined according to a theoretical condition of minimized sound power. A theoretical point source model, based on the condition previously stated, reveals the location of near-field pressure nulls that may be used to optimize error sensor placement. The actual locations of these near-field pressure nulls for both an axial cooling fan and a monopole loudspeaker were measured over a two-dimensional grid with a linear array of microphones. The achieved global attenuation for each case is measured over a hemisphere located in the acoustic far field of the ANC system. The experimental results are compared to the theoretical pressure null locations in order to determine the efficacy of the point source model. The results closely matched the point source model with a loudspeaker as the primary source, and the sound power reduction was greatly reduced when error sensors were placed in non-ideal locations. A weakness of the current near-field modeling process is that a point monopole source is used to characterize the acoustic noise from an axial cooling fan, which may have multipole characteristics. A more complete characterization of fan noise may be obtained using a procedure based on the work of Martin and Roure [J. Sound Vib. 201 (5), 577--593 (1997)]. Pressure values are obtained over a hemisphere in the far field of a primary source and the contributions from point source distributions up to the second order, centered at the primary source, may be calculated using a multipole expansion. The source information is then used in the aforementioned theoretical near-field calculation of pressure. The error sensors are positioned using the complete fan characterization. The global far-field attenuation for the multipole expansion model of fan noise is compared to that of previous experiments. Results show that the multipole expansion model yields a more accurate representation the near field, but is not successful in achieving greater sound power reductions in the far field. fan cooling fan cooling fans fans axial fan axial fans axial cooling fan fan noise fan noise control active noise control ANC active control fan noise modeling fan noise model error sensor error sensor placement near field near-field pressure near-field error sensor near-field error sensors pressure mapping multipole multipole expansion spherical harmonics multipoles Astrophysics and Astronomy Physics
17	Evaluation of Target Tracking Using Multiple Sensors and Non-Causal Algorithms Vestin, Albin, Strandberg, Gustav January 2019 (has links) Today, the main research field for the automotive industry is to find solutions for active safety. In order to perceive the surrounding environment, tracking nearby traffic objects plays an important role. Validation of the tracking performance is often done in staged traffic scenarios, where additional sensors, mounted on the vehicles, are used to obtain their true positions and velocities. The difficulty of evaluating the tracking performance complicates its development. An alternative approach studied in this thesis, is to record sequences and use non-causal algorithms, such as smoothing, instead of filtering to estimate the true target states. With this method, validation data for online, causal, target tracking algorithms can be obtained for all traffic scenarios without the need of extra sensors. We investigate how non-causal algorithms affects the target tracking performance using multiple sensors and dynamic models of different complexity. This is done to evaluate real-time methods against estimates obtained from non-causal filtering. Two different measurement units, a monocular camera and a LIDAR sensor, and two dynamic models are evaluated and compared using both causal and non-causal methods. The system is tested in two single object scenarios where ground truth is available and in three multi object scenarios without ground truth. Results from the two single object scenarios shows that tracking using only a monocular camera performs poorly since it is unable to measure the distance to objects. Here, a complementary LIDAR sensor improves the tracking performance significantly. The dynamic models are shown to have a small impact on the tracking performance, while the non-causal application gives a distinct improvement when tracking objects at large distances. Since the sequence can be reversed, the non-causal estimates are propagated from more certain states when the target is closer to the ego vehicle. For multiple object tracking, we find that correct associations between measurements and tracks are crucial for improving the tracking performance with non-causal algorithms. evaluation target tracking multiple sensors non-causal smoother smoothing tracking vehicle tracking camera lidar estimate estimation prediction vehicle dynamics sensor fusion real-time tracking extended kalman filter filter validation validation position estimation velocity estimation dynamic model model complexity multi object tracking multiple object tracking single object tracking data association tracking fundamentals iterated kalman filter track management gnn global nearest neighbour mahalanobis mahalanobis distance performance evaluation differential gps dgps roi ego several sensors sensors rmse root mean square error invertible motion anti-causal motion anti-causal tracking constant velocity gnn imu tfs two filter smoother ekf rts radar inertial measurement unit nonlinear nonlinear systems mono camera monocular camera noise model tracking performance fixed interval smoothing m/n logic centralized fusion non-causal object tracker car tracking car dynamics automotive active safety object tracking automotive industry thesis master reverse dynamics reverse tracking reverse sequence sequence tracking data propagation ground truth estimating ground truth additional sensors mounted sensors true estimates environment comparison algorithm independent targets overlapping measurements occluded track switch improve lower uncertainty more certain state process noise covariance sampling image sprt adas cnn cv pdf track target ego tracker tentative track observatiom online tracking offline tracking online offline recorded sequences robust self driving self-driving car traffic trajectory true state scenario scenarios future accurate output advanced driver assistance systems non-linear complex noise pedestrian truck bus maneuvering vehicles processed measurement frame state correction probability density function tuning likelihood transition measurement motion model recursion gaussian approximation distribution linear jacobian multiplicative noise ratio ad hoc ad hoc state space approach backward auction euclidean distance statistical threshold gating association margin normalize covariance matrix fusion confirmed rejected tentative history absolute error modular ego motion parameters variables logg hardware specification fused causal factorization independent uncorrelated transform moving rotation translation oncoming overtaking Control Engineering Reglerteknik

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