Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 24 for “"Nyquist rate"”.
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High-Resolution Nyquist -Rate Analog -to -Digital Converter
… error-averaging technique can perform an accurate multiply-by-two (x2) function required in high-resolution pipelined ADCs, while a high gain op-amp has been designed to minimize error due to finite DC gain. Three clock phases are required by the capacitor error-averaging technique (rather …
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An ARM-based sequential sampling oscilloscope
… waveforms with frequencies beyond the Nyquist rate. This thesis documents the prototype of a digital ARM-based sequential sampling oscilloscope with peripheral hardware and software. Discussed are the designs and obstacles of various analog circuits and signal processing methods. By …
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Reconstruction Resolution Of Coherent Point Sources With Helmholtz Equation Least Squares
… spacing must exceed the spacing derived from the Nyquist rate to mitigate the risk of aliasing. HELS is not limited by the Nyquist rate due to its ability to synthesize field and surface points.</p> <p>The resolution capability of HELS is tested through numerical simulation and experimental …
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High-speed infrared video system for detection of thermal aliasing.
… second). Scene events that occur faster than the Nyquist rate (one-half the sampling frequency, or 15 Hz, in this case) result in an effect called aliasing, which gives misleading information about the scene's true temporal content. Decreasing the camera's integration time (analogous to shutter …
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Low Latency Compressive Sensing using Multi-Resolution Analysis In Radar Signal Processing
… speeds and a wider signal bandwidth. The Shannon/Nyquist sampling theorem states, the ADC must sample the signal at a rate two times faster than the signal bandwidth in order to avoid data loss. However, the advances of ADC cannot always meet these demands. Considerable research has been done to …
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Compressive sensing based imaging via belief propagation
… Propagation (BP). The CS technique can accurately recover any compressible or sparse signal from a lesser number of non-adaptive, randomized linear projection samples than that specified by the Nyquist rate. In this work, we demonstrate how CS-based encoding generates measurements from the …
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Pipelined oversampling analog-to-digital converters
… to achieve accuracy that exceeds that of integrated-circuit components. Such converters have an inherent tradeoff between accuracy and speed, whereby resolution in amplitude is achieved at the expense of resolution in time. Although much attention has been focused on improving the speed and …
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Optimized techniques for real-time microwave and millimeter wave SAR imaging
… sampling criteria supports sampling below the Nyquist rate. The results of these studies demonstrate optimum sampling given design requirements that fully explain resolution dependence on sampling criteria. This work was then extended to manually-selected and nonuniformly distributed samples …
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A hardware platform to test analog-to-information conversion and non-uniform sampling
The Nyquist-Shannon sampling theorem tells us that in order to fully recover a band-limited signal previously converted to discrete data points, said signal must have been sampled at a frequency greater than twice its bandwidth. This theorem puts a burden on circuits like ADCs, in the sense that …
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Low-power high-performance SAR ADC with redundancy and digital background calibration
… mismatches, design of new architecture to incorporate redundancy within the architecture itself while achieving 94% better energy eciency compared to conventional switching algorithm, development of a new capacitor DAC structure to improve the SNR by four times with improved matching, joint design …
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Spiral 2D array designs for volumetric imaging
… elements than a periodic grid sampled at the Nyquist rate) based on geometric spiral structures, with the aim to reduce the number of array elements, and therefore transmit-receive channels required to meet a given acoustic specification. The aperiodic structure of these array designs is shown …
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Random observations on random observations: Sparse signal acquisition and processing
… the increasingly high-dimensional raw data generated by modern sensing systems. Despite extraordinary advances in computational power, processing the signals produced in application areas such as imaging, video, remote surveillance, spectroscopy, and genomic data analysis continues to pose a …
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Sampling and quantization for optimal reconstruction
… sinc interpolation. When the average sampling rate is less than the Nyquist rate, i.e., in sub-Nyquist sampling, the artifacts produced when these reconstruction methods are applied to the nonuniform samples can be preferable in certain applications to the aliasing artifacts, which occur in …
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Informative sensing : theory and applications
… random measurement samples, even far below the Nyquist rate. Despite the successful story, we question how the theory would change if we had a more precise prior than the simple sparsity model. Hence, we consider the settings where the prior is encoded as a probability density. In a Bayesian …
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Compressive Sensing Approaches for Sensor based Predictive Analytics in Manufacturing and Service Systems
… as opposed to the traditional sampling strategy following the Shannon Nyquist rate. By CS theory, a signal can be reconstructed from a reduced number of samples, hence, this motivates developing CS based approaches to facilitate predictive analytics using a reduced number of sensors. The …
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Adaptive MIMO Radar for Target Detection, Estimation, and Tracking
… two different antenna configurations: widely-separated: distributed) and colocated. Distributed MIMO radar exploits spatial diversity by utilizing multiple uncorrelated looks at the target. Colocated MIMO radar systems offer performance improvement by exploiting waveform diversity. Each antenna …
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Distortion-optimal parallel MRI with sparse sampling: from adaptive spatio-temporal acquisition to self-calibrating reconstruction
… is a sparse support. We develop a highly-accelerated real-time dynamic MRI technique, dubbed PARADISE, which incorporates a physiologically-driven sparse support model in the joint spatial domain and temporal frequency dimension. The imaging scheme gains its acceleration from: (i) sparsity of …
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Compressive Detection and Estimation with Applications to Cognitive Radio and Radar
According to Nyquist Sampling theorem, a band-limited signal can be reconstructed accurately if the sampling rate exceeds twice the maximum frequency of the signal. In many scenarios, this Nyquist sampling rate cannot be achieved due to hardware limitations. Compressive sensing (CS) is a technique …
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Bridging Mri Reconstruction Across Eras: From Novel Optimization Of Traditional Methods To Efficient Deep Learning Strategies
… scanning, requiring novel techniques to accelerate data acquisition. Such techniques are poised to improve clinical patient throughput, reduce motion artifacts, enhance subject comfort, and allow higher resolution imaging in many applications. Several methods have been proposed to accelerate …
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Source localization via time difference of arrival
Accurate localization of a signal source, based on the signals collected by a number of receiving sensors deployed in the source surrounding area is a problem of interest in various fields. This dissertation aims at exploring different techniques to improve the localization accuracy of …
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