http://hdl.handle.net/1957/7302 Search the Channel search http://ir.library.oregonstate.edu/dspace/simple-search http://hdl.handle.net/1957/8947 Title: Substrate noise coupling in ring oscillator-based phase locked loops <br/> <br/>Abstract: In this thesis, the performance degradation of a phase-locked loop due to substrate noise is examined. A new analytical equivalent circuit model for substrate noise coupling is derived for a heavily doped silicon substrate. The model has been validated with measured data from a 0.35 μm CMOS process. Since the model is physical, it can be used to predict substrate noise coupling without the need for extensive computer simulations using three-dimensional finite difference or Green's function solvers. This is followed by an evaluation of the effect of substrate noise in a PLL. A PLL test chip fabricated in a 0.13 μm CMOS process has been characterized over a wide range of substrate noise frequencies. The measured results combined with extensive simulations provide insight into the mechanisms for noise coupling in a PLL. Based on an understanding of the noise coupling, guidelines for minimizing the impact of substrate noise are presented. <br/> <br/>Description: Graduation date: 2009 http://hdl.handle.net/1957/8935 Title: Digital pulse shape discrimination methods for triple-layer phoswich detectors using wavelets and fuzzy logic <br/> <br/>Abstract: A two-channel data acquisition system for simultaneous detection and discrimination of beta particles and gamma rays has been developed. Each channel measures and analyzes the input pulses resulting from the absorption of radiation in the layers of the detector. The detector is a triple-layer phoswich (phosphor sandwich) scintillation detector followed by a photomultiplier tube (PMT). The PMT amplifies the photons and converts them into an electric signal. The signal is digitized and sent to the host computer for further processing. Two new digital algorithms based on Fuzzy Logic and on the Continuous Wavelet Transform have been developed and are discussed in this thesis. In the first method, a de-noising algorithm based on the Wavelet Transform is implemented to reduce the effect of noise introduced by the analog channel and by the photomultiplier tube. Three new timing features are extracted and given as input to a fuzzy interface system. The main goal of fuzziness in a data set is to reduce the system complexity and to provide a model that allows for approximate results. Compared to the method which was originally implemented for this detector, the fuzzy algorithm shows a better performance in separating beta and gamma spectra, especially at high energies. Also, absorption in multiple layers is detected more efficiently. The second algorithm is based on the Continuous Wavelet Transform. The novelty of this method consists in using scale-domain features. Since the output pulse shape of the photomultiplier tube is a non-stationary signal, conventional Fourier methods are not efficient for analyzing these signals and most of the existing pulse shape discrimination methods use time-domain features. Therefore, a time-frequency space is better suited to analyze these non-stationary signals. This method shows better performance over existing time-domain methods in terms of robustness to noise and reliability. The simultaneous detection of beta particles and gamma rays has several applications (for instance detection of underground nuclear explosions). The methods presented in this thesis could also be used in alpha/beta/neutron/gamma discrimination systems for cancer diagnosis and treatment. <br/> <br/>Description: Graduation date: 2009 http://hdl.handle.net/1957/8932 Title: Power efficient H.264 video decoding in embedded multiprocessor <br/> <br/>Abstract: This thesis presents a novel methodology that enables power efficient video decoding in an embedded system based on MPSoC (Multiprocessor System on Chip). This methodology is a physical combination of parallel processing which reduces power consumption of processors by exploiting thread-level parallelism and Dynamic Voltage Frequency Scaling (DVFS) that allows a processor to dynamically change its speed and voltage at run time. The video decoding process must be well optimized to improve performance continuously due to the many complex computation units. Since these intense computation functions have their own specific patterns, they were mainly performed by specialized hardware device. This kind of device, one that combines a main processor and an Intellectual Property (IP), still dominates the multimedia market place because of its adjustable performance, power, and convenience of manufacturing, even though the powerful multi-core embedded processor was released the market a few years ago. Approach of this thesis exploits inherent advantages of the multiprocessor without additional hardware implementation, and presents a thorough analysis of video decoding process in an embedded system. A target application is H.264/AVC, a well-adapted video coding standard for current multimedia environments which is used for many portable devices. <br/> <br/>Description: Graduation date: 2009 http://hdl.handle.net/1957/8930 Title: 1/f noise of GaAs resistors on semi-insulating substrates, and 1/f noise due to temperature fluctuations in heat conduction <br/> <br/>Abstract: This research work focuses on the mechanism of 1/f noise in GaAs resistors on semi-insulating substrates and 1/f noise due to temperature fluctuations in heat conduction in resistors, diodes, and bipolar transistors. The goal of this research is to generate accurate models to explain physical origin of 1/f noise in semi-insulating substrate and semiconductor devices dissipating high power. The model is based on a distributed equivalent circuit representation of the substrate, and shows that 1/f noise bulk phenomena associated with high resistivity substrates. One consequence of the theory is that in this particular instance Hooge's parameter is given by a formula and it is not an empirical parameter. Power dissipation at high currents and voltages in semiconductor devices results in significant heat generation and heat conduction towards the heat sink. The device temperature is only an average value and there are as a consequence of the diffusion equation for heat flow itself temperature fluctuations about this average value. It will be shown that these temperature fluctuations can result in 1/f noise at moderately low frequencies where these frequencies are determined by the physical dimensions over which the heat flows and the diffusion transit time. The results are then related to the shot noise or white noise due to the collector current allowing a determination of the 1/f noise corner frequency. <br/> <br/>Description: Graduation date: 2009