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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
171

Design of a DCO for an All Digital PLL for the 60 GHz Band : Design of a DCO for an All Digital PLL for the 60 GHz Band

Balasubramanian, Manikandan, Vijayanathan, Saravana Prabhu January 2013 (has links)
The work was based on digitally controlled oscillator for an all-digital PLL in 65nm process. Phase locked loop’s were used in most of the application for clock generation and recovery as well. As the technology grows faster in the existinggeneration, there has to be quick development with the technique. In such case ananalog PLL which was used earlier gradually getting converted to digital circuit.All-digital PLL blocks does the same work as an analog PLL blocks, but thecircuits and other control circuitry designed were completely in digital form, becausedigital circuit has many advantages over analog counterpart when they arecompared with each other. Digital circuit could be scaled down or scaled up evenafter the circuits were designed. It could be designed for low power supply voltageand easy to construct in a 65 nm process. The digital circuit was widely chosento make life easier. In most of the application PLL’s were used for clock and data recovery purpose,from that perspective jitter will stand as a huge problem for the designers. Themain aim of this thesis was to design a DCO that should bring down the jitter asdown as possible which was designed as standalone, the designed DCO would belater placed in an all-digital PLL. To understand the concept and problem aboutjitter at the early stage of the project, an analog PLL was designed in block leveland tested for different types of jitter and then design of a DCO was started. This document was about the design of a digitally controlled oscillator whichoperates with the center frequency of 2.145 GHz. In the first stage of the projectthe LC tank with NMOS structure was built and tested. In the latter stage the LCtank was optimized by using PMOS structure as negative resistance and eventuallyended up with NMOS and PMOS cross coupled structure. Tuning banks were oneof the main design in this project which plays a key role in locking the system ifthe DCO is placed in an all-digital PLL system. So, three types of tuning bankswere introduced to make the system lock more precisely. The control circuits andthe varactors built were all digital and hence it is called as digitally controlledoscillator. Digital control circuits, other sub-blocks like differential to single endedand simple buffers were also designed to optimize the signal and the results wereshown.DCO and tuning banks were tested using different types of simulation and were tested for different jitter qualities and analysis. The simulation results are shownin the final chapter simulation and results.
172

A Ring Oscillator Based Truly Random Number Generator

Robson, Stewart January 2013 (has links)
Communication security is a very important part of modern life. A crucial aspect of security is the ability to identify with near 100% certainty who is on the other side of a connection. This problem can be overcome through the use of random number generators, which create unique identities for each person in a network. The effectiveness of an identity is directly proportional to how random a generator is. The speed at which a random number can be delivered is a critical factor in the design of a random number generator. This thesis covers the design and fabrication of three ring oscillator based truly random number generators, the first two of which were fabricated in 0.13µ m CMOS technology. The randomness from this type of random number generator originates from phase noise in a ring oscillator. The second and third ring oscillators were designed to have a low slew rate at the inverter switching threshold. The outputs of these designs showed vast increases in timing jitter compared to the first design. The third design exhibited improved randomness with respect to the second design.
173

Defining Roles for Cyclin Dependent Kinases and a Transcriptional Oscillator in the Organization of Cell-Cycle Events

Simmons Kovacs, Laura Anne January 2009 (has links)
<p>The cell cycle is a series of ordered events that culminates in a single cell dividing into two daughter cells. These events must be properly coordinated to ensure the faithful passage of genetic material. How cell cycle events are carried out accurately remains a fundamental question in cell biology. In this dissertation, I investigate mechanisms orchestrating cell-cycle events in the yeast, <italic>Saccharomyces cerevisiae</italic>. </p><p>Cyclin dependent kinase (CDK) activity is thought to both form the fundamental cell-cycle oscillator and act as an effector of that oscillator, regulating cell-cycle events. By measuring transcript dynamics over time in cells lacking all CDK activity, I show that transcriptional oscillations are not dependent on CDK activity. This data indicates that CDKs do not form the underlying cell-cycle oscillator. I propose a model in which a transcription factor network rather than CDK activity forms the cell-cycle oscillator. In this model, CDKs are activated by the periodic transcription of cyclin genes and feedback on the network increasing the robustness of network oscillations in addition to regulating cell-cycle events. </p><p>I also investigate CDK-dependent and -independent mechanism regulating the duplication of the yeast centrosome, the spindle pole body (SPB). It is critical for the formation of a bipolar spindle in mitosis that the SPB duplicates once and only once per cell cycle. Through a combination of genetic and microscopic techniques I show that three distinct mechanisms regulate SPB duplication, ensuring its restriction to once per cell cycle. </p><p>Together, the data presented in this dissertation support a model in which CDKs, periodic transcription, and a TF-network oscillator are all important cell-cycle regulatory mechanisms that collaborate to regulate the intricate collection of events that constitute the cell cycle.</p> / Dissertation
174

Market efficiency in the portfolio strategy of technical indicators in the bull and bear stock markets

Chang, Tze-Wei 26 June 2012 (has links)
The study uses Moving Average, On Balance Volume, and KD (Stochastic Oscillator) to analyze that the technical analysis in which the bull or bear stock markets is efficiency. Also, verifies the changes of market efficiency before and after the financial crisis and whether it can earn excess returns or not by using technical analysis. That is, the returns earned by using technical analysis significantly greater than buy and hold which means the efficiency of technical analysis. Nevertheless, the study also aims to realize that whether the returns of the portfolio of technical indicators better than unit indicator. The companies in our samples are selected by the size of market value top 30 companies in the industries of electronic and finance in order to avoid the effect of market micro structure. Our results are as follows: (1) The returns in bear market are significantly higher than bull market by using MA6-144. (2) The MA6-72 and MA6-144 of financial stock before financial crisis, the returns of technical analysis are significantly better than buy and hold. In the other hand, in the electronic stock, we can use MA6-22-250, KD, and OBV to beat the buy and hold strategy and verify that the market efficiency does not exist. (3) The returns which combine of KD and OBV indicators are significantly higher than KD.
175

Femtosecond near-IR optical parametric oscillator based on periodically poled 5-mol. % MgO-doped lithium niobate

Wu, Ping-Tsung 04 September 2006 (has links)
The synchronously pumped femtosecond optical parametric oscillator (OPO) based on was periodically poled 5-mol.% MgO-doped lithuium niobate was demonstrated by means of non-critical quasi phase matching. The femtosecond OPO is cable of operating at room temperature and shows no photorefractive damage. The spectrum can be tuned by varying the cavity length up to 70 £gm, the temperature of the nonlinear crystal from room temperature to 150¢J, and the grating periods. The cavity was designed to resonate at 1.33 £gm with bandwidth of 100 nm. The maximum output intensity of the signal is 43 mW with TEM00 mode. The signal slope efficiency is 11%. The spectrum range of the idler is tunable from 1.8 to 2.8 £gm.
176

Millimeter Wave Gunn Diode Oscillators

Luy, Ulku 01 August 2007 (has links) (PDF)
This thesis presents the design and implementation of a millimeter-wave Gunn diode oscillator operating at 35 GHz (Ka (R) 26.5-40 GHz Band). The aim of the study is to produce a high frequency, high power signal from a negative resistance device situated in a waveguide cavity by applying a direct current bias. First the physics of Gunn diodes is studied and the requirements that Gunn diode operates within the negative differential resistance region is obtained. Then the best design configuration is selected. The design of the oscillator includes the design of the waveguide housing, diode mounting and the bias insertion network. Some simulation tools are used to predict, approximately, the behaviour of the oscillator and the bias coupling circuit. For tuning purposes, a sliding backshort and a triplescrew- tuner system is used. For different bias values and different positions of the tuning elements oscillations are observed. A much more stable and higher magnitude oscillations were obtained with the inclusion of &ldquo / resonant disc&rdquo / placed on top of the diode. 15 dBm power was measured at a frequency of 28 GHz. Laboratory measurements have been carried out to determine the oscillator frequency, power output and stability for different bias conditions.
177

Design and Implementation of 2.4 GHz Two-Point Voltage-Controlled Oscillators on a Multilayer LTCC Substrate with Embedded Inductors and Capacitors

Lee, Sheng-Feng 24 July 2003 (has links)
In the first, we design and implement a Two -Point Voltage-Controlled Oscillator which applied in Open-Loop and Two-Point Close-Loop Modulation Bluetooth transmitter and include Hybrid and CMOS RFIC design. Second, we design six LTCC embedded components including inductors and capacitors. The extraction result via traditional equivalent £kmodel match the simulation and the frequency response of adopted model can accurate to device¡¦s Self-Resonant-Frequency nearby compare with measurement. In the end, we design and implement a LTCC Two-Point Voltage-Controlled Oscillator module and effective ly reduce the module size.
178

Sliding-mode amplitude control techniques for harmonic oscillators

Marquart, Chad A. 17 September 2007 (has links)
This thesis investigates both theoretical and implementation-level aspects of switching- feedback control strategies for the development of voltage-controlled oscillators. We use a modified sliding-mode compensation scheme based on various norms of the system state to achieve amplitude control for wide-tuning range oscillators. The proposed controller provides amplitude control at minimal cost in area and power consumption. Verification of our theory is achieved with the physical realization of an amplitude controlled negative-Gm LC oscillator. A wide-tuning range RF ring oscillator is developed and simulated, showing the effectiveness of our methods for high speed oscillators. The resulting ring oscillator produces an amplitude controlled sinusoidal signal operating at frequencies ranging from 170 MHz to 2.1 GHz. Total harmonic distortion is maintained below 0:8% for an oscillation amplitude of 2 Vpp over the entire tuning range. Phase noise is measured as -105.6 dBc/Hz at 1.135 GHz with a 1 MHz offset.
179

Thermal Response of Lithium Tantalate for Temperature Measurement

Agastra, Ardit 01 January 2011 (has links)
This thesis describes the study of the thermal response of the pyroelectric material named lithium tantalate or LT (LiTaO3) in aid of this material's possible use for temperature measurement. The temperature range studied was between 5-99oC. The sensor was excited using a silicon rubber heater. The lithium tantalate sensor and the rubber heater were enclosed such that the temperature would reach steady state faster. The enclosure was a small insulated box in order to reduce any extraneous effects on the sensor. The output signal of the lithium tantalate sensor was then amplified by using four different amplifying circuits and the voltage output was studied. The amplifying circuits included Current Mode, double Current Mode, Voltage Mode, and a modified Wien Oscillator. Results demonstrated linear dependencies of the voltage output as a function of temperature for the Voltage Mode and the modified Wien Oscillator. Using the modified Wien Oscillator amplifying circuit the slope of the line a 2.1mV/oC and for the Voltage Mode the slope was 1mV/oC. For both cases it was found that the range for the standard deviation of the measurements was 0.5< The data showed that the lithium tantalate sensor could be used as a temperature measuring device for the range mentioned above. The resolution of the data is high enough to be able to be detected with modern measuring devices and the standard deviation is low enough to allow for such measurements. Moreover, the linear dependence of the data allows for accurate measurements at each temperature within the range.
180

Terahertz Local Oscillator Via Difference Frequency Generation in III-V Semiconductors Using Frequency Stabilized Lasers

Herman, Gregory S. January 2013 (has links)
Terahertz (THz) heterodyne receiver systems are required by NASA to monitor gas concentrations related to the Earth's ozone depletion. To this end, NASA needs compact, solid state, tunable THz local oscillators. THz LOs have been developed using three means: 1) All-electronic LOs using mixers in combination with Gunn oscillators, 2) Hybrid Photo-electronic LOs using a cw analog of the Auston switch, and 3) All-photonic THz LOs using coherent sources, such as vapor lasers or solid-state Quantum Cascade Lasers, and down converting lasers using nonlinear crystals. In this dissertation, we began with two frequency stabilized Nd:YAG lasers, locked to a common reference cavity, as a starting point to having a stable input into a nonlinear optical frequency conversion system. Following this, we explored the nonlinear crystals useful for THz generation, and the phasematching schemes that could be employed by each. We concluded by settling on highly insulating III-V semiconductor crystals as the proper choice of nonlinear element, and put together a new phasematching method that is most useful for them.

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