Browsing by Subject "Filter"
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Item A CMOS 500MHz continuous-time fourth order 0.05degree equiripple linear phase filter with automatic tuning(Texas A&M University, 2004-09-30) Pandey, PankajThe growing demand of portable electronic equipment and system-on-a-chip has been pushing the industry to design circuits with very low power supply voltage and low power consumption. The Hard Disk drive industry is looking for developments in the read channel chip to push the data rates to higher speed, along with a low voltage and low cost solution. Read channel requires high-speed linear phase filters to meet these objectives. The primary objective of this project is to design, layout, and characterize a 4th-order continuous-time equiripple linear phase filter with automatic tuning system. The main requirements for design are high speed, low group delay variations, good linearity and power efficiency. This filter features wide cut-off frequency 500MHz, which is far beyond the current state-of-the-art. The linear phase filter is based on Gm-C biquadratics. Higher speed has been achieved by minimizing the parasitics and a complementary input stage OTA. A common mode feedback (CMFB), which ensures stability at such high frequencies, has also been designed. The inaccuracies of the filter are compensated by using a simple automatic tuning system. The design is fabricated in 0.35 um TSMC CMOS process technology. The design was simulated in Cadence using SPICE models provided by MOSIS for the 0.35 um TSMC process in the presence of parasitic capacitance and transistor non-idealities. Cut-off frequency of 500 MHz was achieved along with a 9% variation in the group delay.Item Humidity effects on hygroscopic particles deposited on HEPA filters and silicon wafer surfaces(2012-12) Ponkala, Mikko Juha Viljami; Ezekoye, Ofodike A.; Haglund, John SSemiconductor wafer manufacturing facilities (fab) must maintain extremely clean air environments to minimize the number of wafers scrapped due to contamination which would result in reduced yields. The fab air is cleaned bypassing it through either HEPA or ULPA filters. A number of airborne fab contaminants may be hygroscopic causing them to exist as a solid or a liquid when in equilibrium with their environment's relative humidity. The effect of relative humidity on such contaminants is poorly documented whether they were to be captured in a filter or deposited on a wafer. The work presented here experimentally characterizes NaCl evolution within HEPA filters when exposed to humidity fluctuations and the effect of humidity on NH4Cl corrosiveness when deposited on cobalt coated wafers with a TiN layer. Successive deliquescence and efflorescence fluctuations were imposed on particles captured on a glass fiber HEPA filter. Scanning Electron Microscopy (SEM) and Environmental SEM (ESEM) studies of the filters showed that the NaCl, under humidity excursions, did not penetrate deep into the filter but deliquesced and effloresced near the top surface of the filter. Pressure drop measurements for filters containing NaCl particles showed differences in pressure drop associated with relative humidity changes. These pressure drop changes suggested some redistribution particle properties. When exposed to a relative humidity of 20%, the NH4Cl particles did not corrode the cobalt wafer beyond the location of the initial deposit. At 61% relative humidity, the surrounding areas of the particles were corroded with a solid artifact left at the original location. At 76% relative humidity the NH4Cl particles were observed to have deliquesced, which is below the expected deliquescence relative humidity. The corrosion of the cobalt wafer was most extensive when the NH4Cl particles had deliquesced.Item Navigation filter design and comparison for Texas 2 STEP nanosatellite(2009-12) Wright, Cinnamon Amber; Lightsey, E. Glenn; Bishop, Robert H.A Discrete Extended Kalman Filter has been designed to process measurements from a magnetometer, sun sensor, IMU, and GPS receiver to provide the relative position, velocity, attitude, and gyro bias of a chaser spacecraft relative to a target spacecraft. An Extended Kalman Filter with Uncompensated Bias has also been developed for the implementation of well known biases and errors that are not directly observable. A detailed explanation of the algorithms, models, and derivations that go into both filters is presented. With this simulation and specific sensor selection the position of the chaser spacecraft relative to the target can be estimated to within about 5 m, the velocity to within .1 m/s, and the attitude to within 2 degrees for both filters. If a thrust is applied to the IMU measurements, it takes about 1.5 minutes to get a good position estimate, using the Extended Kalman Filter with Uncompensated Bias. The error settles almost immediately using the general Extended Kalman Filter. These filters have been designed for and can be implemented on almost any small, low cost, low power satellite with this inexpensive set of sensors.Item Proximity operations of nanosatellites in Low Earth Orbit(2013-12) Almond, Scott Douglas; Lightsey, E. GlennA mission architecture consisting of two NASA LONESTAR-2 satellites in Low Earth Orbit is considered. The craft are equipped with cross-communication radios and GPS units. Analyses are conducted for ejection, thruster and attitude maneuvers to achieve objectives of the mission, including sustained communications between the craft. Simulations are conducted to determine the duration of the communication window following the initial separation of the two craft. Recommendations are made to maximize this window while accounting for attitude constraints and the effects of atmospheric drag. Orbital mechanics and control theory are employed to form an algorithm for filtering GPS position fixes. The orbit-determination algorithm accounts for the effects of drag and Earth’s oblateness. Procedures are formed for verifying the initial separation velocities of two spacecraft and for measuring the velocity imparted by impulsive thruster maneuvers. An algorithm is also created to plan the timing and magnitude of corrective thruster maneuvers to align the orbital planes of the two craft. When the craft pass out of communication range, a ground station is used to relay data and commands to conduct state rendezvous procedures. A plan for coordinated attitude maneuvers is developed to strategically utilize the cumulative effects of drag and orbit decay to align the craft over long time periods. The methodologies developed here extend prior research into close proximity operations, forming the foundation for autonomous on-orbit rendezvous under a broader set of initial conditions.Item Tunable erbium-doped fiber ring laser using an intra-cavity filter(Texas A&M University, 2004-11-15) Fadel, Hicham JosephLinear tuning the frequency of an erbium-doped fiber ring laser using both a Fabry-Perot filter and an electro-optic tunable filter has been experimentally demonstrated. The rate of frequency change is determined by monitoring the fringes produced by laser light transmitted through a fiber Fabry-Perot interferometer. The fiber ring laser has been tuned over a 50 nm spectral range when using the Fabry-Perot filter and a tuning rate of 16480 nm/s has been achieved. The spectral width of the laser is 0.049 nm and the nearest sidelobe to the main peak is more than 30 dB below the central lobe. When the electro-optic tunable filter is used, a spectral range of 11 nm is reached. The spectral width is 2.33 nm and is in close agreement with the filter theoretical results. The sidelobe to main peak difference is around 13 dB.