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.
Results
Showing 1 to 20 of 155 for “"Operating Frequency"”.
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Tolerance Study of Reflector Antenna Systems (Random Surface Errors, Retrodirective Array, Focal Shift)
… acute due to the large antenna size, the high operating frequency, and the hostile antenna operating environment. In this thesis, three topics related to the tolerance problem in reflector antenna systems are addressed.
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Recent Development in Low Frequency Integral Equation Method
… steps because the time step is small and the operating frequency is low. Our numerical results show several orders magnitude of saving, both in CPU time and memory.
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Design of reconfigurable intelligent surface for 5G wireless communication system
… [1]. A two state, 25 elements RIS, has operating frequency at 5.8 GHz, is designed and simulated by using full-wave simulator. The unit cell of the prototype design can be controlled by using a RF switch, which can switch between two states, [0, 180], to change the reflectivity of the …
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Electrical Impedance Tomography in Nerve Cuffs: Towards an Intuitive Control Interface for Neural-Prosthetics
… improving the signal to noise ratio, and (ii) frequency multiplexing of EIT drive currents. In Chapters 1 and 2, an introduction to neural prosthetics and literature review of electrical impedance tomography of neural activity, respectively, are presented, followed by a short overview of the …
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Controle por modos deslizantes aplicado a um conversor boost intercalado bidirecional de três células
… a setback to ensuring a fixed and predetermined operating frequency. The works presented on the regulation of interleaved converters, using variable structure controllers, such as sliding mode control, usually lack understanding of the controller design methodology and the limitations for …
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Advancing the Performance of a Switched-Mode Radio Frequency Power Generation Architecture
… to be used in applications such as radio frequency plasma generation for semiconductor fabrication. Improvements in efficiency are desired due to the high frequency and power levels seen during this process. There are two main aspects of the proposed thesis. The first aspect of the thesis …
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Design and implementation of L and X-band filters for the NeXtRAD front end
… (UCL). It has been designed to operate in two frequency bands, designated as L and X-bands. NeXtRAD will be used as a research tool, for the purposes of measuring sea targets and detecting sea clutter. The measured data will be stored in a database, and it will be made freely available to the …
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Cavity-backed T-fed slot antenna
… have a low radar cross section out of their operating frequency bands. Like thin microstrip patch antennas, cavity-backed slot antennas typically have a narrow impedance bandwidth of 1 to 6 percent of center frequency, which limits their usage. A new method of feeding a thin cavity slot …
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Clock division as a power saving strategy in a system constrained by high transmission frequency and low data rate
… are often restricted to have higher transmission frequency than required by their data rates. Possible constraints include channel attenuation, power requirements, and backward compatibility. As a result these systems have unused band- width, leading to inefficient use of power. In this thesis, I …
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Multiphase Isolated DC-DC Converters for Low-Voltage High-Power Fuel Cell Applications
… an interleaving control scheme produces a high operating frequency with a low switching frequency, and the high operating frequency reduces size of passive components. Thirdly, use of a transformer provides electrical isolation and a high conversion ratio. Lastly, several multiphase converters …
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Characterization of process variability and robust optimization of analog circuits
… circuits. CMOS millimeter-wave applications operating at more than 50GHz frequencies has become viable in sub-100nm CMOS technologies, providing advantages in cost and high density integration compared to other heterogeneous technologies such as SiGe and III-V compound semiconductors. …
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POWER-AWARE PERFORMANCE OPTIMIZATION ON MULTICORE ARCHITECTURES
… studies. We focus to scale the clock speed/operating frequency of mul- ticore processor to optimize the overall power consumption for a specific workload. Our work consists of four major parts. In the first part we propose a metric to determine core criticality. In multicore processing, …
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Design and Implementation of Low Jitter Clock Generators in Communication and Aerospace System
… obtain maximum performances with respect to high operating frequency, low noise, small area, and low power consumption. Clock generators are essential components in numerous circuits, for instance, frequency synthesizers for high speed transceivers, clock sources for microprocessors, noise …
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Resonance Compensation of Large AC Drivetrains with Significant Time Lag
… is torque ripple which is a function of the operating frequency. Even a small value of ripple, at an underdamped plant resonant frequency, may be multiplied by the plant "Q" to a large enough value to cause trouble. Typical classical approaches used in the rolling mill industry to deal with …
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Reduction of energy losses: a key to improved rock drilling?
… column that is 152.4 m (500 ft) long. This is a frequency slightly less than the first undamped natural frequency of the drill column. For the same column, viscous rotational power losses of over 74.56 W ( 0.1 hp) are expected at rotational speeds of 10.47 rad/s (100 rpm). Rotational and …
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Radio frequency power amplifiers for portable communication systems
… systems require, in part, high-efficiency radio frequency power amplifiers (RF PA) if battery lifetime is to be conserved. Conventional amplifier classifications and definitions are presented in a unified and concise format. The Bipolar Junction Transistor (BJT) and Metal-Semiconductor Field …
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On-chip self-rolled-up nanomembrane tube inductor for RFIC performance enhancement
… the performance and functionality of radio frequency integrated circuits (RFICs). Numerous improvement methods have been demonstrated but all fail to fundamentally solve the intrinsic drawbacks of planar spiral structure, especially the most critical issue – substrate effects. A new design …
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Sound field reproduction
… the reproduction of focused sources or when the operating frequency corresponds to one of the Dirichlet eigenvalues of the control region.<br/>An important analogy is also drawn between the problem of sound field reproduction and the theory of acoustic scattering. In a later part of this work, …
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Research and Development of Low-Profile, Small Footprint Antennas for VHF-UHF Range Applications
… between the physical length and resonant frequency of an antenna, which is a measure of its operating frequency range, is well known. A direct correlation between an antenna's physical length and radiation efficiency has also been established. Therefore, a combination of these constraints …
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Non-foster matching of an RFID antenna
In this thesis, novel designs of radio-frequency identification (RFID) tag antennas with better matching characteristics to achieve extended range for passive tags have been investigated in the ultra-high frequency (UHF) band. A variety of cavitybacked/coupled microstrip dipole antennas in 915 MHz …
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