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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.
41

Design, analysis, and synthesis of 16 bit arithmetic logic unit using reversible logic gate

Midde, Bharath Reddy 23 April 2016 (has links)
<p> In the modern world, an Arithmetic Logic Unit (ALU) is one of the most crucial component of an embedded system and is used in many devices like calculators, cell phones, computers, and so on. An ALU is a multi-functional circuit that conditionally performs one of several possible functions on two operands A and B depending on control inputs. It is nevertheless the main performer of any computing device. This project proposes the design of programmable reversible logic gate structures, targeted for the ALU implementation and their use in the realization of an efficient reversible ALU. This ALU consists of sixteen operations, the arithmetic operations include addition, subtraction, multiplication and the logical operations includes AND, OR, NOT and XOR. All the modules are being designed using the basic reversible gates. </p><p> Using reversible logic gates instead of traditional logic AND/OR gates, a reversible ALU is constructed whose function is the same as traditional ALU. Comparing with the number of input bits and the discarded bits of the traditional ALU, the reversible ALU significantly reduces the use and loss of information bits. The proposed reversible 16-bit ALU reuses the information bits and achieves the goal of lowering delay of logic circuits by 42% approximately. Programmable reversible logic gates are realized in Verilog HDL.</p>
42

Orthogonal Frequency Division Multiplexing (OFDM) channel estimation using pilot based parametric scheme

Rajanna, Sowmya 18 February 2016 (has links)
<p>This paper is aimed at parametric Multiple Input Multiple Output (MIMO) ? Orthogonal Frequency Division Multiplexing (OFDM) channel estimation that increases the spectrum efficiency of the wireless communication systems. OFDM technology has been widely used due to its high data rate and low multipath distortion. The estimation of channel for OFDM is required in vehicular environments and many other cutting-edge technology applications. To develop such reliable vehicular wireless communication systems, it is necessary to set up the standards and models of propagation channel with respect to the environment and scenarios. The proposed parametric scheme can accomplish super resolution by assessing the delays in arbitrary paths, making this scheme more suitable for wireless channels. The channel estimation precision is increased by using the spatial and temporal correlations in the wireless MIMO channel. The average pilot overhead for each antenna is reduced because of the temporal correlation of MIMO channels. Thus, the parametric scheme is promising for future wireless technologies as it accomplishes better spectral efficiency and better robustness for the multipath fading channels.
43

Temperature and Total Ionizing Dose Characterization of a Voltage Reference in a 180 nm CMOS Technology

Shetler, Kevin Joseph 11 April 2016 (has links)
A voltage reference is a critical component of analog and mixed signal systems because it provides a global signal used for a variety of system functions. The precision of a voltage reference is critical, so it must be designed such that variation is minimized due to factors such as temperature, power supply variation, and radiation exposure. In this thesis, techniques are presented for minimizing shifts in the output of a typical voltage reference design due to changing temperature and increased radiation exposure. This includes a CMOS variation of a basic bandgap design to implement first order temperature coefficient cancellation and an active thermal regulation feedback loop to minimize effects of temperature, and the use of dynamic-threshold MOS transistors (DTMOSTs), a resistive current mirror, and chopper stabilization to minimize the effects of radiation. A voltage reference circuit was designed and fabricated in IBM CMRF7SF 180nm bulk CMOS technology using these. This circuit was tested at varying temperatures to calibrate variable resistances on-chip, used to calibrate first order temperature coefficient cancellation and the thermal feedback loop, and to demonstrate the effectiveness of the techniques used. Isolated DTMOSTs and the complete reference circuit were tested using X-rays to experimentally verify the radiation tolerance of the individual devices, and the effectiveness of using them along with chopper stabilization as a radiation hardening technique.
44

Thermal Transient Study of Silica Aerogel Insulated Micro-hotplates

Edpuganti, Koutilya 28 January 2016 (has links)
<p> We studied the temperature transient behavior of an airpit-insulated micro hotplate (&micro;HP) and aerogel-insulated &micro;HP with different airpit heights and aerogel thicknesses. The &micro;HP insulated by 1.3&micro;m-thick aerogel consumes 26.7mW of power at 82&deg;C with a time constant of 114.5 &micro;sec, while the &micro;HP insulated by 4?&micro;m-thick aerogel consumes 35.6mW of power to provide 220&deg;C with a time constant of 211.6 &micro;sec. At the same time, a 100 &micro;m-deep airpit-insulated ?HP consumes 18mW of power to reach approximately 400&deg;C. The time constant of aerogel does not depend just on material properties but also on the structural design of the micro-heater. The temperature transient response time of &micro;HPs is continued to improve from using air-pited, recessed silica aerogel, to thick-film silica aerogel.</p>
45

Radiation Response and Reliability of High Speed AlGaN/GaN HEMTs

CHEN, JIN 27 July 2016 (has links)
In recent years, GaN-based high-electron-mobility-transistors (HEMT) have demonstrated excellent high power and high frequency performance compared with counterparts based on other materials. Although AlGaN/GaN HEMTs are of great interest owing to the large band gap of GaN (3.4 eV), high breakdown field (~3.1 MV/cm), high saturation electron velocity (~2.5 Ã 107 cm/s) and the presence of a high-mobility two-dimensional electron gas (2DEG) at the hetero-interface, the reliability of devices can be limited by a number of factors, impeding the way to commercialization. GaN HEMTs have demonstrated very good radiation tolerance. In this work, the radiation response and reliability issues of AlGaN/GaN HEMTs grown using molecular beam epitaxy (MBE) are studied. Devices are subjected to 1.8 MeV proton irradiation and/or voltage stress are characterized via DC and RF measurements. Low frequency 1/f noise measurements are employed to help understand the defects that affect the reliability and radiation response of AlGaN/GaN HEMTs, and density functional theory (DFT) calculation is used to identify possible defect candidates. The temperature-dependent noise spectra show changes in defect distributions. Hydrogenated ON defects, Fe complexes and VGa-VN-Hx divacancies are some of the dominating defects limiting the device radiation response and reliability. The results of combined high field and radiation effects provide better insight into device response in practical space applications.
46

Interference mitigation effects on synthetic aperture radar coherent data products

Musgrove, Cameron H. 23 July 2016 (has links)
<p> Both radio frequency interference from sources external to the synthetic aperture radar system and techniques to mitigate radio frequency interference can degrade the quality of the image products. Often it is the second order data products derived from the images that are of the most value for a synthetic aperture radar system. Preserving the quality of these data products, in the presence of radio frequency interference, is paramount to maintaining the utility of the sensor. </p><p> This dissertation examines the effects of interference mitigation upon coherent data products of fine-resolution, high frequency synthetic aperture radars using stretch processing. Novel interference mitigation techniques are introduced that operate on single or multiple apertures of data that increase average coherence compared to existing techniques. A novel contrast metric is combined with existing image quality and average coherence metrics to compare multiple mitigation techniques. The characteristics of interference mitigation techniques that restore coherence are revealed.</p>
47

Location privacy in wireless sensor network using reciprocal protocol

Mohan, Rakshitha 15 July 2016 (has links)
<p> Location privacy has been one of the greatest threats in wireless systems. The utilization of k-anonymity in Wireless Sensor Networks (WSNs) protects the location privacy. This characteristic feature enables the server to receive aggregate k-anonymized locations of internally connected sensor nodes. These k-anonymized locations are comprised of, a minimum of k persons. Nevertheless, an intruder model is used to high point the readiness of privacy risks in overlapping aggregate locations because an adversary can deduce the overlapping areas contained in an area with less than k persons whose requirement violates k-anonymity privacy. Hence, a reciprocal protocol (REAL) is used for establishing location privacy in Wireless Sensor Networks (WSNs). </p><p> The sensor nodes organize a group of non-overlapping areas and k-anonymized locations into sensing areas. To overcome the privacy threats in REAL, a process state transition is designed with a time delay mechanism that provides accuracy of the messages received and a locking mechanism is designed to enhance reciprocity property. The generation of an error-free query reply and securing location privacy and decreasing computational and communication costs is achieved by the experimental analysis of the REAL protocol .</p>
48

Extension of sensor battery life in wireless sensor networks using sink relocation

Patel, Aashna 16 July 2016 (has links)
<p> Wireless Sensor Networks (WSN) consist of a large number of battery-powered devices (nodes), which transmit their data to a central node called the sink. Multi-hopping techniques are used to deliver the sensed data to the sink. The nodes that are close to the sink receive high volume of data from the rest of the network, and they have to forward these data to the sink. As a result, these nearby nodes drain their batteries and die quicker than other nodes in the network. </p><p> The Energy Aware Sink Relocation (EASR) is a method that prolongs the life of sensors by moving the sink to various locations in the network. By not keeping the sink at any specific location for too long, EASR improves the lifetime of sensors. This project presents an application of EASR to multi-sink networks. Simulation results show that the proposed method extends battery life of the network nodes.</p>
49

A Radiation-Reliability Assurance Case using Goal Structuring Notation for a CubeSat Experiment

Austin, Rebekah Ann 06 July 2016 (has links)
CubeSats have become an attractive platform for university-based spacecraft designs because they are cheaper and quicker to launch than full-scale satellites. One way of keeping costs for CubeSats low is using commercial off-the-shelf parts (COTS) instead of using space-qualified parts. Space-qualified parts are often costly, larger, and consume more power than their commercial counterparts prohibiting their use within a CubeSat. Given typical power budgets, monetary budgets, and timelines for CubeSat missions, conventional radiation hardness assurance, like the use of hardened parts and radiation testing campaigns of COTS parts, is not possible, requiring a system-level approach to radiation effects mitigation. In this thesis an assurance case for the radiation reliability of a CubeSat experiment is expressed using Goal Structuring Notation (GSN), a graphical argument standard. The case specifically looks at three main mitigation strategies for the radiation environment: total ionizing dose (TID) screening of parts, detection and recovery from single-event latch-ups (SEL) and single-event functional interrupts (SEFI). The graphical assurance case presented makes a qualitative argument for the radiation reliability of the CubeSat experiment using part and system-level mitigation strategies and is supported by functional and system models of the system.
50

Fully Integrated Hybrid Voltage Regulator for Low Voltage Applications

Park, Yongwan 07 July 2016 (has links)
<p>A novel hybrid regulator topology is proposed to alleviate the weaknesses of existing hybrid topologies. Contrary to the dominant existing practice, a switched-capacitor converter and a resistorless LDO operate in a parallel fashion to supply current and regulate the output voltage. The proposed topology targets a fully integrated regulator without using any inductors and resistors. The primary emphasis is on maximizing power efficiency while maintaining sufficient regulation capability (with ripple voltage less than 10% of the output voltage) and power density. The first implementation of the proposed topology operates in a single frequency mode. Simulation results in 45 nm technology demonstrate a power efficiency of approximately 85% at 100 mA load current with an input and output voltage of, respectively, 1.15 V and 0.5 V. The worst case transient response time is under 20ns when the load current varies from 65 mA to 130 mA. The worst case ripple is 22 mV while achieving a power density of 0.5 W/mm<sup>2</sup>. This single-frequency hybrid voltage regulator is useful (due to its fast and continuous response and high power efficiency) when the output load current is relatively constant at a certain nominal value. However, the performance is degraded when the load current varies significantly beyond the nominal current since the current provided by switched-capacitor converter is constant. The second implementation of the proposed hybrid regulator topology partially alleviates this issue by employing two different frequencies depending on the load current. This design is also implemented in 45 nm technology. It is demonstrated that the power efficiency is maintained within 60% to 80% even though the load current varies by more than 100 mA. The power density remains the same (0.5 W/mm<sup>2</sup>). The simulation results of the proposed topology are highly competitive with recent work on integrated voltage regulators. </p>

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