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Articles 1 - 30 of 31
Full-Text Articles in Engineering
Refinement And Performance Analysis Of The Stepped Frequency Microwave Radiometer In Extra Tropical Cyclone Conditions, Jezabel Vilardell Sanchez
Refinement And Performance Analysis Of The Stepped Frequency Microwave Radiometer In Extra Tropical Cyclone Conditions, Jezabel Vilardell Sanchez
Doctoral Dissertations
The Stepped Frequency Microwave Radiometer (SFMR) is a key instrument for estimation of ocean surface wind speed and rain rate in tropical and extra-tropical cyclones research. Through the observed brightness temperature (TB) over a range of six C-band frequencies, the SFMR derives these key parameters used by hurricane specialists to issue watches and warnings. The information gathered with this instru- ment is also pivotal for post-storm studies and satellite calibrations. Currently, the SFMR requires an average time of 5-10 seconds of averaging to cycle through the six di↵erent frequency channels, so in regions with strong wind/rain gradients such as the …
Security Of Hardware Accelerators In Multi-Tenant Fpga Environments, Shayan Moini
Security Of Hardware Accelerators In Multi-Tenant Fpga Environments, Shayan Moini
Doctoral Dissertations
Field-programmable gate arrays (FPGAs) play an important role in the acceleration of computationally expensive algorithms for machine learning, aerospace, and ASIC prototyping. The emergence of FPGAs in the cloud (cloud FPGAs) has accelerated FPGA adoption in various applications due to their low initial cost and the ability to quickly prototype a design. Multi-tenancy, in which multiple users execute circuitry in the same FPGAs simultaneously with logical isolation, reduces cloud FPGA usage cost and increases FPGA utilization. Multi-tenancy introduces new security challenges, such as remote side-channel and fault injection attacks, that cannot be addressed with traditional countermeasures against attacks. In this …
Frontiers In The Self-Assembly Of Charged Macromolecules, Khatcher O. Margossian
Frontiers In The Self-Assembly Of Charged Macromolecules, Khatcher O. Margossian
Doctoral Dissertations
The self-assembly of charged macromolecules forms the basis of all life on earth. From the synthesis and replication of nucleic acids, to the association of DNA to chromatin, to the targeting of RNA to various cellular compartments, to the astonishingly consistent folding of proteins, all life depends on the physics of the organization and dynamics of charged polymers. In this dissertation, I address several of the newest challenges in the assembly of these types of materials. First, I describe the exciting new physics of the complexation between polyzwitterions and polyelectrolytes. These materials open new questions and possibilities within the context …
X-Band Phased-Array Weather-Radar Polarimetry Testbed, William Heberling Iv
X-Band Phased-Array Weather-Radar Polarimetry Testbed, William Heberling Iv
Doctoral Dissertations
Phased-array weather radar have potential to replace reflector dish radar in major weather radar networks such as NEXRAD, providing faster update times and greater scan flexibility. However, the use of electronic scanning introduces polarization errors on weather radar measurables, requiring polarimetric bias calibration. The sources of polarimetric bias have been described theoretically, but experimental verification is still limited. Additionally, no standard method of calibration for polarimetric bias exists for phased-arrays. Therefore, the University of Massachusetts Amherst (UMass) presents a fully operational X-Band phased-array weather radar polarimetric testbed. The testbed evaluates the calibration of a planar dual-polarization X-band phased-array radar through …
Planar Ultra-Wideband Modular Antenna (Puma) Arrays For High-Volume Manufacturing On Organic Laminates And Bga Interfaces, James R. Lacroix
Planar Ultra-Wideband Modular Antenna (Puma) Arrays For High-Volume Manufacturing On Organic Laminates And Bga Interfaces, James R. Lacroix
Masters Theses
This work proposes wideband and broadband Planar Ultra-wideband Modular Antenna (PUMA) arrays designed to improve cost and reliability for high production volume commercial and military applications. The designs feature simplified PCB stack-ups with high dielectric constant (Dk) dimensionally stable materials to improve the manufacturing cost and yield. Additionally, the packages use ball grid array (BGA) interconnects, commonly used in digital electronics, for simple solder reflow integration with radio frequency (RF) electronics. While high Dk materials present practical manufacturing benefits, theoretical background will show how and why PUMA arrays lose frequency bandwidth and scan volume with high Dk materials. Further, a …
Silicon Germanium Bicmos Integrated Circuits For Scalable Cryogenic Sensing Applications, Mohsen Hosseini
Silicon Germanium Bicmos Integrated Circuits For Scalable Cryogenic Sensing Applications, Mohsen Hosseini
Doctoral Dissertations
This dissertation is focused on an investigation of BiCMOS cryogenic low noise amplifiers (LNAs) based on Silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) for simultaneous low noise and low power design and also taking advantage of CMOS circuitry for adding flexibility to the LNA design. Cryogenic LNAs' scalability challenges are discussed and addressed in the dissertation. To achieve that, first, HBTs of three state-of-the-art technologies are characterized and modeled at cryogenic temperature. It is shown that SiGe HBT provides a promising compromise of noise temperature, power consumption, and bandwidth. Moreover, a scalable on-chip approach is proposed and verified for biasing of …
Thermoelectric Transport In Disordered Organic And Inorganic Semiconductors, Meenakshi Upadhyaya
Thermoelectric Transport In Disordered Organic And Inorganic Semiconductors, Meenakshi Upadhyaya
Doctoral Dissertations
The need for alternative energy sources has led to extensive research on optimizing the conversion efficiency of thermoelectric (TE) materials. TE efficiency is governed by figure-of-merit (ZT) and it has been an enormously challenging task to increase ZT > 1 despite decades of research due to the interdependence of material properties. Most doped inorganic semiconductors have a high electrical conductivity and moderate Seebeck coefficient, but ZT is still limited by their high lattice thermal conductivity. One approach to address this problem is to decrease thermal conductivity by means of alloying and nanostructuring, another is to consider materials with an inherently low …
Electro-Thermal Transport In Two-Dimensional Materials And Their Heterostructures, Arnab K. Majee
Electro-Thermal Transport In Two-Dimensional Materials And Their Heterostructures, Arnab K. Majee
Doctoral Dissertations
”Smaller is better” is the mantra that has driven semiconductor industry for the past 50 years. The on-going quest for faster electronic switching, higher transistor density, and better device performance, has been driven by a self-fulfilling prophecy popularly known as Moore’s law, according to which the number of transistors per unit area of a chip doubles itself approximately every two years. A modern smartphone has about 8 billion transistors, which is as large as current earth’s population. Although each transistor dissipates negligible power, but the collective power dissipation from all the transistors in an electronic gadget and inefficient heat removing …
Addressing Security Challenges In Embedded Systems And Multi-Tenant Fpgas, Georgios Provelengios
Addressing Security Challenges In Embedded Systems And Multi-Tenant Fpgas, Georgios Provelengios
Doctoral Dissertations
Embedded systems and field-programmable gate arrays (FPGAs) have become crucial parts of the infrastructure that supports our modern technological world. Given the multitude of threats that are present, the need for secure computing systems is undeniably greater than ever. Embedded systems and FPGAs are governed by characteristics that create unique security challenges and vulnerabilities. Despite their array of uses, embedded systems are often built with modest microprocessors that do not support the conventional security solutions used by workstations, such as virus scanners. In the first part of this dissertation, a microprocessor defense mechanism that uses a hardware monitor to protect …
Time-Difference Circuits: Methodology, Design, And Digital Realization, Shuo Li
Time-Difference Circuits: Methodology, Design, And Digital Realization, Shuo Li
Doctoral Dissertations
This thesis presents innovations for a special class of circuits called Time Difference (TD) circuits. We introduce a signal processing methodology with TD signals that alters the target signal from a magnitude perspective to time interval between two time events and systematically organizes the primary TD functions abstracted from existing TD circuits and systems. The TD circuits draw attention from a broad range of application fields. In addition, highly evolved complementary metal-oxide-semiconductor (CMOS) technology suffers from various problems related to voltage and current amplitude signal processing methods. Compared to traditional analog and digital circuits, TD circuits bring several compelling features: …
The Umass Experimental X-Band Radar (Umaxx): An Upgrade Of The Casa Ma-1 To Support Cross-Polarization Measurements, Jezabel Vilardell Sanchez
The Umass Experimental X-Band Radar (Umaxx): An Upgrade Of The Casa Ma-1 To Support Cross-Polarization Measurements, Jezabel Vilardell Sanchez
Masters Theses
Ground-based radars are instruments commonly used to surveil the precipitation climate of the surrounding areas. Weather events are characterized by collecting backscatter data and analyzing computed products such as the Reflectivity Factor, the Doppler Velocity, the Spectrum Width, the Differential Reflectivity, the Co-polar Correlation Coefficient and the Differential Propagation Phase. The ability of the radar to transmit different polarization waves, such as horizontal and vertical polarization, allow for further analysis of the weather given the capability to perform co-polar and cross-polar measurements. The Linear Depolarization Ratio is another computed product based on the difference in power between the co-polarized and …
A Discrete-Time Technique For Linearity Enhancement Of Wideband Receivers, Mohammad Ghadiri Sadrabadi
A Discrete-Time Technique For Linearity Enhancement Of Wideband Receivers, Mohammad Ghadiri Sadrabadi
Doctoral Dissertations
A new signal processing technique is introduced to enhance the linearity performance of wideband radio frequency (RF) receivers. The proposed technique combines the advancements in mixer first architectures with a library of binary sequences as local oscillator signals to enable wide instantaneous bandwidth and high linearity for the RF receiver. To do so, N-bit pseudo-random-binary-sequences (PRBS) are used as local oscillator signals. The RF input signal is multiplied with the PRBS at the mixer and then averaged over the full sequence. This in effect reduces the amplitude of the signal and improves the overall linearity of the system. In order …
Energy Efficiency Of Computation In All-Spin Logic: Projections And Fundamental Limits, Zongya Chen
Energy Efficiency Of Computation In All-Spin Logic: Projections And Fundamental Limits, Zongya Chen
Masters Theses
Built with nanomagnets, a spintronic device called the all-spin logic (ASL) device carries information with only spin currents, resulting in a low power supply--10 mV. This voltage is 100 times smaller than the conventional CMOS devices (usually 0.8~1V). The potential for improved energy efficiency made possible by the low operating voltage of ASL makes it one of the most promising devices among its post-CMOS competitors.
The basic working principles of ASL device are introduced in this thesis and two complementary approaches to studying energy efficiency of computation are applied to a common set of ASL circuits: (1) a circuit simulation …
Silicon-Germanium Heterojunction Bipolar Transistors For Large-Scale Low-Power Cryogenic Sensing Systems, Shirin Montazeri
Silicon-Germanium Heterojunction Bipolar Transistors For Large-Scale Low-Power Cryogenic Sensing Systems, Shirin Montazeri
Doctoral Dissertations
Cryogenic low noise amplifiers (LNAs) are one of the key components in many emerging applications such as radio astronomy or quantum computing in which a weak incoming signal needs to be read out. There have been extensive studies on the feasibility of leveraging silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) to implement cryogenic LNAs in the past. The deployment of such LNAs in the future large-scale systems in radio astronomy or quantum computing is contingent upon the possibility of developing LNAs with reduced DC power dissipation to enable the cooling of a large number of array elements inside a cryogenic cooler. …
On-Chip Communication And Security In Fpgas, Shivukumar Basanagouda Patil
On-Chip Communication And Security In Fpgas, Shivukumar Basanagouda Patil
Masters Theses
Innovations in Field Programmable Gate Array (FPGA) manufacturing processes and architectural design have led to the development of extremely large FPGAs. There has also been a widespread adaptation of these large FPGAs in cloud infrastructures and data centers to accelerate search and machine learning applications. Two important topics related to FPGAs are addressed in this work: on-chip communication and security. On-chip communication is quickly becoming a bottleneck in to- day’s large multi-million gate FPGAs. Hard Networks-on-Chip (NoC), made of fixed silicon, have been shown to provide low power, high speed, flexible on-chip communication. An iterative algorithm for routing pre-scheduled time-division-multiplexed …
Materials Engineering, Switching Mechanism And Novel Applications Of Memristive Devices, Hao Jiang
Materials Engineering, Switching Mechanism And Novel Applications Of Memristive Devices, Hao Jiang
Doctoral Dissertations
Memristive devices have attracted tremendous interests because of their highly desirable properties such as a simple structure, low switching voltage, fast switching speed, excellent scalability, multiple conductance states and great compatibility with the Complementary Metal–Oxide–Semiconductor technology. Hence, they stand out as promising candidates for next-generation non-volatile memory and electronic synapses in artificial neural network. This thesis reports systematic studies of the memristive switching phenomena in oxide based material systems, in aspects of materials engineering, switching mechanism and novel applications. We demonstrated efficient ways of engineering device performances such as metal doping and further presented a highly reliable hafnium oxide based …
Analog Computing Using 1t1r Crossbar Arrays, Yunning Li
Analog Computing Using 1t1r Crossbar Arrays, Yunning Li
Masters Theses
Memristor is a novel passive electronic device and a promising candidate for new generation non-volatile memory and analog computing. Analog computing based on memristors has been explored in this study. Due to the lack of commercial electrical testing instruments for those emerging devices and crossbar arrays, we have designed and built testing circuits to implement analog and parallel computing operations. With the setup developed in this study, we have successfully demonstrated image processing functions utilizing large memristor crossbar arrays. We further designed and experimentally demonstrated the first memristor based field programmable analog array (FPAA), which was successfully configured for audio …
Three-Dimensional Memristor Integrated Circuits And Applications, Peng Lin
Three-Dimensional Memristor Integrated Circuits And Applications, Peng Lin
Doctoral Dissertations
New computing paradigms are highly demanded in the “Big Data” era to efficiently process, store and extract useful information from overwhelmingly rich amount of data. New computing systems based on large scale memristor circuits emerges as a very promising candidate due to its capability to both store and process information, thus eliminating the von Neumann bottleneck in the conventional complementary metal oxide semiconductor (CMOS) based computers. As the lateral scaling of the device geometry approaching its physical limit, three-dimensional stacking of multiple device layers becomes necessary to further increase the packing density. Moreover, innovations in the 3D circuits design can …
Dynamic Range Limitations Of Low-Noise Microwave Transistors At Cryogenic Temperatures, Ahmet Hakan Coskun
Dynamic Range Limitations Of Low-Noise Microwave Transistors At Cryogenic Temperatures, Ahmet Hakan Coskun
Doctoral Dissertations
Dynamic range is an important metric that specifies the limits of input signal amplitude for the ideal operation of a given receiver. The low end of dynamic range is defined by the noise floor whereas the upper limit is determined by large-signal distortion. While dynamic range can be predicted in the temperature range where compact transistor models are valid, the lack of large-signal models at temperatures below -55 C prevents the prediction and optimization of dynamic range for applications that require cryogenic cooling. For decades, the main goal concerning the performance of these applications was lowering the noise floor of …
Kasi: A Ka-Band And S-Band Cross-Track Interferometer, Gerard Ruiz Carregal
Kasi: A Ka-Band And S-Band Cross-Track Interferometer, Gerard Ruiz Carregal
Masters Theses
A dual-frequency system is needed to better understand natural processes that constitute the environment and seasonal cycles of the Earth. A system working at two different wavelengths acquiring data simultaneously will give a valuable dataset since the conditions on the ground will be exactly the same. Hence, elements such as wind, soil moisture or any other changes on the ground will not interfere in the mea- surements. This thesis explains how an S-band radar was built and tested. Moreover, the experiments done with a Ka-band radar used as a scatterometer are explained as well as the data processing and analysis. …
The Impact Of Quantum Size Effects On Thermoelectric Performance In Semiconductor Nanostructures, Adithya Kommini
The Impact Of Quantum Size Effects On Thermoelectric Performance In Semiconductor Nanostructures, Adithya Kommini
Masters Theses
An increasing need for effective thermal sensors, together with dwindling energy resources, have created renewed interests in thermoelectric (TE), or solid-state, energy conversion and refrigeration using semiconductor-based nanostructures. Effective control of electron and phonon transport due to confinement, interface, and quantum effects has made nanostructures a good way to achieve more efficient thermoelectric energy conversion. This thesis studies the two well-known approaches: confinement and energy filtering, and implements improvements to achieve higher thermoelectric performance. The effect of confinement is evaluated using a 2D material with a gate and utilizing the features in the density of states. In addition to that, …
Topography Measurements Using An Airborne Ka-Band Fmcw Interferometric Synthetic Aperture Radar, Kan Fu
Topography Measurements Using An Airborne Ka-Band Fmcw Interferometric Synthetic Aperture Radar, Kan Fu
Doctoral Dissertations
Radar interferometry at millimeter-wave frequencies has the ability of topography measurement of different types of terrain, such as water surfaces and tree canopies. A Ka-band interferometric radar was mounted on an airborne platform, and flown over the Connecticut river region in western Massachusetts near Amherst on June 11, 2012. More than 20 Gigabytes of raw data was recorded. This dissertation outline presents the results of the data processing, which includes (1) the estimation and removal of the embedded high frequency phase error in the raw data; (2) the synthetic aperture processing; (3) the interferometric processing. The digital elevation model (DEM) …
Low Cross-Polarization Vivaldi Arrays, John Logan
Low Cross-Polarization Vivaldi Arrays, John Logan
Doctoral Dissertations
Ultra-wideband (UWB) electronically scanned arrays (ESA) with high efficiency, excellent polarization agility, and wide-scan matching remain essential for servicing multifunctional RF front-ends and other communications, sensing, and jamming or countermeasure systems. To this day, the most popular antenna array element in modern UWB-ESA systems is the Vivaldi, or flared notch, due to its superior wide-scan wide impedance bandwidth, well-known design guidelines, and practical embodiment versatility. Despite their popularity, these arrays tend to radiate unacceptably high cross-polarization levels, thus encouraging a great research opportunity. This dissertation presents the theory and design of a new class of UWB-ESAs, termed Sliced Notch Antenna …
Development Of A Portable Cmos Time-Domain Fluorescence Lifetime Imager, Hongtao Wang
Development Of A Portable Cmos Time-Domain Fluorescence Lifetime Imager, Hongtao Wang
Doctoral Dissertations
Modern laboratory equipments to measure the excited-state lifetime of fluorophores usually include an expensive picosecond pulsed-laser excitation source, a fragile photomultiplier tube, and a large instrument body for optics. A portable and robust device to make fluorescence lifetime measurement in nanosecond scale is of great attraction for chemists and biologists. This dissertation reports the development of a portable LED time-domain fluorimeter from an all-solid-state discrete-component prototype to its advanced CMOS integrated circuit implementation. The motivation of the research is to develop a multiplexed fluorimeter for point-of-care diagnosis. Instruments developed by this novel method have higher fill factor, are more portable, …
Integrated Solar Technologies With Outdoor Pedestrian Bridge Superstructure Decking, Richard K. Racz
Integrated Solar Technologies With Outdoor Pedestrian Bridge Superstructure Decking, Richard K. Racz
Masters Theses
Solar technology has been a major topic in sustainable design for many years. In the last five years, however, the solar technology industry has seen a rapid growth in installations and technological advances in cell design. Combined with a rapidly declining overall system cost, the idea of introducing solar technology into a wider range of applications is becoming a focus for engineers and scientists around the world. So many variables which alter solar energy production, such as the sun and surrounding environment, determine whether a solar design is beneficial. This thesis presents a bridge deck surface integrated with solar cells …
Skybridge: A New Nanoscale 3-D Computing Framework For Future Integrated Circuits, Mostafizur Rahman
Skybridge: A New Nanoscale 3-D Computing Framework For Future Integrated Circuits, Mostafizur Rahman
Doctoral Dissertations
Continuous scaling of CMOS has been the major catalyst in miniaturization of integrated circuits (ICs) and crucial for global socio-economic progress. However, continuing the traditional way of scaling to sub-20nm technologies is proving to be very difficult as MOSFETs are reaching their fundamental performance limits [1] and interconnection bottleneck is dominating IC operational power and performance [2]. Migrating to 3-D, as a way to advance scaling, has been elusive due to inherent customization and manufacturing requirements in CMOS architecture that are incompatible with 3-D organization. Partial attempts with die-die [3] and layer-layer [4] stacking have their own limitations [5]. We …
Architecting Skybridge-Cmos, Mingyu Li
Architecting Skybridge-Cmos, Mingyu Li
Masters Theses
As the scaling of CMOS approaches fundamental limits, revolutionary technology beyond the end of CMOS roadmap is essential to continue the progress and miniaturization of integrated circuits. Recent research efforts in 3-D circuit integration explore pathways of continuing the scaling by co-designing for device, circuit, connectivity, heat and manufacturing challenges in a 3-D fabric-centric manner. SkyBridge fabric is one such approach that addresses fine-grained integration in 3-D, achieves orders of magnitude benefits over projected scaled 2-D CMOS, and provides a pathway for continuing scaling beyond 2-D CMOS.
However, SkyBridge fabric utilizes only single type transistors in order to reduce manufacture …
Novel Method For Broadband On-Chip Noise Characterization, Mohammad Ghadiri Sadrabadi
Novel Method For Broadband On-Chip Noise Characterization, Mohammad Ghadiri Sadrabadi
Masters Theses
A novel method for on-chip noise characterization of mm-wave circuits is presented. Different available methods for noise measurements and requirements for on-chip noise mea-surements are studied. The Y-factor method is chosen to be the more suitable method for in-situ applications since it does not require absolute measurements. A state of the art CMOS noise source is implemented in 32nm SOI CMOS technology to enable the in-situ noise measurements of a 20-35 GHz reconfigurable low noise amplifier. Measurement results show that the ENR of the noise source is repeatable enough so that the calibration of the noise source is only required …
Design Of Non-Uniform Linear Array Via Linear Programming And Particle Swarm Optimization And Studies On Phased Array Calibration, Hua Bai
Masters Theses
For a linear array, the excitation coefficients of each element and its geometry play an important role, because they will determine the radiation pattern of the given array. Side Lobe Level (SLL) is one of the key parameters to evaluate the radiation pattern of the array. Generally speaking, we desire SLL to be as low as possible. For the linear array with uniform spacing, there are some classic methods to calculate the excitation coefficients to make the radiation pattern satisfy the given requirements. For the linear array with non-uniform spacing, linear programming and particle swarm optimization are proposed to calculate …
Beam Steering Control System For Low-Cost Phased Array Weather Radars: Design And Calibration Techniques, Rafael H. Medina-Sanchez
Beam Steering Control System For Low-Cost Phased Array Weather Radars: Design And Calibration Techniques, Rafael H. Medina-Sanchez
Doctoral Dissertations
Phase array antennas are a promising technology for weather surveillance radars. Their fast beam steering capability offer the potential of improving weather observations and extending warning lead times. However, one major problem associated with this technology is their high acquisition cost to be use in networked radar systems. One promising technology that could have a significant impact in the deployment of future dense networks of short-range X-band weather radars is the ``Phase-Tilt Radar'', a system that uses a one-dimensional phase scanned antenna array mounted over a tilting mechanism. This dissertation addresses some of specific challenges that arise in designing and …