Devavrat Likhite PhD final defense

UNIVERSITY OF UTAH

ELECTRICAL AND COMPUTER ENGINEERING DEPARTMENT

 

DISSERTATION DEFENSE FOR THE DEGREE OF

DOCTOR OF PHILOSOPHY

 

by

 

Devavrat Likhite

Advisor: Edward DiBella

 

 

Challenges in quantitative cardiovascular magnetic resonance perfusion

 

 

Medical imaging has evolved with leaps and bounds in the last century. Several medical imaging modalities such as X-rays, single photon emission computer tomography (SPECT), positron emission tomography (PET), computer tomography (CT), magnetic resonance imaging (MRI) have developed. However, MRI has a distinct advantage over most of these imaging techniques. MRI does not use ionizing radiation and hence is considered a safer option for non-invasive imaging. However, every imaging modality comes with its set of limitations and challenges. Although quantitative myocardial perfusion MRI has been studied by researchers over a few decades now, it has still not developed into a clinical tool. There is no consensus on the choice of imaging protocol to be used. The scientific community is still divided on the choice of pharmacokinetic model to be used for quantification of myocardial perfusion. In this dissertation, novel techniques were developed and implemented to address few of the challenges faced by fully quantitative myocardial perfusion MRI. We strive to make it more simple and more accurate. It is with the development of such easy-to-use techniques that cardiac perfusion MR will find more and more clinical use. These developments are in a direction to transition quantitative myocardial perfusion MRI from an ‘evolving tool’ to an ‘evolved and matured tool’.

 

 

 

Thursday December 1, 2016

11:00 AM

Imaging and Neurosciences Center (Building 888),

729 Arapeen drive,

Downstairs large conference room

The public is invited

Jotham Vaddaboina Manoranjan PhD final defense

UNIVERSITY OF UTAH

ELECTRICAL AND COMPUTER ENGINEERING DEPARTMENT

 

DISSERTATION DEFENSE FOR THE DEGREE OF

DOCTOR OF PHILOSOPHY

 

by

 

Jotham Vaddaboina Manoranjan

Advisor: Ken Stevens

 

 

Relative Timing Based Verification and Design with Delay Insensitive Signal Path Modeling with Application for FPGAs

 

 

The relative timing (RT) based asynchronous design methodology has been successfully been used to create ASIC designs that are a process generation ahead of their synchronous counterparts in terms of power, performance and energy. However, while the implementation of RT asynchronous circuits has been dealt with successfully in the ASIC domain, there has been limited exploration of utilizing the design methodology on FPGAs. This dissertation seeks to address the challenges in implementing RT asynchronous circuits on FPGAs. 

Relative Timing uses path based timing constraints to guarantee that a circuit conforms to its behavioral specification. A methodology for the design of glitch free burst-mode asynchronous controllers on FPGAs is presented. Path based timing constraints are implement to ensure circuit functionality. A flow for the modeling of the circuit, extraction of relative timing constraints and implementation of the extracted constraints is presented. Optimizations that enable faster implementation and more robust designs are discussed. 

The dissertation also presents a framework to evaluate and rank relative timing constraint sets for a given circuit. Multiple constraint sets are possible for a single circuit. The constraint sets are evaluated on the basis of robustness of the constraints and conflicts between constraints in the same set. The methodology is used to optimize the extraction of relative timing constraints. 

An FPGA architecture capable of relative timing based digital implementations is designed. Modifications are made to a traditional synchronous FPGA architecture to make it asynchronous capable, while retaining its capability as a fully functional synchronous FPGA. A MIPS design is used to test the FPGA. A performance improvement of 1.7× and a power improvement of 2.3×.

Furthermore, a novel reconfigurable circuit capable of implementing the entire family of 2-phase and 4-phase latch protocols is presented. The circuit is implemented on the IBM Artisan 65nm node and its performance is compared with implementations on a Xilinx Virtex-5 chip that is manufactured on a similar node. A 4× improvement in speed and 2.7× improvement in energy per cycle is achieved.

 

 

 

Wednesday November 30, 2016

12-2 PM, Eccles Boardroom

Warnock Engineering Building (WEB) room 1605

The public is invited

Arslan Majid PhD final defense

UNIVERSITY OF UTAH

ELECTRICAL AND COMPUTER ENGINEERING DEPARTMENT

 

DISSERTATION DEFENSE FOR THE DEGREE OF

DOCTOR OF PHILOSOPHY

 

by

Arslan Majid

Advisor: Behrouz Farhang

 

 

Secure Communications In Filter-Bank Multi-Carrier

Spread Spectrum Systems

 

 

 

A fundamental characteristic of wireless communications are in their broadcast nature,

which allows accessibility of information without placing restrictions on a user’s location.

However, the ease of accessibility also makes it vulnerable to eavesdropping. This dissertation

considers the security issues of spread spectrum systems and in this context, a secure information transmission system compromised of two main parts is presented. The first component makes use of the principle of reciprocity in frequency-selective wireless channels to derive a pair of keys for two legitimate parties. The proposed key generation algorithm allows for two asynchronous transceivers to derive a pair of similar keys. Moreover, a unique augmentation – called strongest path cancellation (SPC) – is applied to the keys and has been validated through simulation and real-world measurements to significantly boost the security level of the design. In the second part of the secure information transmission system, the concept of artificial noise is introduced to multi-carrier spread spectrum

systems. The keys generated in the first part of the protocol are used as spreading code sequences for the spread spectrum system. Artificial noise is added to further enhance the security of the communication setup. Two different attacks on the proposed security system are evaluated. First, a passive adversary following the same steps as the legitimate users to detect confidential information is considered. The second attack studies a more sophisticated adversary with significant blind detection capabilities.

 

 

 

 

 

Tuesday November 22, 2016

9:00 AM, ECE conference room

Merrill Engineering Building (MEB) room 3235

The public is invited

Suresh Venkatesh PhD final defense

UNIVERSITY OF UTAH

ELECTRICAL AND COMPUTER ENGINEERING DEPARTMENT

 

DISSERTATION DEFENSE FOR THE DEGREE OF

DOCTOR OF PHILOSOPHY

 

by

Suresh Venkatesh

Advisor: David Schurig

 

 

Metamaterials and their Applications in Imaging

 

Microwave/millimeter-wave imaging systems have become ubiquitous and have found applications in areas like astronomy, bio-medical diagnostics, remote sensing, and security surveillance. These areas have so far relied on conventional imaging devices (employing Nyquist principles) which at best can provide diffraction-limited images. With the advent of metamaterials, unique and extraordinary electromagnetic responses can be achieved which can potentially revolutionize imaging devices. Such extraordinary responses include: negative refraction, strong anisotropy, gradient-index response, perfect absorption, magneto-electric effects (chirality), and many more. When adopted into imaging devices, these response characteristics could potentially: beat diffraction-limits, improve imaging performance or lead to unprecedented control over light propagation. Along with metamaterials, mathematical tools like transformation optics or torsion optics (which leverages Riemannian geometry under the geometrical optics limit) facilitate the design and development of systems with exclusive effects such as invisibility cloaking, perfect and/or aberration-free lensing, near-field magnification, and total control of the polarization field. When metamaterial devices are combined with computational imaging techniques, the resulting systems can exploit apriori information to reach previously unattainable trade-off positions in the space of: image quality, size, weight, power and cost. In this dissertation we present and discuss metamaterial based imaging devices, and associated principles and techniques that achieve such enhanced imaging performance (See Fig.0.1).

In Chapters. [1 & 2], we present a novel “medium-as-device” approach to experimentally demonstrate a metamaterial, perfect-absorber-based focal plane array. The microwave focal plane array was demonstrated both as an intensity detector and as a vector signal detector. The former setup was used to perform interferometric direction finding of RF emitters.

In Chapter. [3], we present a transformation optics designed near-field magnifier, for sub-wavelength imaging. We discuss and present various design parameters and trade-offs associated with such magnifiers. We adopt grid relaxation techniques that result in material properties that are more amenable to implementation. In Chapter. [4], we present a novel “Torsion Optics” design method, leveraging Riemannian geometric concepts, which facilitates the design of devices with gradient chiral material properties, giving an unprecedented control over the polarization field.

In Chapter. [5], we demonstrate a prototype W-band (75 -110 GHz) sparse, syntheticaperture, computational imaging system that leverages intrinsic frequency diversity in the sparse aperture. We also formulate an information-based metric to evaluate the performance of a given image transfer matrix for noise-limited, computational imaging systems. In Chapter. [6], we describe a computationally-fast approach for propagation of vector electromagnetic fields through an axi-symmetric medium (such as a lens) using cylindrical harmonic decomposition techniques. The motivating application is to computational imaging systems, where the forward propagation model must be computed quickly, for real time results. This approach was also applied in the near-field magnifier design and analysis.

In Chapter. [7], as a part of future directions, we exploit all of the above approaches to propose a multi-functional RF system leveraging commercial off-the-shelf integrated circuits. We propose to investigate, in particular, the synergies that result when a single hardware platform can support: focusing-optic-free computational imaging, satellite links on mobile platforms, and electronic targeting of non-lethal force.

 

 

 

Wednesday October 26, 2016

9:30 AM, ECE conference room

Merrill Engineering Building (MEB) room 2109

The public is invited

Daimei Zhu PhD thesis final defense

UNIVERSITY OF UTAH

ELECTRICAL AND COMPUTER ENGINEERING DEPARTMENT

 

DISSERTATION DEFENSE FOR THE DEGREE OF

DOCTOR OF PHILOSOPHY

 

by

Daimei Zhu

Advisor: V. Jon Mathews

 

 

 

Blind Modulation Identification of QAM and PSK Signals in Dual-polarized Channels

 

In many optical and RF communication systems, information is transmitted through two-polarizations of the carrier to improve transmission capacity. The ability to blindly identify of the modulation types of signals in dual-polarized channels will help the communication systems build more powerful receivers. This dissertation deals with blind modulation identification of quadrature amplitude modulations (QAM) and phase-shift keying (PSK) signals in dual-polarized channels in digital communication systems.

The problems addressed in this dissertation are as follows: First, blind modulation identification of QAM and PSK signals in single channel with Gaussian noise is explored. Second, blind separation of the two information streams in a dual-polarized channel and identification of the modulation types of the two information streams are developed. Finally, blind modulation identification of the signals arriving through multipath channels is studied. A likelihood-based blind modulation identification for QAM and PSK signals in single channel with Gaussian noise is developed first. The likelihood-based algorithms identify the modulation type by maximizing the likelihood function of the amplitudes or the phase difference between nearby samples of the received signal. Results in this dissertation demonstrate that the proposed method can identify different QAM and PSK signals with 4-15 dB lower signal-to-noise-ratio (SNRs) than other available methods in the literature with 10,000 symbols. Second, a likelihood-based adaptive blind source separation (BSS) and identification method for dual-polarized signals is developed. The algorithm separates the two information-bearing signals arriving in time-varying polarization by maximizing the likelihood functions of the received signals for the hypothesized modulation types. This algorithm recovers the input signal with small symbol error rate in a wide range of SNRs and tracks the channel coefficients with small errors. The combination of the likelihood-based BSS and the likelihood-based modulation identification algorithm is able to identify the PSK and QAM signals in dual-polarized channels with high accuracy. Finally, blind modulation identification method combining constant modulus amplitude (CMA) equalizer and the likelihood functions for signals in multipath channels is proposed. The combination of CMA equalizer and the likelihood-based modulation identification algorithm is able to identify the lower order QAM (16-, 32-, 64- QAM) types of the received signals in the multipath channels with 100\% accuracy at SNR above 14 dB with 20,000 symbols. The modified likelihood-based modulation identification can identify different PSK modulations of the received signals in a two-path channel at SNR above 11 dB with 10,000 symbols.

 

 

Monday October 17, 2016

9:00 AM, ECE conference room

Merrill Engineering Building (MEB) room 3235

The public is invited

Tarek Haddadin-MS final thesis defense

UNIVERSITY OF UTAH
ELECTRICAL AND COMPUTER ENGINEERING DEPARTMENT

DISSERTATION DEFENSE FOR THE DEGREE OF
MASTER OF SCIENCE

by

Tarek Haddadin
Advisor: Behrouz Farhang

CHANNEL AND NOISE VARIANCE ESTIMATION IN A SPREAD SPECTRUM COMMUNICATION SYSTEM

Filter Bank Multicarrier (FB-MC) is a technique similar to Orthogonal Frequency Division Multiplexing (OFDM), used to divide the spectrum of a transceiver into multiple subcarriers or channels. When a single symbol is repeated across all subcarriers the energy is spread across the entire spectrum. This is referred to as Filter Bank Multicarrier Spread Spectrum (FB-MC-SS). The design of a preamble or training sequence used in the packet construction of a FB-MC-SS transceiver system is explored in this thesis. The preamble is used to acquire an estimate of the channel impulse response and noise variance for each subcarrier. This information is then used to undo the effect of the channel and perform Maximum Ratio Combining (MRC) across all subcarriers. An alternating {+1, −1} sequence has been previously proposed for its implementation simplicity. An alternating {+1,−1} sequence leads to detection advantages as a result of the impulse response of the matched filter. An alternating {+1,−1} sequence also presents many disadvantages. Mainly, the sequence is susceptible to interference because of its distinct frequency. The alternating {+1, −1} sequence also has a higher probability of detection by non authorized users. To combat these deficiencies of the alternating {+1,−1} sequence, pseudorandom sequences are explored in this thesis. The goal of the pseudorandom sequence is to gain robustness without forfeiting the packets detectability by intended receivers. Pseudorandom Polyphase and Maximum Length Binary sequences are explored as randomized preambles. Both the alternating {+1, −1} sequence and the pseudorandom sequence are implemented separately in the FB-MC-SS transceiver on a Xilinx FPGA to compare resource utilizations. Pseudorandom Polyphase preamble sequences lead to robust channel frequency response and noise variance estimation in interfered environments. Although alternating {+1, −1} sequence lead to straightforward packet detection and simple FPGA implementation, the susceptibility of an alternating {+1,−1} preamble to interference make a pseudorandom preamble sequence more desirable.

Thursday August 16, 2016
10:00 AM

Merrill Engineering Building (MEB) room 2325
The public is invited

Bing Shen PhD final defense

UNIVERSITY OF UTAH
ELECTRICAL AND COMPUTER ENGINEERING DEPARTMENT

DISSERTATION DEFENSE FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY

by

Bing Shen
Advisor: Rajesh Menon

Computational Silicon Nanophotonic Design

Photonic integration circuits (PICs) are receiving overwhelming attention in the past few decades due to various advantages over electronic circuits including absence of Joule effect and huge bandwidth. The most significant problem obstructs its commercial application is the integration density, which is largely determined by the signal wavelength that is in the order of microns. In this dissertation, we are focused on enhancing the integration density of PICs to warrant its practical applications.

In general, we believe there are three ways to boost the integration density. The first is to downscale the dimension of individual integrated optical component. As an example, we have experimentally demonstrated an integrated optical diode with footprint 3 × 3 m2, an integrated polarization beamsplitter with footprint 2.4 × 2.4 m2, and a waveguide bend with effective bend radius as small as 0.65 m. All these devices offer the smallest footprint when compared to their alternatives. A second option to increase integration density is to combine the function of multiple devices into a single compact device. To illustrate the point, we have experimentally shown an integrated mode-converting polarization beamsplitter, and a free-space to waveguide coupler and polarization beamsplitter. Two distinct functionalities are offered in one single devices without significantly sacrificing the footprint. A third option for enhancing integration density is to decrease the spacing between the individual devices. For this case, we have experimentally demonstrated an integrated cloak for non-resonant (waveguide) and resonant (microring-resonator) devices. Neighboring devices are totally invisible to each other even if they are separated as small as /2 apart.

Inverse design algorithm is employed in demonstrating all of our devices. The basic premise is that via nanofabrication, we can locally engineer the refractive index to achieve unique functionalities that is otherwise impossible. Nonlinear optimization algorithm is used to find the best permittivity distribution and focused ion beam is used to define the fine nanostructures.

Our future work lies in demonstrating active nanophotonic devices with compact footprint and high efficiency. Broadband and efficient silicon modulator, and all-optical and high-efficiency switch are envisioned with our design algorithm.


Thursday August 18, 2016
1:30 PM
Warnock Engineering Building, Wiggins Seminar room WEB 2470
The public is invited

Steven Brown-MS final defense

UNIVERSITY OF UTAH
ELECTRICAL AND COMPUTER ENGINEERING DEPARTMENT

DISSERTATION DEFENSE FOR THE DEGREE OF
MASTER OF SCIENCE

by

Steven Brown
Advisor: Neal Patwari



Designing a High-speed, Low-cost Electrical Impedance Tomography Data Acquisition System Using Commercial Off-The-Shelf Components

As unattended, remote controlled, and self-driving aerial and ground vehicles become increasingly prevalent, the need for real-time structural health monitoring (SHM) systems that can sense, localize and quantify internal structural damage with low latency, low power, and small size and weight requirements, is increasing. One such methodology, electrical impedance tomography (EIT), shows promising results, but is limited in its scalability and portability due to lack of hardware support outside of expensive and bulky laboratory-grade equipment. In this master’s thesis, a data acquisition system of low cost and small form factor is designed and created to rapidly and efficiently collect EIT measurements for SHM applications. System scalability is abstracted to small data acquisition modules that communicate to a host computer via a USB connection. Fitting the palm of your hand, and at a cost of only 250 USD, each module is capable of collecting EIT data at a rate of 10,000 voltage measurements per second with 10-bit resolution. This study describes the design process that attempts to achieve the desired data collection rate, transfer speed, and size requirements for this application using only readily-available commercial off-the-shelf electronic components. The performance, precision, accuracy and EIT reconstruction results of the designed EIT measurement system are characterized and compared to a laboratory-grade EIT data acquisition system.

Thursday August 11, 2016
11:00 AM

ECE conference room
Merrill Engineering Building (MEB) room 3235
The public is invited

Wen Yuan PhD final thesis defense

UNIVERSITY OF UTAH
ELECTRICAL AND COMPUTER ENGINEERING DEPARTMENT

DISSERTATION DEFENSE FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY

by

Wen Yuan
Advisor: Jeffrey Walling

Digital CMOS RF Power Amplifiers

High speed wireless communication systems (e.g., LTE, WiFi) operate with high bandwidth and large peak-to-average power ratios (PAPRs).This is largely due to the use of orthogonal frequency division multiplexing (OFDM) modulation that is prevalent to maximize the spectral efficiency of the communication system. The power amplifier (PA) in the transmitter is the dominant energy consumer in the radio, largely because of the PAPR of the input signal. To reduce the energy consumption of the PA an amplifier that simultaneously achieves high efficiency and high linearity. Furthermore, to lower the cost for high volume production, it is desirable to achieve a complete System-on-Chip (SoC) integration.
Linear amplifiers (e.g., Class-A, -B, -AB) are inefficient when amplifying signals with large PAPR that is associated by high peak-to-average modulation techniques such as LTE. OFDM. Switching amplifiers (e.g., Class-D, -E, -F) are very promising due to their high efficiency when compared to their linear amplifier counterparts. Linearization techniques for switching amplifiers have been intensively investigated due to their limited sensitivity to the input amplitude of the signal. Deep-submicron CMOS technology is mostly utilized for logic circuitry, and the Moore’s law scaling of CMOS optimizes transistors to operate as high-speed and low-loss switches rather than high gain transistors. Hence, it is advantageous to use transistors in switching mode as switching amplifies and use high-speed digital logic circuitry to implement linearization systems and circtuitry.
In this work, several linearization architectures are investigated and demonstrated. An envelope elimination and restoration (EER) transmitter that comprises a class-E power amplifier and a 10-bit DAC controlled current modulator is investigated. A pipelined switched-capacitor DAC is designed to control an open-loop transconductor that operates as a current modulator, modulating the amplitude of the current supplied to a class-E PA. Such a topology allows for increased filtering of the quantization noise that is problematic in most digital PAs (DPA). The proposed quadrature and multiphase architecture can avoid the bandwidth expansion and delay mismatch associated with polar PAs. The multiphase SCPA was proposed after the quadrature SCPA and it significantly improves the power efficiency.


Thursday March 17, 2016
2:00 PM
ECE conference room, Merrill Engineering Building (MEB) room 3235
The public is invited

Srikant Kamesh Iyer PhD final thesis defense

UNIVERSITY OF UTAH
ELECTRICAL AND COMPUTER ENGINEERING DEPARTMENT

DISSERTATION DEFENSE FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY

by

Srikant Kamesh Iyer
Advisor: Tolga Tasdizen

Improved Total Variation Reconstruction Methods
for Cardiac Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) is an important tool in the detection and assessment of cardiovascular diseases. MRI, being free of ionizing radiation, is considered a safer imaging modality when compared to SPECT, PET and X-ray CT. However, every imaging modality comes with its set of limitations and challenges. In cardiac MRI, acquiring high resolution motion free data is a challenge. The physical limitations of the scanner preclude the simultaneous achievement of high spatial and high temporal resolution. Depending on the application, one is usually traded for the other. For example, in dynamic contrast enhanced (DCE) cardiac perfusion imaging, high spatial resolution is traded for high temporal resolution to allow for rapid tracking of contrast kinetics. As the MRI scanner acquires data in Fourier space or k-space, acquiring undersampled data in k-space leads to aliasing or other artifacts in the reconstructed image. Advancements in compressed sensing (CS) have made it possible to reconstruct high quality images from relatively few k-space samples by leveraging sparsity constraints to reconstruct artifact-free images. Total variation (TV) based reconstruction methods are widely used, including in the field of MRI. One drawback associated with TV implementations is smoothing of edges and loss of fine texture in the image. In addition, the rate of convergence with traditional minimization techniques is slow. This dissertation develops methods to improve the current TV-based reconstruction techniques with respect to image quality and reconstruction speed, in order to handle challenges associated with cardiac imaging. The reconstruction algorithms were developed and tested specifically to improve DCE cardiac perfusion imaging (gated and ungated) and 3D late gadolinium enhanced (LGE) images of the left atrium (LA).


Monday March 7, 2016
10:00 AM
Merrill Engineering Building (MEB) room 2109
The public is invited