M.S. - Electrical Engineering

Permanent URI for this collectionhttps://hdl.handle.net/10125/2047

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Design of liquid-metal reconfigurable reflectarrays with supporting computational tools
(University of Hawai'i at Manoa, 2025) Kouchi, Matthew Takiso; Ohta, Aaron; Shiroma, Wayne; Electrical and Computer Engineering
Fifth-generation (5G) and beyond wireless networks use high-band frequencies to offer ultra-fast data rates with minimal latency. However, operating in these high-band regimes introduces significant challenges such as increased path loss and reduced signal penetration. Reconfigurable reflectarrays (RAs) present a cost-effective and efficient solution, capable of dynamically steering electromagnetic beams using phase-tunable unit cells. Traditionally, RA designs have relied on solid-state devices like PIN diodes, MEMS switches, or tunable materials for phase tuning. These approaches, though effective, are often hampered by fabrication complexity, considerable power consumption, and limited scalability. This thesis introduces a reconfigurable reflectarray that leverages the unique fluidic properties of the liquid metal Galinstan, enabling mechanical phase tuning without the drawbacks associated with solid-state devices, such as increased power consumption and limited scalability. This represents a substantial step forward in RA technology, as Galinstan’s deformability allows for innovative unit cell designs that can be reshaped and actuated via microfluidic techniques like continuous electrowetting (CEW) and electrocapillary actuation (ECA). These novel methods facilitate precise and low-power reconfiguration of reflectarray elements, setting this work apart from previous research. Several unit cell designs were modeled using Ansys HFSS, fabricated via soft lithography and laser micromachining, and tested in custom 3.5-GHz and 28-GHz antenna testbeds. Measured results demonstrate an ability to perform anomalous beam steering within an accuracy of 2 degrees for all fabricated prototypes, highlighting the precision and effectiveness of the proposed approach. In addition to these hardware innovations, this work developed a suite of computational tools that significantly streamline the reflectarray design workflow. These tools automate phase distribution calculations, optimize radiation patterns, and enable rapid prototyping of unit cell geometries, thereby reducing development time and minimizing human error throughout the design process. The presented liquid-metal RA paradigm offers a scalable, low-power alternative to conventional RA technologies and is particularly well-suited for dynamic wireless environments in which virtual line-of-sight links (VLoS) need to be reestablished.
Resiliency-centric optimization for microgrid sizing: A holistic approach with renewable and hydrogen energy infrastructure
(University of Hawai'i at Manoa, 2025) Kerkau, Spencer Mitsuo; Green, Daisy; Electrical Engineering
The traditional power grid in the United States is often regarded as one of the largest machines in the world. Also referred to as the conventional grid—or simply, the grid— it is a vast network of interconnected power plants, transmission and distribution lines, substations, transformers, sensors, and other power electronics that work together to deliver electricity. This research targets a subset of electrical infrastructure known as a microgrid. Microgrids are commonly thought of as smaller sites that utilize distributed energy resources (DER) as a means to satisfy energy requirements. Microgrids are typically connected to the traditional grid using point of connection (POC) but retain the ability to operate independently. This trait is known as operating in islanded mode. Examples of microgrids are small islands, military bases, research facilities, and more. The goal of this research is to demonstrate a holistic optimization model that recommends a combination of DER components with sizing configurations to meet energy, resiliency, and financial requirements for grid-connected microgrids. The model must make improvements on existing industry accepted software or prior established research through the customization of features, increased functionality, or addressing gaps in knowledge. To accomplish this, the Natural Energy Laboratory of Hawaiʻi Authority (NELHA) was used as a case study site due to being a microgrid native to Hawaiʻi, access to high quality gross load and PV data, and unique scenario utilizing an electrolyzer to refill hybrid fuel cell electric busses (FCEB). Through the use of a hybrid Mixed-Integer Linear Programming-Particle Swarm Optimization (MILP-PSO) approach, various normal and resiliency scenarios were simulated demonstrating sizing configurations that met all normal and critical load, hydrogen demands, and financial constraints. The model also made improves on academic research providing a greater focus on the role of hydrogen infrastructure within grid-connected and islanded microgrids.
Prototyping of reflective metasurfaces and reconfigurable intelligent surfaces using liquid metal
(University of Hawai'i at Manoa, 2025) Manio, Glan Allan Villanueva; Shiroma, Wayne; Electrical Engineering
5G communication networks promise enhanced connectivity with higher speeds and larger bandwidth. Due to their reliance on higher frequency bands, these networks are subject to connectivity challenges such as line-of-sight requirements and sensitivity to physical obstacles. Anomalous reflectors, such as reflectarrays, reflective metasurfaces, and reconfigurable intelligent surfaces, offer a low-cost, passive/semi-passive solution for re-establishing connectivity between a blocked line-of-sight path. These devices work by redirecting incident signals towards the desired direction. This thesis focuses on the use of Galinstan liquid metal, a high electrical conductivity and deformable alloy, to replace typical materials used by anomalous reflectors. Using liquid metal, progressing degrees of reconfigurability are explored to improve connectivity for 5G frequency bands.
EVALUATING DYNAMICS IN CONVERTER DOMINATED POWER SYSTEMS: AN RMS AND EMT SIMULATION APPROACH
(University of Hawai'i at Manoa, 2024) Pramanik, Abrar Shahriar; Green, Daisy; Electrical Engineering
The transition from conventional power systems to converter-based microgrids has fostered advancements in sustainability, clean energy, and enhanced reliability. However, this shift also introduces significant challenges, originating from the intermittent behavior of renewable energy sources and the nonlinear properties of the power electronics, requiring dynamic models to simulate system behavior in real-time and ensure stability and reliability during fluctuations. Additionally, power electronics introduce nonlinear dynamics that can lead to issues such as voltage fluctuations and harmonic distortions. Dynamic modeling aids in predicting these effects and developing strategies to maintain system stability, particularly in managing voltage and frequency regulation, where traditional synchronous machines provide inertia. Dynamic modeling also enables the optimization of microgrid design and the evaluation of system resilience during disturbances. In this research, the dynamics of a converter-based microgrid were evaluated using Root Mean Squared (RMS) and Electromagnetic Transient (EMT) simulation techniques. The studied microgrid was modeled dynamically using the proposed method in DIgSILENT PowerFactory software. The simulated data for current, voltage, and instantaneous power were compared with recorded data collected from three locations in the microgrid using SEL 735 meters. The findings indicated that EMT and RMS simulations effectively captured the microgrid’s dynamic behavior, demonstrating their superiority as dynamic modeling approaches.
PROTON EXCHANGE MEMBRANE FUEL CELL MODIFICATION FOR CATALYTIC COGENERATION OF HYDROGEN PEROXIDE AND ELECTRICITY
(University of Hawai'i at Manoa, 2024) Fernandez, Alexandra M.; St-Pierre, Jean; Electrical Engineering
Proton exchange membrane fuel cells are susceptible to airborne sulfur contaminants that cause catalyst degradation, disrupting the oxygen reduction reaction and producing hydrogen peroxide as an undesired intermediate product within the membrane electrode assembly. Sulfur adsorbs onto the surface of the platinum/carbon catalyst, blocking active platinum sites and changing the reaction mechanism from a 4e- pathway producing water, to a 2e- pathway producing hydrogen peroxide. Today, 95% of commercially available hydrogen peroxide is made from an expensive, energy-intensive, and environmentally harmful anthraquinone oxidation process. This thesis seeks to take advantage of the described fuel cell vulnerability and uses ex-situ rotating ring-disk electrode methodology to validate the concept for a modified catalyst for cogeneration of hydrogen peroxide and electricity. Mechanisms behind this electrochemical process could provide a scalable, environmentally friendly, and more cost-effective production method of hydrogen peroxide.In this work, a catalyst modification process is developed using sulfur adsorption on platinum and for the first time, the stability of the modified catalyst and peroxide production is tested over long periods of time and under potential control. Cyclic voltammetry confirmed the stability of the modified catalyst for a minimum of 24 hours. The activity after catalyst modification is measured under polarization (0 V  1V), as well as potentiostatic control at 0.1 V, 0.2 V, 0.3 V, and 0.4 V over time. The results reveal a possible preferred condition for the maximized production of H2O2 and electricity at an applied potential near 0.3 V. While existing studies rely on an indirect method of peroxide quantification, the production of peroxide is confirmed via a dual traditional-potentiometric titration in the bulk solution after long term stability testing of 24 hours. Experiments reveal a possible rearrangement of adsorbed sulfur or some other change to the surface previously unknown from short-term tests. The concept for the modified catalyst was validated in these ex-situ tests and should be repeated in-situ in a single cell proton exchange membrane fuel cell for scaled-up production.
Optical Jitter Metrology for Precision Pointing Satellites
(University of Hawai'i at Manoa, 2024) Urasaki, Chase Masao; Zhu, Frances; Bottom, Michael; Electrical Engineering
In recent years, the popularity of CubeSatellites, or CubeSats, for space missionshas grown exponentially. They provide a miniature, standardized form factor and prioritize the use of commercial-off-the-shelf (COTS) components that reduce the size, weight, and power of space missions. Their compact size and cost-effectiveness are well suited to demonstrate and raise the technology readiness of smaller and higher-performing payloads. However, the increasing pointing requirements that come with these payloads and lower overall satellite mass means that jitter caused by moving or vibrating parts in CubeSats is a fundamental limit in their performance. Typical methods of characterizing jitter involve complex finite element methods, measuring jitter requires high costs in equipment and laboratory setups, as well as significant modification in the mass and inertial properties of the subject. This is due to adapting plates on dynamometers which introduce both size and frequency constraints. Alternatively, jitter measurements taken in space after launch do not allow the modification of the satellite or its components to achieve more optimal jitter characteristics. This makes in-situ measurements useful as a method of evaluation since there are no external damping effects, but, because the satellite is in space, cannot be a part of the design process. In this thesis, I describe a novel method of characterizing jitter for small satellite systems that is low-cost, simple, and minimally modifies the subject’s mass distribution. The metrology system is comprised of a COTS fiber-coupled laser source, a small mirror that is rigidly mounted to the satellite structure, and a lateral effect position-sensing detector. The system samples at a frequency of 1kHz and can measure jitter as low as 0.154 arcseconds over a measurement distance of 1 meter. I also developed a procedure that incrementally analyzes vibrating sources to establish causal relationships between sources and the vibrating frequency modes they create. Results from power spectral density plots show that this method can detect fundamental and higher-order vibrating modes in a fully integrated 6U spacecraft. The analysis is focused on attributing the causation of these modes to vibrating sources (such as reaction wheels and the cryocooler), verifying these correlations, and determining their pointing error contribution. We expect that this metrology system can serve to not only detect and characterize jitter in fully integrated small satellites and imaging systems from vibration sources but also verify vibrating satellite bus component performance like those from reaction wheels.
DESIGN, FABRICATION, AND MEASUREMENT OF GENETIC PROGRAMMING DEVELOPED BROADBAND RF METAMATERIAL ABSORBERS
(University of Hawai'i at Manoa, 2024) McDowell, Zion; Yun, Zhengqing; Electrical Engineering
Metamaterial absorbers are devices and surfaces specially designed to absorb electromagneticenergy. These absorbers are of critical interest for many applications, such as radar camouflage, EMI shielding, and antenna design. However, it is challenging to design compact absorbers with broadband performances. Experimental verification is even more difficult with current manufacturing processes. In this work, a hybrid genetic programming (HGP) approach has been used to develop several uniquely patterned broadband metamaterial absorbers with absorption characteristics spanning from 2-18GHz. A simple and efficient fabrication method has been developed for cutting unique and highly detailed patterns from a carbon-loaded polyethylene conductive film. This has then allowed for the experimental verification of several new HGP- developed designs. The metamaterials have features including broadband performance, incident angle stability up to 60°, polarization independence, compact 3-layer design, readily available materials, and a simple fabrication process. This thesis covers the design, fabrication, and experimental verification process for three unique conductive film-based designs. These designs are found to agree well with simulation and demonstrate the effectiveness of the HGP approach and unique metamaterials.
Voltage Response Insights into Lithium-Ion Battery Diagnostic Techniques
(University of Hawai'i at Manoa, 2023) Fernando, Alexa; Dubarry, Matthieu; Electrical Engineering
Efficient lithium-ion batteries are increasingly necessary, especially with the growing demand for energy storage. To enhance their efficiency, these batteries require an accurate and reliable method for online diagnosis. This thesis explores improving online diagnosis by examining the battery voltage response of commercial cells under varied cycling conditions. The first study investigates battery voltage relaxation, which is the gradual process of voltage equalization following the cutoff of current flow. Voltage relaxation could be pivotal in online cell state determination, however, research in this area is currently underdeveloped. This study reveals that voltage relaxation behavior is complex and is influenced by the depth of discharge, charge rate, temperature, and cell chemistry. The results provide a unique, comprehensive dataset for further research into voltage relaxation. This dataset is used to validate the efficiency of three voltage relaxation models and three voltage relaxation characterization techniques. The second study examines the effect of temperature on battery voltage response and looks at how it can be integrated into a mechanistic model. This model simulates the battery’s voltage response by quantifying the interactions between a cell’s positive and negative electrodes. The results of this study prove that it is possible to emulate the behavior of a cell at temperatures outside of the typical room temperature testing conditions by altering the charge/discharge rate. Lastly, this thesis analyzes the accuracy of optimization methods for generating synthetic battery data using mechanistic modeling. The results indicate that an exhaustive search technique outperforms optimization algorithms.
Methods for Extraction of Physiological Signals From Wrist-Worn PPG Sensor and Doppler Radar
(University of Hawai'i at Manoa, 2022) Stankaitis, Grant; Boric-Lubecke, Olga; Electrical Engineering
This research presents methods developed to extract physiological signals from subjects using both contact and non-contact devices. This research covers the tools used to extract respiration rate (RR) and applications for these tools. A waveform analysis will be performed to compare the signals recorded and discuss the physical phenomena associated with the alignment of the signals. Three tools will be presented to extract RR: a wrist-worn photoplethysmography (PPG) sensor, Doppler radar, and wireless data transfer. A PPG sensor in a watch-like formfactor is used to detect physiological signals such as pulse and respiration at the wrist of a subject. Doppler radar is used to detect physiological signals such as respiration from the physical rising and falling movement of the chest. The average maximum and minimum difference between Doppler radar extracted RR and PPG, HRV RSA, and accelerometer extracted RR is 0.342285 b/m and 0.170964 b/m, respectively. Wireless data transfer is implemented to transfer and process Doppler radar samples in real-time. Two applications for the methods developed will then be presented: remote patient monitoring and smart building applications. Doppler radar physiological sensing coupled with sensing using a wrist-worn PPG sensor in a watch-like form-factor allows a patient to have access to comfortable contact and non-contact options that can be used to monitor vital signs. Additionally, Doppler radar-based occupancy sensors are currently under development for accurate building monitoring systems. With wireless connectivity implemented, Doppler radar occupancy sensor data is processed in real-time and uploaded to a user interface to display occupancy statistics of a given room or building over time.
Toward Assessment of Lung Water Content Using Wireless Cardio-Pulmonary Stethoscope Measurements
(University of Hawaii at Manoa, 2023) Leong, Christopher James; Iskander, Magdy F.; Electrical Engineering
Detecting abnormal excessive buildup of fluid in the lungs, or pulmonary edema, is crucial in preventing conditions such as heart failure, kidney failure, and acute respiratory distress syndrome (ARDS). Most existing methods for measuring fluid accumulation in lungs are either expensive and invasive, thus unsuitable for continuous monitoring, or inaccurate and unreliable. To provide continuous and non-invasive monitoring of lung water status, Hawaii Advanced Wireless Technologies Institute (HAWTI) invented the Cardio-Pulmonary Stethoscope (CPS), a low-cost device with chest patch radio frequency (RF) sensors that was proven to be able to detect heart rate, respiration rate, and changes in lung water content from a single RF measurement. The CPS measurement procedure and the accuracy of results have been verified in a National Institute of Health (NIH) sponsored clinical trial conducted in collaboration with The Queen’s Medical Center in Honolulu.This thesis presents recent advances in expanding the capability of the CPS for assessing lung water status, in addition to monitoring the change in lung water, using artificial intelligence (AI). An important first step in our AI pipeline is to build a database of a diverse patient population. To this end, we utilize an NIH dataset consisting of CT-scans of patients of various genders, ages, and body fat compositions. We then develop an automatic workflow that reads the CT-scans and creates 3-D models for high-fidelity simulation in Ansys High Frequency Structure Simulator (HFSS). From HFSS, we obtain scattering parameters (S-parameters) measured by the CPS at various lung water levels. Compared to data collection from clinical trials, this “Virtual Clinical Trial” approach is low-cost, less time-consuming, and risk-free. Using the database we built, we develop AI models which use the patient metadata, namely gender, age, fat thickness, and S-parameters from the CPS as input, and output its assessment of the lung water status (i.e., normal, edematous, and severely edematous statuses). For a cohort of over 200 diverse individuals, our AI models achieve above 70% accuracy in assessing the lung water status. Furthermore, our AI models are interpretable and simple to explain
A Novel Genetic Algorithm Based Method for Measuring Complex Permittivity of Dielectric, Lossy and Multilayered Materials with Thin Features Using Open-Ended Coaxial Probe
(University of Hawaii at Manoa, 2023) Zhang, Sunny Shuxuan; Iskander, Magdy F.; Electrical Engineering
The growing demands for novel smart and enabling metamaterial designs and semiconductor devices in health, energy, communication, and automatic industries have attracted researchers to develop designs of materials with “thin” features. For broadband complex permittivity measurements using open-ended coaxial probe (OECP), thin sample measurements present sig- nificant challenges since a large amount of power may go through the sample making the measured complex permittivity values unreliable. We developed a new approach for accurate measurement of thin material properties by back- ing the thin sample with a thick material of known complex permittivity. The process involves measuring the reflection coefficient of the layered unknown and known materials and using genetic algorithm (GA) to determine the complex permittivity in a broadband frequency range (can be from 200MHz to 20GHz) by comparing measurements with the simulated reflection coef- ficient of the same experimental arrangement using HFSS simulation. We have obtained complex permittivity results of multiple thin, dielectric, lossy, and multilayered materials in 1 to 10 GHz. Air gap between the OECP and thin material under test (MUT) can dominate the error terms in obtaining accurate measurement results, particularly for high permittivity and lossy materials. Some possible solutions to overcome the air gap problem, limi- tations of measuring high complex permittivity of materials, and minimum sample thickness are discussed.
Genetic Programming in Designing Advanced Metamaterial Absorbers
(University of Hawaii at Manoa, 2022) Chong, Edmond CM; Iskander, Magdy F.; Electrical Engineering
Metamaterials are artificial materials that possess properties otherwise not found in nature. The current state of metamaterial absorbers (MMA) in the lower gigahertz frequency (1-11 GHz) is sparse and commonly resides in the X-band (8-12 GHz). Typical 2D MMA have topologies designed by trial and error and are either compact with discrete operational frequencies or bulky and lossy to achieve broadband performance. Hybrid genetic programming (HGP) is proposed to create new compact design topologies in the lower gigahertz frequency with new material development. HGP can create new topologies optimized per input parameters, such as low frequency and high broadband absorptivity. These designs are built and simulated in Ansys High-Frequency Simulation Software (HFSS) and evaluated by HGP. Additional topologies, such as graphene and resistive sheet patterning, and resistive sheet insert, are explored and implemented with HGP to create compact, low-gigahertz frequency and high-absorptivity MMAs. The graphene-based and resistive sheet-based patterned designs achieved 80% bandwidth above 80% absorptivity from 4.6 to 11 GHz, up to 15 GHz, and from 3.83 to 9.13 GHz, respectively. Preliminary measurements of a fabricated resistive sheet insert design aligned with simulated results.
Identifying Consumer Drones Via Encrypted Traffic
(University of Hawaii at Manoa, 2022) Liang, David Vincent; Dong, Yingfei; Electrical Engineering
While consumer drones have been broadly adopted for many recreational applications, they have also become a low-cost and versatile tool for malicious activities. To address these threats, we need effective drone management and counter-drone measures. Identifying the concrete type of an invading drone is the crucial initial step. While most existing drone identification methods leverage radar, acoustic, or image processing, to the best of our knowledge, almost none of these investigate the unique communication patterns of drones for detection. In this thesis, we focus on the communication protocol between a drone and its controller and conduct an in-depth analysis of both encrypted and plaintext drone traffic. We propose a framework for identifying a specific type of drone among a known set of drones by analyzing its encrypted Wi-Fi communication traffic between a drone and its controller. The main idea of this approach is to utilize our understanding of drone communication details to match communication patterns in encrypted traffic to communication patterns in plaintext traffic. To explore the common cases on popular consumer drones, we select drones equipped with the most popular open-source drone control system, ArduPilot. Because the communications on these drones use the most popular communication protocol, MAVLink, we are able to conduct in-depth analysis of their plaintext communication traffic and identify patterns for our detection and classification. Collecting drone traffic and identifying concrete patterns in plaintext traffic is the first focus of this thesis. However, communication between a drone and its controller often is encrypted with a state-of-art protocol (802.11 WPA2 or WPA3). We will need a method to discover the communication patterns in such encrypted traffic and match them with patterns discovered in plaintext communication. This is the second focus of this thesis. In the first focus, we capture the encrypted traffic between our drones and their controllers, decrypt the traces, and analyze the corresponding plaintext traces to build a profile for each type of drone. We discovered that, as traffic in many control systems, the plaintext communications contain many messages with Unique and Non-Varying (UNV) sizes across multiple traces; such UNV messages also show strong periodical patterns, which make them ideal candidates for building traffic patterns. Furthermore, looking into the encryption protocols, we notice that 802.11 WPA2 (or WPA3) uses the AES-CCMP (Counter Mode CBC MAC Protocol) for encryption, which encrypts a plaintext into a ciphertext with a fixed 44-byte size increase. Using this fact, we can easily infer the plaintext message size based on the size of an encrypted message. Therefore, based on our analysis of both plaintext and ciphertext traffic, we have identified a set of UNV message sizes that helps us associate message patterns in the encrypted traffic with the message patterns in plaintext traffic. Specifically, we collect Wi-Fi traffic traces for three ArduPilot drones (3DR Solo, Intel Aero, and SkyViper Journey), and build their corresponding profiles. In the second focus, we propose two classification methods utilizing the drone profiles built in the first focus. To match the patterns in a target trace with the drone profiles, we first propose similarity-based methods to classify the target drone. Furthermore, we utilize well-known machine learning methods to compare the detected patterns in the target encrypted traffic with patterns in the drone class profiles. By utilizing our knowledge of the intricacies of the drone communication protocol, we are able to develop these unique methods which differ from existing approaches. We have conducted a concrete performance evaluation with our collected data to evaluate the proposed classification methods. Our results show that the similarity-based methods work well in many cases but also have clear limitations; the machine-learning-based methods have shown very high accuracy for all testing cases, proving the effectiveness of the proposed framework. In addition, we have implemented an existing method that uses the short-term statistics of encrypted traffic for detection. We compare the method with the proposed method with our data traces. The results show that the proposed framework has significant advantages over the existing method. It confirms that utilizing the details of both encrypted and plaintext drone traffic can further improve the performance of our method. In summary, we have proposed a drone classification framework based on our understanding of the unique characteristics of drone traffic, and the performance evaluation has shown the effectiveness of the proposed framework. In the meantime, there are several directions we like to explore to further improve the current methods and evaluation, e.g., collecting more traces under various flight patterns and modes, and expanding the proposed idea to other automated devices (e.g., self-driving cars).
Robust 5G/B5G Millimeter Wave MIMO Communication in a Sparse Scattering Environment
(University of Hawaii at Manoa, 2022) Chang, Willy; Zheng, Yao; Electrical Engineering
Wireless sensing and communication is heading into a new era with the advent of fifth generation (5G) capabilities. Although these higher frequency bands are expected to increase throughput and reduce latency to meet increasing mobile user demands, they face significant challenges due to changes in physical characteristics that require different solutions compared to existing methods. One such method is multiple-input, multiple-output (MIMO), a way to increase the capacity of a communication link by exploiting multipaths that exist in the environment. While this rich scattering environment provides the diversity required, at mm-Wave, such paths are non-existent as a consequence of the rapid attenuation shorter wavelengths experience and blockages that prevent the signal from propagating through them. To support MIMO operations, existing research opt to focus on line-of-sight (LoS) MIMO to ensure an orthogonal channel matrix. However, these optimizations are unfeasible over longer distances and limited separation distances for both the transmitter and the receiver. We investigate the non-LoS (NLoS) channels via reflectors as an alternative to a LoS link for a robust procedure in maintaining the communication link. Several preliminary ideal simulations of the channel matrix under 2x2 and 3x3 MIMO were implemented to identify key areas of interest for antenna elements to guide their transmitted singal in order to maximize the channel capacity. We also conducted real-world experiments at 28 GHz to demonstrate that the measured channels are in good agreement with the theory for NLoS MIMO. We also conduct a theoretical analysis of the time complexities for potential path finding and path selection algorithms that leverage the given information to achieve the best possible throughput while minimizing overhead.
Real-time Stealth GPS Spoofing Attacks On Consumer Drones
(University of Hawaii at Manoa, 2022) Banh, Nguyen; Dong, Yingfei; Electrical Engineering
While vulnerabilities in unmanned drone software have been extensively explored, hardware vulnerabilities have received less attentions. In this project, we focus on the weaknesses of civilian GPS receivers on consumer drones and investigate their impacts on these drones. By exploiting the vulnerabilities of drone control software and civilian GPS systems, we develop a novel framework for GPS spoofing attacks on consumer drones. In this thesis, we will first introduce the details of drone control systems and the GPS system. We will then present the design of the proposed framework and the evaluation of the framework. Different from most existing GPS spoofing attacks which mostly use brute force approaches, we develop a real-time spoofing framework that utilizes live satellite ephemeral data to significantly improve the success rate of spoofing attacks and achieve better stealth spoofing effects. We also modified the open source bladeGPS software to generate and send real-time GPS signals. While the tests in our laboratory have shown that the proposed framework is very effective, it is still very challenging to evaluate it in practical testing, due to the limitations of the common off-shelf equipment available for the tests, the environment circumstances, and other factors beyond our control, such as wind velocity and cloud cover. We have conducted a number of experiments to better understand the practical challenges, as well as to show that the capabilities of the proposed framework. Furthermore, we present our results and findings and discuss future research issues.
Liquid-metal Devices And Circuits For Thermal Applications And Communications
(University of Hawaii at Manoa, 2022) Dacuycuy, Saige Jeremiah Ulep; Shiroma, Wayne A.; Electrical Engineering
The unique properties of liquid metal, such as high electrical conductivity, high thermal conduc-tivity, and deformability, offers promising opportunities for emerging devices and circuits. The focus of this thesis is on actuating liquid metal for potential applications in hot-spot cooling, sens-ing, and communications. First, continuous electrowetting of a liquid-metal droplet is demon-strated for controlled two-dimensional actuation and selective hot-spot cooling. In a 3 cm  3 cm well, a Galinstan liquid-metal droplet could move at a terminal velocity of 13.3 cm/s with an ac-tuation voltage of 11 V DC. For an actuation voltage of 10 V DC, the liquid-metal droplet de-creases the temperature of a localized hot spot by approximately 7 °C. Next, controlled defor-mation of liquid metal by electrocapillary actuation is demonstrated in fluidic channels at the sub-millimeter-length scale. In 100-µm-deep channels of varying widths, the Galinstan liquid metal could move at velocities greater than 40 mm/s. The dynamic behavior and physical limitations of the liquid metal as it moves in the fluidic channels is described and is useful for designing mi-crosystems that use liquid metal as a functional material.
The Design, Characterization, and Testing of the CRYO ASIC Front End Motherboard for the Deep Underground Neutrino Experiment
(University of Hawaii at Manoa, 2021) Kleyner, Jeffrey; Varner, Gary; Electrical Engineering
The Deep Underground Neutrino Experiment is currently in its design and testing stages where two sets of detectors will be used, 1300 km apart. The Far Detector will be the largest liquid argon neutrino detector ever built, and will incorporate 4 separate modules, each containing 10 kilotons of liquid argon. The electronics internal to these modules make use of wire planes that interface to a Front End Motherboard. Here we design a potential board which incorporates the CRYO ASIC.[18] We discuss the testing of this design, as well as the revisions made for the most recent version. We present the noise measurements across the electronics and all input channels and determine them to meet the specifications of < 1000 electrons per channel. We compare the power spectra to simulation and determine the level of capacitance and external shielding needed to yield the desired results. Further testing within liquid nitrogen models predicted performance at liquid argon temperature, and these tests expose areas where better quality yield is required. The continuation of design of these electronics will be tested within the ICEBERG detector at Fermilab, and become one of the potential solutions to be incorporated in the DUNE Far Detector, 2029.
Advanced Basestation Technology for Wireless Connectivity in Rural Areas
(University of Hawaii at Manoa, 2021) Shukla, Pratiksha; Iskander, Magdy F.; Electrical Engineering
This thesis introduces smart physical layer based advanced directional networking technologywhich achieves full directional capability using “smart nodes” or “advanced nodes”, that are equipped with multiple directional antennas, smart algorithms, and propagation modeling capabilities. The advanced nodes have their six communication link antenna array structured in hexagonal from such that it divides the space around it into six-sectors. The scanning array used for user discovery is mounted separately and performs the 360-degree sweep to discover the users equipment seeking connection. Based on angle-of-arrival (AoA) estimation algorithm the incoming signal direction is identified and, optimized beamforming algorithm is employed to establish communication link between the user and antenna array of the sector where user is discovered. All these operations are performed through the coordination of multiple directional antenna arrays and smart algorithms, without the necessity of changes in MAC layer as has been the norm to overcome directional antenna deafness. Thus, it remains in compliance with the timing restrictions of the wireless standards. Simulations had been done previously on the WIFI and LTE single mobile user tracking and signal integrity. Multiple mobile user case also had been studied for the WiFi. This thesis includes the research done as the continuation of these simulation where multiple mobile users are tracked through the sector, and from one sector to another for LTE and 5G radio standards. The initial results of simulation show continued connectivity and tracking with high data rate in multiuser LTE and 5G environment can be achieved. This thesis explains the advanced nodes system concept in detail and includes the result for LTE and 5G simulations. Due to its capabilities, this system can work as fully functioning base station on its own or can be installed on the existing infrastructure as an upgrade.
Next-Generation Amplifiers for Beyond-5G Applications
(University of Hawaii at Manoa, 2021) Fujitani, Ian; Shiroma, Wayne A.; Electrical Engineering
This thesis focuses on developing indium-phosphide heterojunction-bipolar-transistor-based amplifiers for applications in the RF spectrum above 5G frequencies. Advanced modifications of the Darlington configuration have produced high-gain, high-bandwidth, and low-power amplifiers with DC-200 GHz operating frequencies. Models were developed to improve the ability to predict measurement results, allowing the designs to be fine-tuned for optimal performance. An original figure of merit was designed to compare the prospective performance of the amplifiers with various state-of-the-art publications. The amplifiers produced have higher figures of merit than all state-of-the-art amplifiers examined. Additionally, the use of resettable fuses for high-frequency circuit protection was discussed. These fuses were characterized by their power levels, input return loss, and response time. A set of specifications were developed as the minimum criteria for a fuse to protect a microwave circuit. Fuses of ceramic, polymeric, and electronic types were characterized and compared against the minimum criteria to show that the maturity of the technology is inadequate. This thesis concludes with suggestions for future research.
Practical Gps Spoofing Attacks On Consumer Drones
(University of Hawaii at Manoa, 2020) Cao, Jianqiu; Dong, Yingfei; Electrical Engineering
While the security of drones and unmanned automatic systems has become increasingly important, software vulnerabilities have been broadly examined but hardware vulnerabilities on these systems have not been well investigated. In this project, we utilize the recently popular software-defined radio cards to investigate vulnerability on these unmanned systems from both software and hardware aspects, epically focused on the security of civilian GPS receivers on consumer drones. We have developed a smart GPS spoofing attack framework on consumer drones, based on our understanding of the drone control software and the vulnerability of civilian GPS system. We will first introduce the background and related work on drone control systems and the GPS system; we will further present the design of our attack framework and our experimental results. Although simple GPS spoofing has been conducted in various settings, as far as we know, most of them are brute-force attacks without precise control. In this project, we have developed a practical framework to achieve better control of drone movement, based on the deep understanding of consumer drone specific issues. The proposed attack has been very successful in our lab environments; however, there are many practical challenges in field tests due to the limitation of the devices, field environments, and other reasons out of our control, e.g., wind speed. We have conducted many field tests to understand and address the practical limitations and show the capabilities of the proposed system. We will then present our research results and conclude this thesis with discussion and future work.

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