Thesis (M.S. in Electronic Warfare Systems Engineering and M.S. in Electrical Engineering)--Naval Postgraduate School, September 2009. / Thesis Advisor(s): Tummala, Murali ; Jenn, David. "September 2009." Description based on title screen as viewed on November 6, 2009. Author(s) subject terms: Cooperative Spectrum Sensing, Source Localization, Multi-Resolution Spectrum Sensing, Three-Bit Hard Combination, RSS-Based Localization, Cognitive Radio, Wireless Sensor Networks, Electronic Warfare. Includes bibliographical references (p. 87-90). Also available in print.

The use Yttria-Stabilized Zirconia (YSZ) as a buffer layer for YBa2Cu3O7-x (YBCO) thin films on (100) silicon (Si) substrates is investigated. YSZ was grown using on-axis pulsed D.C. (PDC) and R.F. magnetron sputtering from a 99.9% pure YSZ target [(Y2O3)0.08(ZrO2)0.92]. Sputtering was carried out in Argon/Oxygen atmosphere at total pressures ranging from 6 to 320 mTorr containing 0.1 to 10% Oxygen. Substrate temperatures were varied from 300° C to 900° C. (111), (100) and mixed (100) and (111) oriented YSZ films were produced with thickness of 50 to 200 nm. YBCO films, 200 nm thick, were then grown by pulsed-laser deposition in an atmosphere of 0.5 Torr 02 at 750° C. The critical temperature (TC(R=0)) of the films produced was 75 K - 81K. A "T" resonator design was patterned on the YBCO/YSZ/Si structure and tested. Results show a band-reject response centered at 3.872 GHz with a quality factor of 20,000.

The purpose of this thesis was to create and simulate a model of an existing Campus network with a view to predict future performance. This thesis also suggests ways in which such a network can be optimized. Such simulation and modeling can be referred to as "Predictive Performance Modeling'. In this research a model of Florida International University (University Park campus) High Speed Network was created. Simulation of the model was carried out and an ATM Backbone Analysis was done. The results obtained were compared with corresponding results obtained by network performance monitoring and measurement software tools. A strong correlation between measured and simulation results were observed. A more detailed model was also created for the Engineering and Applied Science (EAS) Local Area Network. Various performance parameters results were collected and analyzed. Based on simulated results, predictions were made in regards to the scalability and optimization of this network in light of expected future requirements.

Oral communication has constituted as a necessary aspect of how people interact with one another, but there are always situations where this form of communication can create distractions, irritation, or even danger. Take for example, a student in a laboratory who needs to communicate effectively with a lab partner without creating a distraction to those trying to work around said student or a soldier on a battlefield who needs to relay information effectively to his or her comrades without revealing his or her position to the enemy. It becomes apparent that people need a more exclusive form of communication in order to ensure not only the safety of soldiers, but efficiency in the workplace as well. This project focuses on solving these problems by developing a small, concealable, and non-invasive, electronic device capable of transmitting communication silently by linking to a phone, computer, or radio channel. This device ensures completely silent communication between only those who use communicating devices and only requires that the user apply nodes to his or her throat when thinking of what he or she wishes to communicate with another for proper operation. Unlike other devices which rely on EEG and thus involve cumbersome headwear, this device performs as easily removable, concealable, hands free, conveniently pocket-sized, compatible with other devices used for communication, and able to have a user input versus device output accuracy of at least 70%. Using wavelet analysis and a MSP432 microcontroller, subvocal signals originating from the throat can be classified to an overall accuracy of at least 70% within a project budget of $50.

To understand and model the energetics of the Sun-Earth connection, measurements of specific atmospheric molecules are beneficial. The objective is to formulate an algorithm to derive temporally varying atmospheric water vapor concentrations as functions of altitude, latitude, and longitude from solar irradiance absorption measurements. The Visidyne SAM (Sun and Aureole Measurement) instrument, which studies the size and distribution of cloud particles, was used to obtain the experimental data. By introducing a spectrometer to the SAM instrument, column water vapor is produced as part of the data product. A new model optimized algorithm is developed and tested versus existing algorithms. Through a least-squares analysis, the new algorithm showed an improvement of a factor of 23 over the industry standard. A test was also conducted to determine which water absorption bandpass produces the smallest error. Through these tests a model optimized algorithm has been produced.

The recent advances in electronic technologies are geared towards a combination of continued miniaturization in device components and their integration onto unconventional platforms. These efforts are aimed towards achieving electronic devices with various form factors and novel functionalities which are unattainable from traditional devices. Among these envisioned 'futuristic' technologies, electronic devices which are mechanically reconfigurable and operable under harsh operational conditions in the form of stretching, twisting and folding offer tremendous amount of unparalleled opportunities. This dissertation studies two-dimensional (2D) transition metal dichalcogenide (TMDs), a distinct class of materials with peculiar optical, electrical and mechanical properties for mechanically reconfigurable electronics. Owing to their two-dimensional geometry, hence small thickness and extremely large mechanical tolerance, they offer a unique set of advantages unattainable with conventional three-dimensional silicon (Si). We used a novel chemical vapor deposition (CVD) technique to synthesize large-area ( > cm2) 2D TMDs of different compositions onto various rigid and polymeric substrates. Additionally, we developed viable green transfer approached based on water to integrated them onto secondary target substrates, further extending their applicability. In particular, we configured viable strain-engineering concepts to three-dimensionally architect 2D TMD layers into tailored geometries, which can ensure high mechanical stability accompanying well preserved and tunable electrical/optical properties. Moreover, we investigated the strain variable and invariable electrical, optical, mechanical, and structural properties of these materials, explained using simulations and experimental demonstrations. Finally, by combining the novel synthetic and transfer techniques with strain engineered 2D-3D modulations of the TMD layers, we demonstrated several applications of 2D TMDs for futuristic electronics, including ultra-stretchable conductors and transistors for electronic components, wearable heaters and smart tattoos for healthcare, transparent conductors for smart windows, and electromechanical actuators for soft robotics. These studies are part of a new paradigm shift using creative growth and patterning techniques for the development of uniquely mechanically reconfigurable devices.

In order to overcome the drawbacks associated with conventional bulk lithium niobate photonic, thin-film lithium-niobate-on-silicon has been pursued recently. This work presents contributions made to electro-, and nonlinear-optic applications of this technology. For electrooptic applications, detailed modeling and design guidelines of optical and radio-frequency parameters of ultracompact modulators are developed and their accuracy in predicting the high-speed performance of such devices have been verified by comparison with experimental results. Novel design techniques and pathways for ultrahigh-speed (sub-terahertz) operation of such modulators, achieving up to 400 GHz modulation bandwidth, are also presented. For optical interconnect applications, novel structures for ultralow-power consumption modulators are designed and fabricated. Coherent modulation schemes, such as quadrature phase shift keying, is also pursued on the same thin-film platform for advanced optical communication systems. For nonlinear-optic applications, fabrication integrability of thin-film lithium niobate and chalcogenide glass waveguides on a single silicon chip for future directions, such as on-chip self-referenced optical frequency comb generation, is experimentally demonstrated. That is a pathway for both second- and third-order optical nonlinearity occurring on lithium niobate and chalcogenide, respectively, is designed and presented. An innovative and robust foundry-compatible back-end-of-line integration method is also proposed, in order to integrate thin-film lithium niobate devices with silicon or silicon-nitride photonic circuitry. Overall, this work extends the capabilities of the thin-film lithium niobate technology for novel electro- and nonlinear-optic applications. Finally, extensions of the aforementioned results suitable for future work are discussed.

Neuromorphic computing using post-CMOS technologies is gaining increasing popularity due to its promising potential to resolve the power constraints in Von-Neumann machine and its similarity to the operation of the real human brain. To design the ultra-low voltage and ultra-low power analog-to-digital converters (ADCs) for the neuromorphic computing systems, we explore advantages of tunnel field effect transistor (TFET) analog-to-digital converters (ADCs) on energy efficiency and temperature stability. A fully-differential SAR ADC is designed using 20 nm TFET technology with doubled input swing and controlled comparator input common-mode voltage. To further increase the resolution of the ADC, we design an energy efficient 12-bit noise shaping (NS) successive-approximation register (SAR) ADC. The 2nd-order noise shaping architecture with multiple feed-forward paths is adopted and analyzed to optimize system design parameters. By utilizing tunnel field effect transistors (TFETs), the Delta-Sigma SAR is realized under an ultra-low supply voltage VDD with high energy efficiency. The stochastic neuron is a key for event-based probabilistic neural networks. We propose a stochastic neuron using a metal-oxide resistive random-access memory (ReRAM). The ReRAM's conducting filament with built-in stochasticity is used to mimic the neuron's membrane capacitor, which temporally integrates input spikes. A capacitor-less neuron circuit is designed, laid out, and simulated. The output spiking train of the neuron obeys the Poisson distribution. Based on the ReRAM based neuron, we propose a scalable and reconfigurable architecture that exploits the ReRAM-based neurons for deep Spiking Neural Networks (SNNs). In prior publications, neurons were implemented using dedicated analog or digital circuits that are not area and energy efficient. In our work, for the first time, we address the scaling and power bottlenecks of neuromorphic architecture by utilizing a single one-transistor-one-ReRAM (1T1R) cell to emulate the neuron. We show that the ReRAM-based neurons can be integrated within the synaptic crossbar to build extremely dense Process Element (PE)–spiking neural network in memory array–with high throughput. We provide microarchitecture and circuit designs to enable the deep spiking neural network computing in memory with an insignificant area overhead.

This dissertation focuses on information recovery under two general types of sensing constraints and hardware limitations that arise in practical data acquisition systems. We study the effects of these practical limitations in the context of signal recovery problems from interferometric measurements such as for optical mode analysis. The first constraint stems from the limited number of degrees of freedom of an information gathering system, which gives rise to highly constrained sensing structures. In contrast to prior work on compressive signal recovery which relies for the most part on introducing additional hardware components to emulate randomization, we establish performance guarantees for successful signal recovery from a reduced number of measurements even with the constrained interferometer structure obviating the need for non-native components. Also, we propose control policies to guide the collection of informative measurements given prior knowledge about the constrained sensing structure. In addition, we devise a sequential implementation with a stopping rule, shown to reduce the sample complexity for a target performance in reconstruction. The second limitation considered is due to physical hardware constraints, such as the finite spatial resolution of the used components and their finite aperture size. Such limitations introduce non-linearities in the underlying measurement model. We first develop a more accurate measurement model with structured noise representing a known non-linear function of the input signal, obtained by leveraging side information about the sampling structure. Then, we devise iterative denoising algorithms shown to enhance the quality of sparse recovery in the presence of physical constraints by iteratively estimating and eliminating the non-linear term from the measurements. We also develop a class of clipping-cognizant reconstruction algorithms for modal reconstruction from interferometric measurements that compensate for clipping effects due to the finite aperture size of the used components and show they yield significant gains over schemes oblivious to such effects.

Wireless communication systems have rapidly evolved over the past decade which has led to an explosion of mobile data traffic. Since more and more wireless devices and sensors are being connected, the transition from the current 4G/LTE mobile network to 5G is expected to happen within the next decade. In order to improve signal-to-noise ratio (SNR), system capacity, and link budget, beam steerable antenna arrays are desirable due to their advantage in spatial selectivity and high directivity. Electronically steerable parasitic array radiator (ESPAR) that can achieve low-cost continuously beamsteering using varactor diodes have attracted a lot of attention. This dissertation explores bandwidth enhancement of the ESPAR using frequency-reconfigurable microstrip patch and cavity-backed slot (CBS) antennas. In chapter 2, an ESPAR of three closely-coupled rectangular patch elements that do not use phase shifters is presented; the beamsteering is realized by tunable reactive loads which are used to control the mutual coupling between the elements. Additional loading varactors are strategically placed on the radiating edge of all the antenna elements to achieve a 15% continuous frequency tuning range while simultaneously preserving the beamsteering capability at each operating frequency. Therefore, this frequency-reconfigurable ESPAR is able to provide spectrum diversity in addition to the spatial diversity inherent in a frequency-fixed ESPAR. A prototype of the patch ESPAR is fabricated and demonstrated to operate from 0.87 to 1.02 GHz with an instantaneous fractional bandwidth (FBW) of ~1%. At each operating frequency, this ESPAR is able to scan from -20 to +20 degrees in the H plane. However, the beamsteering of the patch ESPAR is limited in the H-plane and its instantaneous S11 fractional bandwidth (FBW) is very narrow. This dissertation also explores how to achieve 2-D beamsteering with enhanced FBW using CBS antennas. A 20-element cavity-backed slot antenna array is designed and fabricated based on a CBS ESPAR cross subarray in chapter 5. This ESPAR array is able to steer the main beam from +45 degrees to -45 degrees in the E plane and from +40 degrees to -40 degrees in the H plane, respectively, without grating lobes in either plane. The impedance matching is maintained below -10 dB from 6.0 to 6.4 GHz (6.4% fractional bandwidth) at all scan angles. In addition, the CBS ESPAR exhibits minimum beam squint at all scan angles within the impedance matching bandwidth. This array successfully demonstrates the cost savings and associated reduction in the required number of phase shifters in the RF front end by employing ESPAR technology.