The proposed research focuses on utilizing strategies for energy-synchronous direct antenna modulation (DAM) to both realize and quantify gains in the effective bandwidth-efficiency product of electrically small transmit systems. This work includes several aspects of the design and analysis of direct antenna modulation systems, including the study of metrics for comparing non-LTI DAM methods against fundamental bounds on LTI systems, considering device- and system-level efficiency measures, scaling and optimizing preliminary ����������������proof-of-concept��������������� DAM architectures to increase performance gains, development of an FPGA-based DAM prototype that does not rely on complex lab instrumentation to operate, and test and evaluation spanning analytic methods to over-the-air measurements.

INTERACT is an innovative, experiential STEM program designed to provide Naval personnel with the technical background and skills to fight the next fight where control and understanding of the electromagnetic spectrum and systems is essential. The program also will engage and motivate young sailors, high-school and undergraduate students in their career trajectories into STEM and electronics and electrical engineering. At the core of INTERACT is a unique systems and hands-on experiential learning approach. Through an innovative digital platform, integrated design tools and a lab-in-a-kit, participants are able to learn through online digital media and then design/build (by hand) and test the foundational building block of many of the Navy������������������s electronic sensing and communication systems. INTERACT is a scalable education program suitable for insertion into a variety of points into the Navy Training pipeline and can impact a wide range of personnel such as ROTC midshipmen or to supplement skills and provide professional development at the senior enlisted and mid-grade officer levels. In addition, as communication technology is integral part of the general work force, INTERACT������������������s simple and interactive approach will provide a new education vehicle for military connected students to learn new skills and technology.

Reconfigurable antennas and metasurfaces require non-linear devices such as diodes and varactors on the antenna aperture to adapt their properties in real time. Most studies on these reconfigurable apertures focus on the design of element properties and placement to induce the desired change of state and analysis of the system-level impact of the reconfiguration. However, the introduction of non-linear devices on the aperture creates the potential for non-linear distortion in the presence of the variety of unintended signals that may impinge on the aperture. While non-linearities in the RF front-end are generally well-understood and carefully controlled, reconfigurable apertures introduce new mechanisms for non-linear behavior that have not been studied. Thus, new risks or vulnerabilities created by reconfigurable apertures need to be better understood.

The major goal of National Science Foundation������������������s Broadband Wireless Access and Applications Center (BWAC) lead by the University of Arizona is ����������������advancing wireless technologies and providing cost-effective and practical solutions for next-generation (5G & beyond) wireless systems, millimeter-wave communications, wireless cybersecurity, shared-spectrum access systems, full-duplex transmissions, massive MIMO techniques, and others.��������������� The North Carolina State University (NCSU) is planning to join NSF BWAC center starting in 2019 with at least four full industrial members. The addition of NCSU into BWAC will synergistically complement BWAC mission and vision, by introducing new and complementary research areas, including millimeter wave (mmWave) theory, circuits, antennas, and experimentation, drone based communications, visible light communications (VLC), antenna design for broadband communications, non-orthogonal multiple access (NOMA) and its variants, among other areas.

Military communication, navigation, and radar systems must operate in electromagnetically contested environments with high fidelity. In this environment, the ideal electromagnetic (EM) platform consists of a multi-functional (sensing, communications, electronic attack) and highly adaptive, able to generate and sense radiation across a wide range of frequencies, with controllable directional and polarization sensitivity. Among the critical needs for such ����������������smart��������������� radios are reconfigurable antennas that can dynamically change their radiation patterns or frequency response. Here we propose networks of liquid metal embedded in the skin of a vehicle, aircraft, or other communications/sensing platform. These electrofluidic (EF) networks are physically reconfigurable ������������������ the conductors can be moved in and out of particular channels to change the electromagnetic characteristics of the platform. The proposed work encompasses several goals towards controlling and realizing these EF networks.

In this project, we will develop models and a design flow to move from a canonical lens design to a transformed lens of convenient form with gradient permittivity, appropriate discretized unit cells to emulate the desired permittivity, and full wave models of the entire collection of unit cells. To transform the lens shape, conformal and quasi-conformal transformation optics (QCTO) techniques will be investigated. These methods map geometric deformations into material property variations to achieve the same effect in the deformed structure. Under appropriate conditions, TO and QCTO transformations can produce simple nearly isotropic material properties requiring only positive dielectric constants. This avoids the need to create resonant metamaterials that tend to be lossy and narrowband. However, the greater the deformation, the greater the range of material properties required; thus, high permittivity materials with spatially varying permittivity or gradient index (GRIN) will be required.

A program providing research experiences and workshops in electronic warfare will be provided to ROTC cadets at NC State University and at neighboring colleges with the aim of presenting EW-focused workshops to all ROTC cadets at NC State University and close-by institutions. We will develop a research program for ROTC cadets in Electrical Engineering during the semester for NC State-based cadets and during the summer available to any US ROTC cadet. The emphasis will be on research experiences in wireless communication, radios, radars and sensors with the level of experience adapted to background. Students will learn how the range of architectures used in radios, radars and sensors; their vulnerabilities; how to identify vulnerabilities, and how they can be adapted to mitigate effects.

Long distance communications rely on HF, VHF, and UHF wireless systems where wavelengths are over 1 meter long. Conventionally, resonant antennas are used in mobile applications in these bands, due to the large size required for more broadband structures. A resonant antenna in steady state can only effectively transmit a narrow range of frequencies. However, if the antenna������������������s properties are modulated at a rate on the order of the symbol frequency, then the antenna becomes a time variant system that may circumvent the physical limitations of small antennas. Experiments have indicated that unusually wideband emissions from small antennas are possible, though further study is needed to address the fundamental questions in this area and improve the present understanding of time-varying radiators. The overall scientific goal of this proposal is to establish models and design methodologies for radiating systems with rapidly time-varying properties.

The goal of this project is use information-theoretic principles to design compact broadband multi- antenna receivers that exhibit the best possible tradeoff between power and bandwidth efficiency. Our overall approach is to develop antenna structures, matching networks and communication algorithms that act in concert to maximize the capacity of the underlying wireless channel. Three main topics are addressed: (a) design of novel, co-located antennas that seek to capture the most informative modes of the incident electromagnetic field; (b) design of agile, adaptive broadband antenna matching networks with the ability to optimize performance in the presence of frequency- selective coupling and noise; (c) information-theoretic criteria to guide the design of antenna arrays that maximize capacity of the resulting channel, and (d) communication and signal processing algorithms that sense and adjust the matching networks to changing channel conditions.

Emerging communication, sensing, and tracking applications continue to require smaller antennas, driven by the form factor of wireless devices. However, while many electronic components benefit from rapidly decreasing size according to Moore������������������s Law, antennas face miniaturization limitations when their sizes are below a quarter-wavelength that negatively impact their gain, efficiency, system range, and bandwidth. Due to physical requirements on the amount of electromagnetic energy stored in the near field of resonant structure such as a small antenna, a modulated pulse applied to the antenna inherently experiences some ����������������ringing��������������� in the time domain. In the frequency domain this is equivalent to a narrowband response. Because of this response, the antenna effectively acts as a narrowband filter, and wideband, short-time pulses cannot be effectively transmitted or received, thereby limiting the data rate. Recent evidence suggests that it may be possible to increase the data rate while maintaining a small electrical size by directly modulating the antenna������������������s impedance in sequence with the modulated carrier wave applied to the antenna������������������s feed. However, no comparison has been made between the direct antenna modulation (DAM) scheme and a conventional scheme using typical communications metrics. In this project, we will 1) design and simulate a DAM transmitter and conventional receiver in order to understand how varying signal to noise ratios (SNR) affect key system metrics such as bit error rate (BER) and 2) develop a testbed to generate DAM signals with a reconfigurable antenna in order to characterize the performance of these systems.