Master of Science in Engineering (MSEgr), Wright State University, 2012, Electrical Engineering

Given the UHF bands properties of foliage and round penetration, a UHF-SAR image contains both above- and below-surface scatterers. The problem of detecting sub-surface objects is problematic due to the presence of above-surface scatterers in the detection images. In case of a single-pass anomaly image or a two-pass change image, the resulting anomalies or changes are due to scatterers above and below the surface, where the above surface anomalies/changes act as confusers. LIDAR digital elevation models (DEM) provide georegistered information about the above-surface objects present in the UHF-SAR scene. Detection of the above-surface objects in the LIDAR domain is used to rule out above-surface false-alarms in the UHF-SAR domain detection images. A complementary sensor fusion algorithm is implemented which exploits the limited ground penetrating capabilities of UHF-SAR and the false-alarm removal using LIDAR. For unitemporal and multitemporal UHF-SAR collections (both containing multiple-passes and multiple- polarizations) anomaly detection and change detection are implemented, respectively. In this thesis, various pixel-based and feature-based change detection algorithms are implemented to study the effectiveness of multitemporal change detection algorithms. In addition, incorporation of UHF-SAR multiple-passes and multiple-polarizations further improves detection results. The algorithms are tested using data collected under JIEDDOs Halite-1 program, which provides both UHF-SAR and LIDAR DEM.

Committee: Arnab Shaw PhD (Advisor); Lang Hong PhD (Committee Member); Brian Rigling PhD (Committee Member); Kefu Xue PhD (Other); Andrew Hsu PhD (Other) Subjects: Electrical Engineering

MS, University of Cincinnati, 2011, Engineering and Applied Science: Electrical Engineering

The unusual properties exhibited by left-handed metamaterials have been of great interest to researchers, especially in the field of RF and Microwave communication. The property of backward-wave propagation has led to a number of applications which were not possible with natural right-handed materials. One of the most exciting applications of these left-handed metamaterials is the Zeroth Order Resonator (ZOR) wherein resonance is achieved even at the zeroth mode, which is not possible with the traditional right-handed materials. This has led to the design of Composite Right/Left-Handed (CRLH) ZOR antennas whose resonance frequency does not depend on the physical length of the resonator. In this thesis the theory behind the ZOR antennas is studied and their applicability for use as RFID tag antennas is explored. Three novel CRLH ZOR antenna configurations are proposed targeting the UHF RFID tag application. The antennas are simulated using Agilent ADS Momentum and the simulation results are compared with those of the traditional 2-cell and 4-cell CRLH ZOR antennas that have been previously designed. The novel antennas are also compared with a simple rectangular patch antenna to demonstrate the reduction in size achieved through the use of left-handed metamaterials. The novel antennas are also simulated with varying values of the substrate height, metal thickness, and dielectric loss tangent and the effect of these parameters on antenna performance is analyzed. The three novel antennas and a rectangular patch antenna are fabricated and the experimental results are presented. The novel antennas are found to be around 30 times smaller than the rectangular patch antenna radiating at the same frequency.

Committee: Altan Ferendeci PhD (Committee Chair); Joseph Thomas Boyd PhD (Committee Member); Carla Purdy PhD (Committee Member) Subjects: Electrical Engineering

Master of Science, The Ohio State University, 2012, Electrical and Computer Engineering

A novel UHF antenna for a handheld RFID reader is proposed, designed and optimized using ANSYS HFSS simulation software. The optimized design is fabricated and tested, for S ¿¿¿¿¿¿¿¿¿¿¿¿“ parameters and gain, using a network analyzer. The antenna structure designed is low ¿¿¿¿¿¿¿¿¿¿¿¿“ profile, planar, end ¿¿¿¿¿¿¿¿¿¿¿¿“ fire radiating and dual ¿¿¿¿¿¿¿¿¿¿¿¿“ polarized. It is a promising substitute to other existing conventional antennas used such as patch antennas (broadside radiating and linearly/circularly polarized) and helical antennas (end ¿¿¿¿¿¿¿¿¿¿¿¿“ fire radiating and circularly polarized) which are comparatively bulkier to be mounted on a handheld reader. The proposed antenna provides dual ¿¿¿¿¿¿¿¿¿¿¿¿“ polarized gain so that the tags of both orientations (horizontal and vertical) can be read effectively when the reader is pointed at them. Due to its attribute of dual polarization, it forms a vital substitute to the already available planar and end ¿¿¿¿¿¿¿¿¿¿¿¿“ fire radiating antenna designs like Yagi, which are capable of providing only one kind of a polarization. This constraint renders the tags of opposite polarizations to be left unread by the reader, unless the reader itself is twisted to align the polarization direction with the orientation of the tag to be read. The dual polarization of this antenna is provided by combining two different antenna geometries, yielding orthogonal polarizations, onto a single platform and having different excitation ports to feed the two structures when connected to a two ¿¿¿¿¿¿¿¿¿¿¿¿“ port reader.

Committee: Dr. Robert Burkholder (Advisor); Dr. Prabhakar Pathak (Committee Member) Subjects: Electrical Engineering; Electromagnetics

Doctor of Philosophy, The Ohio State University, 2012, Electrical and Computer Engineering

There is much interest in developing body-centric wireless communication systems (BWCS) for mobile health care systems. However, the realization of a BWCS is challenging due to the body's interference with the antenna's operation. More specifically, body-worn antennas suffer from impedance detuning, pattern deformation, and gain reduction caused by the body. Therefore, it is important to consider these effects in evaluating body-worn antennas. In this regard, a diversity technique is proposed to improve body-worn antenna performance. More specifically, a channel decomposition method (CDM) is proposed and used to evaluate body-worn antenna systems. The CDM significantly reduces computation time when evaluate body-worn antennas and is applicable to various surrounding environments without recalculation of the more complex interaction. A second contribution of this dissertation is design of a diversity systems which automatically determines the minimum number of antennas while maximizing performance. This approach is employed to design body-worn antenna diversity systems for given communication scenarios. The results obtained via this process demonstrated that this simple method can substantially reduced computation time in designing body-worn antenna diversity system. As a demonstration of the proposed methodology, a vest-mounted UHF body-worn antenna diversity system (BWADS) is developed using 4 light-weight antennas. The proposed BWADS is transparent and unobtrusive to the users but provides performance superior to commercial antennas. A variety of tests were performed to validate the proposed BWADS. It was found that the proposed BWADS provided 7 dB (outdoor) to 16.5 dB (indoor) of higher gain as compared to commercial antennas. The dissertation concludes by proposing other applications of the developed body-worn antennas and design methods.

Committee: John Volakis PhD (Committee Chair); Chi-Chih Chen PhD (Advisor); Fernando Teixeria PhD (Committee Member); Dimitris Psychoudakis PhD (Committee Member) Subjects: Electrical Engineering; Electromagnetics

Doctor of Philosophy, The Ohio State University, 2011, Electrical and Computer Engineering

Unmanned aerial vehicles (UAVs) have become increasingly popular for scientific research, remote sensing, transportation of goods, search and rescue as well as military applications. UAVs have several key advantages over piloted aircrafts including low cost and the ability to penetrate unattainable areas that would be classified as unsafe. Technological advances and miniaturization allow communication devices to be placed on small UAVs. To improve aerodynamics it is thus necessary to design antennas conformal to host structure of UAVs. However, at VHF/UHF the UAVs often become electrically small, making it challenging to design wideband communication antennas. In this research, the theory of characteristic modes (CMs) is used for the analysis and design of complex conformal antennas. Traditionally, CM theory is used as an analysis tool. However, research efforts in this dissertation are focused on expanding characteristic mode theory for the design of antennas. First, two systematic simplification procedures are developed which reduce the number of characteristic modes considered for complex antenna structures. This lays the foundation for simplifying the analysis of complex antenna structures allowing the designer to focus on a small subset of critical modes. Later, thorough analysis of the input admittance of CMs is conducted. It is shown that if a mode contributes to the conductance, it ultimately contributes to the radiated pattern. For higher order modes this is typically undesirable. Thus, it will be shown how to suppress the effects of higher order modes by proper feed placement. By suppressing a higher order mode's admittance, the bandwidth of an antenna can be increased. Using the simplification procedures, an investigation of electrically small square and rectangular ground planes is conducted. The analysis identified four important modes and allowed thorough analysis of the eigen properties of each mode. Results showed that antenna elements with electri (open full item for complete abstract)

Committee: Roberto Rojas (Advisor); Fernando Teixeira (Committee Member); Robert Garbacz (Committee Member) Subjects: Electrical Engineering; Electromagnetics