Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 42 for “"Beam-Scanning"”.
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Broadband Approaches And Beam-Scanning Techniques For Reflectarray Antenna
… drawbacks, such as limited bandwidth and scanning range, which are targeted in this dissertation. At first, the array theory approach for radiation analysis of reflectarray antennas is described and implemented. Numerical results are then presented and compared with reference results to …
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Beam scanning offset Cassegrain reflector antennas by subreflector movement
… the systems required for the mission was a wide scanning, high gain reflector antenna system for use in radiometric remote sensing from geostationary orbit. This work describes research conducted at Virginia Tech into techniques for beam scanning offset Cassegrain reflector antennas by …
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A high gain tri-reflector antenna configuration for beam scanning
… antenna configuration capable of precision beam scanning over a range of several degrees in all directions while minimizing vibration and inertial torque such as to have minimal effect on the other instruments sharing the platform. Desirable characteristics of such a reflector configuration …
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Single-band and Dual-band Beam Switching Systems and Offset-fed Beam Scanning Reflectarray
… because of its high-gain, low profile, and beam reconfiguration capability. Beam scanning capability and multi-band operation of the microstrip reflectarray have been main research topics in the reflectarray design. Narrow bandwidth of the reflectarray is the main obstacle for the various …
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Design and Analysis of an Electronically Steerable Microstrip Patch and a Novel Coplanar Waveguide (CpW) Fed Slot Antenna Array
… attractive for their high gain, low profile, and beam scanning ability while being conformal to their mounting surface. Among them are microstrip patch phased arrays and wideband slot phased arrays which are of particular significance.</p> <p>In this work, first the study, design, and …
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Advanced Design Methodologies and Novel Applications of Reflectarray Antennas
… with low-loss features at infrared. • Multi-beam reflectarray antennas are studied and it is demonstrated that by optimizing the phase of the elements, a desirable multi-beam performance can be achieved using a single-feed. Local and global phase-only optimization techniques have been …
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Development and investigation of devices for ultrahigh speed gastrointestinal Optical Coherence Tomography imaging
… devices had limited fields of view and imprecise beam scanning mechanisms, limiting image quality and coverage. This thesis develops a wide range of new fiber optic devices that substantially extend OCT capabilities in the GI tract, either by greatly increasing field of view for wide field mapping …
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Enhancing Signal Coverage for UHF RFID Systems
… A novel UHF RFID reader antenna with 2D beam-scanning ability, a wide axial ratio (AR) beamwidth and tunable polarisation performance is designed, simulated, measured and tested in Chapter 3 of this thesis. It is experimentally verified that the antenna’s AR minima follow its gain maxima, …
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A precision laser scanning system for experimental modal analysis: its test and calibration
… and experimental modal analysis. A laser scanning system that provides position accuracy, speed, and flexibility plays a key role in this technique. This thesis gives an overview of various laser scanning techniques and the requirements of a laser scanning system for the LDV and modal …
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Area Based Fan Beam Projection Model for Computed Tomography
… referred to as projection data, from x-ray scanning. This projection data is often modeled using line integrals, but x-rays are of finite width in reality, so the accuracy of the projection data can be improved if an area based approach is used instead. In addition emitter beam shapes affect …
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Advancing 5G Coverage: Novel Methods for Metasurface Characterization and Leaky-Wave Antenna Reconfigurability
… Ka-band, a contactless excitation method enables beam-steering, benefiting communication systems with cost-effective flexibility. This approach also facilitates beam scanning, bandwidth, and polarization reconfiguration. This thesis provides innovative solutions to wireless communication …
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Reflectarray Antenna based FMCW Radar System Development: High Isolation Radar Antenna Design and Feasibility of Affordable Switched-Beam for the UAV Detection
… and isolation) as well as enables a switched beam or beam scanning capability is introduced. In this study, a reflectarray technique called the bifocal design was adapted, and the antenna was fabricated and characterized. The initial numerical modeling results showed that a bifocal …
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Development of Efficient Techniques for the Analysis and Design of Antennas in Dual-Reflectarray Configuration
… of these kind of configurations to scan the beam and to generate contoured beams. In the first part, a general tool has been implemented to analyze high gain antennas which are constructed of two flat reflectarray structures. The classic reflectarray analysis based on MoM under local …
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Unconventional Optical Phased Array Design for Next-Generation Wireless Systems
… (OPAs), aiming to achieve high-quality far-field beamforming and near-field focusing through a multi-objective (MO) optimization framework. The method addresses the challenge of selecting which antenna elements should be retained or removed from a fully populated linear OPA arranged on a uniform …
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Evaluation of Radiobiological Effects in Intensity Modulated Proton Therapy : New Strategies for Inverse Treatment Planning
… clinical relevance of a variable RBE for beam scanning techniques, new strategies for the evaluation of radiobiological effects and for the incorporation of the RBE into the inverse planning process are presented. These strategies are based on a fast algorithm for three-dimensional …
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Interferometry-based Free Space Communication And Information Processing
… features large aperture, wide scan angles, 3-D beam control, no moving parts, and high beam scanning resolution. A C-MOS based free space optical transceiver for bi-directional communication has also been experimentally demonstrated. For high speed, large bandwidth, and high frequency operation, …
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Reconfigurable microstrip antennas with tunable radiation pattern characteristics
Reconfigurable beam antenna systems are capable of changing their radiation characteristics in real time, such as beam direction, beam shape, beamwidth, etc. Such antenna system is desired for various wireless applications because of many reasons among them; it helps to enhance signal strength …
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Characteristic mode theory for closely spaced dipole arrays
… impedance and array current distributions for beam scanning and sidelobe reduction. The modes are then calculated and interpreted for higher order dipole resonances to understand their behavior over a wide frequency band. Lastly, the modes of a dipole array with a backing ground plane are …
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Geometry of cone-beam reconstruction
… we use to unify all existing analytical cone-beam reconstruction methods. These reconstructions are based on formulae derived by Tuy [Tuy, 1983], Smith [Smith, 1985] and Grangeat [Grangeat, 1991] which explicitly link the cone-beam data to some intermediate functions in the Radon transform …
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