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 31 for “"Geometrical optics"”.
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Spherical reflector feed field synthesis by geometrical optics and spherical wave expansion.
Thesis: M.S., Massachusetts Institute of Technology, Department of Electrical Engineering, 1970
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Propagation prediction for PCS design in urban microwave channels
… tool developed is based on the principle of geometrical optics and Fresnel-Kirchoff diffraction. Geometrical optics enables computer software to automatically trace the propagation of radio wave energy from the transmitter to the receiver. The ray tracing techniques presented are optimized …
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Site-specific propagation prediction for wireless in-building personal communication system design
This dissertation describes a geometrical optics model to predict propagation in buildings for personal communication system (PCS) design. Background on the growth of wireless communications is given, and the importance of accurate propagation models is discussed. The peculiarities of propagation …
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Multiple feed reflector antenna analysis
… illuminated by a feed array is developed. Geometrical optics is used to determine the incident field via a coordinate transformation approach. The incident field from each element is superimposed to form the total field used in finding the surface currents of the physical optics radiation …
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Analysis and Optimization of Reflector Antenna Systems (Pattern Calculation, Optimum Directivity, Sidelobe Reduction)
… The methods of analysis used are physical optics (PO) and the application of the Fast Fourier Transform (FFT) to the aperture fields obtained using geometrical optics (GO), geometrical theory of diffraction (GTD) and a brute-force FFT. Key features of the present work are (i) the reflector …
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Approximate solutions to the wave equation for a medium with one discontinuity
… are shown to propagate along rays predicted by geometrical optics. The solutions are computed up to an error which approaches zero as the pulse approaches the particle limit. The method gives a closed solution to the question of where the energy propagates. We assume that the n dimensional space …
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New Test Set for Video Quality Benchmarking
… based on extensive application of Photometry, Geometrical Optics, and Digital Media.</p> <p>The benchmarking takes into account the target’s contrast sensitivity, its color characteristics, and several aspects of human vision such as visual acuity and dynamic response. The standard observer is …
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Finite difference techniques for body of revolution radar cross section
… staircase and conformal grids, a hybrid FD-TD/geometrical optics method, and a body of revolution parabolic wave equation method. In addition, the use of the monostatic-bistatic equivalence principle is explored in approximating monostatic RCS at multiple angles from a single FD-TD simulation. …
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A wave-kinetic numerical method for the propagation of optical waves
… each Gaussian beamlet propagates along a geometrical optics ray trajectory, it can correctly describe diffraction effects, and the propagation of optical waves through caustics or ray crossings. The numerical results agree well with either the Monte-Carlo method or the first Born …
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Spectral characteristics of low-frequency variability in compact extragalactic radio sources
… resulting intensity distribution in the limit of geometrical optics. We then produce light curves by taking trajectories in the simulated intensity distribution plane and we compare our results with statistical properties of existing data from a 5—year monitoring program of 32 extragalactic …
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Beam scanning offset Cassegrain reflector antennas by subreflector movement
… The test case is beam scanned using two geometrical optics methods of determining the optimum subreflector position for the desired scanned beam direction. Physical optics far-field results are given for the beam scanned systems. The test case system is found to be capable of beam …
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Advanced Site-Specific Propagation Prediction Techniques
… in the latter half of the thesis. The use of geometrical optics for terrestrial microwave propagation is discussed as well as an overview of the numerous ray tracing techniques that exist in the literature. Finally, a new 3D ray launching method is presented which improves upon many of the …
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Synthesis of Offset Dual Reflector Antennas Transforming a Given Feed Illumination Pattern Into a Specified Aperture Distribution
… system is investigated using the concepts of geometrical optics. A numerically rigorous solution for the reflector surfaces is developed. The solution gives an exact aperture phase distribution and an aperture amplitude distribution accurate to within some numerical tolerance. In a previous …
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Visual pathology rectification
… Another possible method is the use of geometric optics. Optics describe the properties of a ray of light as it propagates through an optical system. These properties are described in a transfer matrix, which is then used to improve an image for a visual impaired user. Results show that while …
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Modelling of Electromagnetic Scattering at Infrared Wavelengths by Pristine Ice Crystals
… In this work, a new approach basedon physical optics is presented in which the scattering by smooth prismatic dielectric ice crystalswhich are electrically large is evaluated. In this method, the total scattered amplitude in anydirection can be evaluated by application of the reaction theorem …
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New Vistas in Solar Concentration with Gradient Index Optics
… perform at nature's cardinal limits (within the geometrical optics approximation - valid for essentially all solar applications), i.e. perfect imaging and ideal nonimaging performance for monochromatic radiation and unprecedented image fidelity and near-ideal flux concentration for the full solar …
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Microcellular radio channel prediction using ray tracing
… site-specific environmental data with a geometrical optics model to trace the propagation of energy from the transmitter to the receiver. Software written in C++ is used to automatically trace rays that are reflected, transmitted, scattered, or diffracted as they propagate through the …
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Design of experimental apparatus for generation and measurement of an aerosol
… scattering theory's intense use of calculations Geometrical optics approximation method is used which agrees well with the Mie theory for all the particles above 1µm. Chapter 4 presents experimental results of measurement which includes particle size distribution, density measurement of aerosol. …
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Improving Millimetre Wave Coverage in Indoor Environments using Convex Passive Reflectors
… for coverage using convex passive reflectors. A geometrical optics model has been developed to analytically evaluate coverage in office and straight corridor environments using convex spherical reflectors. Various reflector deployment strategies have been investigated by changing reflector …
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Fabrication and Optoelectronic Characterization of Nanoscale Resonance Structures
… which couples to the structure. Traditional geometrical optics has alternatively used discrete optical components such as lenses, gratings, and polarizers to accomplish equivalent control over optical radiation. This dissertation contributes to the larger body of literature that applies …
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