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Full-Text Articles in Signal Processing
Antenna Gain Enhancement Using A Photonic Band Gap Reflector, Karl C. Schloer
Antenna Gain Enhancement Using A Photonic Band Gap Reflector, Karl C. Schloer
Theses and Dissertations
Scientists have long known that periodic structures can filter electromagnetic (EM) waves. In the last decade, extension of one- and two-dimensionally periodic structures into a third periodic dimension has produced photonic band gap (PBG) structures. A PBG structure is characterized by its omnidirectional stop band at a set of frequencies determined by the structure's periodicity and permittivity. In the present research, we investigate such a structure as an antenna reflector. We aim to develop a modeling approach that provides accurate computations of PBG behavior without relying on massively parallel processing. We also construct and measure the bulk reflection and transmission …
A Climatology-Based Model For Long-Term Prediction Of Radar Beam Refraction, Todd S. Pittman
A Climatology-Based Model For Long-Term Prediction Of Radar Beam Refraction, Todd S. Pittman
Theses and Dissertations
The National Air Intelligence Center, WPAFB, OH, needs more accurate predictions of radar beam refraction. A new mode was developed for this thesis replacing the standard atmosphere approach with raytracing and climatology. Usually a microwave radio beam bends towards the earth with a radius of curvature greater than the earth's surface. However, seasonal and climatic variations influence the bending, and at times create temperature or moisture inversions that redirect the energy along the earth's surface leaving radio holes where there is no coverage. This model uses iterative raytracing to determine the most direct path from radar to target through the …