UMD Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/3

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.

More information is available at Theses and Dissertations at University of Maryland Libraries.

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    WAVE CHAOS STUDIES FOR TWO-DIMENSIONAL CAVITIES USING THE RANDOM COUPLING MODEL (RCM) AND OTHER HIGH FREQUENCY METHODS
    (2021) Adnan, Farasatul; Antonsen, Thomas; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Wave coupling within systems with irregular boundaries is a common phenomenon in many branches of science such as acoustics, vibrations, electromagnetics, and others. If the wavelength of the incident wave is small compared with the structure size, and the dynamics of the ray trajectories within the scattering region are chaotic, the scattering properties of the cavity will be extremely sensitive to small perturbations. These structures are then termed wave chaotic. Exact solutions of such systems are not feasible and various alternative methods are sought. In the first part of this dissertation, such alternative methods are used to calculate the power delivered to a port in a two-dimensional wave chaotic enclosure. These methods are the ray tracing (RT), the Dynamical Energy Analysis (DEA) and the Power Balance methods (PWB). Particularly, the RT and DEA are used to calculate power received at an aperture and are compared with the established PWB. These results indicate that the RT and DEA are equivalent methods. Additionally, RT is compared with direct numerical simulations of the wave fields and found to be accurate if the wavelength is sufficiently small. The Random Coupling Model (RCM) gives a statistical description of coupling of radiation in and out of large enclosures through localized and/or distributed ports. The RCM, in contrast to DEA, PWB, and standard RT, includes both amplitude and phase information. It combines both deterministic and statistical information and makes use of wave chaos theory to extend the classical modal description of the cavity fields in the presence of boundaries that lead to chaotic ray trajectories. In the second part of this dissertation, a correction to the RCM termed the Short Orbit Formulation (SOF) is used to calculate successfully the impedance of a two-port wave chaotic enclosure in two dimensions using RT. Also, a directed beam approach was used to launch energy in a wave chaotic enclosure to break the so called 'random plane wave hypothesis', a fundamental basis of the RCM formulations. Results show that launching of such directed beams lead to enhanced short orbit effects which make the RCM inapplicable.
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    Using Commercial Ray Tracing Software to Drive an Attenuator-Based Mobile WIreless Testbed
    (2012) Taylor, Keith Richard; Jaja, Joseph; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    We propose and build a prototype architecture for a laboratory-based mobile wireless testbed that uses highly detailed, site-specific channel models to dynamically configure a many-to-many analog channel emulator. Unlike similar systems that have used abstract channel models with few details from the physical environment, we take advantage of commercial ray tracing software and high-performance hardware to make realistic signal power and characteristics predictions in a highly detailed environment. The ray tracing results are used to program a many-to-many analog channel emulator. Using this system, we can conveniently, repeatedly, and realistically subject real wireless nodes to the effects of mobility. We use our prototype system and a detailed CAD model of the University of Maryland campus to compare field test measurements to measurements made from the same devices in the same physical scenario in the testbed. This thesis presents the design, implementation, and validation phases of the proposed mobile wireless testbed.