| The intent of this dissertation is to obtain estimates of the effects of natural terrain features on the propagation and scattering of waves. It begins with the rough edge case, moves into rough surfaces and finally concludes with several approaches to a foliage covered rough surface. Each of these problems is encountered in radar, remote sensing and communication systems.; The first topic in this dissertation is the study of the effect of random edge roughness on the diffraction of a wave by a randomly rough knife edge. This has been accomplished by approximating the field beyond the diffracting half-plane through the use of spectral techniques and the Kirchhoff approximation.; Next, rough surface scattering effects are addressed. Extending the idea of the knife edge diffraction, this dissertation builds on the topic of a wedge on a plane by extending the Method of Multiple Ordered Interactions (MOMI) to the dielectric surface.; Propagation and scattering by a volume of scatterers over a bounding surface is then examined. Starting from the radiative transfer equations, a model is developed herein for scattering from vegetated rough terrain.; Extending the basic model to volumes for which multiple scattering is important is accomplished through the use of effective parameters. It is these effective parameters that are obtained by comparing the model with pulsed radar data at normal incidence, i.e., looking directly down through the foliage and onto the ground.; The use of this simple model assumes that multiple interactions are insignificant and that only narrow-band signals and narrow-beamwidth antenna patterns are used. Consequently, a more general radiative transfer approach is applied to the propagation of a beam through the random medium.; Finally, the effects of multiple scattering between the volume and its boundary, the rough surface, have been investigated. Using a numerical implementation (MOMI) of a scatterer over a rough surface, the orders of significant multiple interactions between the rough surface and the volume scattering components have been simulated. It is demonstrated that foliage components well above the rough surface may be treated as non-interacting. (Abstract shortened by UMI.)... |
