Scalar and vector electromagnetic boundary-value theories of surface scattering have been applied to a microrough sample of fused silica coated with aluminum. Surface profiles were made with a mechanical and interferometric profilometer. The resulting values of rms surface height and autocorrelation length were used to calculate the scattering for various angles, wavelengths, and polarization conditions. Bidirectional reflectance distribution function (BRDF) measurements associated with scatter value were made and their corresponding power spectra were generated. Both were used to compare with the theoretical values. Special attention was also paid to the various methods of determining optical parameters with the BRDF data and the corresponding power spectra.

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This work is a study of the scattering of electromagnetic waves from random media of discrete scatterers. The object is primarily the investigation of existing general discrete-scatterer theories and the development of more accurate ones, the technique of Monte Carlo computer simulation being employed to provide "exact" experimental results for comparison with theoretical data. A one-dimensional model of randomly-positioned planar scatterers is used as a tool in the investigation and as a means of providing insight into the physical and statistical characteristics of discrete-scatterer media. The limitations of the one-dimensional forms of Twersky's theories for the coherent field are illustrated by a presentation of results for a wide range of scattering parameters, and requirements necessary for the approximate validity of these theories are given. Accurate series expressions for several average field functions of interest in the problem of plane-wave scattering from distributions of uniformly-random planar scatterers are presented and verified from simulation results. The asymptotic scattering behavior for a low average density of scatterers is emphasized; a modification to the one-dimensional form of Twersky's free-space theory for the coherent transmitted field to give exact asymptotic behavior is shown to be a considerable improvement for higher average densities also. The relation of the one-dimensional model theory and results to more complex three-dimensional models is discussed where possible. Simulation methods for the generation of a non-uniform distribution of planar-scatterer configurations weighted towards "periodicity" are presented. Based on the scattering results obtained, criteria for the assumption of a uniform distribution are given. The physical conditions necessary for the approximate validity of the bivariate Gaussian distribution in describing the total field statistics of the one-dimensional model are discussed and quantitative results based on the third and fourth field moments given. Also presented is a new physical model of a random medium of discrete spherical scatterers for use in controlled laboratory experiments at millimeter-wave frequencies. The main feature of this model is that the scatterer statistics are directly controlled by an application of the Monte Carlo method. The results of an experimental investigation into the suitability of the model are given. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

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This was a study to measure surface roughness using scattering of electromagnetic waves in the Ka and X microwave frequency bands. The detected fluctuations of the reflected field intensity is a measure of surface roughness. The reflected field intensity depends on the wavelength, the angle of incidence and the electrical properties of the media. Since the surface presents irregularities with randomly distributed facets, the characteristics of the rough-surface reflected wave can only be described by the statistical properties of the field intensity. The dependence of the normalized moments of the returned scatter on distance from the rough surface to the receiving antenna was analyzed as a function of surface roughness distribution at two different frequency-bands.

This thesis presents an introduction to rough surface scattering and describes techniques that were used during the course of this project to measure and characterize electromagnetic scattering from a rough surface. An analytical model is described that accurately predicts the statistics of the measured scattering data. The CW measurement process that was used is described and scattering measurement results are presented. Calculated and measured statistical moments are compared in order to show agreement of measurements with various statistical scattering models. Recommendations for additional work in the area of measurement and analytical modeling of rough surface scattering are given.

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Call number: LD2668 .T4 1966 K96 / Master of Science

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