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Full-wave multiple scattering and depolarization of electromagnetic fields from rough surfaces
Abstract
Using the full wave approach, the single and the double scattered electromagnetic fields from deterministic one dimensionally rough surfaces are computed. Full wave expressions for the single and the double scattered far fields are given in terms of multidimensional integrals. These integrals are evaluated using a supercomputer*. Applying the steepest descent approximation to the double scattered fields expression, the dimension of the integrals are reduced from four to two in the case of one dimensionally rough surfaces. It is shown that double scatter in the backward direction is significant only for near normal incidence when the rough surface is highly conducting and its mean square slope is very large. Even for one dimensionally rough surfaces, depolarization occurs when the reference plane of incidence is not parallel to the local planes of incidence and scatter. A geometrical optics approximation is used to interpret the results of the doubly scattered fields for normal incidence near backscatter. The physical interpretation of the results could shed light on the observed fluctuations in the enhanced backscatter phenomenon as the angle of incidence increases from near normal to grazing angles. For surfaces with large mean square slopes, it is found that the double scattered fields are large in the near specular direction. The results show that multiple scattering strongly depends upon the slope of the rough surface, the angle of incidence, and the conductivity of the rough surface. The analysis is extended to the two dimensional deterministic rough surfaces. Full wave expression for double scatter from the two dimensional surfaces is given in terms of four dimensional integrals. This work provides physical insight to problems of scattering from random rough surfaces. Two approaches for multiple scatter cross sections from random rough surfaces are presented in this work. In the first approach the double scatter cross section expression reduces to a product of two single scatter cross sections. This is because the stationary phase points on the surface which contribute mostly to the double scatter are assumed to be far and statistically independent. In the second approach the surface is regarded to be a random distribution of realistic models of rough surface scatterers with different mean square height and slope, width and mean depth. The full wave results of single and multiple scatter from random rough surfaces are consistent with experimental results. ftn*IBM/3090 Cornell National Supercomputer Facility, Cornell Theory Center, Cornell University.
Subject Area
Electrical engineering|Geophysics|Optics
Recommended Citation
El-Shenawee, Magda Osman, "Full-wave multiple scattering and depolarization of electromagnetic fields from rough surfaces" (1991). ETD collection for University of Nebraska-Lincoln. AAI9208105.
https://digitalcommons.unl.edu/dissertations/AAI9208105