Volumetric effects in the depolarization of electromagnetic waves scattered from rough surfaces

Abstract

Theoretical investigations of electromagnetic scatter from rough interfaces have been of interest for many years. Of particular interest is the depolarization of electromagnetic waves scattered from rough surfaces. Early works treated depolarization as a surface effect. These approaches have met with limited success. Recent theoretical and experimental investigations have shown that subsurface interaction may be responsible for the depolarization phenomena. The report establishes, by deductive reasoning, the depolarization mechanism as a multiple scattering phenomena within the volume. A detailed discussion of significant surface scattering theories is included. The report also includes the development of a new backscatter theory, with an analysis of this model behavior as a function of scene parameters. Polarized and depolarized microwave measurements were performed and compared to model predictions. The microwave measurements of the rough surfaces showed the existence of a subsurface depolarization mechanism. The theoretical model accounts for the general trends in the data including the response of the like and cross polarized cross section as a function of subsurface contribution and incident angle. Recommendations for future experimental programs designed specifically to more clearly characterize the depolarization phenomena and the effect of the volumetric contributions have also been identified.