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Microwave scattering and synthetic aperture radar imaging of targets buried in random media

Abstract : Detection and identification of targets buried within layers of vegetation or geophysical media such as snow, ice, or soil, continues to be an area of substantial interest and active research. Analysis of electromagnetic sensor systems for applications of this type share the common difficulty that the natural environment surrounding the buried target can not easily be characterized in a deterministic manner, and a statistical description of the media and the resulting electromagnetic propagation and scattering must be employed. Coupling between the deterministic target and its random surroundings modifies the signature of the target and lends an incoherent component to the signal measured by the sensing system. Prediction of these physical effects of the random environment is necessary before the performance of individual sensing mechanisms may be analyzed, however, little theoretical modeling has previously been done to support this prediction. Hence, to provide greater physical insight into the effects of a random environment on the scattering characteristics of a buried target, several entirely new models are developed for the fields scattered from targets beneath or within layered regions of continuous random media. In the simplest case, the deterministic scatterer is taken as a point target, located beneath a slab of isotropic random media, characterized by a spherically symmetric correlation function. Strong fluctuation theory is applied to determine the effective mean permittivity of the random region, and the first order distorted Born approximation is utilized in computing the incoherent field scattered by the random media.