Investigations on the polarimetric behavior of a target near the soil

Abstract

The polarimetric behavior of the diffracted field from an object located close to the ground is investigated for a varying incidence angle. Here, the field is described by the Geometrical Theory of Diffraction (GTD) in accordance to its asymptotic formulas (k → ∞). As a result a ray system composed of 13 different rays was implemented for the monostatic case by applying the principle of Fermat. The different spatial and creeping waves give a physical insight in the mechanisms involved in the entire scattering process. By varying the angle from perpendicular to grazing incidence 0 • − 90 • , geometrical Surface Shadow Boundaries (SSB) are present for the backscattered field. At such boundaries the spatial waves are replaced by their corresponding creeping waves leading to a strong attenuation. The diffracted field for look angles related to the transition zones has a characteristic polarimetric behavior which can be represented on the Poincaré sphere. The typical locations on the sphere can be exploited in order to get information about the geometrical parameters of the target and its height above the ground.

A Refined GTD Ray System for an Embedded Object and Its Polarimetric Behavior

“…The fields of the waves 3, 4, and 5, which creep on an arc along the cylinder, can be neglected in comparison to the waves 1 and 2. The example shows that the main GTD ray contributors 1 and 2 accurately describe the main polarimetric features according to Marquart et al [13].…”

“…Substituting (13) in (9), for ∆ϕ i ≈ ∆ϕ r ≈ 0, and after some algebra, the final expression for the modified radius of curvature is obtained as…”