A comparison between IEM-based surface bistatic scattering models

The original IEM surface scattering model used a simplified surface current estimate leading to relatively simple but accurate results for forward and backscattering configurations. Since then other estimates of the surface current based upon the same set of integral equations have appeared in the literature. A major reason for considering a more complex estimate is because in the original IEM model the phase in the Green´s function was not included in the integration process over the surface current to find the scattered field. Thus, it is not applicable to multiple scattering calculations. Currently, there are three different modifications suggested by different investigators: (1) use of the phase factor in the Green´s function of the upper medium for integration over surface current, (2) use of the phases in the Green´s function in both the upper and lower medium for integration over surface current, and (3) in addition to (2) further modify the Fresnel reflection coefficient to be the sum of reflection coefficients evaluated at the incident and scattering angles divided by two. In this paper we want to compare model predictions based on the use of the above surface current estimates under backscattering and bistatic conditions.