A transition model for the reflection coefficient in surface scattering

In the development of wave scattering models for randomly dielectric rough surfaces, it is usually assumed that the Fresnel reflection coefficients co uld be approximately evaluated at either the incident angle or the specular angle. However, these two considerations are only applicable to their resp ective regions of validity. A common question to ask is what are the condit ions under which we would choose one or the other of these two approximatio ns? Since these approximations are basically roughness-dependent, how can w e handle the in-between cases where neither is appropriate? In this paper, a physical-based transition function that naturally connects these two appr oximations is proposed. The like-polarized backscattering coefficients are evaluated with the model and are compared with those calculated with a mome nt method simulation for both Gaussian and non-Gaussian correlated surfaces . It is found that the proposed transition function provides an excellent p rediction for the backscattering coefficient in the frequency and angle tre nds.