Calculation of scattered power from a layer with randomly distributed particles for the application to the detection of water contents in soil

Moist soil is regarded as the mixture of air, soil, bound water and free water; then it may be assumed a dense random medium. A radiative transfer equation in a dense random medium has been derived from a wave equation with quasi-crystalline approximation with coherent potential (QCA-CP) and ladder approximation, L. Tsang et al. (1987). Under these approximations, a random medium is considered as a homogeneous medium with the effective permittivity, and the scattering and extinction coefficients are evaluated by QCA-CP in Rayleigh scattering region. The radiative transfer equation includes more scattering effects than the conventional one (CRTE), but does not include the effect of backscattering enhancement. This paper considers a three layered model, composed of air, moist soil layer and perfect conductor for developing a method for detecting water contents in soil by active remote sensing. The moist soil layer may be regarded as a homogeneous soil layer with densely distributed water particles. For this model, they used a dense medium radiative transfer equation (DMRTE) with the parameters evaluated by their method to calculate the bistatic scattering coefficients of the soil layer and the degree of polarization of scattered waves by changing the polarization of incident plane waves and the fractional volume of particles.