In the study of microwave remote sensing and wave propagation in a medium, it is interesting and important to model and calculate the interaction of the electromagnetic wave with the medium, as the backscattering returns from the medium will be recorded and processed to produce satellite radar images and the wave attenuation while propagating in the medium will affect the microwave and mobile communications.

Traditionally, theoretical modelling of this problem assumes that the scatterers are interacting with the wave independently. However, in real nature, the coherence effect of these interactions due to the close-spacing of the scatterers cannot be ignored, especially in the case of an electrically dense medium. Traditional theoretical modelling also assumes that wave-interface effects are only due to single scattering on the surface. This is also less accurate since multiple scattering can also contribute to the effect, especially for rough surfaces. It is also assumed that the surface-volume interaction is only due to first order surface-volume scattering. However, second order surface-volume scattering is also important and should not be ignored. Therefore, a good and reliable theoretical model for wave scattering in the natural earth terrain should be developed for the use in microwave remote sensing, communications and satellite-based natural resource monitoring.

In this research, the backscattering model for an electrically dense medium is developed. This model incorporates the coherent effects due to the close-spacing of the scatterers. Improvement is done by considering the multiple surface scattering effect, together with the single surface scattering effect on the surface scattering formulation based on the existing integral equation model (IEM) for both the top and the bottom surfaces of the layer of the model. The backscattering model is also improved by considering up to second order surface-volume scattering. Its effect on surface, surface-volume and volume scattering terms are investigated to understand the effect of multiple surface scattering and second order surface-volume scattering in more detail. The effects of individual backscattering components to the total backscattering coefficient for co- and cross-polarized return are studied and analyzed. Comparisons are made with the field measurement results to validate the theoretical model developed.