The Research On Analytical Methods Of Electromagnetic Scattering From Randomly Rough Surfaces

The electromagnetic scattering from randomly rough surfaces has been attracting wide interest of researchers, thanks to their significant application in the spheres of military, oceanography and so on. This dissertation makes intensive research on electromagnetic(EM) scattering from randomly rough surfaces from analytical theory.In this paper, the fundamental theory of electromagnetic scattering from the rough surfaces is introduced; different methods of electromagnetic scattering from the rough surfaces including the small perturbation method and the Kirchhoff approximation are discussed. When using the conventional Kirchhoff approximation to calculate the slope of rough surface, people used to use zero-order approximation of the steady point, and neglect the random characteristics of surface. The height and slope of two neighboring points on rough surfaces are seen as independent, while calculating the scattering coefficient by using the conventional Kirchhoff approximation model. In fact, their height and the opponent's slope could be related, if the level distance between any two neighboring points on rough surfaces is no more than the correlation length of rough surfaces (however, is more than the incident wave length). In addition, it is obvious that the contribution of the correlation of height and slope to scattering intensity, and it should be considered while calculating the scattering intensity.On the above issues, a new KA algorithm is proposed for two-dimensional Gaussian rough surface, which is called COR-KA algorithm. Comparing the COR-KA algorithm with the conventional KA algorithm, there are two improvements between them. First, the slope at any point on the rough surface is presented by the first-order approximation of a steady point in COR-KA algorithm. And then statistical method can be adopted to process the local coordinates, the slope and the Fresnel's reflection coefficient on the random surface(the conventional KA algorithm uses the zero-order approximation of a steady point, which overlooks the feature of the points on the randomly rough surfaces). Second, this algorithm introduces the heights and vector's joint probability distribution function (6-dimensional) of two points to represent random distribution of height and slope, which fully describes the relevance of height and height, height and slope, slope and slope of the points on the two-dimensional rough surface.In this paper, the derivation process of two-dimensional rough surface scattering of the COR-KA algorithms are detailed, and the analytical expressions of the scattering coefficient are acquired. And more accurately gains two-dimensional scattering model of rough surface. Finally, the paper makes a simulation of the COR-KA algorithms, and conventional KA, and compares and contrasts the results with MOM's results. It shows that the effectiveness of the COR-KA algorithm.