Study On Beam Scattering From Rough Surfaces And Its Applications

Beam scattering from rough surfaces is of importance in detonator, radar and other scientific and technological fields since these fields deal with it by responding to practical needs. In this dissertation, beam scattering from rough surfaces is systematically investigated including theoretical research and its applications in engineering. The main works and results are as follows: 1. Scattering of a Gaussian beam by a rough dielectric surface is studied based on the plane wave spectrum expansion and Kirchhoff approximation theory, the formulas of scattered field and the incoherent scattering cross-section for Gaussian beam illumination of a rough surface are derived. And the numerical results for incoherent back scattering cross section are given and discussed. 2. Based on the method of the simulation of a large beam by a sum of narrow beams, studied is the characteristics of beam scattering from a perfectly conducting, randomly rough surface illuminated by a incident large beam. The results obtained by this beam simulation method are compared with the exact solutions showing good agreement. The accuracy of the results obtained by the simulation method depends on the numbers of subbeams, the index of refraction and the roughness of rough surfaces, and the polarization characteristics of incident beams. 3.Characteristics of scattering by a statistically rough surface with the Neumann boundary condition for small grazing angles is studied by using small perturbation theory. Incoherent scattering cross section is derived. In the case of plane wave incidence, it is proportional to the second power of the grazing angle with respect to the incident and scattered directions, and to the fourth power of the grazing angle for the backscattering situation. In the case of beam incidence, the angular dependence of the incoherent scatting cross section depends on the beamwidth : for sufficiently wide beams, the scattering cross section coincides with the result obtained for infinite plane wave ; while, for narrow beams, it tends to constant for small grazing angles. 4. Detonator laser beam scattering by an object in near field is studied. Firstly, based on the measure data, a mathematical description of the angular distribution of detonator laser beam is given. Secondly, by using the scattering characteristics of rough surface, the relation formula between received power and transmitted power of remote system for a facet is derived. Finally, a computing method of the received power of remote system for a complex object is given. And the received power of remote system for Fl 6 aeroplane, as an example, is computed.