Numerical Analysis of Electromagnetic Scattering from a Dielectric Rough Surface Cylinder

1.Introduction The wave scattering from rough surfaces is an important problem which closely relates to the measurement technology or diagnosing techniques by using microwave, millimeter wave, light wave or acoustic wave (1). Various kinds of theoretical models and methods for analyzing the wave scattering from random rough surfaces have been proposed so far. However, they have often used approximated boundary conditions(2), for example Kirchhoff approximation, perturbation approximation, or impedance boundary approximation. Moreover, in many cases, the rough surfaces considered in them have infinite extent and also the plane-wave incident cases are treated. However, in order to measure the scattering characteristics from rough surfaces in a laboratory system, the condition of finite area illumination by the incident wave such as a beam wave is more or less inevitable. The author has analyzed the scattering of a focused beam from random rough surfaces by computer simulation(3). In the present paper, the scattering of a focused beam from a dielectric cylinder with a random rough surface is analyzed by computer simulation. Such a scattering problem can be applicable to the measurement of microscopic surface roughness of optical fibers. A sample cylinder with Gaussian radius distribution and periodic radius correlation function is numerically generated by a computer. The scattered field from a realized sample cylinder is numerically calculated by using the boundary-element method (BEM) based on the integral equation(4). The mean intensity of the scattered field and its coherent component are obtained by calculating the mean square value of the scattered fields from all computer-generated sample cylinders. The dependence of the scattering characteristics on the roughness parameters is examined.