Average Scattered Field From a PEMC Cylinder With Random Radius

Abstract

Average scattered field from a perfect electric conductor (PEC) cylinder and per fect electromagnetic conductor (PEMC) cylinder with random radius is investigated. Uniform and normal distributions of the radius are considered. First, a very small cylinder is considered and analytical expressions for average scattered field can be written using small approximation of cylindrical wave functions. Co polarized aver age scattered field from a very small PEMC cylinder depends upon only zeroth order scattering coefficient while higher order coefficients contribute in cross polarized aver age scattered field. Zeroth order scattered field of a very small PEMC cylinder can be written as sum of zeroth and first order scattered field of a PEC cylinder. For a small and large cylinder, it is not possible to write down analytical expressions for average field so numerical average is done. Average scattered field from a small PEC cylinder of random radius differs from the scattered field from a PEC cylinder with mean radius for both transverse magnetic (TM) and transverse electric (TE) polarizations respectively. For a small PEMC cylinder it has been observed that the average co polarized scattered field is equal to scattered field from a cylinder with mean radius. This is not true in case of cross polarized scattered field and difference can be seen for most of the scattering angles. In case of large PEC/ PEMC cylinders it is worth mentioning that the average scattered field is almost equal to the scattered field from a cylinder with mean radius. In the second problem, the perturbation theory (PT) is used to calculate the scattered field from a slightly perturbed PEC/PEMC cylinder for shape perturba tion. Both transverse magnetic (TM) and transverse electric (TE) polarized inci dence fields are considered. A relation between the PT and the model for random cylinder (RC) generation is developed which is important for the PT to remain valid during the numerical simulations. The scattered field expressions obtained using the PT are verified using the result obtained by method of moments (MoM) in case of a PEC cylinder. The solution obtained by using the PT is more efficient in terms of simplicity and computational time. The scattering cross section for both the PEC and PEMC random cylinders is analyzed by varying the perturbation parameter B and the parameter describing the RC generation N. In particular, the distinctions due to perturbation are pronounced in the forward and backward scattering. It is noticeable that both B and N control the roughness of the cylinder and hence affect the scattering pattern.