The contribution of evanescent waves to the scattering width of a cylinder

Near-field evanescent waves can contribute to the scattering width of a very long cylinder placed within several wavelengths of the aperture of an antenna, particularly if the antenna aperture is not more than several wavelengths in width. The scattered waves are expressed as a series of Hankel functions, where the coefficients in the expansion are determined from the boundary conditions at the surface of the perfectly conducting cylinder. The scattering width is investigated as a function of the angle of incidence, the angle of scattering, and the normalized radius of the cylinder.