Scattering by a helical sheath

A harmonic series solution is obtained for the scattering of electromagnetic waves by a unidirectionally conducting helical sheath when the incident field is
E
-polarized. Due to the anisotropic nature of the boundary, both
E
and
H
polarizations are present in the scattered and the transmitted fields. The expressions for the total scattering cross section, the backscattering cross section, the current, and the surface charge density are also obtained. Some numerical results are presented for a helical structure with a radius that is small or moderate in comparison with the wavelength. An interesting behavior as the pitch angle approaches
\pi/2
is described.