Physical optics approach for scattering by thin helical wires


  • A. Sezginer,

  • J. A. Kong


A physical optics formulation of scattering by thin wire helices of finite and infinite extent is presented. The high frequency limit of the integral representation of the physical optics field is obtained by the saddle point technique and is shown to be identical to the field computed by the geometrical optics approximation. For thin wire helices of finite extent, the physical optics approximation to the current should be supplemented by current waves traveling along the wire that are excited by the discontinuities at the ends of the wire. This modified physical optics approach is found to be a useful approximation to compute scattering by nonresonant helices that have a larger pitch than approximately 5 wavelengths. A hybrid method composed of the modified physical optics technique and the method of moments is applied, for the degenerate case of a linear wire, in order to extend the region of validity to cover the resonant cases. The modified physical optics approach is typically 5–10 times faster than Galerkin's method, and most important, it provides physical insight into the scattering phenomenon.