Electromagnetic scattering model for a tree trunk above a ground plane

Electromagnetic scattering from a tree trunk is of importance because of its application in microwave remote sensing of a forest stand. Physically, a tree trunk can be regarded as a stratified cylinder with corrugated outer layer above a dielectric ground plane. The bistatic scattering response of the cylinder is obtained by invoking two approximations. In the microwave region the height of the tree trunks are usually much larger than the wavelength. Therefore the interior fields in a finite length cylinder representing a tree trunk can be approximated with those of an infinite cylinder with the same physical and electrical radial characteristics. The equivalence principle is used to replace the cylinder with fictitious electric and magnetic surface currents. Also approximate image theory is used to account for the presence of the dielectric ground plane which simply introduces an image excitation wave and an image scattered field. The corrugated bark layer is modeled by an uniaxial anisotropic layer. When the diameter of the tree trunk is large compared to the wavelength the solution based on the eigenfunction expansion becomes in efficient and in this case an asymptotic solution (physical optics) is used to calculate the scattered field