|
In this thesis the inverse scattering of a multi-layered
anisotropic cylinder is investigated. Assume that a TE and/
or TM wave is incident upon objects of unknown dielectric
distribution and the scattered fields are measured
outside. By properly processing the scattered field, the
dielectric distribution of the objects can be reconstructed. A
cylindrical object with arbitrary cross-section shape is
considered, which may consist of single layer or multi-
layered anisotropic material with homogeneous and
inhomogeneousdistribution.
We use unrelated illumination method to solve this inverse
scattering problem, theoretically, the scattered problems can
be analyzed using the concept of equivalent current. By
applying appropriate boundary conditions, a set of nonlinear
integral equations can be derived. The forward scattering
formula and inverse scattering formula are derived by the use of
moment methodand unrelated illumination method, respectively,
based on a set of integral equations mentioned above. For
numerical simulation, the scattered fields from a known
object are generated by the forward scattering formula, then the
scattered field data are plugged into the inverse scattering
formula, from which the dielectric distribution of the object
can be reconstructed. The dielectric parameters of
anisotropic materials depend on the specified coordinate
system, so previous researches all require the knowledge of the
principal axes of the measured object in advance. But the
purpose of this research is to develop the inverse algorithm
for reconstructing the distribution of the material
permittivity (a tensor) of the measured object, of which the
principal axes are assumed unknown in general, and, furthermore,
apply this on a multi-layered and/or inhomogeneous cylinders.
Satisfactory reconstruction had been obtained from this inverse
algorithm. We'll present various kinds of inhomogeneous and
multi-layered anisotropic cylinder with different cross-
sections, which include rectangular, square and circular shape.
In addition, the effects of the number of external measured
points and the noise level upon the scheme are also
investigated.
|