Time domain inverse problem of a buried dielectric cylinder

This paper presents an image reconstruction approach based on the time-domain and particle swarm optimization (PSO) for a 2-D homogeneous dielectric cylinder buried in a half-space. The computational method combines the finite difference time domain (FDTD) method and the particle swarm optimization (PSO) to determine the shape and location of the underground scatterer with arbitrary cross section. The subgirdding technique is implemented in the FDTD code for modeling the shape of the cylinder more closely. In order to describe an unknown cylinder with arbitrary shape more effectively, the shape function is expanded by closed cubic-spline function instead of frequently used trigonometric series. The inverse problem is resolved by an optimization approach, and the global searching scheme PSO is then employed to searching the parameter space. In order to reduce the number of the unknown parameters for the inverse scattering, the shape function of the cylinder is interpolated in terms of the closed cubic-spline. Numerical results demonstrate that, even when the initial guess is far away from the exact one, good reconstruction can be obtained.