Time Domain Microwave Imaging of a Buried Homogeneous Dielectric Cylinder in a Slab Medium by Asynchronous Particle Swarm Optimization

A time-domain inverse scattering technique for estimating the location, shape, and permittivity of a dielectric cylinder in a slab medium is proposed. In this paper, the finite-difference time domain is employed for the analysis of the forward scattering part, and asynchronous particle swarm optimization (APSO) is applied for the reconstruction of the two-dimensional homogeneous dielectric cylinder. For the forward scattering, several electromagnetic pulses are launched to illuminate the unknown scatterers, and then the surrounding scattered electromagnetic fields are measured. In order to efficiently describe the details of the shape, a sub-gridding technique is implemented in the finite-difference time domain method. Then, the simulated electromagnetic fields are used for inverse scattering, in which APSO is employed to transform the inverse scattering problem into an optimization problem. APSO is a population-based optimization approach that aims to minimize a cost function between measurements and computer-simulated data. The numerical results presented for the two examples of scatterers under transverse-electric incidence demonstrate that the proposed method is capable of reconstructing a complicated shape with a rapid rate of convergence and robust immunity to noise.