Microwave imaging of a partially immersed non-uniform conducting cylinder

[[abstract]]In this paper, we investigate the imaging problem to determine both the shape and the conductivity of a partially immersed non-uniform conducting cylinder from the knowledge of scattered far-field pattern of TM waves by solving the ill-posed nonlinear equation. Based on the boundary condition and the measured scattered field, a set of nonlinear integral equations is derived and the inverse problem is reformulated into an optimization one. The steady-state genetic algorithm is then employed to find out the global extreme solution of the object function. As a result, the shape and the conductivity of the conductor can be obtained. Numerical results are given to demonstrate that even in the presence of noise, good reconstruction can be obtained.[[notice]]補正完畢[[incitationindex]]SCI[[booktype]]電子

Electromagnetic scattering of metallic cylinders of arbitrary shape by using asynchronous particle swarm optimization and non-uniform steady state genetic algorithm

[[abstract]]Two techniques for the shape reconstruction of multiple metallic cylinders from scattered fields are investigated in this paper, in which two-dimensional configurations are involved. After an integral formulation, the method of moment (MoM) is applied to solve it numerically. Two separate perfect-conducting cylinders of unknown shapes are buried in one half-space and illuminated by the transverse magnetic (TM) plane wave from the other half space. Based on the boundary condition and the measured scattered field, a set of nonlinear integral equation is derived and the imaging problem is reformulated into optimization problem. The non-uniform steady state genetic algorithm (NU-SSGA) and asynchronous particle swarm optimization (APSO) are employed to find out the global extreme solution of the object function. Numerical results demonstrate even when the initial guesses are far away from the exact shapes, and the multiple scattered fields between two conductors are serious, good reconstruction can be obtained. In addition, the effect of Gaussian noise on the reconstruction results is investigated and the numerical simulation shows that the reconstruction results are good and acceptable, as long as the SNR is greater than 20 dB.[[incitationindex]]SCI[[booktype]]電子版[[booktype]]紙

Time Domain Inverse Scattering for a Buried Homogeneous Cylinder in a Slab Medium Using NU-SSGA

[[abstract]]A time-domain inverse scattering technique for reconstructing a buried homogeneous cylinder with arbitrary cross section in a slab medium is proposed. For the forward scattering, the FDTD method is employed to calculate the scattered E fields. Base on the scattering fields, these inverse scattering problems are transformed into optimization problems. The non-uniform steady state genetic algorithm (NU-SSGA) is applied to reconstruct the location shape and permittivity of the two-dimensional homogeneous dielectric cylinder. The NU-SSGA is a population-based optimization approach that aims to minimize the objective function between measurements and computer-simulated data. A set of representative numerical results is presented for demonstrating that the proposed approach is able to efficiently reconstruct the electromagnetic properties of homogeneous dielectric scatterer even when the initial guess is far away from the exact one. In addition, the effects of Gaussian noises on the image reconstruction are also investigated.[[notice]]補正完畢[[incitationindex]]SCI[[booktype]]電子

Self-adapting control parameters in dynamic differential evolution on inverse scattering problems: SADDE for inverse scattering

[[abstract]]The application of two techniques for the reconstruction of shape reconstruction of the perfectly conducting cylinder from scattered field measurements is studied in the present paper. These approaches are applied to two-dimensional configurations. After an integral formulation, a discretization using the method of moment (MoM) is applied. The inverse scattering problems are transformed into optimization problems. Considering that the microwave imaging is recast as a nonlinear optimization problem, an objective function is defined by the norm of a difference between the measured scattered electric field and that calculated for an estimated the shape of the perfectly conducting cylinder. Thus, the shape of metallic cylinder can be obtained by minimizing the objective function. In order to solve this inverse scattering problem, two techniques are employed. The first is based on a dynamic differential evolution (DDE). The second is a new version of the DDE algorithm with self-adaptive control parameters (SADDE). Numerical results indicate that the self-adaptive dynamic differential evolution algorithm (SADDE) outperforms the DDE in terms of reconstruction accuracy.[[conferencetype]]國際[[conferencedate]]20110926~20110930[[conferencelocation]]Seoul, Kore

Inverse Problem of Multiple Conductors Buried in a Half-Space

[[abstract]]Electromagnetic imaging of buried multiple conductors by using genetic algorithm has been presented. Two separate perfectly conducting cylinders of unknown shapes are immersed in one half-space and illuminated by transverse magnetic (TM) polarization plane wave from the other half-space. Based on the boundary condition and the measured scattered field, we have derived a set of nonlinear integral equations, and the imaging problem is reformulated into an optimization problem. For describing the shapes of conductors, the Fourier series is selected to expanding the shape functions. In inverse algorithms, the improved steady state genetic algorithm is employed to search for the global extreme solution of objective function. Numerical results have demonstrated that the powerful performance of the inverse algorithm. The reconstructed shapes are considerably accurate even when the initial guesses are far away from the exact ones and the buried depths of the conductors are large compared to wavelength.[[conferencetype]]國際[[conferencedate]]20070816~20070818[[booktype]]紙本[[iscallforpapers]]Y[[conferencelocation]]Xi'an, Chin

Comparison of Particle Swarm Optimization and Asynchronous Particle Swarm Optimization for Inverse Scattering of a Two- Dimensional Perfectly Conducting Cylinder

[[abstract]]This paper reports a two dimensional time domain inverse scattering algorithm based upon the finite-difference time domain method for determining the shape of perfectly conducting cylinder. Finite difference time domain method (FDTD) is used to solve the scattering electromagnetic wave of a perfectly conducting cylinder. The inverse problem is resolved by an optimization approach and the global searching scheme asynchronous particle swarm optimization (APSO) is then employed to search the parameter space. By properly processing the scattered field, some EM properties can be reconstructed. One is the location of the conducting cylinder, the others is the shape of the perfectly conducting cylinder. This method is tested by several numerical examples; numerical results indicate that the APSO outperforms the PSO in terms of reconstruction accuracy and convergence speed. Both techniques have been tested in the case of simulated measurements contaminated by additive white Gaussian noise.[[incitationindex]]SCI[[incitationindex]]EI[[booktype]]紙

Modeling EMI Resulting from a Signal Via Transition Through Power/Ground Layers

Signal transitioning through layers on vias are very common in multi-layer printed circuit board (PCB) design. For a signal via transitioning through the internal power and ground planes, the return current must switch from one reference plane to another reference plane. The discontinuity of the return current at the via excites the power and ground planes, and results in noise on the power bus that can lead to signal integrity, as well as EMI problems. Numerical methods, such as the finite-difference time-domain (FDTD), Moment of Methods (MoM), and partial element equivalent circuit (PEEC) method, were employed herein to study this problem. The modeled results are supported by measurements. In addition, a common EMI mitigation approach of adding a decoupling capacitor was investigated with the FDTD method

13th Annual Review of Progress in Applied Computational Electromagnetics at the Naval Postgraduate School, Monterey, CA, March 17-21, 1997, Conference Proceedings Volumes I & II

Includes Volumes 1 &