In this paper, genetic algorithms is employed to determine the shape of a conducting cylinder buried in a half-space. Assume that a conducting cylinder of unknown shape is buried in one half-space and scatters the field incident from another half-space where the scattered filed is measured. Based on the boundary condition and the measured scattered field, a set of nonlinear integral equations is derived and the imaging problem is reformulated into an optimization problem. The genetic algorithm is then employed to find out the nearly global extreme solution of the object function such that the shape of the conducting scatterer can be suitably reconstructed. In our study, even when the initial guess is far away from the exact one, the genetic algorithm can avoid the local extremes and converge to a reasonably good solution. In such cases, the gradient-based methods often get stuck in local extremes. Numerical results are presented and good reconstruction is obtained both with and without the additive Gaussian noise.

In this paper, an efficient optimization algorithm for solving the inverse problem of a two-dimensional lossless homogeneous dielectric object is investigated. A lossless homogeneous dielectric cylinder of unknown permittivity scatters the incident wave in free space and the scattered fields are recorded. Based on the boundary condition and the incident field, a set of nonlinear surface integral equation is derived. The imaging problem is reformulated into optimization problem and the steady-state genetic algorithm is employed to reconstruct the shape and the dielectric constant of the object. Numerical results show that the permittivity of the cylinders can be successfully reconstructed even when the permittivity is fairly large. The effect of random noise on imaging reconstruction is also investigated.

This paper presents a computational approach to the imaging of a partially immersed conducting cylinder. Both cubic-spline method and trigonometric series for shape description are used and compared. Based on the boundary condition and the recorded scattered field, a set of nonlinear integral equations is derived and the imaging problem is reformulated into an optimization problem. The genetic algorithm is employed to find out the global extreme solution of the object function. It is found that the shape described by Fourier series can be reconstructed by cubic-spline. In the opposite case, the shape described by cubic-spline and reconstructed by Fourier series expansion will fail. Even when the initial guess is far away from the exact one, the cubic-spline expansion and genetic algorithm can avoid the local extreme and converge to a global extreme solution. Numerical results are given to show that the shape description by using cubic-spline method is much better than that by the Fourier series. In addition, the effect of Gaussian noise on the reconstruction is investigated.

For indoor wireless communication systems, transceivers need to be placed strategically to achieve optimum communication coverage area at the lowest cost. Unfortunately the coverage region for a transceiver depends heavily on the type of building and on the placement of walls within the building. This paper proposed a slab model to simulate the wave transmission in the wall and employed this simple path loss model to predict the coverage region. This method prevents the complicated computation of wave propagation, so it could predict the coverage area real time. Numerical results show predicted path loss date are well agreed with the measurement ones.

The genetic algorithm is used to reconstruct the shapes of multiple perfectly conducting cylinders. Based on the boundary condition and the measured scattered field, a set of nonlinear integral equations is derived and the imaging problem is reformulated into an optimization problem. The genetic algorithm is then employed to find out the global extreme solution of the object function. Numerical examples are given to demonstrate the capability of the inverse algorithm. Good reconstruction is obtained even when the multiple scattering between two conductors is serious. In addition, the effect of Gaussian noise on the reconstruction results is investigated.

This paper use a site-specific model to characterize the performance of millimeter wave BPSK system with single cochannel interference. Shooting and bouncing ray/image techniques are applied to compute the impulse responses for concrete-wall-partition rooms and plasterboard-wall-partition rooms. By using the impulse responses of these multipath channels, the BERs (Bit Error Rates) for high-speed BPSK (binary phase shift keying) systems with phase and timing recovery circuits are calculated. In addition, the carrier-to-interference ratio is also computed. Numerical results show that the interference for the plasterboard-wall-partition rooms is more severe than that for the concrete-wall-partition rooms.

The genetic algorithm is used to synthesize the directional circular arc array as a sectored antenna. Then, the performance of this sectored antenna in indoor wireless millimeter wave channel is investigated. Based on the desired pattern and the topography of the antennas, the synthesis problem can be reformulated into an optimization problem and solved by the genetic algorithm. The genetic algorithm will always converge to global extreme instead of local extreme and achieves a good approximation to the desired pattern. Next, the impulse responses of the indoor channel for any transmitter-receiver location are computed by shooting and bouncing ray/image techniques. By using the impulse response of multipath channel, the performance of the sectored antenna on BPSK (binary phase shift keying) system with phase and timing recovery circuits is presented. Numerical results show that the synthesized sectored antenna is effective to combat the multipath fading and can increase the transmission rate of indoor millimeter wave system.