ELECTROMAGNETIC WAVES INTERACTING WITH MATTER

Author: GARCÍA RUIZ FRANCISCO JAVIER.
Year: 2004.
University: GRANADA [www.ugr.es].
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: The development of this thesis is parallel to the European project FRACTALCOMS, whose main objective has been exploring the limits of the fundamental and technological small antennas based on the geometry prefractal. The thesis has been divided into two blocs. One is in the range of numeric codes for the resolution of the Maxwell equations in the time domain, and then apply them to study these antennas prefractales. The second section provides new designs of small wire antennas based on geometry prefractal or optimizations using genetic algorithms multiobjetivo. Within the first block, has worked with two numerical methods, the code DOTIG5 based on the Method of Moments in the time domain (MoMTD), and the hybrid method ADI-FDTD/MoMTD. These methods have been expanded to allow structures with flat land of electrical conductor perfect union between threads, segmentation is not uniform modeling threads, and so on. As for the design of small wire antennas, it has been carried out in vacuum, and then study the behavior of the antennas are designed when applied to mobile communications and therefore radiate close to a human head. In this thesis has shown that the antennas based on geometry prefractal do not improve the characteristics of the antennas based on more conventional geometries euclídeas (eg meandar and zigzag). We have submitted two of the effects that may restrict the behavior of small antennas thread: shortcuts in the path followed by the flow over the wire, and the links between segments parallel nearby. Lastly, and given the commitment to achieve significant among the various parameters of the small antennas (efficiency, bandwidth, frequency resonance, and so on.) Has been chosen to carry out new designs of small antennas thread through genetic algorithms multiobjetivo, demonstrating the antennas are designed using this technique always manage to improve the performance of antennas prefractales. Finally, as has been said, has studied the behavior of some of the antennas are designed to radiate close to a model of a human head, making use of this hybrid method ADI-FDTD/MoMTD. It has been found that this method is ideal for this kind of study, allowing accurate modeling of both wire antennas orientation as arbitrary body inhomogéneos and dispersive. It has studied the interaction between the antennas and head from two points of view that should be considered for a designer: the effect that the presence of the head is on the antenna (Check this thesis variation in the input impedance and frequency resonance of the antennas studied), and energy absorption in the head, which has developed an innovative algorithm that meets the IEEE's new regulations for calculating the Specific Absorption Rate (SAR) Check how using that this algorithm can be calculated SER in each and every one of the celadas composing the head model employee.