Advanced electromagnetic modeling of the interaction of the microwave field with human tissues.

摘要

This thesis contributes significantly to the advanced electromagnetic (EM) modeling of the interaction of the microwave field with human tissues. The proposed EM models achieve unprecedented computational efficiency, accuracy, and reliability.;In this thesis, an efficient EM/thermal analysis of the interaction of the radio-field (RF) fields of mobile phones with the human eyes is presented. Another advanced application developed here is the solution of inverse problem in microwave imaging and detection by making use of response sensitivity analysis.;Two methods are proposed for the evaluation of the maximum specific absorption rate (SAR) in the human eyes due to RF exposure from handheld devices. They account for the existence of resonance in the eye and arc applied to the case of near-field exposure. The first method is semi-analytical. As an input, it requires the measured or simulated open-space near field of the device under test in the absence of the eye. As an output, depending on the mutual position and orientation of the eye and the device, it produces the maximum SAR value in the eye averaged over 1 and 10 grams of tissue. The second method is experimental. It requires the fabrication of a simple eye phantom and relies on a measurement with an SAR robot. The proposed methods allow for the fast and reliable SAR evaluation of newly developed handheld devices in an industrial environment. Results concerning the temperature rise in the eyes are also presented. They are based on detailed simulation eye models.;A conceptually new detection algorithm is proposed in this thesis for the localization of electrically small scatterers in a known background medium. The algorithm requires the knowledge of the electric field distribution inside the known background medium where no scatterers are present. It is based on a self-adjoint response sensitivity computation which can be performed in real time. Using the E-field distribution in the background medium, it provides three-dimensional maps of the Frechet derivative within the imaged volume. The peaks and dips in these maps identify the locations where the permittivity and conductivity of the measured medium differ from those in the background medium. The background medium can be heterogeneous. The performance of the detection algorithm is studied in terms of the number of transmission/reception points, the dielectric contrast of the scatterer compared to the background medium, and the size of the scatterer. Its resolution is also addressed. The proposed detection algorithm is successfully applied in breast cancer detection.;The EM modeling is crucial in (a) multiphysics and (b) EM analysis in support of optimization procedures with applications in design optimization and inverse problem solutions. The challenge in such applications stems from the fact that EM modeling requires extensive computational resources. Therefore, the reduction of these computational requirements is necessary in order to handle the complexity of multiphysics modeling and microwave imaging.