Gain Optimization of a Near-Field Focusing Array for Hyperthermia: Theory and Experiment

A new variation of the array gain optimization problem has arisen in the study of microwave arrays used for hyperthermia, the heating of biological tissue. For a given array configuration and arbitrary medium, we show how to maximize the (VBAR)(')E(VBAR)('2) power deposition at the observation point in the near field of the array, analogous to the loss- less case of radiation maximization in a particular direction. In this formulation the medium need be neither homogeneous nor lossless, and the array elements need not be identical. Some practical cases are simulated with both lossy and lossless media showing how a closed-form solution gives results that closely follow the optimum when the dominant polarization from linearly polarized radiators is maximized. A comparison is also made with the conjugate-field or time-reversal excitation, a scheme which is slightly less efficient in most cases and which causes significantly higher focal shifts for some off-axis scan situations. In a medium as lossy as water, the field strength decays away from any practical array.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Electrical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Loane, Joseph Turner

• Engineering, Electronics and Electrical

Identifier

(UMI)AAI8610957

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/69334