טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentAnastasia Cherkassky
SubjectOptimization of Electromagnetic Power Absorption in a Lossy
Circular Cylinder
DepartmentDepartment of Electrical Engineering
Supervisor Professor Einziger Pinchas
Full Thesis textFull thesis text - English Version


Abstract

Recently, electromagnetic power absorption in biological tissues has became of significant interest. While efficient numerical algorithms have been developed to obtain accurate power distributions in complicated configurations, their physical interpretation and explicit dependence of the problem parameters are still hard to grasp.

An alternative approach utilizing simplified prototype models has recently led to analytical closed-form solutions. These models, treating a semi-infinite absorbing medium in the vicinity of either finite (line current) or infinite (planar current sheet) sources, resulted in an explicit dependence of the power relations on both the geometrical and physical parameters and provided an effective mean for obtaining physical insight into the basic power absorption mechanisms as well as tight bounds and estimates on the power relations.

In some realistic configurations, however, including cellular phone interaction with living tissues, and electromagnetic hyperthermia-based treatments, the absorbing structure's curvature must be incorporated into the model in order to make its implementation effective. Herein, the Leontovich surface impedance approach, applied for finite-size cylindrical absorbing medium, leads to a discrete Parseval's representation for the power relations in terms of the individual cylindrical harmonics' (spectral) power content. Asymptotic evaluation of the continuous Parseval's identity, obtained via Watson transform, results in a closed-form expressions for the power relations involved. The expressions, obtained for both TE and TM polarizations, can be readily interpreted as for the previous (planar) case but with a curvature correction term, which depends, continuously, on the effective surface curvature and the source location. The inclusion of the curvature correction terms for both polarizations, whenever applicable, is thereby enables a better understanding and design of prototype systems, which involve electromagnetic sources closely coupled to highly lossy structures.