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Revista Facultad de Ingeniería - Universidad de Tarapacá

versión On-line ISSN 0718-1337

Rev. Fac. Ing. - Univ. Tarapacá v.11 n.1 Arica jun. 2003

http://dx.doi.org/10.4067/S0718-13372003000100002 

  REVISTA FACULTAD DE INGENIERÍA, U.T.A. (CHILE), VOL. 11 Nº1, 2003, pp. 3-9

SAR SIMULATION FOR CHIRAL WAVES IN HEAD MODEL

Héctor Torres S.1     Mario Zamorano L.1

[1] Universidad de Tarapacá, Departamento de Electrónica, Casilla 6-D, Arica - Chile, htorres@uta.cl, mzamorano@uta.cl


ABSTRACT

A numerical model of an electromagnetic wave, propagating in a chiral media, characterized by the Born-Fedorov formalism, is presented. FDTD numerical method, adapted to chiral media, is used. The classical Yee algorithm, implemented by several authors for non chiral media, does not provide, for the same time instant, knowledge of the transverse field components (both incident and induced by the chirality). This problem is solved by the authors, delaying one of the field components when it incides in the achiral-chiral interface, storing the values corresponding to the times n and n -1, in order to solve for the the field at time n+1. The simulation results of propagating Gaussian pulses in chiral media, in the range of microwaves, show the chiral curl of the polarization plane. The results show that the use of the box model in combination with a realistic model of the head derived of a resonance image, is important for accurate determination of the near chiral fields induced in the head. It was found that, through SAR (Specific Absorption Rate) parameter, about 20% of the antenna input power is absorbed in the head. It is proposed that the chiral effect is due to a microscopic mechanism, where the typical cell membrane is a fairly fluid bilipid layer, with a few big protein molecules embedded in it. Every protein molecule is polar and will tend to align itself with an electric field and often rotate helically in its socket, so any volume of brain tissue must have a few cells bearing protein molecules that happen to resonate at its rotation frequency.

Keywords: Maxwell equations, chirality, FDTD, SAR.


ACKNOWLEDGMENTS

The authors thank the Chilean Agency CONICYT for their financial support. FONDECYT No. 1010300, and University of Tarapacá Projects Nºs. 8721-03 and 8722-03. Also we greatly appreciate the help received from M Sc. Enrique Fuentes H.

REFERENCES

[1] H. Torres Silva; "Waves in a Chiral-Plasma Media", The Japanese Journal of Physics, Vol. 67, pp. 850-857, 1998.        [ Links ]

[2] Taflove and S.C. Hagness; "Computational Electrodynamics: The Finite-Difference Time Domain Method", Artech House, Second Edition, 2000.        [ Links ]

[3] V. Lindell, A. H. Sihvola, S.A Tretyakov and A. J. Viitanen; "Electromagnetic Waves in Chiral and Bi-isotropic Media", Artech House, Second Edition, 2000.         [ Links ]

[4] H. Torres Silva; "Propagación de Ondas Pulsadas en un Chiroplasma Magnetizado", Rev. Mexicana de Física, N° 44 Supl. 3, pp. 53.58, Dic. 1998.         [ Links ]

[5] K. S. Yee; "Numerical solution of initial boundary value problems involving Maxwell's equations in isotropic media", IEEE Trans. Antennas Propagat, Vol. AP-14, N° 5, pp. 302-307, 1966.         [ Links ]

[6] H. Chen, H. Wang; "Current and SAR Induced in Human Head Model by the Electromagnetic Fields Irradiated from a Cellular Phone", IEEE Trans. Microwave Theo. And Tech, Vol. 42, N° 12, pp. 2249-2254, 1994.         [ Links ]

[7] F. Ortiz; "Análisis de la Propagación de Ondas Electromagnéticas en Medios Quirales Mediante el método FDTD", Proyecto de Título Ing. Civil Electrónica, UTA, 2001.         [ Links ]

[8] H. Torres Silva, M. Zamorano; "FDTD Algorithm Used to Calculate the RF Chiral Waves in the Human Head", 2nd International Workshop Biological Effects of EMFs, Rodees-Grecia, 2002.         [ Links ]


Recibido el 22 de julio de 2003, aceptada el 25 de agosto de 2003.