GHz," Physics in Medicine and Biology, Vol. 38, pp. 361
that this may not be indicative of the greater percentile of the
368, 1993.
populace.
[7] Drossos, A., Santomaa, V., and Kuster, N., "The
dependence of electromagnetic energy absorption upon
V. CONCLUSIONS
human head tissue composition in the frequency range of
3003000 MHz," IEEE Transactions on Microwave Theory
The data suggests that for large dipole to phantom
and Techniques, Vol. 48, No. 11, pp. 19881995, Nov. 2000.
separations, the 20mm fat layer has some impact on the
computed average SAR results, possibly due to some
[8] Gabriel, C., Gabriel, S., and Corthout, E., "The dielectric
resonance effects between the higher conductivity muscle
properties of biological tissues: I. Literature survey," Physics
and skin layers.
in Medicine and Biology, Vol. 41, No. 11, pp. 22312249,
1996.
An observation has been made that it is possible to create a
heterogeneous model which could be "tuned" for distance
[9] Gabriel, S., Lau, R. W., and Gabriel, C., "The dielectric
specific scenarios of dipole to tissue boundary conditions,
properties of biological tissues: III. Parametric models for
and that it may be possible to create a model which is
the dielectric spectrum of tissues," Physics in Medicine and
significantly more conservative than the accepted
Biology, Vol. 41, No. 11, pp. 22712293, 1996.
homogeneous model. Caution should be taken though when
applying this logic as it needs to be verified physically
against scientifically correct anatomical models. At this time
there is a need for more data to be published which provides
further information on anatomical studies of complex tissue
and layering structures which can be used for more accurate
studies.
VI. ACKNOWLEDGEMENTS
The authors would like to thank Dr. Michael Smith and Dr.
Christopher Collins of Pennsylvania State University
(Hershey Medical Centre Department of NMR) for their
assistance in defining dielectric properties and dimensions of
tissues used within this study. The authors of this paper wish
to also acknowledge the WiFi Alliance for their help in
sponsoring this research.
VI. REFERENCES
[1] IEEE 1528 Recommended Practice for Determining the
Peak Spatial-Average Specific Absorption Rate (SAR) in the
Human Body Due to Wireless Communications Devices:
Experimental Techniques.
[2] IEC 62209 Human exposure to radio frequency fields
from hand-held and body-mounted wireless communication
devices Human models, instrumentation, and procedures
Part 1: Procedure to determine the Specific Absorption Rate
(SAR) for hand-held devices used in close proximity of the
ear (frequency range of 300 MHz to 3 GHz).
[3] Federal Communications Commission (FCC), FCC web
site on Tissue Dielectrics [http://www.fcc.gov/fcc-
bin/dielec.sh].
[4] C. Gabriel, "Compilation of the Dielectric Properties of
Body Tissues at RF and Microwave Frequencies," Brooks
Air Force Base, report no. AL/OE-TR-1996-0037, 1996.
[5] Kunz K S, and Luebbers R J, "The Finite Difference
Time Domain Method for Electromagnetics", CRC Press,
1993.
[6] Dimbylow, P. J., "FDTD calculations of the SAR for a
dipole closely coupled to the head at 900 MHz and 1.9
3
Submitted to Asia Pacific EMC Taipei City, Taiwan 2005