| dc.description.abstract | The research in this thesis involves the investigation of the specific absorption rate (SAR) in a human head model exposed to electromagnetic fields. The SARs (1-g and
10-g) were compared inside various models of the human head. Investigation is aimed
at the study of the effect of the use of a realistic implant retained prosthetic ear attached to the side of the head and metal-frame glasses. A set of dipole antennas operating at a
common frequency of 900, 1800 and 2100 MHz were rotated to investigate the effect of
frequency and polarization. Two situations were considered in the thesis; radiation at
the front of the face, and at the side of the head. Initial studies were conducted using a
simplified model of the head and metal object to minimize the duration of the
simulation. Four types of simple geometrical head were used; brick, cylindrical,
spherical and elliptical cylinders were simulated with and without the simple shape of
the nose to investigate its possible effects. At the same time, a straight metal rod was
initially employed to represent the metal-frame glasses. The parameters were further
expanded to the different conductivities of the metal rod, the dimensions of a model of
the head, the curvature of the rod and the radii of the rod. In the side radiation case, the
investigation of the ear prosthesis was initiated by looking at the effect of different
dielectric properties of the artificial ear. Moreover, the combined use of these metal
objects with realistic shapes of both glasses and implant (ear) were investigated in detail
using homogeneous and heterogeneous models of a human head. The results suggest
that different sections of the implant resonate depending on the frequency and
polarization, and furthermore, demonstrate that this real implant is a complex scattering
element. The implant focuses and reflects the incident radio frequency (RF) energy. The
nearby tissue of the head will also have a secondary dielectric loading effect. The
relative enhancement on the SAR10g due to the implant was much smaller. The SAR
distribution shows that the increase in the SAR due to the metallic implant is extremely
local with regards to the implant. This explains the change in the SAR1g and the much
smaller changes to the 10g SAR. However, the metal-frame glasses selected in this
investigation had given a negative significant increment of SARs at any orientation of
the dipole and frequency chosen. Overall, with regard to the ear prosthesis, exposure to
900 MHz from any device adjacent to the implant may cause harm. It also is suggested
that patients with ear prostheses should not be exposed to any near-body
communication at any frequency range, because there is evidence that metal implanted
inside certain materials has different behavior from the same metal that has not been
implanted in any material. | en_US |
