Biomedical Engineering Reference
In-Depth Information
Fig. 7.12 Side view of the
simulated 10 g averaged SAR
variation in the adult voxel
head model a-c when the
antenna main lobe is situated
outwards of the brain for the
peak spectral power limits of
a -41.3 dBm/MHz
b -27.4 dBm/MHz and
c 0.9 dBm/MHz d when the
antenna main lobe is situated
towards the brain for the peak
spectral power limit of -
41.3 dBm/MHz
(a)
(b)
Max. SAR 0.116 mW/kg.
Max SA= 0.232 pJ/kg
Max. SAR =2.43 mW/kg.
Max SA= 4.86 pJ/kg
(c)
(d)
Max. SAR =1.99 W/kg.
Max SA= 3.98 nJ/kg
Max. SAR =0.123 mW/kg.
Max SA= 0.246 pJ/kg
increased version of the pulse shown in Fig.
7.4
, but violates the FCC regulations
for IR-UWB indoor propagation.
The effect of the antenna orientation is also considered in these simulations.
Two cases are considered, depending on whether the main lobe is situated out-
wards or inwards of the brain. In the former case, the SAR variation is obtained by
placing the antenna main lobe outwards of the brain for an adult head model aged
at 30 years. In the latter case, the antenna main lobe radiates towards the brain.
These two scenarios are used to represent various possible applications of wireless
transmission in the head. For both cases, an FCC regulated IR-UWB pulse has
been considered. The results obtained are shown in Fig.
7.12
a, d. The SAR value
for the adult head model with the antenna main lobe pointing towards the brain is
0.007 mW/kg higher than its counterpart shown in Fig.
7.12
a. This is a compar-
atively negligible value and is caused by the different orientations in the near field.
7.4.3 SAR Variation in Different Tissue Materials
in the Human Head
The SAR variation percentages for all the tissue types involved in the simulation
of the IR-UWB signal with a peak power limit of -27.4 dBm/MHz and when the
antenna main lobe is located outwards from the brain are shown in Fig.
7.13
: this
case corresponds to the simulation depicted in Fig.
7.12
c. The mass percentage of
each tissue type is indicated alongside the SAR. The total SAR recorded for this
