0
25
50
75
100
150
125
175
Ankle
Knees
Bladder
Maximum
Liver
Heart
Eyes
Grounded man model with shoes
Ungrounded man model w/o shoes
Neek
Height above feet (cm)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
Peak current (mA)
56
Electromagnetic Fields in Biological Systems
FigurE 1.33 Peak currents induced for various sections of the body of a human male for shoewearing grounded and ungrounded conditions: E peak = 1.1 V/m. (From Lin, J. C., and P. Bernardi.
2007. Computer methods for predicting field intensity and temperature change. In Bioengineering
and Biophysical Aspects of Electromagnetic Fields, ed. F. Barnes and B. Greenebaum, Chapter 10,
293–380. Boca Raton, FL: CRC Press. With permission.)
are given in Figures 1.32 and 1.33. The calculated peak currents for the various sections
are about 1.1–3.2 mA/(V/m). It is interesting to note that there is very little difference in
the induced currents irrespective of whether the model is grounded or not. This is due
to the fact that most of the energy in the pulse is at frequencies in excess of 300 MHz,
where the effect of the ground plane on the induced currents or the SARs is minimal.
In Figure 1.33, the peak current for each section of the body is shown with a section
resolution of 1.31 cm. The maximum peak sectional current of 3.5 mA, which is equal to
3.2 mA/(V/m), occurs at a height of 96.3 cm above the bottom of the feet. Similar results
were observed for calculations using isolated and grounded models of the human body
for plane-wave exposures at frequencies of 350–700 MHz, where the highest induced
currents on the order of 3.0–3.2 mA/(V/m) were calculated for sections of the body that
are at heights of 85–100 cm relative to the feet.
The SA and the total absorbed energy for exposure to the UWB pulse can be calculated using Equations 1.67 and 1.68. The total energies absorbed by the body exposed to
a single pulse of the type shown in Figure 1.30 are 2.0 and 1.91 pJ (picojoules) for isolated
and shoe-wearing grounded conditions, respectively (Lin and Bernardi 2007).
1.12.6 Summary of Short and Ultra-Wideband Pulse Coupling
It should be mentioned that in general the interaction of pulsed fields with biological
systems can be very different from exposure of systems to continuous wave fields. In
addition to EMP and UWB, pulse operations are commonly found in radar and MRI
systems. A distinguishing feature in these cases is that they all involve radiation of