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URL: https://www.es-forum.com/Does-the-human-body-block-or-absorb-RF-energy-tp4032064p4032072.html



http://essay.utwente.nl/66071/1/Dove_MA_TE.pdf


In this research the radio propagation inside a human body
has been analyzed by investigating the physical characteristics
of a new developed multilayer model.
A  novel  method  of  calculating  the  absolute  losses  and  travel
times  of  the  propagation  path  has  been  introduced.  The  per-
formed numerical analysis is independent of the measurement
environment, equipment or antenna mismatches. The propaga-
tion path is determined not by averaging tissue characteristics
but  rather  including  the  influences  of  all  tissue  layers  from
in-body  to  on-body,  based  on  a  new  multilayer  model.  The
benefits of the developed multilayer model are that it is easy
to adjust and to extend. This analysis takes the complex tissue
characteristics  into  account  both  for  the  travel  time  as  for
signal  strength  analysis.  New  insights  on  the  different  types
of  absorptions  are  gathered.  The  propagation  loss  and  travel
time analysis is done for different human types and different
frequencies.
The  losses  due  to  the  impedance  differences  between  the
layers  are  of  significant  value  and  almost  the  same  for  all
frequencies.  The  signal  attenuation  inside  fat  layers  is  small
such  that  there  are  no  big  differences  in  the  attenuation  for
different  thicknesses  of  fat  layers.  The  attenuation  due  to
muscle  tissue  layer  variation  and  SI  tissue  layer  thickness
cause big attenuation differences for all frequency bands.
For the determination of the travel times the group velocity as
propagation speed is considered rather than the phase velocity.
Furthermore, the conductivity characteristics of human tissue
are included in these calculations. The resulting group velocity
in  the  lossy  human  body  tissue  material  differs  significantly
from the phase velocity calculations of lossless material as it
was assumed in literature. The SI and muscle tissue layers give
the most influence on the travel time for all frequency bands.

The  propagation  delay  due  to  the  fat  layers  are  the  same  for
the different frequencies.
From  the  results  it  is  investigated  that  the  absorption  and
delay  are  not  that  frequency  dependent  as  is  expected  and
mentioned in literature. This can be due to the limited number
of effects which are analyzed or the other characteristics which
have  been  taken  into  account.  An  important  conclusion  is
that  reflections  on  the  boundaries  have  major  impact  on  the
attenuation.
In  future  work  the  influence  of  oblique  incidence  on  the
power  attenuations  and  reflections  have  to  be  investigated
as  well  as  other  effects  as  multipath  and  diffraction.  The
physical multilayer model should also be extended to a 2D/3D
model  to  gain  more  insight  into  the  absorptions  and  travel
times  changes.  Attenuation  due  to  reflections  have  to  be
considered for a deeper location of the endoscopy capsule in
the small intestines. After that the possibility of implementing
localization  could  better  be  assessed.  A  statistical  model  has
to be developed to take different human types and effects into
account for the real localization of a sensor inside the human
body.
From  the  research  it  can  be  concluded  that  describing
and  analyzing  in-body  radio  propagation  is  challenging  for
localization purposes