Does the human body block or absorb RF energy?
I heard that the human body, by virtue of its water content, absorbs RF energy emitted by a bodypack transmitter. Since then I have found a definite pattern among customers complaining of inexplicable wireless problems which for no apparent reason seem confined to a particular user rather than a particular transmitter or receiver. Those users almost always turn out to be -- how shall I say -- corpulent, implying a more bountiful internal water reservoir. UHF systems seem to suffer more than VHF systems, I suppose because of the shorter wavelength of UHF signals.
The human body is both a reflector and an absorber of RF energy. This is likely to be even more apparent at higher frequencies, e.g. 2.4 GHz. Try this experiment. If you have a portable FM radio, tune in a station and do a 360 degree spin. Note how the station fades as you turn your body.
Positioning a large human body between the transmitter's antenna and the receiver's antenna can cause a degradation in RF performance. The human body is made up primarily of "salt water." Salt water is an effective absorber of RF energy. (Submarines have to surface to send FM radio signals.) The more body fat a person has, the more RF is absorbed. Our tests show that a body pack transmitter can be 50 to 70% less effective than a handheld transmitter simply because of the antenna location being against the human body. Thus the reason RF antennas in theatres are often placed above the
The Effects Of Radio Waves On Human Body
We consider that radio waves, after these evidences, are dangerous (especially for long exposition) for human body because, even if they are not unhealthy in a short period, they can cause cells’ death by apoptosis and necrosis and DNA damage. Thus they can cause organs failure and generalized problems to organism.
In reply to this post by Plop Plop
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
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
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
From the research it can be concluded that describing
and analyzing in-body radio propagation is challenging for
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