Finding a Tunnel’s Sweet Spot
Security forces and law enforcement agencies depend as much on wireless communications as teenagers and plugged-in executives.
So what will they do when
an emergency strikes in a tunnel or mine, and
their communications start breaking down? (Radio
signals have a hard time traveling through
deep tunnels and even long corridors in some
buildings.) Researchers at NIST are trying to find
a solution, a sweet spot in the frequency range
at which signals travel several times farther than
at other frequencies. For a typical subway tunnel,
researchers determined the sweet spot is
between 400 MHz and 1 GHz. They also believe tunnels
act like giant waveguides, with the tunnel dimensions,
materials, and flatness of the floor determining their effects
on RF signals. And at the sweet spot, the shape of
the tunnel reduces losses caused by RF signals being absorbed
or scattered by structures. NIST personnel hope
their work will lead to wireless communication devices
for search and rescue robots used in tunnels and mines.
MORE
INFO
National Institute
of Science and
Technology
Gaithersburg, MD
nist.gov