| ABSTRACT:
An electromagnetic signal having originally the time variation of
a rectangular pulse is transmitted into a medium with conductivity .sigma..
It is distorted by the medium to a signal f(.sigma.,d,t) if it traveled
the distance d from a transmitter to a scattering or reflecting object
and the same distance d back to the transmitter. The time variation f(.sigma.,d,t)
of the distorted signal can be calculated for any conductivity .sigma.
and distance d. Using the conductivity .sigma. known from previous measurements,
the returned, distorted signal f(t) is compared with computed distorted
signals f(.sigma.,d,t) for various distances d. The computed signal f(.sigma.,d,t)
that is most similar to the actually received signal f(t) determines the
distance d to the scattering or reflecting object. The comparison between
the computed, distorted signals and the actually received signal is done
by cross-correlations. The peak amplitude or the energy of the received
signal becomes unimportant if cross-correlation is used, which means the
physical size or radar cross-section of the scattering or reflecting object
becomes unimportant. |