Introduction
Time reversal is a kind of mathematical operation or procedure in physics where we reverse the
symmetry of process by using the negative values of time. This normally shift back the
corresponding event in time or it generally run the process backward. As a general example we
can reverse back a sine or cos curve on CRO by the same principle.
There are variety of applications of this mechanism and it’s widely been applied in physics and
mathematics and even other field of science as well.
Time reversal and EMT
Although this process has variety of applications in all major fields but as the matter of
requirement we will study it for the case of electricity and magnetism. As electricity and
magnetism deals mostly with the electromagnetic waves or electric signals we can study it for
time reversed electric signal processing.
It’s a kind of spatial focusing method where we utilize the cable less paths for signal processing.
We can generally understand it as to detect a signal that has already been processed or to detect it
from the transmitted place. We catch the signal from number of locations that are actually
transmitted locations, where signals have already been processed. That could be a far location or
a close location. It’s understood that the far location will take more time to receive the signal,
and the close location will take less time for signal process. We will gather this data and
formulize it for time reversal. An application of reversed time with a negative sign in the
equation of respective signal will show them on their source locations, the previously
sent/transmit locations will be now received location. To the preserve the order of receiving we
will see the far signals that take the most time will be transmitted on earliest and vise versa.
These signals will be focused in space and optimized in time like real signals from an antenna.
Time reversal process in the complex environment
The time reversal signal will not only valid in free space but this will also be valid in an
environment with multiple reflections and refractions and scattering of signals. This is likely to
happen in an environment with number of antennas in the pathway and they will delay the signal
processing and we might receive attenuated version of the original signal on the time reversal
same process is reversed in time. It happens because the signal is some how time dispersive. Or
it has barriers and obstacles to the processing of signals going through it. As we apply the
mathematics and reverse the signal we see signal time reversal as signal is divided in different
time delayed components. Now the signal respective components follow the channel and try to
reverse and converge in the same direction and in the same location of source. This is followed
that this happens in both space and time.
