Spatially focusing electromagnetic field in a multi-path environment using time-reversal

It was demonstrated that a field from a large phase conjugate array is a statistical estimate of the spatial correlation of the wave propagation channel. In many situations the spatial correlation is known, and decays very fast. Hence the focusing of electromagnetic field within a few wavelength distances can be achieved by time reversal as seen in simulations, and the lowest limit of the beamwidth of the focused pulse can be estimated without any effort.