EIGENMODES OF THE TIME-REVERSAL OPERATOR - A SOLUTION TO SELECTIVE FOCUSING IN MULTIPLE-TARGET MEDIA

The iterative time reversal mirror provides an elegant way of focusing in multiple target media oh the most reflective one. This paper prese nts a method to focus on the other targets. It is derived from a theor etical Study of the iterative time reversal process. The iterative pro cess can be described at each frequency by a time reversal operator wh ich can be diagonalized. The eigenvectors of this operator are eigenmo des of the time reversal process. In the case of well resolved targets of different ''brightness'', the rank of the time reversal operator i s equal to the number of targets and each eigenvector of non zero eige nvalue provides the optimal phase and amplitude law focus on the corre sponding target. An experimental validation of these results is given.