N-ary maximum likelihood target detection with time reversal

A time reversal (TR) device has the capability of receiving a time varying signal, saving it in memory, and retransmitting the stored signal back into the medium in the reversed direction of time. The paper designs an N-ary maximum likelihood TR detector capable of detecting the presence of a target and classifying the detected target as an unknown enemy target or one of the (N - 2) known friendly targets. In our experiments, the proposed N-ary TR detector provides a gain of over 5 dB over conventional detectors at low signal to noise ratios (SNR).