This paper presents a detailed analysis of the effects of noise (reverberation) on the focusing performance of de-composition of the time reversal operator (DORT) in a noise-limited case and in a reverberation-limited case, respectively. Quantitative results obtained from simulations and experiments are presented. The results show the DORT method can be effi-ciently applied to target detection with enough source level to yield significant backscatter. For a target placed on the bottom, the influence of the reverberation on the focusing performance is slight. However, distinguishing between a target and constant backscattering returning from strong local clutter on the bottom (false alarms) needs further research.
The target detection and localization in uncertain environment with robust time reversal （TR） technique was investigated. TR is a physical process as well as a method of signal processing. Therefore, it is natural to perform beamforming via TR, i.e., TR beamforming （TRBF）. To reduce the effects of environmental uncertainty on TR spatio-temporal focusing, transmitting TRBF with modeled instead of physical probe source was studied and robust minimum-variance receiving TRBF with diagonal loading was put forward. Both of them were applied to the detection and distance estimation of the target, which was dealt with in a waveguide experiment. The experimental results show the validity of the methods in uncertain environment.
