Robust time reversal focusing based on Maximin criterion in a waveguide with uncertain water depth

Time reversal processing (TRP) might be regarded as matched field processing with known environmental knowledge. However, the performance of TRP is degraded in an uncertain environment. A technique based on the Maximin criterion is proposed for enhancing the robustness of TRP in a waveguide with uncertain water depth. The relationship between the water depth and the focal spot translation is examined based on the waveguide-invariant theory. Then the time reversal transmission scheme with the Maximin criterion is performed to maximize the minimum transmission power on a target of interest. At the receiving end, coherent summation operation is carried out over the received data by a reception focusing bank. If it is necessary to enhance the target echo further, the iterative time reversal can be considered where the target echo corresponding to the first time reversal transmission is regarded as a secondary source. Numerical simulations and experimental results of the target localization in a waveguide tank have verified the effectiveness of robust TRP.