中文摘要：

水声信道存在多径效应、多卜勒频偏及各种噪声干扰。时反法能利用声波的互易性原理及波动方程的时反不变性，将收到的信号进行时间反转后再重新发射，使得声音信号能够在原声源位置实现聚焦，可以有效地消除水声信道的多途效应。综述三种基于时反处理的水下目标探测方法：反复迭代法、DORT法（时反算子分解法）及MUSIC法（多信号分类算法）。通过反复迭代进行时反操作，可以明显提高聚焦信号能量；DORT法和MUSIC法是在迭代时反的基础上进一步分析时反算子而得出的主动时反定位算法。利用DORT法及MUSIC法，可以对水下目标实现主动探测，定位出目标的具体位置。

英文摘要：

There are severe muhipath effects,Doppler spread and noise in underwater acoustic channels. Time Reversal makes use of sound wave reciprocity principle and time reversal invariance of wave equation. If the received sound signal was reversed the time and retransmitted back, the signal would focus on the original acoustic source position. This may effectively eliminate the multipath Effects of underwater acoustic channel, corrects the signal, three kinds underwater detection methods based on the time reversal are summarized： Repeated time rever- sal iteration, DORT（De-composition of the Time Reversal Operator） and MUSIC （Multiple Signal Classification）. Repeated time reversal iteration can obviously enhance the focus signal energy. The methods of DORT and MUSIC are modified algorithms on the basis of time reversal iteration. By using the methond of DORT or MUSIC active detection to underwater target can be realized and the specific location of target can be located as well.