Echo-to-reverberation enhancement based on decomposition of time reversal operator with forward and backward reverberation nulling constrains

Combined the decomposition of time reversal operator and the time reversal reverberation nulling, a new time reversal processing approach for echo-to-reverberation ratio enhancement is proposed. In this method, a 2-dimensional signal subspace for the range of the target and two bottom focusing weight vectors for the ranges near the target are obtained by the decomposition of time reversal operator. From the signal subspace and focusing weight vectors, a constrained optimal excitation weight vector of source receiver array can be deduced to null the acoustic energy on the corresponding bottom and maximize the energy at the target. This method remedies the shortages of conventional time reversal processing, time reversal reverberation nulling and time reversal selective focusing method. It focuses sound energy at the target and nulls the energy at the bottom beside the target range simultaneously, therefore enhancing the echo-to-reverberation ratio, in the condition of no probe source and no prior-knowledge of the target and the bottom relative scatter intensity. Numerical simulations in typical shallow water environments showed the availability of the proposed method and its improved performance for echo-reverberation enhancement than conventional time reversal processing.