Reverberation is a key limitation factor for improving sonar detection performance. In this paper, a novel method taking advantage of the symmetrical signal which is named Flip Array Conventional Beamforming method is proposed to suppress reverberation. First, in centrosymmetric arrays, the array-time-flipped snapshot matrix is constructed by rotating the temporal snapshot matrix of the centrosymmetric array 180°. Compared with the temporal snapshot matrix, the echo delay of the corresponding row in the array-time-flipped snapshot matrix is unchanged, but the waveform is flipped. The matching covariance matrix is the cross-correlation of the temporal snapshot matrix and the array-time-flipped snapshot matrix. Second, any waveform can be decomposed into a temporal symmetrical sub-waveform and temporal odd symmetrical sub-waveform. Through active sonar waveform design, the signal has only symmetrical sub-waveform, random reverberation has two sub-waveforms. The cross-correlation power of the signal and its time-flipped signal is equal to its power, while that of reverberation is the difference of the two sub-waveforms' power which is less than the reverberation's power. So reverberation can be suppressed by using the matching covariance matrix for beamforming. An experiment was conducted in an artificial lake, and the proposed approach was applied to the experimental data, compared with the conventional method, the average value of the reverberation spatial spectrum of the proposed method is reduced by about 5 dB.

中文翻译：

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信号对称性和中心对称阵列的水下混响抑制方法

混响是提高声纳探测性能的关键限制因素。本文提出了一种利用对称信号抑制混响的新方法，即翻转阵列传统波束形成方法。首先，在中心对称阵列中，阵列时间翻转快照矩阵是通过将中心对称阵列的时间快照矩阵旋转180°来构造的。与时间快照矩阵相比，阵列时间翻转快照矩阵中相应行的回波延迟不变，但波形翻转。匹配协方差矩阵是时间快照矩阵和阵列时间翻转快照矩阵的互相关。其次，任何波形都可以分解为时间对称子波形和时间奇对称子波形。通过主动声纳波形设计，信号只有对称的子波形，随机混响有两个子波形。信号及其时间翻转信号的互相关功率等于其功率，而混响的互相关功率是两个子波形的功率之差，该差小于混响的功率。因此可以通过使用匹配协方差矩阵进行波束形成来抑制混响。在人工湖中进行了实验，将所提方法应用于实验数据，与传统方法相比，所提方法的混响空间谱平均值降低了约5 dB。