A Time-Frequency Joint Time-Delay Difference Estimation Method for Signal Enhancement in the Distorted towed Hydrophone Array

• Published in: Remote sensing (Basel, Switzerland) Vol. 13; no. 22; p. 4586
• Main Authors: Zhu, Chuanqi, Fang, Shiliang, Wu, Qisong, An, Liang, Luo, Xinwei, Cao, Hongli
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.11.2021
• Subjects: Accuracy; Algorithms; Ambiguity; array shape distortion; Arrays; Beamforming; Delay; Estimates; Fluid mechanics; Hydrophones; Markov chain; Markov chains; Noise; Passive sonar; passive sonar system; Performance degradation; Phase shift; Remote sensing; signal enhancement; Signal processing; Signal to noise ratio; sonar; time-delay difference estimation; underwater acoustic radiated noise
• ISSN: 2072-4292; 2072-4292
• DOI: 10.3390/rs13224586

To acquire the enhanced underwater ship-radiated noise signal in the presence of array shape distortion in a passive sonar system, the phase difference of the line-spectrum component in ship-radiated noise is often exploited to estimate the time-delay difference for the beamforming-based signal enhancement. However, the time-delay difference estimation performance drastically degrades with decreases of the signal-to-noise ratio (SNR) of the line-spectrum component. Meanwhile, although the time-delay difference estimation performance of the high-frequency line-spectrum components is generally superior to that of the low-frequency one, the phase difference measurements of the high-frequency line-spectrum component often easily encounter the issue of modulus 2π ambiguity. To address the above issues, a novel time-frequency joint time-delay difference estimation method is proposed in this paper. The proposed method establishes a data-driven hidden Markov model with robustness to phase difference ambiguity by fully exploiting the underlying property of slowly changing the time-delay difference over time. Thus, the phase difference measurements available for time-delay difference estimation are extended from that of low-frequency line-spectrum components in a single frame to that of all detected line-spectrum components in multiple frames. By jointly taking advantage of the phase difference measurements in both time and frequency dimensions, the proposed method can acquire enhanced time-delay difference estimates even in a low SNR case. Both simulation and at-sea experimental results have demonstrated the effectiveness of the proposed method.