Line Array Sonar Research Articles

Multipath Track Association Technique using Characteristics of Conical Bearing in Horizontal Line Array Sonar

This paper conducts a study on methods for associating multipath tracks received by a horizontal line array sonar. The horizontal line array sonar introduces conical bearing ambiguities due to its array-shaped characteristics. Target signals are often subject to multipath propagation in the ocean, resulting in errors in target bearing estimation due to these bearing ambiguities. Recent research efforts have been directed toward using multipath tracks to estimate the positions of targets. However, there has been a lack of research dedicated to identifying multipath tracks from the measurements of a horizontal line array sonar. Therefore, this study identifies the conical bearing characteristics of multipath signals based on the result of experiment and establishes criteria for associating multipath tracks. Additionally, Simulations are performed to determine the ability to associate multipath tracks.

Array invariant-based range-only target motion analysis for ship noise measured by two vertical line arrays in shallow water

A novel approach for underwater acoustic localization by using passive line array sonar will be proposed in this talk. In the case of the received signal having a finite pulse duration, the target location can be easily estimated using the time-difference-of-arrival (TDOA) method between sensors. However, it is difficult to use the TDOA method for signals that exist for a relatively long time, such as ship noise. An array invariant method has been proposed to measure the source-receiver distance, but it does not accurately estimate the target location. In this talk, target localization will be performed with the range-only target motion analysis method using non-linear target tracking after estimating the target range by the array invariant method. The proposed method is tested using the ship noise of the R/V Onnuri measured by two vertical line arrays during the Shallow-water Acoustic Variability Experiment (SAVEX-15), and the result will be discussed in this talk. [This research was supported by the Ministry of Oceans and Fisheries of Korea (PM63010, 2022).]

Noise Suppression of Towed Line Array Sonar Platform Based on Spatial Filtering Technique

The problem of interference caused by the radiated noise of the towed line array sonar platform to the hydrophone line array and the formation of detection blind area in the direction of the end head of the line array is addressed. In this paper, the optimal spatial matrix filter is designed using the plane wave array manifold, the platform radiation noise copy vector, and the weighted coefficient matrix. Through iteration of the weighted coefficient matrix, the null matrix filter achieves the effect of equalizing the response of each direction of the far-field plane wave signal under the condition of zero response constraint of the platform radiation noise. The method of generalized singular value simplified decomposition is used to analyze and check the correctness of the optimal solution of the filter in theory. From the simulation results, the filter with iterative calculation is more effective in processing far-field plane waves and the signal has lower distortion.

A study on wideband adaptive beamforming based on WBRCB for passive uniform line array sonar

A study on wideband adaptive beamforming based on WBRCB for passive uniform line array sonar

DOA Estimation for Underwater Wideband Weak Targets Based on Coherent Signal Subspace and Compressed Sensing.

Direction of arrival (DOA) estimation is the basis for underwater target localization and tracking using towed line array sonar devices. A method of DOA estimation for underwater wideband weak targets based on coherent signal subspace (CSS) processing and compressed sensing (CS) theory is proposed. Under the CSS processing framework, wideband frequency focusing is accompanied by a two-sided correlation transformation, allowing the DOA of underwater wideband targets to be estimated based on the spatial sparsity of the targets and the compressed sensing reconstruction algorithm. Through analysis and processing of simulation data and marine trial data, it is shown that this method can accomplish the DOA estimation of underwater wideband weak targets. Results also show that this method can considerably improve the spatial spectrum of weak target signals, enhancing the ability to detect them. It can solve the problems of low directional resolution and unreliable weak-target detection in traditional beamforming technology. Compared with the conventional minimum variance distortionless response beamformers (MVDR), this method has many advantages, such as higher directional resolution, wider detection range, fewer required snapshots and more accurate detection for weak targets.

Flow Noise Calculation and Experimental Study for Hydrophones in Fluid-Filled Towed Arrays

Understanding the physical features of the flow noise for hydrophones in a fluid-filled towed array is important for designing a towed line array sonar. The flow noise of hydrophones in fluid-filled towed arrays generated by the turbulent pressure is derived by the frequency–wave number decomposition method. The results show that the flow noise increases rapidly with the towed speed and decreases with the length of the hydrophone. Meanwhile, the flow noise is closely related to the material parameters of the elastomer tube. It decreases with the attenuation factor, outside radius, and thickness of the elastomer tube. Furthermore, a spatial filter designed by the constant sector inverse-beamforming method is used for suppressing the tow-ship-radiated noise and the ambient noise from the sensor data. The analysis results of the experimental data are consistent well with the theoretical values, which indicate that the tow-ship-radiated noise and the ambient noise are suppressed effectively by the spatial filter. In addition, the correlation features of the flow noise received by the acoustic array are analyzed, which is important for the sonar system design.

누적 일괄추정 기법을 이용한 수동 선배열 소나 방위 주파수 -표적기동분석 연구

Bearing and frequency measurements of TMA (Target Motion Analysis) in passive line array SONAR have lower bearing rate and frequency doppler, and are not detected or tracked continuously because of various ocean environments. This is a main reason to effect the TMA performance and it takes a long time to get TMA solutions. We propose the bearing and frequency TMA(BFTMA) using accumulative batch estimation to solve the TMA problem of line array passive SONAR. The accumulative batch estimation structure is based on MLE (Maximum Likelihood Estimation) but used accumulative measurements. The accumulative batch estimation is applied for the BFTMA with nonlinear Kalman filter to estimate the target range, speed and course. Simulation and sea data analysis were carried out to verify the performance and applicability of the proposed techniques.

Adaptive Beamforming Method for Turning Towed Line Array SONAR

수중의 음향 신호를 탐지하기 위하여 다양한 배열 형태를 가지는 소나가 개발되어 왔으며, 그 중 하나로 견인선배열 소나가 널리 사용된다. 견인 선배열 소나는 매우 긴 형태의 배열을 사용하므로, 회전에 의한 형상 왜곡에 의해 성능이 저하되는 단점이 있다. 이를 해결하기 위하여 회전하는 견인 선배열 소나에 대한 포물선 형태의 형상 모델을 이용하는 기법이 고안되었다. 본 논문에서는 포물선 모델을 이용하여 간섭 신호를 제거하는 적응 빔 형성기 설계 기법을 제안한다. 고안된 빔형성기 시스템은 일반화된 부엽 제거기 구조와 자가 조율 시스템에 기반을 두어 개발되었다. In order to detect underwater acoustic signals, various SONAR array types have been developed, including towed line array SONAR system (TASS). However, the TASS suffers from performance degradation which is caused by aperture deformation during a turn, because the TASS have a long-aperture array. A parabolic array model for turning TASS have been developed to solve the degradation problem occurred during a turn. In this paper, adaptive beamforming system is developed using the parabolic TASS model to cancel interference signals. The developed beamforming system is based on generalized sidelobe canceller (GSC) structure and self-tuning adaptive algorithm.

中国水声信号处理30年

The advances of new technology and theoretical development in 30 years of underwater acoustic signal processing and its applications in sonar design are presented in this paper. The topics include the research work in the field of underwater acoustic signal modeling, acoustic field matching, ocean waveguide and internal wave, the exaction and processing technique of acoustic vector signal information, space/time correlation characteristics of low frequency acoustic channel, the invariant feature of underwater target radiated noise, the transmission technology of underwater voice/image data, and its anti-interference technique. Some frontier technologies in sonar design are also discussed, including large aperture towed line array sonar, high resolution synthetic aperture sonar, deep sea siren and deep sea manned subsea vehicle, diver detection sonar and demonstration projector of national ocean monitoring system in China, etc.

Analysis of influence of line array beamforming on the target modulation feature

In the line array sonar, the target signal was obtained after beamforming processing. The beamforming processing could improve the Signal to Noise Ratio (SNR) by using array signal's spatial processing gain. But the distortion would be brought in signal characteristics under non-ideal conditions during line array beamforming in practical application, which increased the difficulty of target characteristics extraction. As an important basis for target classification and recognition, the performance of modulation characteristics detection and extraction is affected by SNR, signal bandwidth, modulation depth and other factors. In this paper, the influence of the time delay error on target characteristics was analyzed based on the conventional beamforming of linear array. And then a method with the combination of theroy and simulation is proposed to analyze the influence of plane wave assumption, azimuth estimation error and disturbance of array shape on modulation characteristics.

An experimental evaluation of split-beam processing as a broadband bearing estimator for line array sonar systems

This paper examines the potential improvements in bearing estimation performance of split-beam processing over full-aperture beamforming for broadband signals. It presents theoretical results in order to define the details of the signal flow in a split-beam processor, and it provides theoretical performance predictions by using Cramer–Rao lower bound (CRLB) analysis. The split-beam processing scheme was implemented in a real-time line array system. Good agreement between the theoretical performance predictions and the associated experimental broadband results were obtained. The experimental results indicate that the advantage of improved bearing estimation performance of the split-beamformer over the conventional full-aperture beamformer may be practically insignificant for passive line array applications because of the split-beamformer’s poor performance in detecting very weak broadband signals.

A computerized system for assessing towed array sonar functionality and detecting faults

A computer-based system that processes hydrophone and beam noise data from a towed horizontal line array sonar has been developed. The system also produces various displays that can be used to help assess the functionality of the sonar and to identify faults that cause degraded performance. The system-and various statistics used for characterizing or quantifying a given aspect of the sonar's performance are discussed. The results are presented in visual formats to aid in rapid assessment and quantification of the sonar's performance. Examples obtained from the system during recent towed array ambient noise measurement exercises are given to illustrate its utility for real-time performance monitoring and its capability for providing clues to aid in fault localization. >