• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.228-231
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• 1999

3차원 공간상의 표적의 위치는 방위각, 고각, 거리의 세가지요소로 나타내어 질 수 있다. 이 논문에서는 등각적 선배열 센서로 이루어진 3개의 부분센서배열을 이용한 3차원 표적의 위치추정 알고리듬을 제안하였다. 원거리 표적의 방위각 추정 알고리듬으로 근거리 표적의 방위각을 추정하면 추정된 방위각은 실제 근거리 표적의 방위각과 고각과 거리의 비선형 대수적 관계식으로 주어진다. 제안한 알고리듬은 3개의 부분센서배열에서 각각 표적을 원거리에 있다고 가정하고 원거리입체각을 추정하여 위의 대수적 관계식을 얻은 후 이들 관계식을 연립하여 실제 근거리 표적의 위치를 추정하였다. 다중표적의 경우 각각의 부분센서배열에서 추정한 원거리입체각이 어떤 표적에 대한 추정치인지 연관시켜주는 알고리듬이 필요하다. 이 논문에서는 추정한 원거리입체각의 모든 조합으로부터 3차원 MUSIC 스펙트럼값을 비교하여 그 중 표적의 개수만큼을 선별하여 다중표적의 위치를 추정하였다.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.245-248
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• 2002

본 논문에서는 이동체에 Beam Loss를 위한 분석적 모델을 소개하고 시변 방위 추정 알고리즘을 적용하였을 때와 일반 알고리즘을 적용했을 때의 성능개선 정도를 비교한다.

• The Journal of the Acoustical Society of Korea
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• v.37 no.6
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• pp.412-421
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• 2018

The Line array sonar consisting of several hydrophones increases array gain and improves the performance for detecting the direction of the target compared to single hydrophone. However, line array sonar produces the bearing error that makes it difficult to determine the bearing of incoming source signal due to the relation between bearing angle of target and vertical angle of multipath signals. Vertical angles of multipath are varied with the geometry of receiver and target and various underwater environments, therefore it is necessary to consider the bearing error to estimate accurately the bearing of the target. In this study, acoustic modelling was performed to understand the effect of multipath signals on the target signal. The errors of bearing angle estimated from the bottom bounced signals are calculated with several environment. In addition, the expected bearing line, as a function of source-receiver range, compensated for the bearing error is predicted from the estimated bearing angle.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.2
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• pp.221-228
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• 2020

A sonobuoy is dropped onto the surface of water to estimate the bearing of an underwater target. A Directional Frequency Analysis and Recording (DIFAR) sonobuoy has an error in the specific angular section due to the method of estimating bearing and noise, which causes an error in target localization using multiple sonobuoys. In addition, the position of the sonobuoy continues to move, but since a sonobuoy with a GPS is intermittently arranged, it is difficult to estimate the exact position of the sonobuoy. This also causes target localization performance degradation. In this paper, we propose a technique to improve the target localization performance by compensating for bearing errors using characteristics of the DIFAR sonobuoy and multiple-sonobuoy position errors based on the intermittently arranged active sonobuoy with a GPS.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.49 no.2
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• pp.130-136
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• 2012

In this paper, we propose a near-field range estimation method for a uniform linear array that can calibrate bearing estimation error which give a bad influence on a range estimation process. When a range is fixed, the bearing error is calibrated to maximize the beamformer output by the proposed algorithm based on the gradient method. Simulation results show that the proposed algorithm can compensate the bearing error which is less than the mainlobe beamwidth so that reduce the range estimation error as similar as the case of no bearing error.

• The Journal of the Acoustical Society of Korea
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• v.27 no.2
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• pp.87-91
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• 2008

In this paper, the adaptive chirp beamforming method is proposed to solve the bias problem in the direction-of-arrivals (DOAs) estimation of the wideband chirp signals which have an identical time-frequency parameter and are emanated from different directions. The source location bias results from the interferences impinging on the array from the other directions. The proposed method exploits the time-frequency structure of the chirp signal based on STMV (STeered Minimum Valiance) to improve the DOA estimation performance by minimizing the chirp interferences effectively. Simulation results show the DOA estimation performance achieved by the proposed method as compared to the conventional methods.

• The Journal of the Acoustical Society of Korea
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• v.35 no.5
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• pp.395-402
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• 2016

In this paper, a wideband adaptive beamforming approach for an acoustic vector sensor linear array is presented. It is a very important issue to estimate the stable covariance matrix for adaptive beamforming. In the conventional wideband adaptive beamforming based on coherent signal-subspace (CSS) processing, the error of bearing estimates is resulted from the focusing matrix estimation and the large number of data snapshot is necessary. To alleviate the estimation error and snapshot deficiency in estimating covariance matrix, the steered covariance matrix method in the pressure sensor is extended to the vector sensor array, and the subarray technique is incorporated. By this technique, more accurate azimuth estimates and a stable covariance matrix can be obtained with a small number of data snapshot. Through simulation, the azimuth estimation performance of the proposed beamforming method and a wideband adaptive beamforming based on CSS processing are assessed.

• The Journal of the Acoustical Society of Korea
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• v.36 no.3
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• pp.218-227
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• 2017

In this paper, an algorithm to calculate both bearing and distance error for target detection and localization is proposed using the Cramer Rao lower bound to estimate the minium variance of their error in DOA (Direction Of Arrival) estimation. The performance of arrays in detection and localization depends on the accuracy of DOA, which is affected by a variation of SNR (Signal to Noise Ratio). The SNR is determined by sonar parameters such as a SL (Source Level), TL (Transmission Loss), NL (Noise Level), array shape and beam steering angle. For verification of the suggested method, a Monte Carlo simulation was performed to probabilistically calculate the bearing and distance error according to the SNR which varies with the relative position of the target in space and noise level.

• The Journal of the Acoustical Society of Korea
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• v.17 no.4
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• pp.54-59
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• 1998

이 논문에서는 등간격 선배열 감지기를 사용하여 근거리 표적의 위치 추정을 하는 연산량이 적은 효과적인 대수적 경로 추종 알고리듬을 제안하였다. 원거리 표적의 방위각 추적 알고리듬으로 근거리 표적의 방위각을 추정하면 추정된 방위각은 실제 근거리 표적의 방위각과 거리의 대수적 관계식으로 주어짐을 보였다. 2차원 MUSIC스펙트럼의 극대값을 찾기 위하여 두 개의 결합된 2차원 다항식으로부터 구한 경로를 추종하는 기존의 방식대신 에 이 대수적 관계식을 경로로 사용한다. L개의 감지기에 M개의 표적 신호가 도달하는 경 우, 제안한 알고리듬은 대수적 경로를 따라 M번의 1차원 탐색을 하므로 2차원 다항식으로 부터 경로를 구하여 2L-2번의 1차원 탐색을 하는 기존의 경로 추종 알고리듬보다 연산량을 줄일 수 있다.

• The Journal of the Acoustical Society of Korea
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• v.19 no.5
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• pp.84-90
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• 2000

The bearing detection of radiated target noise is very important at underwater acoustic measurement and passive detection. It differs the arrival tines of received signal at each sensor. Therefore, the bearing can be obtained from the time delay. This paper proposes a new algorithm using the RLSL adaptive filter for TDE. The proposed method is particularly attractive when there is a limitation of priori information about the received signal spectra and when the delay is subject to variation. As the simulation results, it is shown that the proposed algorithm has better convergence characteristics and TDE speed, and so that the usefulness of proposed algorithm is confirmed.