• Journal of the Korea Society for Simulation
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• v.9 no.3
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• pp.1-11
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• 2000

This paper proposes the practical echo-signal synthesis models - UTAHID (Underwater TArget by Highlight Distribution) & M-UTAHID(Modified UTAHID) - of underwater target for active sonar engineering At high frequencies all the echo components that are the specular reflected waves and various elastic scattering wave scan be regarded the summation of individual echo from some equivalent scattering centers, so the underwater target is characterized by highlights distributed in spatial target structure. Proposed models are compared with characteristics of random distributed model & equivalent interval highlight model, and analyzed target strength, echo-elongation effect, target time spread loss and so on. Thus these can be efficiently used in various real systems related to underwater target echo-signal synthesis on active sonar and acoustic countermeasure.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.5
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• pp.586-593
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• 2012

The Navy is in the process of developing a sonar-operation strategy to increase the effectiveness of underwater target searching capability. HMS is the basic strategy to detect underwater targets. The advantages of HMS is that, it has a short preparation time to operate and can be always used regardless of sea conditions and weather. However, it is difficult to effectively detect underwater targets due to the interaction between marine environments and sonar-operations. During the research, the effectiveness of the HMS system's underwater target searching capability was analyzed by integrating various search and defense patterns, and environment conditions into the simulation. In the simulation the ship search an evasive target within a set region. The simulation presented results for an effective searching and defense methods of underwater targets. These research results can be used as foundation for advancing and improving the sonar operational tactics.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.635-638
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• 2001

본 논문에서는 수중 환경에서 분산 소나 시스템의 최적 정보 융합에 관한 알고리즘을 제시하였다. 기존의 방법은 Bayesian 법칙을 이용하여 local 소나와 퓨전 센터의 문턱치를 적절히 조절하여 분산 소나 시스템을 최적화했다. 그러나, 이러한 최적화 과정에서 소나의 개수를 늘려감에 따라 P/sub F/(false alarm probability)가 단조 증가하는 현상이 발생하였고 이러한 단점을 보완하기 위해 P/sub F/를 작은 간에 제한시키고 Bayesian 법칙과 Neyman-Pearson 법칙을 함께 적용하여 분산 소나 시스템을 최적화시킨다. 그러나, 이러한 조건 하에 시스템을 최적화시키는 것은 N-P hard 문제에 의해 계산 부하가 매우 크므로 unate 함수와 SQP(Sequential Quadratic Programming)을 이용하여 계산 부하를 감소시켰다.

• Journal of KSNVE
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• v.8 no.2
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• pp.232-238
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• 1998

선박 방사소음은 군사적 목적의 수동소나가 탐지대상으로 하는 수중음향 표적이라 할 수 있다. 따라서 수동소나 운용자는 대잠전 수행이전에 다양한 선박들에 대한 방사소음을 측정, 분석하여 개별 선박 고유의 음향 특징을 수집함으로써 실전 상황에서 미지 선박이 탐지되는 경우 이들 자료를 식별의 기초자료로 활용하고자 한다. 또한 새로운 수동소나의 개발자나 스텔스 능력의 선박 설계자 역시 선박방사소음 특징자료를 필요로한다. 본 글은 선박방사소음의 발생기구, 측정시스템 및 측정자료의 분석 평가 기술을 연구분석한 내용이다.

• Journal of KSNVE
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• v.12 no.6
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• pp.429-436
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• 2002

함정에 있어서 수중 표적의 탐지나 식별, 피탐 위험으로부터 회피 등은 함정의 생존성과 직결되는 사항으로 방사소음을 최소화하는 함정 음향 스텔스가 중요한 요소이다. 함정의 음향분야 시험평가 결과는 신조함정의 기준 만족도 평가뿐만 아니라 음향식별 정보추출/DB구축, 소음통제 방안설정 및 피탐지 위험성 평가 등 전반적인 음향작전 능력 향상에 활용되고 있다.(중략)

• The Journal of the Acoustical Society of Korea
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• v.12 no.4
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• pp.14-20
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• 1993

본 논문에서는 주변 소음을 감소시키고 표적원의 방사음으로부터 tonal 성분을 추출하기 위한 방법으로서 잡음 정규화 기법에 대하여 연구하였다. 지금까지 알려진 기법들을 정리하였으며, ATW, 최빈치 필터등의 새로운 기법을 도입, 적용하여 그 성능을 평가하였다. 그리고 tonal 성분을 검출하기 위한 임계값 결정을 위해 오경보확률과 검출확률을 시뮬레이션을 통해 구하였다.

• The Journal of the Acoustical Society of Korea
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• v.42 no.1
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• pp.25-31
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• 2023

In order to estimate the radial speed of an underwater object so-called target with active sonar, Continuous Wave (CW) pulse is generally used, but if a target is slow and at near distance, it is not easy to estimate the radial velocity of the target due to acoustic reverberation in the ocean. In 2017, Wang et al. utilized broadband signal of two Hyperbolic Frequency Modulation (HFM) pulses, which is known as a doppler-invariant pulse, with equal frequency band and in opposite sweep directions to overcome this problem and successfully estimate the radial speed of slow-moving nearby target. They demonstrated the estimation of the radial velocity with computer simulation using the parameters of two HFM starting time differences and receiving times. However, for it uses two HFM pulses with equal frequency, cross-correlation between the two pulses negatively affect the detection performance. To mitigate this cross-correlation effect, we suggest using two different band HFM with the opposite sweep directions. In this paper, a method of radial velocity estimation is derived and simulated using two HFM pulses with the pulse length of 1 second and bandwidth of 400 Hz. Applying the suggested method, the radial velocity was estimated with approximately 6 % of relative error in the simulation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.10
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• pp.1973-1980
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• 2017

In the case of a small UUV operating an active synthetic aperture sonar, various velocity disturbances may occur on the path due to the influence of external underwater environment, and this causes phase errors in coherent synthetic aperture processing, which has a large influence on the detected image. In this paper, when a periodic sinusoidal velocity disturbance is generated in the traveling direction, the phase generated by the round trip slope range at each position is estimated the cross correlation coefficient for multiple received signals and compensated the position variation in the overlapped DPC by the average value within the maximum allowable width. Through simulations, it has been confirmed that the images degraded by the velocity disturbance amplitude and fluctuating frequency of the UUV are removed from the false targets and the performance of azimuth resolution is improved by the proposed phase compensation method.

• Journal of the Korean Magnetics Society
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• v.21 no.5
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• pp.167-173
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• 2011

Underwater static magnetic field signature for the naval ship has been widely used as the detonating source of the influence mine system because it is possible to make an accurate target detection in the near field although the magnetic field falls off relatively fast with distance in comparison with the underwater radiated noise signal. In this paper, we describe the prediction results about the underwater static magnetic field by the ferromagnetic hull, the internal structures and the main on-board equipment for the target vessel using the commercial FEM software. Also we analyze the degaussing effectiveness for the target vessel through the degaussing coils arrangement.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.251-257
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• 2021

An underwater platform operating a passive sonar needs to acquire the target position to perform its mission. In an environment where sea-floor reflections exist, the position of a target can be estimated using the difference in the arrival time between the signals received through multipaths. In this paper, a method of localization for passive sonar is introduced, based on the EKF (Extended Kalman Filter) using the multipath time difference of arrival in underwater environments. TMA (Target Motion Analysis) requires accumulated measurements for long periods and has limitations on own-ship movement, allowing it to be used only in certain situations. The proposed method uses an EKF, which takes measurements of the time differences of the signal arrival in multipath environments. The method allows for target localization without restrictions on own-ship movement or the need for an observation time. To analyze the performance of the proposed method, simulation according to the distance and depth of the target was performed repeatedly, and the localization error according to the distance and water depth were analyzed. In addition, the correlation with the estimated position error was assessed by analyzing the arrival time difference according to the water depth.