• Title/Summary/Keyword: Target echo signal

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An Analysis of Pulse Length Effect on Underwater Simulated Target Strength Estimated Model (수중 모의표적 강도예측 모델의 펄스길이 효과 고찰)

  • 김부일;박명호;권우현
    • The Journal of the Acoustical Society of Korea
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    • v.20 no.2
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    • pp.44-51
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    • 2001
  • This Paper the practical echo signal synthesis model to predict the target strength and signal shape of a submarine for a valuable tool to active sonar engineer. It is based on UTAHID (Underwater TArget by Highlight Distribution) model which is relocated highlight points along to external hull for aspect angle, and synthesized echo signal by modified grouping highlights to internal scatter cloud. Proposed model is analyzed target strength characteristics on various incident pulse length, and synthesis signal signature, target time spreading loss, echo elongation effect and so on. Thus it can be efficiently used in various real systems related to underwater target echo signal synthesis, that is, active sonar, acoustic countermeasure and surveillance system.

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Echo Signal Synthesis of Underwater Target by Distributed Highlight Model (하이라이트 분포 모델에 의한 수중표적 에코신호 합성)

  • 김부일;박명호;권우현
    • The Journal of the Acoustical Society of Korea
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    • v.19 no.7
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    • pp.15-22
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    • 2000
  • This paper proposes a distributed highlight algorithm to generate efficiently echo signal for underwater target. In this algorithm, echo signal is synthesized by discontinuity highlights that are varied to incident angle, by equivalent and specified position highlights according to the spatial target structure. Completed UTAHID(Underwater TArget by Highlight Distribution) model is confrimed that PTS, ETS, echo elongation effect, target time spreading loss and envelope fluctuation are satisfied to expected values by various simulations. Thus it can be efficiently used in all sorts of real systems related to underwater target echo signal synthesis in active sonar.

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An Analysis of Highlight Distribution Modeling for High Frequency CW Pulse Signal Reflection on Underwater Target (수중표적의 고주파수 CW 펄스신호 반사를 위한 하이라이트 분포 모델링 해석)

  • 김부일;이형욱;박명호;권우현
    • 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.

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A Comparative Analysis of Target Strength Estimated Models for Underwater Echo Signal Synthesis (수중 반사신호 합성을 위한 표적강도 예측모델 비교분석)

  • 김부일
    • Journal of the Korea Institute of Military Science and Technology
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    • v.4 no.1
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    • pp.93-103
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    • 2001
  • A reflection signal in an active sonar using a high frequency is mainly formed of a specular reflection from the surface of an object along with several equivalent scatters inside, which are characterized by the spatial distribution of the highlight on the object. This study analyze the existing echo signal synthesis models eq, random distribution model, equivalent interval distribution model & MUTAHID(Modified Underwater TArget by HIlight Distribution) model for simulated target, and compare the characteristics of the reflected signal synthesis results for each model in various conditions. These highlight distribution models can be efficiently applied to the simulated target signals synthesis of various real systems requiring the echo signal synthesis on the underwater target.

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Modeling and Experimental Verification of Echo Characteristics of 3 Dimensional Underwater Target (3차원 수중 표적의 반향특성 모델링과 실험적 검증)

  • You, Seung-Ki;Kim, Sunhyo;Choi, Jee Woong;Kang, Donhyug;Jeong, Dongmin
    • The Journal of the Acoustical Society of Korea
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    • v.33 no.3
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    • pp.174-183
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    • 2014
  • When a active sonar signal is transmitted and returned back from a target, it has been distorted by various properties of acoustic channel such as multipath arrivals. And signals have been appeared to be different form by target position and attitude. Therefore, we simulated the target echo signal using 3 dimensional target model include reflects target features. In this paper, we develop components form of a simulated target model is made up equally spaced highlight points, and each part of the target consists of shape function. We can simulate a target echo signal and Target strength (TS) according to wave incident angle. To verify, we made small scale target in kit form and we had got underwater target signal for comparing simulation result in water tank.

Separation of Spectrally Overlapped Broadband Acoustic Scattering Signals from Japanese Needlefish Hypohamphus sajori Using the Fractional Fourier Transform (분수차 푸리에 변환을 이용한 스펙트럼상에서 중첩된 학공치(Hypohamphus sajori)의 광대역 음향산란신호의 분리)

  • Lee, Dae-Jae
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.55 no.2
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    • pp.195-206
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    • 2022
  • The separation of spectrally overlapped broadband echo signals from free-swimming Japanese needlefish Hypohamphus sajori using the fractional Fourier transform (FrFT) was investigated. The broadband echo signals were measured over frequency ranges of 40-80 and 110-220 kHz. The overlapped echo signals were separated after eliminating noise signals in the smoothed pseudo-Wigner-Ville distribution domain. The echo signal from a 40 mm WC sphere suspended just below a chirp transducer was used to calibrate the broadband of the chirp echo sounder and estimate the frequency dependence of target strength for the separated echo signals. The experimental results show that the proposed FrFT method can analyze the time-frequency image of broadband echo signals from free-swimming individual fish effectively and can be used as a quantitative tool for extracting the acoustic features used for fish species identification.

Target Signal Simulation in Synthetic Underwater Environment for Performance Analysis of Monostatic Active Sonar (수중합성환경에서 단상태 능동소나의 성능분석을 위한 표적신호 모의)

  • Kim, Sunhyo;You, Seung-Ki;Choi, Jee Woong;Kang, Donhyug;Park, Joung Soo;Lee, Dong Joon;Park, Kyeongju
    • The Journal of the Acoustical Society of Korea
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    • v.32 no.6
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    • pp.455-471
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    • 2013
  • Active sonar has been commonly used to detect targets existing in the shallow water. When a signal is transmitted and returned back from a target, it has been distorted by various properties of acoustic channel such as multipath arrivals, scattering from rough sea surface and ocean bottom, and refraction by sound speed structure, which makes target detection difficult. It is therefore necessary to consider these channel properties in the target signal simulation in operational performance system of active sonar. In this paper, a monostatic active sonar system is considered, and the target echo, reverberation, and ambient noise are individually simulated as a function of time, and finally summed to simulate a total received signal. A 3-dimensional highlight model, which can reflect the target features including the shape, position, and azimuthal and elevation angles, has been applied to each multipath pair between source and target to simulate the target echo signal. The results are finally compared to those obtained by the algorithm in which only direct path is considered in target signal simulation.

A study on the target detection method of the continuous-wave active sonar in reverberation based on beamspace-domain multichannel nonnegative matrix factorization (빔공간 다채널 비음수 행렬 분해에 기초한 잔향에서의 지속파 능동 소나 표적 탐지 기법에 대한 연구)

  • Lee, Seokjin
    • The Journal of the Acoustical Society of Korea
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    • v.37 no.6
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    • pp.489-498
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    • 2018
  • In this paper, a target detection method based on beamspace-domain multichannel nonnegative matrix factorization is studied when an echo of continuous-wave ping is received from a low-Doppler target in reverberant environment. If the receiver of the continuous-wave active sonar moves, the frequency range of the reverberation is broadened due to the Doppler effect, so the low-Doppler target echo is interfered by the reverberation in this case. The developed algorithm analyzes the multichannel spectrogram of the received signal into frequency bases, time bases, and beamformer gains using the beamspace-domain multichannel nonnnegative matrix factorization, then the algorithm estimates the frequency, time, and bearing of target echo by choosing a proper basis. To analyze the performance of the developed algorithm, simulations were performed in various signal-to-reverberation conditions. The results show that the proposed algorithm can estimate the frequency, time, and bearing, but the performance was degraded in the low signal-to-reverberation condition. It is expected that modifying the selection algorithm of the target echo basis can enhance the performance according to the simulation results.

A Study on the Low-frequency Active Echo Reduction Technology for Reducing Underwater Target Echo Signal (수중 표적 신호 방해를 위한 저주파 능동 반향음 감소 기술 연구)

  • Kim, Jaepil;Ji, Youna;Park, Young-cheol;Noh, Eunghwy;Ohm, Won-Suk;Choi, Yonggyu;Kim, Daeup;Seo, Youngsoo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.27 no.1
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    • pp.43-50
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    • 2017
  • Acoustic tiles are typically installed on the surface of pressure vessels in submarines to minimize echoes based on the ship's own noise and active sonar. In this study, we studied low frequency active echo reduction techniques to reduce underwater target echo signals. Active control algorithms using tile type projectors and FxLMS logic have been developed and the projectors have been installed in the assumed hull structure. The effectiveness of projectors and control algorithms has been evaluated in time and frequency domain analysis through experiments in the tank.

Multi-aspect Based Active Sonar Target Classification (다중 자세각 기반의 능동소나 표적 식별)

  • Seok, Jongwon
    • Journal of Korea Multimedia Society
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    • v.19 no.10
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    • pp.1775-1781
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    • 2016
  • Generally, in the underwater target recognition, feature vectors are extracted from the target signal utilizing spatial information according to target shape/material characteristics. In addition, various signal processing techniques have been studied to extract feature vectors which are less sensitive to the location of the receiver. In this paper, we synthesized active echo signals using 3-dimensional highlight distribution. Then, Fractional Fourier transform was applied to echo signals to extract signal features. For the performance verification, classification experiments were performed using backpropagation and probabilistic neural network classifiers based on single aspect and multi-aspect method. As a result, we obtained a better recognition result using proposed feature extraction and multi-aspect based method.