• Title/Summary/Keyword: Active sonar signal

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Torpedo defense system research using HMS(Hull Mount Sonar) of PCC(Patrol Combat Corvette) (초계함용 HMS(Hull Mount Sonar)를 이용한 어뢰방어시스템 연구)

  • Kim, Hee-Earn;Kim, Young-Kil
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2011.10a
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    • pp.349-352
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    • 2011
  • HMS(Hull Mount Sonar) equipment mounted on PCC(Patrol Combat Corvette) is suitably designed for active mode, and the specific character of sensor or system is not appropriate for the frequency range to detect a torpedo. In this article, in order to implement the function of detecting torpedoes with HMS of existing PCC, I will analyze the feature of input signals each PCCs and design a circuit to compensate reversly for the input signal in certain frequency. And also, I will suggest the most adequate torpedo defense system suitable for the special operating environment and the charateristic of naval vessels, implementing functions such as AGC of input signal and fixing the frequency range of different input signals per different warships.

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Active Sonar Target Detection Using Fractional Fourier Transform (Fractional 푸리에 변환을 이용한 능동소나 표적탐지)

  • Baek, Jongdae;Seok, Jongwon;Bae, Keunsung
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.20 no.1
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    • pp.22-29
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    • 2016
  • Many studies in detection and classification of the targets in the underwater environments have been conducted for military purposes, as well as for non-military purpose. Due to the complicated characteristics of underwater acoustic signal reflecting multipath environments and spatio-temporal varying characteristics, active sonar target detection technique has been considered as a difficult technique. In this paper, we describe the basic concept of Fractional Fourier transform and optimal transform order. Then we analyze the relationship between time-frequency characteristics of an LFM signal and its spectrum using Fractional Fourier transform. Based on the analysis results, we present active sonar target detection method. To verify the performance of proposed methods, we compared the results with conventional FFT-based matched filter. The experimental results demonstrate the superiority of the proposed method compared to the conventional method in the aspect of AUC(Area Under the ROC Curve).

Target detection method of the narrow-band continuous-wave active sonar based on basis-group beamspace-domain nonnegative matrix factorization for a reverberant environment (잔향 환경을 위한 기저집단 빔공간 비음수 행렬 분해 기반의 협대역 지속파 능동 소나 표적 탐지 기법)

  • Lee, Seokjin
    • The Journal of the Acoustical Society of Korea
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    • v.38 no.3
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    • pp.290-301
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    • 2019
  • The proposed algorithm deals with a detection problem of target echo for narrow-band continuous-wave active sonar in the underwater environment in this paper. In the active sonar systems, ping signal emitted for target detection produces a signal that consists of multiple reflections by many scatterers around, which is called reverberation. The proposed algorithm aims to detect the low-Doppler target echo in the reverberant environment. The proposed algorithm estimates the bearing, frequency, and temporal bases based on beamspace-domain multichannel nonnegative matrix factorization. In particular, the bases are divided into two basis groups - the reverberation group and the echo group, then the basis groups are estimated independently. In order to evaluate the proposed algorithm, a simulation with synthesized reverberation was performed. The results show that the proposed algorithm has enhanced performance than the conventional algorithms.

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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Improving target recognition of active sonar multi-layer processor through deep learning of a small amounts of imbalanced data (소수 불균형 데이터의 심층학습을 통한 능동소나 다층처리기의 표적 인식성 개선)

  • Young-Woo Ryu;Jeong-Goo Kim
    • The Journal of the Acoustical Society of Korea
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    • v.43 no.2
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    • pp.225-233
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    • 2024
  • Active sonar transmits sound waves to detect covertly maneuvering underwater objects and detects the signals reflected back from the target. However, in addition to the target's echo, the active sonar's received signal is mixed with seafloor, sea surface reverberation, biological noise, and other noise, making target recognition difficult. Conventional techniques for detecting signals above a threshold not only cause false detections or miss targets depending on the set threshold, but also have the problem of having to set an appropriate threshold for various underwater environments. To overcome this, research has been conducted on automatic calculation of threshold values through techniques such as Constant False Alarm Rate (CFAR) and application of advanced tracking filters and association techniques, but there are limitations in environments where a significant number of detections occur. As deep learning technology has recently developed, efforts have been made to apply it in the field of underwater target detection, but it is very difficult to acquire active sonar data for discriminator learning, so not only is the data rare, but there are only a very small number of targets and a relatively large number of non-targets. There are difficulties due to the imbalance of data. In this paper, the image of the energy distribution of the detection signal is used, and a classifier is learned in a way that takes into account the imbalance of the data to distinguish between targets and non-targets and added to the existing technique. Through the proposed technique, target misclassification was minimized and non-targets were eliminated, making target recognition easier for active sonar operators. And the effectiveness of the proposed technique was verified through sea experiment data obtained in the East Sea.

A Study of Performance Characteristics for Active Sonar in Korean Shallow Seawater Temperature Structures (한국 천해 수온구조에서의 능동소나 성능 특성 연구)

  • Kim, Won-Ki;Bae, Ho Seuk;Son, Su-Uk;Hahn, Jooyeong;Park, Joung-Soo
    • Journal of the Korea Institute of Military Science and Technology
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    • v.24 no.5
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    • pp.482-491
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    • 2021
  • It is obvious that understanding the effects of shallow water environment of Korea is very important to guarantee the optimal performance of active sonar such as monostatic and bistatic sonar. For this reason, in this paper, we analyzed the detection performance characteristics for various depth deployments of sonar in summer, winter and water temperature inversion environments, which environments are frequently observed in shallow water of Korea such as the Yellow sea. To analyze only effects of water temperature structures on target detection performance, we applied range independent conditions for bottom, sea surface and water temperature characteristics. To understand the characteristics of detection performance, we conducted transmission loss and signal excess modeling. From the results, we were able to confirm the characteristics of detection performance of active sonar. In addition, we verified that operation depth of transmitter and receiver affects the detection performance. Especially in the water temperature inversion environment, it was confirmed that the shadow zone could be minimized and the detection range could be increased through bistatic operation.

Effects of Wind-Generated Bubbles on Sound Propagation (음파전달에 미치는 풍성기포의 영향)

  • Lee, Won-Byoung;Kim, Young-Shin;Joo, Jong-Min;Lee, Chang-Won;Na, Jung-Yul
    • The Journal of the Acoustical Society of Korea
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    • v.25 no.8
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    • pp.395-402
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    • 2006
  • When an active SONAR works in the subsurface. its detection Performance is limited by the reverberation. The winds Play a primary role in the Production of bubbles in the ocean. And the bubbles as efficient scatters contribute to the reverberant field. In this Paper the effects of wind-generated bubbles on sound propagation in the subsurface are investigated as a mid-frequency Hull-mounted SONAR works. The active signal excess is calculated at source depths 3. 5. and 10m considering bubble layer for frequencies 5. 7.5, and 10kHz. The change of the near-surface sound speed tend to increase surface reverberation levels and change the active signal excess. In the 10m/s winds. the maximum detection range reduces over 3km through the near-surface . The reason is the upper refraction due to the wind-generated bubbles.

Whitening Method for Performance Improvement of the Matched Filter in the Non-white Noise Environment (비백색 잡음 환경에서 정합필터 성능개선을 위한 백색화 기법)

  • Kim Jeong-Goo
    • Journal of Korea Society of Industrial Information Systems
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    • v.11 no.3
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    • pp.15-19
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    • 2006
  • In shallow water active sonar environment, reverberation which is a non-white noise is one of the main source of performance degradation of target detection. In this case, the received signal is whitened before applying matched filter known as an optimum filter in the presence of white noise. However implementation of this method is very difficult because of the non-stationary characteristic of reverberation. Traditionally reverberation is assumed local stationary. In this paper, we estimate a range of stationary of reverberation signal, and then propose a pre-whitening method which improve the performance of pre-whitening block normalized matched filter in presence of non-white reverberation noise. Proposed whitener shows better whitening performance than traditional whitener because it use later as well as before reverberation of target signal. To evaluate performance of the proposed whitener, an actual measurement data sampled at the East-Sea is used for computer simulation. The target detector with new whitener is shown better performance than detector with traditional whitener.

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A robust detection algorithm against clutters in active sonar in shallow coastal environment (연안 환경에서 클러터에 강인한 능동소나 탐지 알고리듬)

  • Jang, Eun Jeong;Kwon, Sungchur;Oh, Won Tcheon;Lee, Jung Woo;Shin, Keecheol;Kim, Juho
    • The Journal of the Acoustical Society of Korea
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    • v.38 no.6
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    • pp.661-669
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    • 2019
  • High frequency active sonar is appropriate for detecting small targets such as a diver in coast environment. In case of using high frequency active sonar in shallow coastal environment, a false alarm rate is high due to clutters caused by marine biological noise, ship noise, wake, etc. In this paper, we propose an algorithm for target detection which is robust against clutter in active sonar system in shallow coastal environment. The proposed algorithm increases the rate of reduction clutter using calculation of statistical characteristics of signal and a clustering method. The algorithm is evaluated and analysed with sea trial data, as a result, that shows the rate of reducing rate of clutter of 96 % and over.

Optimum Frequency Analysis for Sonar Transmit Signal design (소나 송신신호 설계를 위한 최적 주파수 분석)

  • Kim, Sunho;Jung, Jangwon;On, Baeksan;Im, Sungbin;Seo, Iksoo
    • Journal of the Institute of Electronics and Information Engineers
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    • v.53 no.5
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    • pp.47-54
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    • 2016
  • In the underwater environment, high resolution can be achieved in the range direction by transmitting and receiving a signal of a particular band and/or waveform. The design of a transmit signal used in the active sonar is very important in order to detect a cylindrical object within a short distance less than 1 km, which is the detection distance of this paper. Designing a transmit signal optimal to a sonar requires appropriate selection of its center frequency and bandwidth, which allows the maximum detection distance of a sonar. In this paper, in terms of maximizing echo excess and signal to noise ratio (SNR), optimum frequency analysis is carried out under various conditions of diverse parameters. In addition, the investigation focused on the determinating a bandwidth is also performed for the purpose of satisfying the performance requirement of range resolution and azimuth resolution.