• Title/Summary/Keyword: DIFAR

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Target Localization for DIFAR Sonobuoy compensated Bearing Estimation and Sonobuoy Position Error (방위각 추정 및 소노부이 위치 오차를 보상한 DIFAR 소노부이의 표적 위치 추정 성능 향상 기법)

  • Gwak, Sang-Yell
    • 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.

Adaptive Beamforming Applied to Bearing Estimation of DIFAR Signal with Highly Directional Noise (높은 방향성 소음환경에서 DIFAR 수신센서 신호의 적응 빔형성에 의한 방위추정)

  • Shin, Kee-Cheol;Kim, Jea-Soo
    • The Journal of the Acoustical Society of Korea
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    • v.30 no.8
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    • pp.474-481
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    • 2011
  • Conventional beamforming is ineffective in producing directional information in system with sparse degree of the freedom such as DIFAR (DIrectional Frequency Analysis and Recording) sonobuoy and in the presence of high directional noise. In this paper, Adaptive beamforming techniques are applied to produce directional spectra from a small number of sensors in highly directional noise environment. Conventional method as well as minimum variance and eigenvectors as adaptive method are evaluated via numerical test and real data.

The Bearing Estimation of Narrowband Acoustic Signals Using DIFAR Beamforming Algorithm (DIFAR 빔형성 알고리듬을 이용한 협대역 음향신호의 방향성 추정)

  • 장덕홍;박홍배;정문섭;김인수
    • Journal of the Korea Institute of Military Science and Technology
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    • v.5 no.2
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    • pp.169-184
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    • 2002
  • In order to extract bearing information from the directional sensors of DIFAR(directional frequency analysis and recording) that is a kind of passive sonobuoy, the cardioid beamforming algorithm applicable to DIFAR system was studied in the frequency domain. the algorithm uses narrow-band signals propagated though the media from the acoustic sources such as ship machineries. The proposed algorithm is expected to give signal to noise ratio of 6dB when it uses the maximum response axis(MRA) among the Cardioid beams. The estimated bearings agree very well with those from GPS data. Assuming the bearings from GPS data to be real values, the estimation errors are analyzed statistically. The histogram of estimation errors in each frequency have Gaussian shape, the mean and standard deviation dropping in the ranges -1.1~$6.7^{\circ}$ and 13.3~$43.6^{\circ}$, respectively. Estimation errors are caused by SMR degradation due to propagation loss between the source and receiver, daily fluctuating geo-magnetic fields, and non-stationary background noises. If multiple DIFAR systems are employed, in addition to bearing, range information could be estimated and finally localization or tracking of a target is possible.

Wiener filtering-based ambient noise reduction technique for improved acoustic target detection of directional frequency analysis and recording sonobuoy (Directional frequency analysis and recording 소노부이의 표적 탐지 성능 향상을 위한 위너필터링 기반 주변 소음 제거 기법)

  • Hong, Jungpyo;Bae, Inyeong;Seok, Jongwon
    • The Journal of the Acoustical Society of Korea
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    • v.41 no.2
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    • pp.192-198
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    • 2022
  • As an effective weapon system for anti-submarine warfare, DIrectional Frequency Analysis and Recording (DIFAR) sonobuoy detects underwater targets via beamforming with three channels composed of an omni-direcitonal and two directional channels. However, ambient noise degrades the detection performance of DIFAR sonobouy in specific direction (0°, 90°, 180°, 270°). Thus, an ambient noise redcution technique is proposed for performance improvement of acoustic target detection of DIFAR sonobuoy. The proposed method is based on OTA (Order Truncate Average), which is widely used in sonar signal processing area, for ambient noise estimation and Wiener filtering, which is widely used in speech signal processing area, for noise reduction. For evaluation, we compare mean square errors of target bearing estmation results of conventional and proposed methods and we confirmed that the proposed method is effective under 0 dB signal-to-noise ratio.

A structure and signal processing of directional linear array for left/right discrimination in low frequency band (저주파 대역에서 좌/우 구분이 가능한 지향성배열센서 구조 및 신호처리 기법)

  • Kim, Dae-Kyung;Bae, Eun-Hyon;Jeon, Sang-Tae;Kim, Tae-Hwan
    • The Journal of the Acoustical Society of Korea
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    • v.37 no.4
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    • pp.188-195
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    • 2018
  • A new directional linear array structure and its signal processing method are presented to resolve the left/right ambiguity inherent in a linear array. The array structure combines an ordinary acoustic sensor array with a DIFAR (Directional Frequency Analysis and Recording) sensor array, keeping a linear array configuration and gaining a instantaneous left/right discrimination. It presents better PSRR (Port-Starboard Rejection Ratio) in low frequency band and low SNR (Signal to Noise Ratio) situation as compared with a conventional twin linear array, and good compromise to easily upgrade an existing linear array system to a new one with a left/right discrimination capability.

The Estimaion of Sound source of DIFAR Sonobuoy in Time Domain (DIFAR Sonobuoy의 시간영역에서의 음원 방향 추정)

  • Kim Jung-Hwa;Lee Baek-Lyeol;Bae Hyeon-Gee;Park Soon-Jong;Kim Chun-Duck;Lim Jung-Bin;Lee Yung-Yook
    • Proceedings of the Acoustical Society of Korea Conference
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    • spring
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    • pp.241-244
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    • 2002
  • 시간영역에서의 음원 방향 추정 알고리즘을 이용하여 수동형 DIFAR Sonobuoy 의 도래각 추정 성능 평가 시스템을 구성하고 추정 오차에 대하여 고찰하였다. 일반 실내에서 음원주파수 $f_0(700Hz\~1.7kHz)$로 입사하는 음원에 대하여 도래각을 추정한 결과 한 주기당 한계 ${\pm}10^{\circ}$ 이내로 약 $80\%$ 이상 추정 결과로 나타났으며 특히, 1.7kHz 의 경우는 ${\pm}2.97^{\circ}$로 적은 오차를 보임에 따라 이 대역에서의 기준 주파수로 평가 시스템에 적용할 수 있음을 확인하였다.

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Depth estimation of an underwater target using DIFAR sonobuoy (다이파 소노부이를 활용한 수중표적 심도 추정)

  • Lee, Young gu
    • The Journal of the Acoustical Society of Korea
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    • v.38 no.3
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    • pp.302-307
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    • 2019
  • In modern Anti-Submarine Warfare, there are various ways to locate a submarine in a two-dimensional space. For more effective tracking and attack against a submarine the depth of the target is a critical factor. However, it has been difficult to find out the depth of a submarine until now. In this paper a possible solution to the depth estimation of submarines is proposed utilizing DIFAR (Directional Frequency Analysis and Recording) sonobuoy information such as contact bearings at or prior to CPA (Closest Point of Approach) and the target's Doppler signals. The relative depth of the target is determined by applying the Pythagorean theorem to the slant range and horizontal range between the target and the hydrophone of a DIFAR sonobuoy. The slant range is calculated using the Doppler shift and the target's velocity. the horizontal range can be obtained by applying a simple trigonometric function for two consecutive contact bearings and the travel distance of the target. The simulation results show that the algorithm is subject to an elevation angle, which is determined by the relative depth and horizontal distance between the sonobuoy and target, and that a precise measurement of the Doppler shift is crucial.

Bearing Estimation of Narrow Band Acoustic Signals Using Cardioid Beamforming Algorithm in Shallow Water

  • Chang, Duk-Hong;Park, Hong-Bae;Na, Young-Nam;Ryu, Jon-Ha
    • The Journal of the Acoustical Society of Korea
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    • v.21 no.2E
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    • pp.71-80
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    • 2002
  • This paper suggests the Cardioid beamforming algorithm of the doublet sensors employing DIFAR (directional frequency analysis and recording) sensor signals in the frequency domain. The algorithm enables target bearing estimation using the signals from directional sensors. The algorithm verifies its applicability by successfully estimating bearings of a target projecting ten narrow-band signals in shallow water. The estimated bearings agree very well with those from GPS (global positioning system) data. Assuming the bearings from GPS data to be real values, the estimation errors are analyzed statistically. The histogram of estimation errors in each frequency have Gaussian shape, the mean and standard deviation dropping in the ranges -1.1°∼ 6.7°and 13.3∼43.6°, respectively. Estimation errors are caused by SNR (signal to noise ratio) degradation due to propagation loss between the source and receiver, daily fluctuating geo-magnetic fields, and non-stationary background noises. If multiple DIFAR systems are employed, in addition to bearing, range information could be estimated and finally localization or tracking of a target is possible.

Design and Realization of Phase Sensitive Detector Circuitry of Two-Channel Ring-Core Flux-Gate Compass (2-체널 링-코어 플럭스-게이트 콤파스의 위상검출 회로 설계와 구현에 관한 연구)

  • Yim, Jeong-Bin
    • Journal of Navigation and Port Research
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    • v.26 no.1
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    • pp.127-136
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    • 2002
  • This paper Presents a discussion on the design and realization for the Phase Sensitive Defector (PSD) circuitry of Flu$\chi$-gate Compass that gives direction information to the Directional Frequency Analysis and Recording (DIFAR) Sonobuoy in Air Anti-Submarine Warfare. PSD circuitry is realized with Twin-T RC networked active band-pass filter. Results of a performance test the PSD circuitry shows that the effectiveness of band-pass filtering of desired $2F_0$ second harmonic signal, which is Pro- portional to the direction of earth's magnetic field. This resulted in the extraction of direction information.

특정 주파수 모의신호 발생을 통한 수중음파의 전달손실 측정

  • 나영남
    • Proceedings of the Acoustical Society of Korea Conference
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    • 1992.06a
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    • pp.112-120
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    • 1992
  • 수심 100m 이하 천해에서 저주파 대역 음파의 전달손실 양상을 규명하기 위해 한국 동해 남부해역 3개 정점에서 특정 주파수 모의신호 발생을 통한 전달손실을 측정하였다. 10개의 특정 주파수에 대해서 연속파(Continuous Wave)를 방생시킬 수 있는 저주파 음원기를 5 kts의 속도로 예인하고, 다시 육상으로 무선전송하여 각 센서에서의 수진준위를 정확하게 보정하였다. 음원으로부터 DIFAR 센서까지의 전달손실은 거리에 대한 Log 함수로 표시할 수 있었으며, 주파수별 전달손실을 비교, 분석한 결과 동해 남부해역에서의 최적 주파수는 800Hz 내외에서 존재하는 것으로 추정된다.

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