The Journal of the Acoustical Society of Korea (한국음향학회지)

The Acoustical Society of Korea (한국음향학회)
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A study on wideband adaptive beamforming based on WBRCB for passive uniform line array sonar

WBRCB 기반의 수동 선배열 소나 광대역 적응빔형성 기법 연구

  • 현아라 (국방과학연구소 소나체계단) ;
  • 안재균 (국방과학연구소 소나체계단) ;
  • 양인식 (국방과학연구소 소나체계단) ;
  • 김광태 (국방과학연구소 소나체계단)
  • Received : 2018.12.03
  • Accepted : 2019.03.26
  • Published : 2019.03.31
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Abstract

Adaptive beamforming methods are known to suppress sidelobes and improve detection performance of weak signal by constructing weight vectors depending on the received signal itself. A standard adaptive beamforming like the MVDR (Minimum Variance Distortionless Response) is very sensitive to mismatches between weight vectors and actual signal steering vectors. Also, a large computational complexity for estimating a stable covariance matrix is required when wideband beamforming for a large-scale array is used. In this paper, we exploit the WBRCB (Wideband Robust Capon Beamforming) method for stable and robust wideband adaptive beamforming of a passive large uniform line array sonar. To improve robustness of adaptive beamforming performance in the presence of mismatches, we extract a optimum mismatch parameter. WBRCB with extracted mismatch parameter shows performance improvement in beamforming using synthetic and experimental passive sonar signals.

적응빔형성 기법은 부엽을 줄이고 약한 신호에 대한 탐지 성능을 향상시킨다. MVDR(Minimum Variance Distortionless Response)과 같은 일반적인 적응빔형성 기법은 설계한 가중벡터와 실제 입사신호의 조향벡터의 불일치에 대해 매우 민감하다. 또한 센서 수가 많은 어레이를 이용하여 광대역 적응빔형성을 할 경우 공분산행렬을 산출하기 위해 긴 관측시간과 많은 연산량이 요구된다. 본 논문은 센서 수가 많은 수동 선배열 소나의 광대역 적응빔형성 성능향상 및 안정성을 위해 WBRCB(Wideband Robust Capon Beamforming)를 적용하였다. 불일치 요소에 강인한 WBRCB 구현을 위해 다양한 불일치 요소를 반영하여 최적의 불일치 파라미터를 도출하였다. 도출된 파라미터를 반영한 WBRCB 기법을 시뮬레이션 및 실험데이터에 적용하여 수동 선배열 소나의 광대역 적응빔형성 성능 향상을 검증하였다.

Keywords

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Fig. 1. Definition of uncertainty parameter.

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Fig. 2. Uncertainty parameter [Eq. (12)] depending on target angle and error of look direction.

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Fig. 3. Uncertainty parameter [Eq. (12)] depending on target angle and error of array spacing.

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Fig. 4. Uncertainty parameter [Eq. (12)] depending on target angle and error of sound speed.

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Fig. 5. Uncertainty parameter depending on incident angle and error of look direction including other mismatches (synthetic data).

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Fig. 6. WBRCB beampower depending on uncertainty parameters for synthetic data with two targets (a) located near end-fire direction of array with 8° angular separation and (b) located on broadside direction of array with 3° angular separation.

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Fig. 7. Uncertainty parameter depending on incident angle and error of look direction including other mismatches (experimental data).

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Fig. 8. Comparison of BTRs obtained using WBRCB with uncertainty parameter = 8 (up), uncertainty parameter = 12 (center), and uncertainty parameter = 50 (bottom).

Table 2. Simulation parameters.

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Table 3. Experimental parameters.

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Table 1. Summary of adaptive beamforming algorithms.

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References

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