• Proceedings of the Acoustical Society of Korea Conference
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• 1993.06a
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• pp.222-225
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• 1993

일반적임 빔 형성기는 표적의 방위탐지가 가능하지만, 구조적인 특성상 대칭적인 빔을 형성하므로 표적의 좌/우 방위 구분이 불가능하기 때문에 표적의 정확한 방위를 탐지하고자 할 때 좌/우 구분이 가능한 빔 형성기가 필수적이다. 좌/우 분리 빔 형성 기법으로는 카디오이드(Cardioid) 빔 형성기법을 일반적인 빔 형성기에 적용시키는 방법이 최적으로 알려져 왔다. 그러나 좌/우 분리 빔을 형성하기 위해서는 많은 연산량과 하드웨어 설계에 대한 고려가 있어야한다. 본 논문에서는 좌/우 분리 빔 형성을 위하여 주파수 빔 형성기법과 카디오이드 빔 형성기법을 합성하여 적용하였다. 주파수 빔 형성 기법은 짧은 수행시간 동안에 표적의 정보추출을 위하여 고려되었으며, 카디오이드 빔 형성기법은 3개의 센서를 이용하여 센서의 기울기를 보상하여 수행하는 기법을 적용하였다. 또한 방향성 있는 시뮬레이션 신호를 생성하여 좌/우 분리 빔 형성 시뮬레이션을 수행하였다.

• Proceedings of the Acoustical Society of Korea Conference
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• 1996.06a
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• pp.18-21
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• 1996

예인형 선배열 소나에서 기존의 선배열 빔형성 기법을 적용하면 예인함 기동시 선배열 형상 변형에 의해 심각한 성능 저하 현상이 나타난다. 이러한 문제 해결을 위해 센서배열 변형을 고려한 견실한 빔형성 기법은 선배열 형상 추정을 위해 칼만필터를 이용한 형상 추정기법을 이용하고, 변형보상 빔형성을 위해 선배열 세그먼트 기울기 추정값을 이용하는 변형보상 빔형성 알고리즘을 제안하였다. 제안된 기법을 기존의 빔형성 기법을 적용하여 시뮬레이션에 의해 제안된 기법의 보상성능을 입증 하였다.

• The Journal of the Acoustical Society of Korea
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• v.39 no.3
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• pp.179-190
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• 2020

In this paper, we estimated the Direction of Arrival (DOA) using Conventional BeamForming (CBF), adaptive beamforming and compressive beamforming. Minimum Variance Distortionless Response (MVDR) and Multiple Signal Classification (MUSIC) are used as the adaptive beamforming, and grid-free compressive sensing is applied for the compressive sensing beamforming. Theoretical background and limitations of each technique are introduced, and the performance of each technique is compared through simulation and real experiments. The real experiments are conducted in the presence of reflected signal, transmitting a sound using two speakers and receiving acoustic data through a linear array consisting of eight microphones. Simulation and experimental results show that the adaptive beamforming and the grid-free compressive beamforming have a higher resolution than conventional beamforming when there are uncorrelated signals. On the other hand, the performance of the adaptive beamforming is degraded by the reflected signals whereas the grid-free compressive beamforming still improves the conventional beamforming resolution regardless of reflected signal presence.

• The Journal of the Acoustical Society of Korea
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• v.37 no.1
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• pp.66-72
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• 2018

In this paper, we propose an adaptive beamforming algorithm of triplet arrays for active sonar systems. The proposed algorithm consists of three steps: matched filters, cardioid beamforming, and line array beamforming. First, we apply a matched filter of a transmitted pulse to received individual sensor signals and obtain filterd signals. Then, we perform the fast Fourier transform to the matched filter results, and make a cardioid beam for each triplet data, respectively. Finally, we apply an adaptive beamforming by assuming that the cardioid beams are input signals of a line array. Experimental results demonstrate that the proposed algorithm provides better performances than conventional algorithms.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06e
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• pp.151-154
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• 1998

이 논문에서 비선형 배열 MUSIC 빔형성 기법을 이용하여 예인형 선배열 센서 시스템의 표적 좌우 방위 분리 방법을 기술하였다. 이 기법은 배열 운동모델 Water-Pully 모델과 방향센서의 정보를 이용하는 칼만필터를 설계하여 예인함 기동에 따른 배열형상을 추정하고 표적의 좌우방위를 분리하기 위하여 추정된 배열형상에서 MUSIC 빔형성 기법으로 신호처리를 수행하였다. 또한 예인주기와 예인진폭과 같은 예인함 기동형태의 전형적인 빔형성 기법과 MUSIC 빔형성 기법으로 표적의 좌우 방위 분리 성능을 비교 분석하였다.

• The Journal of the Acoustical Society of Korea
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• v.36 no.2
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• pp.115-122
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• 2017

We propose a robust adaptive beamforming algorithm for triplet array sonar. The proposed beamforming algorithm obtains robustness to mismatches, left/right discrimination, and has two steps. The first is a cardioid beamformer, which supports left/right discrimination of target signals. It applies the conventional delay-and-subtract to each triplet's signal with its rotation angle and obtains multiple cardioid beams. The second is a robust adaptive beamforming to minimize nearby interferences. We regard cardioid beams as input signals of a line array and apply an adaptive beamforming algorithm to the cardioid beams. Simulations results show that the proposed algorithm provides significantly better performance than the conventional algorithms, while supporting left/right discrimination of target signals.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.4C
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• pp.336-341
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• 2008

In this paper, beamforming algorithm is proposed which can obtain diversity gain in beamforming system that deploy antenna elements with half-wavelength. The proposed algorithm provides beam-pattern using eigen-vectors that span received signal subspace. The criterion to decide optimal rank of eigen-space used for beamforming is also proposed. A beamforming system applied the proposed algorithm shows better performance with diversity gain as getting larger angle spread. This paper provides a description of proposed algorithm with analysis of the performance using various computer simulations.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.7
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• pp.1-5
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• 2009

Random beanforming exploits multiuser diversity gain in static channels. Since the gain is restricted by the user population, some extended works have been proposed. Among them, a codebook-based opportunistic beamforming technique forms multiple random beams with small pilots. The technique however has difficulty in designing beams flexibly by the channel statistics. In this paper, we propose a technique forming the multiple random beams by rotating codebooks. The proposed technique enables the flexible design of beams so that multiuser diversity and beam selection diversity are exploited simultaneously with small pilots robust to the channel statistics.

• The Journal of the Acoustical Society of Korea
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• v.16 no.6
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• pp.12-18
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• 1997

Beamforming method has a limited spatial resolution because of finite aperture size, so that the estimated source distributions are smoothed within the resolution. Especially for low frequency noise such as mechanical noise, this limitation often diminishes the direct use of beamforming method. In this study, the relation between smoothed beamforming and radiation power distribution of plate has been addressed. By adjustment of aperture size of array, the smoothed beamforming power shows radiation power distribution of plate. Numerical simulations are carried for simply supported plate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.12
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• pp.1133-1139
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• 2012

In this paper, hybrid mode beamforming (HMB) which allows simultaneous transmission of joint beamforming and disjoint beamforming is proposed. HMB is proven to be asymptotically optimal beamforming for sum rate growth. Extensive simulations show that HMB achieves nearly the same performance as joint encoding (JE) in symmetric interference channel. It is also shown that it outperforms JE in a more realistic asymmetric interference channel environment, though it still experiences some performance degradation due to power inefficiency of joint beamforming in asymmetric channel.