• 한국소음진동공학회논문집
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• 제13권6호
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• pp.438-444
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• 2003

A method using beamforming algorithm has been developed to measure oblique incidence reflection coefficients of sound absorption materials. MUSIC(multiple signal classification) method detects the angles of incidence and reflection. By separating the incident and reflected waves using beamforming method, the reflection coefficient is calculated. Spatial smoothing technique Is also used to reduce the coherence between the incident and reflected waves. Numerical and experiment results are performed to verify the accuracy of proposed method.

• International journal of advanced smart convergence
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• 제9권1호
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• pp.177-184
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• 2020

In this paper, we studied to direction of arrival (DoA) estimation to use DoA and optimum weight algorithms in coherent interference channels. The DoA algorithm have been considerable attention in signal processing with coherent signals and a limited number of snapshots in a noise and an interference environment. This paper is a proposed method for the desired signal estimation using MUSIC algorithm and adaptive beamforming to compare classical subspace techniques. Also, the proposed method is combined the updated weight value with LCMV beamforming algorithm in adaptive antenna array system for direction of arrival estimation of desired signal. The proposed algorithm can be used with combination to MUSIC algorithm, linearly constrained minimum variance beamforming (LCMV) and the weight value method to accurately desired signal estimation. Through simulation, we compare the proposed method with classical direction of in order to desired signals estimation. We show that the propose method has achieved good resolution performance better that classical direction arrival estimation algorithm. The simulation results show the effectiveness of the proposed method.

• 한국소음진동공학회논문집
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• 제26권5호
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• pp.501-510
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• 2016

Capabilities of several beamforming techniques are compared for estimating the position of a moving source. Beamforming has enabled to widen our perspective of aeroacoustics in wind tunnel experiments and has provided useful approach in array measurements. Meanwhile beamforming techniques have been developed in a way to improve estimation accuracy and to save ing effort at the same time. In order to achieve reasonable outcome from aeroacoustic measurement, it is important to identify the spectral characteristics of source and to select an appropriate beamformer. Though aeroacoustic sources normally generates broadband noises, many array signal processing have been focused on narrowband processing which makes calculation numerically efficient. However, calculation in frequency-domain requires selection of single frequency of interest which affects spatial resolution and sidelobe level as a consequence. To be able to localize broadband noise source, it is proposed to use broadband beamforming. The formulas implements the deletion of diagonal term from cross spectral matrix. In this study, trajectory of flying source emitting broadband noise was simulated and several beamformers are applied.

• 한국정보통신학회논문지
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• 제15권5호
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• pp.1025-1030
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• 2011

이동통신 기지국의 성능을 높이기 위해 빔포밍(beamforming) 기술을 적용하고자 하는 노력이 이루어지고 있다. 하지만, 이러한 빔포밍 기술을 적용하기 위해서는 기존에 $2{\times}2$ MIMO 용으로 제작되었던 2-Tx RU(radio unit)을 버리고 이를 4-Tx 빔포밍 RU 로 대체하여야 하는 문제점을 안고 있다. 본 논문에서는 기존의 2-Tx RU 를 재활용하여 4-Tx 빔포밍 RU 를 구현하는 방안을 제시하고, 이러한 구현에서 안테나 패스간의 보정절차 및 보정검증절차에 대해 제시하였다. 본 논문의 방법은 기존의 2-Tx RU 를 버리지 않고 재활용할 수 있어 경제적으로나 환경적으로 매우 유익한 방법으로 생각된다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권1호
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• pp.280-294
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• 2023

Unmanned aerial vehicles (UAVs) and millimeter-wave frequencies play key roles in supporting 5G wireless communication systems. They expand the field of wireless communication by increasing the data capacities of communication systems and supporting high data rates. However, short wavelengths, owing to the high millimeter-wave frequencies can cause problems, such as signal attenuation and path loss. To address these limitations, research on high directional beamforming technologies continue to garner interest. Furthermore, owing to the mobility of the UAVs, it is essential to track the beam angle accurately to obtain full beamforming gain. This study presents a beam tracking method based on the unscented Kalman filter using hybrid beamforming. The simulation results reveal that the proposed beam tracking scheme improves the overall performance in terms of the mean-squared error and spectral efficiency. In addition, by expanding analog beamforming to hybrid beamforming, the proposed algorithm can be used even in multi-user and multi-stream environments to increase data capacity, thereby increasing utilization in new-radio multiple-input multiple-output orthogonal frequency-division multiplexing systems.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 학술회의 논문집 정보 및 제어부문 B
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• pp.689-692
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• 2003

In this paper, we propose an adaptive beamforming algorithm for array antenna. The proposed beamforming algorithm, based on Block LMS (Block - Least Mean Squares) algorithm, has a variable step size from coefficient update. This method shows some advantages that the convergence speed is fast and the calculation time can reduced using a block LMS algorithm from frequency domain. As the adaptive parameter approaches a stationary state, it could reduce the number of filter coefficient update with the help of various step size. In this paper we compared the efficiency of the proposed algorithm with a standard LMS algorithm which is a representative method of adaptive beamforming.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.969-974
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• 2007

In this paper, a beamforming technique is introduced to measure the acoustic impedance at both normal and oblique incidence in a free field. The acoustic impedance is obtained by separating incident and reflected signals using the adaptive nulling method which is one of the various beamforming algorithms. To obtain better results, pressure vector commonly used in array signal processing is replaced with the transfer function vector between each microphone and the white Gaussian noise is suppressed by a wavelet shrinkage technique. The experiments conducted in a semi-anechoic room show that the proposed method is efficient and accurate in measuring the acoustic impedance of sound absorbing materials under a free field condition.

• 한국통신학회논문지
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• 제32권8A호
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• pp.827-835
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• 2007

본 논문은 ECMA(European Computer Manufacturers Association) 표준의 MB-OFDM(MultiBand-Orthogonal Frequency Division Multiplexing) UWB 시스템에 AAS(Adaptive Antenna Systems)를 적용함으로써 데이터 전송범위를 확장하는 방법을 제안하고, ECMA UWB 시스템의 다중 접속 방법으로 사용되는 CSMA/CA(Carrier Sense Multiple Access with Collision Avoidance) 환경에서 AAS를 적용할 때 발생하는 음영 빔 문제를 해결하기 위해 보완 빔 형성 방법을 제안한다. 제안된 보완 빔은 그람-슈미츠(Gram-Schmidt) 직교화 방법을 이용하여 주 빔에 간섭을 주지 않고 빔 음영 지역의 노드들이 채널의 사용 유무를 감지할 수 있도록 하였으며, 주 빔을 형성할 때 다양한 빔 형성 알고리즘의 적용이 가능한 장점이 있다. 전산 모의실험을 통하여 제안된 AAS 및 보완 빔 방법이 480Mbps 데이터 전송 속도의 데이터 전송 범위를 2m에서 3.95m로 증가시키고, 일반적인 ECMA UWB AAS 시스템에 비해 시스템 전송률을 약 20%정도 향상시키는 것을 확인하였다.

• 한국음향학회지
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• 제22권8호
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• pp.645-651
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• 2003

본 논문에서는 해양음향 토모그래피를 위한 개선된 빔형성 역산 기법을 제안한다. 제안된 역산 기법은 음속 구조 역산을 위해 음파도파관의 특성을 나타내는 군속도와 위상속도의 상관성을 이용한다. 군속도와 위상속도는 수신 신호의 도달시간 및 도달각에 의해 계산 가능하며, 이를 위해 빔형성 신호처리를 사용하여 수신신호의 도달시간 및 도달각 분석을 수행한다. 본 논문에서는 제안된 알고리즘을 사용한 동해 음속구조 역산모의 결과를 서술하였으며, 연구 결과 제안된 빔형성 해양음향 토모그래피 역산 방법을 사용해 동해의 음속 구조 역산이 가능함을 확인할 수 있다.

• 한국철도학회논문집
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• 제15권3호
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• pp.231-236
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• 2012

본 논문에서는 고속철도의 주행 시 발생하는 공력소음에 대한 특성을 도출하는 연구를 수행하였다. 우선, 마이크로폰 어레이 시스템을 이용하여 고속철도 차량의 주행 소음을 측정을 통해서, 주요 공력소음원이 고속철도 차량의 전두부, 팬토그래프, 차간 부위임을 확인하였다. 또한 측정한 데이터를 바탕으로 빔형성 방법을 이용하여 빔출력을 구하였으며, 푸리에 변환을 통해서 주파수 영역에서의 빔파워 스펙트럼을 도출하였다. 본 연구를 통해서 고속철도의 주요 공력 소음원인 전두부, 팬토그래프, 차간 부위에 대한 음압 특성이 빔형성 방법을 이용하여 도출되었다.