• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1876-1879
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• 2003

Due to the conventional half-bridge switch-mode converters for dc motor drive have been usually using unbalanced circuit topologies which generate common-mode currents through parasitic capacitors distributed between the ground and the dc motor frame such as the heat-sink of switching devices or the frame of the dc motor. This paper describes methods that cancel common-mode current generated in half-bridge switch-mode converters by using circuit balancing technique. The circuit balancing is to make the noise pickup or occurring in both conductor lines, signal and return pathes, is equal in amplitude and opposite in phase so that it will be canceled out in the ground plane. The common-mode current cancellation in the proposed converter is confirmed by experimental results.

• Journal of Communications and Networks
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• 제10권2호
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• pp.118-126
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• 2008

The use of beamforming is effective for users in limited power environments. However, when it is applied to the downlink of a cellular system with universal frequency reuse, users near the sector boundary may experience significant interference from more than one sector. The use of a minimum mean square error (MMSE)-type receiver may not sufficiently cancel out the interference unless a sufficient number of receive antennas are used. In this paper, we consider the use of inter-sector beamforming that cooperates with a neighboring sector in the same cell to mitigate this interference problem in time-division duplex (TDD) environments. The proposed scheme can avoid interference from an adjacent sector in the same cell, while enhancing the transmit array gain by using the TDD reciprocity. The performance of the proposed scheme is analyzed in terms of the output signal-to-interference-plus-noise power ratio (SINR) and the output capacity when applied to an MMSE-type receiver. The beamforming mode can be analytically switched between the inter-sector and the single-sector mode based on the long-term channel information. Finally, the effectiveness of the proposed scheme is verified by computer simulation.

• 한국지능시스템학회논문지
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• 제11권2호
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• pp.178-183
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• 2001

Welding is essential for the manufacture of a range of engineering components which may vary from very large structures such as ships and bridges to very complex structures such as aircraft engines, or miniature components for microelectronic applications. Especially, a domestic situation of the welding automation is still depend on the arc sensing system in comparison to the vision sensing system. Specially, the gap-detecting of workpiece using conventional arc sensor is proposed in this study. As a same principle, a welding current varies with the size of a welding gap. This study introduce to the fuzzy membership filter to cancel a high frequency noise of welding current, and ART2 which has the competitive learning network classifies the signal patterns the filtered welding signal. A welding current possesses a specific pattern according to the existence or the size of a welding gap. These specific patterns result in different classification in comparison with an occasion for no welding gap. The patterns in each case of 1mm, 2mm, 3mm and no welding gap are identified by the artificial neural network.

• 한국정보통신학회논문지
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• 제16권11호
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• pp.2388-2396
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• 2012

본 논문에서는 스테레오 음향반향제거기의 수렴특성을 향상시키기 위한 간략화된 직교투사법을 제안한다. 간단하고 안정되어 널리 사용되고 있는 기존의 NLMS 알고리즘과 비교하여, 이 기술은 음성신호와 같이 상호상관도가 높은 신호에 대해 수렴성능이 향상되고 연산량이 감소한다. 본 연구에서 제안한 SOP 알고리즘의 성능을 검증하기 위하여 모의실험용 프로그램을 작성하고 시뮬레이션을 수행하였다. 입력신호의 종류와 적응 알고리즘에 따라서 반향제거기의 수렴특성을 관찰한 결과, 제안한 알고리즘을 적용한 스테레오 반향제거기는 백색 잡음을 입력으로 사용하는 경우 약 3dB 정도, 유색 음성신호를 입력으로 사용하는 경우 약 5dB 이상의 ERLE 성능이 개선되는 것을 보여 주었다.

• IEIE Transactions on Smart Processing and Computing
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• 제3권3호
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• pp.142-152
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• 2014

Vehicular Ad-hoc Networks (VANETs) are comprised of wireless mobile nodes characterized by a randomly changing topology, high mobility, availability of geographic position, and fewer power constraints. Orthogonal Frequency Division Multiplexing (OFDM) is a promising candidate for the physical layer of VANET because of the inherent characteristics of the spectral efficiency and robustness to channel impairments. The susceptibility of OFDM to Inter-Carrier Interference (ICI) is a challenging issue. The high mobility of nodes in VANET causes higher Doppler shifts, which results in ICI in the OFDM system. In this paper, a frequency domain com-btype channel estimation was used to cancel out ICI. The channel frequency response at the pilot tones was estimated using a Least Square (LS) estimator. An efficient interpolation technique is required to estimate the channel at the data tones with low interpolation error. This paper proposes a robust interpolation technique to estimate the channel frequency response at the data subcarriers. The channel induced noise tended to degrade the Bit Error Rate (BER) performance of the system. Parallel concatenated Convolutional codes were used for error correction. At the decoding end, different decoding algorithms were considered for the component decoders of the iterative Turbo decoder. A performance and complexity comparison among the various decoding algorithms was also carried out.

• 한국통신학회논문지
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• 제27권3B호
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• pp.259-266
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• 2002

CDMA 시스템에 있어서 다중접속간섭(MAI : Multiple Access Interference)은 시스템 성능과 사용자 용량을 저하시킨다. 최근 다중접속간섭을 제거하는 기법 중에 하나인 부귀환 다중사용자검파기(feedback detector)로 부귀환 직교 다중사용자검파기(ODFD : Orthogonal decision-feedback detector)와 부귀환 역상관 다중사용자검파기와(DDFD ; decorrelating decision-feedback detector)가 연구되어 왔다. 본 논문에서는 부귀환 직교 다중사용자검파기와 블라인드 등화기를 결합한 블라인드 적응형 다중사용자 검파기를 제안하였다. 부가 백색화 가우시안 잡음(AWGN ; additive white gaussian noise) 채널 환경과 레일리(Rayleigh) 페이딩 채널 환경에서 시뮬레이션을 수행하였으며, 본 논문에서 제안한 블라인드 적응형 부귀환 직교 다중사용자검파기(BA-ODFD)와 블라인드 적응형 부귀환 역상관 검파기(BA-DDFD)을 비교하였다.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 1998년도 추계학술대회 학술발표 논문집
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• pp.527-531
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• 1998

This study introduce to the fuzzy membership filter to cancel a high frequency noise of welding current. And ART2 which has the competitive learning network classifiers the signal patterns for the filtered welding signal. A welding current possesses a specific pattern according to the existence or the size of a welding gap. These specific patterns result in different classification in comparison with an occasion for no welding gap. The patterns In each case of 1mm, 2mm, 3mm, and no welding gap are identified by the artificial neural network. These procedure is an off-line execution. In on-line execution, the identification model of neural network for the classified pattern is located on ahead of the welding plant. And when the welding current patterns pass through the neural network in the direction of feedforward. it is possible to recognize the existence or the size of a welding gap.

• ETRI Journal
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• 제45권5호
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• pp.899-909
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• 2023

In mobile communication, the most exploratory technology of fifth generation is massive multiple input multiple output (MIMO). The minimum mean square error and zero forcing based linear detectors are used in multiuser detection for MIMO single-carrier frequency division multiple access (SCFDMA). When the received signal is detected and regularization sequence is joined in the equalization of spectral null amplification, these schemes experience an error performance and the signal detection assesses an inversion of a matrix computation that grows into complexity. Ordered successive interference cancelation (OSIC) detection is considered for MIMO SC-FDMA, which uses a posteriori information to eradicate these problems in a realistic environment. To cancel the interference, sorting is preferred based on signal-to-noise ratio and log-likelihood ratio. The distinctiveness of the methodology is to predict the symbol with the lowest error probability. The proposed work is compared with the existing methods, and simulation results prove that the defined algorithm outperforms conventional detection methods and accomplishes better performance with lower complication.

• 대한전자공학회논문지SP
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• 제42권1호
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• pp.59-64
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• 2005

상관관계가 있는 간섭신호가 존재하는 경우, 다양한 빔형성 기법들은 어레이 출력 파워를 최소화하기 위해서 목적신호까지 제거하는 현상이 발생한다. 본 논문에서는 이러한 상관관계가 있는 간섭신호에 의한 신호 제거 문제를 해결하는 새로운 기법을 제안한다. 기존에 제시된 상관 간섭신호의 제거 기법들 대신 제안된 빔형성 지법은 상관 간섭신호를 또 다른 목적신호로 간주하여 코히어런트하게 간섭신호들을 더해준다. 제안된 기법은 고유벡터 제한을 이용하여 잡음과 상관관계가 없는 간섭신호를 제거하고, 목적신호와 상관 간섭신호는 유지하도록 한다. 고유벡터 제한 MV 빔형성 기법은 상관 간섭신호에 대한 어떤 사전정보론 필요로 하지 않는다는 장점이 있다. 모의 실험에 의해 상관 간섭신호가 존재하는 경우 제안된 기법은 어레이 출력의 신호 대 잡음비가 개선하여 목적신호 제거 문제를 해결할 수 있음을 보여준다.

• 전자공학회논문지
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• 제52권5호
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• pp.23-32
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• 2015

폭발적으로 증가하고 있는 모바일 데이터 트래픽을 수용하기 위하여 셀 간 간섭을 제어할 수 있는 향상된 수신기에 대한 연구가 필요하다. 이를 위해 3GPP(3rd Generation Partnership Project) 에서는 인접 셀의 간섭 신호를 억제 및 제거하여 수신기의 SINR(Signal-to-Noise-plus-Interference Ratio)을 향상시켜 수신 성능을 올리는 NAICS(Network Assisted Interference Cancellation and Suppression)가 표준에서 논의되고 있다. 본 논문에서는 인접 셀로부터 간섭의 영향을 줄이기 위하여 새로운 하이브리드 수신기 FSC(Full Suppression Cancellation)를 제안한다. 제안한 수신기는 IRC(Interference Rejection Combining)와 SIC(Successive Interference Cancellation)를 결합하여 간섭을 억제 및 제거 할 수 있다. 시스템 레벨 시뮬레이션은 3GPP LTE-Advanced 시스템의 20MHz 대역을 기반으로 이루어 졌으며, 시뮬레이션 결과 제안한 수신기를 통해 기존 수신기보다 SINR, 전송률 및 스펙트럼 효율 측면에서 성능 향상을 가져다주는 것을 확인하였다.