• 한국전자통신학회논문지
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• 제10권10호
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• pp.1183-1188
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• 2015

FM-QCSK(: Frequency Modulated Quadrature Chaos Shift Keying) 시스템은 여러 가지 카오스 통신 시스템 중에서 효율적인 시스템의 하나이다. 그러나 이 시스템의 문제점 중 하나는 반 비트기간 동안을 카오스 기준 신호를 전송하기위해 사용하여 결과적으로 에너지 손실을 증가시키고 데이터률을 감소시킨다. 본 논문에서는, 새로운 구조의 FM-QCSK 시스템을 제안하여 성능향상을 확인한다. 제안된 방식은 기존의 FM-QCSK보다 낮은 BER(: Bit Error Rate) 및 작은 에너지 소비와 더 높은 데이터률로 동작 할 수 있을 것이다. 제안된 카오스 변조방법에 의한 FM-QCSK의 변형은 기본적인 동위상 및 직교 위상 채널 모두에서 다중 정보신호들을 전송하기 위해 하나의 카오스 참조 신호를 사용하는 것이다. 결과는 제안된 방법이 AWGN채널에서 전반적으로 $BER=10^{-3}$일 때 SNR이 3dB정도 이득이 있는 것을 확인 하였다. 또한 참조 신호당 보낼 수 있는 최적의 정보신호의 수가 8임을 확인하였다.

• 방송공학회논문지
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• 제12권6호
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• pp.565-573
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• 2007

본 논문에서는 JVT에서 표준화가 진행 중인 다시점 비디오 부호화의 부호화 효율을 높이기 위해 다시점 비디오의 예측구조의 특성을 고려하여 움직임벡터 예측값을 선택하는 방법을 제안한다. 다시점 비디오 부호화에서 시간 방향과 뷰 방향의 예측을 수행하면서 서로 다른 성향의 움직임벡터가 발생된다. 또한 주변 블록에서 시간 방향과 뷰 방향 참조의 움직임벡터가 혼재하는 상황에서 동일한 성향의 움직임벡터가 선택되지 않는 경우가 발생되어 움직임벡터의 예측 효율이 저하된다. 이에 다시점 비디오 부호화의 예측구조에 따라 움직임벡터 예측값을 선택할 수 있는 방법을 제안한다. 제안하는 움직임벡터 예측값 선택 방법을 통하여 다시점 비디오 부호화의 압축 효율을 높일 수 있었으며, JMVM 3.6에서 움직임벡터 예측값을 선택하는 방법을 사용하는 다시점 비디오 부호화와 비교하여 PSNR(Peak Signal-to-Noise Ratio)이 약$0.03{\sim}0.1$ dB 정도 향상되었다.

• 전기학회논문지
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• 제62권5호
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• pp.667-672
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• 2013

In this paper, we propose a multi-impedance changes localization method of on-voltage underground power cable using the wavelet transform based time-frequency domain reflectometry (WTFDR). To localize the impedance change in on-voltage power cable, the TFDR is the most suitable among reflectometries because the inductive coupler is used to inject the reference signal to the live cable. At this time, the actual on-voltage power cable has multi-impedance changes such as the automatic section switches and the auto load transfer switches. However, when the multi-impedance changes are generated in the close range, the conventional TFDR has the cross term interference problem because of the nonlinear characteristics of the Wigner-Ville distribution. To solve the problem, the wavelet transform (WT) is used because it has the linearity. That is, using WTFDR, the cross term interference is not generated in multi-impedance changes due to the linearity of the WT. To confirm the effectiveness and accuracy of the proposed method, the actual experiments are carried out for the on-voltage underground power cable.

• 전력전자학회논문지
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• 제15권4호
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• pp.288-295
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• 2010

멀티레벨 인버터는 대용량 전력변환 분야의 요구를 만족하면서 파형왜곡을 감소시켜 전력품질 향상시킬 수 있으므로 근래에 상당히 주목받고 있다. 그런데 전압레벨이 증가함에 따라 복잡한 PWM 알고리즘을 구현하는데 FPGA가 적합하다. 본 논문에서는 FPGA로 5-레벨 다이오드 클램핑형 멀티레벨 인버터의 PWM 신호발생 기법을 제시한다. 유도전동기 제어용 DSP와 FPGA사이에 3상 기준전압 값을 안정되게 전송하는 기법을 제시한다. 32-비트 DSP와 cyclone-III FPGA를 사용한 실험 및 시뮬레이션을 통하여 반송신호 발생 방법으로 PWM 신호를 발생시키는 기법의 타당성을 검증한다.

• 오토저널
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• 제14권5호
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• pp.95-106
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• 1992

Active control of acoustic noise is an application area of adaptive digital signal processing with increasingly interest along the last year. This work studies the implementation of the multichannel LMS filter and the application of this algorithm for the reduction of the noise inside a vechicle cabin using a number of 'secondary sources' drived by adaptive filtering of a reference noise source. Firstly, we propose the use of an adaptive method for the time-varient optimal convergence factor. Secondly, we propose the use of adaptive delayed inverse model to estimate the elastic-acoustic transfer function presented in vechicle cabin. The original, primary source is often periodic, with a known fundamental frequency. A suitably filtered reference signal can thus be used to drive the secondary sources. An algorithm is presented for adapting the coefficients of an FIR filter feeding such a secondary source in such a way as to minimize the output of a suitably placed microphone. In this algorithm, the coefficients of adaptive filter driving an array of secondary sources can be adapted to minimize the sum of the squares of the outputs of a number of error microphones. The multichannel LMS algorithm displays that such an algorithm is considered suitable to used for the global suppression of noise in vehicle cabin.

• ETRI Journal
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• 제39권3호
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• pp.398-405
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• 2017

In this paper, an artificial stereo extension method that creates stereophonic sound from a mono sound source is proposed. The proposed method first trains deep neural networks (DNNs) that model the nonlinear relationship between the dominant and residual signals of the stereo channel. In the training stage, the band-wise log spectral magnitude and unwrapped phase of both the dominant and residual signals are utilized to model the nonlinearities of each sub-band through deep architecture. From that point, stereo extension is conducted by estimating the residual signal that corresponds to the input mono channel signal with the trained DNN model in a sub-band domain. The performance of the proposed method was evaluated using a log spectral distortion (LSD) measure and multiple stimuli with a hidden reference and anchor (MUSHRA) test. The results showed that the proposed method provided a lower LSD and higher MUSHRA score than conventional methods that use hidden Markov models and DNN with full-band processing.

• Journal of information and communication convergence engineering
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• 제5권4호
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• pp.328-332
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• 2007

The structure of MMSE receiver frontended by CMA array working in CDMA forward link is proposed. By using the despreaded pilot signal of forward link as a reference signal, CMA array can capture multi-path signals securely even in severely faded mobile channel. The remaining MAl (Multiple Access Interference) is cancelled by the cascaded MMSE receiver. Through computer simulation, it is proved that the proposed system shows much better BER performance than any other systems. As a mobile based spatio-temporal receiver, the proposed system also reduces implemental cost and complexity by adopting the simplest algorithm for its spatial and temporal domain processing.

• 전자공학회논문지A
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• 제32A권3호
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• pp.58-67
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• 1995

In this paper, we present a new HPEJTC system which is capable of real-time multi-target recognition and tracking with better discrimination by extracting the phase signal of reference function from the JTPS of the conventional optical JTC retaining the amplitude signal of the input function. In order to test the correlation discrimination performance of the HPEJTC system, some experiments are carried out on the scenarios susceptible to the false alarms and missing in which many similar targets are periodically loacted. And, the proposed HPEJTC is analyzed to be the real function version of the POF and finally the possibility of the real-time implementation of the POF is suggested, because it can be implemented by using spatial light modulator, CCD detector and some other optical components.

• 융합신호처리학회논문지
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• 제14권1호
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• pp.13-20
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• 2013

A combined DWT and DCT based watermarking technique of low frequency watermarking with weighted correction is proposed. The DWT has excellent spatial localization, frequency spread and multi-resolution characteristics, which are similar to the theoretical models of the human visual system (HVS). The DCT based watermarking techniques offer compression while DWT based watermarking techniques offer scalability. These desirable properties are used in this combined watermarking technique. In the proposed method watermark bits are embedded in the low frequency band of each DCT block of selected DWT sub-band. The weighted correction is also used to improve the imperceptibility. The extracting procedure reverses the embedding operations without the reference of the original image. Compared with the similar approach by DCT based approach and DWT based approach, the experimental results show that the proposed algorithm apparently preserves superiori mage quality and robustness under various attacks such as JPEG compression, cropping, sharping, contrast adjustments and so on.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2001년도 추계종합학술대회
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• pp.331-335
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• 2001

블라인드 형태의 새로운 LMS 알고리즘을 제안한다. 기존의 LMS 알고리즘의 스텝사이즈를 지수를 이용하여 가변시켜서 수렴속도가 향상되도록 한 두가지 방식을 보여준다. 본 제안방식은 디지털 신호의 Finite Constellation 특성을 이용하여 Projection 방식을 이용했다. 제안알고리즘의 성능을 증명하기 위해서, AWGN 채널과 다중경로 Rayleigh Fading 채널상황에서 시뮬레이션을 수행하였다.