• The Journal of Korean Institute of Communications and Information Sciences
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• 제26권6B호
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• pp.760-766
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• 2001

본 논문에서는 차량내 핸즈프리 전화통신을 위한 음향 반향 및 배경 잡음 제거기를 제안한다. 제안한 시스템은 새로운 잔여 반향 제거 기법과 실시간 구현에 적합한 동시통화 검출기를 포함한다. 잔여 반향 제거에서는 근단화자가 없는 구간에 대하여 선형 예측기를 이용하여 잔여 반향 신호의 인접 샘플간의 상관도를 제거하여 잡음 제거기의 입력으로 사용한다. 잔여 반향 신호의 음성특성을 제거함으로써 잡음 제거기를 이용하여 배경 잡음과 더불어 잔여 반향의 전력을 효과적으로 줄일 수 있다. 제안된 시스템에서는 상용 저전송률 음성부호화기와의 결합을 고려하여 IS-127(EVRC)에 포함되어 있는 잡음 제거기를 사용하였다. 90 km/h로 정속 주행하는 차내의 핸즈프리 환경에서 제안된 시스템은 30 dB이상의 간섭신호 제거 성능을 보였다. 제안된 시스템은 16비트 고정 소수점 연산을 하는 저가의 DSP를 이용하여 실시간 구현되었다.

• Proceedings of the Acoustical Society of Korea Conference
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• 한국음향학회 2002년도 하계학술발표대회 논문집 제21권 1호
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• pp.233-236
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• 2002

ES(Exponentially weighted Stepsize) 알고리즘은 연산 과정이 간단하고 수렴 속도가 빠르지만 Stepsize 값을 결정하기 위해 일정한 조건에서 결정된 공간 임펄스 응답들을 이용하기 때문에 외부 잡음이 발생할 경우 음향 반향 제거 성능이 저하된다. 본 논문에서는 기존의 반향 제거기에 Stepsize 생성기를 추가하여 외부 잡음에 대한 ES 알고리즘의 단점을 개선하고 잡음에 대한 강건함을 향상시키는 새로운 반향 제거기를 개발하였다. Stepsize 생성기는 두 개의 이동 평균기를 이용하여 외부 잡음에 크기와는 독립적으로 Stepsize 값을 결정하며, 이로부터 대각선(diagonal) 모양을 가지는 Stepsize 행렬을 생성하여 반향 제거기에 적용한다. 본 논문에서는 NLMS 알고리즘, ES 알고리즘, 제안된 알고리즘의 수렴 특성을 잡음의 크기별로 시뮬레이션 하였으며, 또한 제안된 알고리즘의 잔여 에러의 크기도 다른 두 알고리즘에 비해 5[dB] 에서 10[dB]정도 작아지는 것을 확인하였다.

• The Journal of the Korea Contents Association
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• 제6권4호
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• pp.11-18
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• 2006

A new algorithm for removing salt and pepper impulse noise in image using impulse noise detector and total variation optimization is presented. The proposed two types of noise detectors which are based on the adaptive median filter, can detect impulse noise with high accuracy while reducing the probability of detecting image details as impulses. And the detectors maintain its performance independent of noise density. For removing impulses, total variation optimization is applied only to those detected noise candidate to reduces unnecessary computation. The proposed approach successfully remove impulse noise while preserving image details.

• The Journal of the Acoustical Society of Korea
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• 제19권4호
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• pp.3-15
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• 2000

In this paper we present a new image denoising filter that can suppress additive noise components while preserving signal components in the wavelet domain. The proposed filter, which we call an adaptive wavelet shrinkage(AWS) filter, is composed of two operators: the wavelet killing operator and the adaptive shrinkage operator. Each operator is selected based on the threshold value which is estimated adaptively by using the local statistics of the wavelet coefficients. In the wavelet killing operation, the small wavelet coefficients below the threshold value are replaced by zero to suppress noise components in the wavelet domain. The adaptive shrinkage operator attenuates noise components from the wavelet components above the threshold value adaptively. The experimental results show that the proposed filter is more effective than the other methods in preserving signal components while suppressing noise.

• The Journal of the Acoustical Society of Korea
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• 제22권4호
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• pp.261-268
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• 2003

Conventional acoustic echo cancellers using ES algorithm have simple structure and fast convergence speed compared with those using NLMS algorithm, but they are very weak to external noise because ES algorithm updates the adaptive filter taps based on average energy reduction rate of room impulse response in specific acoustical condition. To solve this problem, in this paper, a new update algorithm for acoustic echo canceller with stepsize matrix generator is proposed. A set of stepsizes is determined based on residual error energy which is estimated by two moving average operators, and applied to the echo canceller in matrix from, resulting in improved convergence speed. Simulations in various noise condition show that the proposed algorithm improves the robustness of acoustic echo canceller to external noise.

• Proceedings of the IEEK Conference
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• 대한전자공학회 2001년도 제14회 신호처리 합동 학술대회 논문집
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• pp.557-560
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• 2001

본 논문에서는 시공간 3차원 잡음 제거기의 ASIC 설계 및 구현결과를 소개한다. 구현된 잡음 제거기는 휘도와 색차신호에 대한 잡음제거 필터들로 구성된다. 휘도에 적용한 필터는 A-MEAN 필터와 A-LMMSE 필터를 결합한 형태의 필터를 시공간적으로 연결한 필터로써, 특히 시간방향으로 IIR 필터 형태를 갖도록 설계하여 평탄한 영상영역에서 보다 강한 잡음 제거 효과를 갖도록 하였다. 한편, 색차신호에 대해서는 5탭 길이를 갖는 1차원 A-MEAN 필터를 적용하였다. C-언어를 이용한 시뮬레이션을 통해 설계된 잡음 제거기의 성능을 평가하였고, VHDL과 C-언어에 의한 시뮬레이션 결과를 비교하여 VHDL-코드의 검증을 수행했다. 구현과정은 시뮬레이션과 논리합성 등 전반부 설계를 Synopsys 툴을 이용하여 수행했고, 레이아웃 등 후반부 설계를 Cadence 툴과 Apollo 툴을 이용하여 수행했다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• 제22권4호
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• pp.481-488
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• 2011

In this paper, we study a novel wireless interference cancellation system(ICS) repeater based on OFDM system with phase noise analysis and performance evaluation. Recently, there were many researches about wireless repeater. The previous study is just considering the feedback channel cancellation algorithm. But, in wireless repeater system, the phase noise effect can exist at up and down converter of wireless repeater. In wireless repeater system, if there are phase noise effects, the performance of system will get worse. So, the phase noise compensator is needed in wireless repeater. Therefore, we propose adaptive phase noise compensator based on OFDM system in order to effectively cancel phase noise. In order to cancel interference, we adapt adaptive phase noise compensator in wireless repeater system. The adaptive phase noise compensator compensates phase noise effect. Therefore, in this paper, we analyze phase noise of wireless repeater based on OFDM system. In this paper, when phase noise power is -15 dBc and phase noise cutoff frequency is 100 kHz at 4QAM, the BER performance of propose algorithm is better about 4 dB than with adaptive equalizer and without phase noise compensator at $10^{-4}$.

• Journal of Advanced Navigation Technology
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• 제13권4호
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• pp.482-489
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• 2009

This paper proposes a CW(Continuous-Wave) bio-radar applying a new adaptive noise canceller based on ALE(Adaptive Line Enhancer) which can remove the Gaussian noise and system noise. Recently the research works on this CW bio-radar which can be used to detect heartbeat and respiration are advanced by the university and research facility. Although the researches describe CW bio-radar not only is vulnerable for the Gaussian noise but also has a disadvantage of decreasing the heart-rate accuracy due to the noise, the researches do not demonstrate the effective method for removing the noise component in a baseband signal. In this paper, a CW bio-radar applying the new adaptive noise canceller based on ALE which can remove the noise component is proposed. This paper compares and analyzes the performance for increasing the heart-rate accuracy according to removing the Gaussian noise and system noise in the baseband signal through the quadrature receiver which can alleviate the demodulation sensitivity to target position.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제35권1C호
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• pp.96-102
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• 2010

This paper proposes a new adaptive algorithm to cancel the acoustic feedback and noise signals in the digital hearing aids. The proposed algorithm improves its convergence performances by canceling the speech signal from the residual signal using two microphones. The feedback canceller firstly cancels the feedback signal among the mic signal, and then it is reduced the noise using the beamforming method. To verify the performances of the proposed algorithm, the simulations were carried out for some cases. As the results of simulations, it was proved that the feedback canceller and the noise canceller advance about 14.43 dB for SFR, 10.19 dB for SNR respectively during speech, in the case of using the new algorithm.

• The Journal of the Acoustical Society of Korea
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• 제20권7호
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• pp.37-46
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• 2001

This paper proposes a new noise suppression method using the Wavelet transform analysis. The noise suppressor using the Wavelet transform shows the more effective advantages in a babble noise than one using the short-time Fourier transform. We designed a new channel structure based on spectral subtraction of Wavelet transform coefficients and used the Wavelet mask pattern with more higher time resolution in high frequency. It showed a good adaptation capability for babble noise with a non-stationary property. To evaluate the performance of proposed noise canceller, the informal subjective listening tests (Mos tests) were performed in background noise environments (car noise, street noise, babble noise) of mobile communication. The proposed noise suppression algorithm showed about MOS 0.2 performance improvements than the suppression algorithm of EVRC in informal listening tests. The noise reduction by the proposed method was shown in spectrogram of speech signal.