• 센서학회지
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• 제25권1호
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• pp.71-78
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• 2016

PPG signal measured by pulse oximeter can measure pulse and the oxygen saturation of arterial blood. But the PPG signal is distorted by finger movement or other movement in the body. To detect pulse from the PPG signal with motion artifact, we use band pass filter(BPF), Independent component analysis(ICA) and nonlinear autocorrelation(NAC). BPF is used to remove DC component and high frequency noise in the PPG signal with motion artifacts. ICA is used to separate pulse signal and motion artifact. However, pulse signal separated by ICA have no choice but to accompany signal distortion because pulse signal and motion artifact are not completely independent. So, we use nonlinear autocorrelation to emphasize the pure pulse signal from the distorted signal.

• 디지털융복합연구
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• 제11권8호
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• pp.183-190
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• 2013

PPG 신호는 심장의 박동에 동기된 유사 주기 신호이다. 본 논문에서는 PPG 신호의 유사주기성을 이용한 지수가중 이동평균필터 방법을 제안한다. 이 필터링 방법은 PPG 신호를 주기적으로 분리하여 각 주기 신호의 같은 순번에 있는 샘플들끼리 평균을 취하는 방법이다. 연속된 PPG 신호의 주기중에 동잡음이 혼입되었다면 주기를 기준으로 PPG 신호를 분리한 후, 각 주기의 샘플수를 조정하여 같은 샘플수를 가지게 만든다. 이 주기들을 2차원으로 배열한 후 현재 주기부터 이전 각 주기의 샘플끼리 평균을 취함으로써 훼손없이 동잡음을 제거할 수 있었다.

• 한국통신학회논문지
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• 제38C권12호
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• pp.1085-1094
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• 2013

본 연구에서는 PPG 신호 측정에서 포함되는 잡음들 중에서 동잡음을 제거하는 신호처리 방안을 제안한다. 측정되는 PPG 신호는 측정 환경 자체의 신호 잡음과 사용자의 동작변화로 발생하는 동잡음 등 여러 잡음이 같이 존재하므로 적절한 신호처리 방법이 요구된다. 본 논문에서는 사용자의 안정된 상태에서 실제 PPG 신호를 측정한 뒤, 이 기준 신호를 바탕으로 여러 채널에서 측정한 다중화된 PPG 신호를 이용하여 동잡음을 제거하는 신호처리 방법을 제안한다. 본 논문의 실험에서는 두 개의 채널을 이용하여 PPG 신호를 측정하며, 각각 20%의 오류율을 가지는 신호를 본 논문에서 제안한 알고리즘으로 처리한 결과 9.56%로 오류율이 감소하였다.

• 대한의용생체공학회:의공학회지
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• 제37권1호
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• pp.1-6
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• 2016

The biomedical information (heart rate, HRV, $SpO_2$ etc) from the Photoplethysmography (PPG) signal section can be estimated without the motion artifacts if the PPG signal section in the motion artifacts is detected accurately. But the PPG signal is easily exposed to the motion artifacts by the decrease of the medical instrument size and applying as portable or wearable. Besides, it is difficult to completely eliminate the motion artifacts from the PPG signal without distortion and ensure reliability as well. In this paper, the method was suggested to determine the motion artifacts or not on the PPG signal of the section divided into intervals of constant length. By comparing the spectrum of each section, it can be determined whether the motion artifacts are or not after obtaining the spectrum of each section by the Goertzel algorithm. Moreover, an amount of computation while maintaining a high detection rate can be reduced by using the Goertzel algorithm.

• 대한의용생체공학회:의공학회지
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• 제30권6호
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• pp.503-509
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• 2009

The development of technology has led to ubiquitous health care service, which enables many patients to receive medical services anytime and anywhere. For the ubiquitous health care environment, real-time measurement of biomedical signals is very important, and the medical instruments must be small and portable or wearable. So, such devices have been developed to measure biomedical signals. In this study, we develop the biomedical monitoring device which is sensing the PPG signal, one of the useful signal in the field of ubiquitous healthcare. We design a watch-like biomedical signal monitoring system without a finger probe to prevent the user's inconvenience. This system obtains the PPG from the radial artery using a sensor in the wrist band. But, new device developed in this paper is easy to get the motion artifacts. So, we proposed new algorithm removing the motion artifacts from the PPG signal. The method detects motion artifacts by changing the degree of brightness of the light source. If the brightness of the light source is reduced, the PPG pulses will disappear. When the PPG pulses have disappeared completely, the remaining signal is not the signal that results from the changing blood flow. We believe that this signal is the motion artifact and call it the noise reference signal. The motion artifacts are removed by subtracting the noise reference signal from the input signal. We apply this algorithm to the system, so we can stabilize the biomedical monitoring system we designed.

• 한국멀티미디어학회논문지
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• 제19권11호
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• pp.1862-1870
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• 2016

A respiration is one of the most useful techniques for vital checking and an abnormal respiration is often the earliest sign of critical illness. Detection of respiration is based on the photo-plethysmography (PPG) with photodiode technique. Because PPG sensor using photodiode can be easily miniaturized, it is suitable for wearable devices. A system to measure respiration rate based on PPG signal is implemented and for a reliable measurement an improved algorithm in accuracy using PPG signal pattern is proposed in this paper. As results regarding to three types of respirations (regular interval, free interval, and weak respiration) the proposed algorithm showed error rate of 0.047, 0.067, and 0.122 respectively.

• 한국컴퓨터정보학회논문지
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• 제17권4호
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• pp.75-82
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• 2012

PPG 신호는 심장의 박동에 동기된 유사 주기 신호이다. 본 논문에서는 PPG 신호의 유사주기성을 이용한 주기적 이동평균필터 방법을 제안한다. 이 필터링 방법은 PPG 신호를 주기적으로 분리하여 각 주기 신호의 같은 순번에 있는 샘플들끼리 평균을 취하는 방법이다. 연속된 PPG 신호의 주기 중에 동잡음이 혼입되었다면 주기를 기준으로 PPG 신호를 분리한 후, 각 주기의 샘플수를 조정하여 같은 샘플수를 가지게 만든다. 이 주기들을 2차원으로 배열한 후 현재 주기부터 이전 각 주기의 샘플끼리 평균을 취함으로써 훼손 없이 동잡음을 제거할 수 있었다.

• 한국정보전자통신기술학회논문지
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• 제2권3호
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• pp.71-78
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• 2009

본 논문에서는 측정된 PPG 신호로부터 심박동수를 추정 하는 방법을 제시한다. PPG 신호는 현관에 흐르는 혈류량을 측정한 것으로 심장의 수축과 이완에 영향을 받아 단일 주파수적인 특성을 가지며 이러한 특성을 이용하여 PPG 주파수를 2차 IIR 적응 놋치 필터로 추적한다. 적응 알고리즘을 통하여 지속적으로 필터 계수를 갱신하여 얻어진 PPG 주파수를 바탕으로 사람의 심박동수를추정한다.

• Journal of information and communication convergence engineering
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• 제8권2호
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• pp.201-204
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• 2010

In the mobile healthcare system, a very important vital sign in analyzing the status of user health is the HRV (heart rate variability). The used signals for measuring the HRV are electrocardiograph and PPG (photoplethysmograph). In extracting the HRV from the PPG signal, an important issue is that extract the exactly HRV from PPG signal distorted from the user's movements. This study suggested a design method of the Kalman filter to solve the problem, and evaluated the performances of a proposed method by PPG signals containing motion artifacts. In the results of experiments that compared with a variable step size adaptive filter proposed in recently, the proposed method showed better performance than an adaptive filter.

• 대한전기학회논문지:시스템및제어부문D
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• 제55권3호
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• pp.138-141
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• 2006

Blood flow is one of vital signals related to human physiological information. Photoplethysmograph (PPG) has been used to measure indirectly heart rate, blood oxygen saturation ($SpO_2$), and so on. Because PPG signal is weak and sensitive to motion artifacts, it is very important to continuously obtain stable PPG signal during free movement. In this study, we applied the scaled Fourier linear combiner (SFLC) using both the adaptive filter and FLC to remove effectively the motion artifacts as well as background noise in the real time without additional signal correlated with motion from a accelerometer. The proposed method would be useful to reduce the movement and background noise which are not synchronized with heart rate.