Journal of the Korea Academia-Industrial cooperation Society (한국산학기술학회논문지)

The Korea Academia-Industrial cooperation Society (한국산학기술학회)
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Detection of Apnea Signal using UWB Radar based on Short-Time-Fourier-Transform

국소 퓨리에 변환 기반 레이더 신호를 활용한 무호흡 검출

  • Hwang, Chaehwan (Department of Biomedical Engineering, Keimyung University) ;
  • Kim, Suyeol (Department of Biomedical Engineering, Keimyung University) ;
  • Lee, Deokwoo (Department of Computer Engineering, Keimyung University)
  • 황채환 (계명대학교 의용공학과) ;
  • 김수열 (계명대학교 의용공학과) ;
  • 이덕우 (계명대학교 컴퓨터공학부 컴퓨터공학 전공)
  • Received : 2019.04.08
  • Accepted : 2019.07.05
  • Published : 2019.07.31
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Abstract

Recently, monitoring respiration of people has been of interest using non-invasive method. Among the vital signals usually used for indicating health status, non-invasive and portable device based monitoring respiratory status is practically useful and enable one to promptly deal with abnormal physical status. This paper proposes the approach to real-time detection of apnea signal based on Short-Time-Fourier-Transform(STFT). Contrary to the analysis of a signal in frequency domain using Fast-Fourier Transform, this paper employs Short-time-Fourier-Transform so that frequency response can be analyzed in short time interval. The respiratory signal is acquired using UWB radar sensor that enables one to obtain respiration signal in contactless way. Detection of respiratory status is carried out by analyzing frequency response, and classification of respiratory status can be provided. In particular, STFT is employed to analyze respiratory signal in real-time, leading to effective analysis of the respiratory status in practice. In the case of existence of noise in the signal, appropriate filtering process is employed as well. The proposed method is straightforward and is workable in practice to analyze the respiratory status of people. To evaluate the proposed method, experimental results are provided.

최근 비침투 또는 비접촉 방식을 활용한 호흡상태 관찰에 대한 관심이 높아지고 있다. 여러 가지 많은 생체신호들 중 호흡신호를 활용하여 건강상태를 점검하는 것은 비정상적인 건강 상태에 대한 신속한 대응을 가능하게 해 준다. 본 논문에서는 국소 퓨리에 변환을 활용한 실시간 무호흡 상태 검출에 대한 방법을 제시한다. 기존의 고속 퓨리에 변환을 활용한 신호해석과 달리, 본 논문에서는 국소 퓨리에 변환을 사용하여 짧은 신호 구간에서의 주파수 응답을 분석한다. 본 연구에서 호흡 신호는 비접촉 방식을 활용하였으며, 초광대역 레이더 모듈을 활용하여 신호를 획득하였다. 국소 퓨리에 변환을 활용하여 호흡 상태를 검출한 후, 검출 결과에 따라 호흡 상태에 대한 분류가 가능하다. 특히 국소 퓨리에 변환은 실시간으로 호흡 상태에 대한 주파수 분석이 가능하도록 하였다. 호흡신호에 잡음이 존재할 경우를 대비하여 적절한 필터링 알고리즘이 적용되었다. 본 논문에서 제안하는 방법은 직관적으로 구현이 가능하고, 실질적으로 사람의 호흡상태에 대한 분석이 가능하도록 해준다. 제안한 방법을 검증하기 위해 호흡신호를 활용한 실험결과를 제시한다.

Keywords

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Fig. 1. Overall flow diagram of the proposed approach

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Fig. 2. Respiration signal obtained using UWB radar

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Fig. 3. Normal respiration during speech activity

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Fig. 4. Overall flow of the experiment.

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Fig. 5. STFT of apnea signal. Apnea occurs at 45second and persists for 15seconds.

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Fig. 6. STFT of apnea signal. Apnea occurs at 30second and persists for 15seconds.

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Fig. 7. STFT of apnea signal. Apnea occurs at 40second and persists for 15seconds.

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Fig. 8. STFT of normal respiration.

Table 1. Accuracy of estimation of apnea

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