Noncontact vital signs detection using joint wavelet analysis and autocorrelation computation
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摘要: 采用調頻連續波(Frequency modulated continuous wave, FMCW)雷達實現非接觸式生理信號檢測,并提出了基于小波分析和自相關計算(Wavelet analysis and autocorrelation computation, WAAC)的檢測方法。首先,毫米波FMCW雷達發射電磁波信號,并接收來自身體的反射信號。然后,通過信號預處理從中頻信號中提取包含呼吸和心跳的相位信息,消除直流偏置并完成相位解纏。最后,基于小波包分解(Wavelet packet decomposition, WPD)從原始信號中得到心跳和呼吸信號,利用自相關計算減小雜波對心跳信號的影響,進而提取高精度的心率參數。應用FMCW雷達對10名受試者進行實驗測試,結果表明本文方法得到的呼吸和心率的平均絕對誤差率平均值分別小于1.65%和1.83%。Abstract: Vital signs are important parameters for human health status assessment, and timely, accurate detection is of great significance for modern health care and intelligent medical applications. Detecting vital signs, such as heartbeat and respiration signals, provides a variety of diseases with reliable diagnosis and effective prevention. Conventional contact detection may restrict the behaviors of users, cause additional burdens, and render users uncomfortable. In recent years, noncontact detection technology has successfully achieved remote long-term detection for respiration and heartbeat signals. Compared to conventional contact-detection approaches, noncontact heartbeat and respiration detection using a millimeter-wave radar is preferable as it causes no disturbance to the subject, bringing a comfortable experience, and detects vital signs under natural conditions. However, noncontact vital signs detection is challenging owing to environmental noise. Especially, heartbeat signals are very weak and are merged with respiration harmonics and environmental noise, and their extraction and recognition are even more difficult. This paper applied a frequency-modulated continuous wave (FMCW) radar to detect vital signs. The study also presented a noncontact heartbeat and respiration signals detection approach based on wavelet analysis and autocorrelation computation (WAAC). The millimeter-wave FMCW radar first transmited the electromagnetic signal and received the reflected echo signals from the human body. Thereafter, the phase information of the intermediate frequency signals was extracted, which included respiration and heartbeat signals. The direct current offset of the phase information was corrected, and the phase was unwrapped. Finally, the wavelet packet decomposition was used to reconstruct heartbeat and respiration signals from the original signal, and an autocorrelation computation was utilized to reduce the effect of clutters on the heart rate detection. Experiments were conducted on ten subjects. Results show that the average absolute error percentage of WAAC is less than 1.65% and 1.83% for respiration and heartbeat rates, respectively.
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表 1 雷達參數配置
Table 1. Radar configuration parameters
fmin/GHz Td/μs S/(MHz·s?1) B/MHz fslow/Hz ffast/MHz 76.4 48 20 960 20 3.2 表 2 10名受試者在不同距離生理特征速率測量平均絕對誤差率
Table 2. AAEP of radar instantaneous vital sign rates detection from ten subjects at six different distances
Subject Gender Height/cm Weight/kg HR AAEP/% BR AAEP/% 0.5 m 1.0 m 1.5 m 2.0 m 2.5 m 3.0 m 0.5 m 1.0 m 1.5 m 2.0 m 2.5 m 3.0 m 1 Male 178 90 0.87 1.08 0.99 1.59 2.80 3.93 0.45 1.38 1.03 2.84 2.77 3.11 2 Male 176 85 0.69 3.02 1.47 2.98 3.60 4.14 0.84 0.63 2.19 3.12 4.61 3.50 3 Male 171 65 2.01 1.69 2.94 3.26 3.73 4.82 1.44 1.55 2.21 3.28 1.65 4.35 4 Male 173 68 1.92 3.45 4.78 4.90 5.76 7.74 3.23 1.10 4.06 2.45 3.96 4.06 5 Male 183 82 1.70 3.86 3.97 4.05 4.14 5.64 2.25 3.63 1.76 3.48 3.50 5.62 6 Male 171 73 2.07 2.98 3.77 4.72 4.90 6.58 0.96 1.53 2.64 2.67 2.45 4.81 7 Female 170 50 2.20 4.24 4.27 4.35 6.66 7.05 1.76 2.68 2.52 3.73 3.77 5.90 8 Female 173 53 2.33 3.95 3.94 4.91 6.80 9.66 1.09 2.39 2.28 2.32 4.82 6.17 9 Female 176 65 2.50 3.08 4.62 5.22 6.36 7.93 1.62 1.94 2.33 2.20 2.12 2.34 10 Female 163 48 2.05 3.02 3.33 3.68 5.35 7.28 2.86 1.68 2.13 2.94 4.77 5.00 Average 1.83 3.03 3.41 3.97 5.01 6.48 1.65 1.85 2.32 2.90 3.44 4.49 表 3 10名受試者在不同距離生理特征速率測量平均絕對誤差
Table 3. AAE of radar instantaneous vital sign rates detection from ten subjects at six different distances
Subject Gender Height/cm Weight/kg HR AAE (bpm) BR AAE (bpm) 0.5 m 1.0 m 1.5 m 2.0 m 2.5 m 3.0 m 0.5 m 1.0 m 1.5 m 2.0 m 2.5 m 3.0 m 1 Male 178 90 0.66 0.73 0.62 0.96 1.80 2.45 0.08 0.22 0.15 0.41 0.38 0.46 2 Male 176 85 0.54 2.34 1.14 1.76 2.27 2.45 0.11 0.10 0.33 0.43 0.57 0.51 3 Male 171 65 1.64 1.37 2.16 1.98 2.39 3.10 0.29 0.29 0.38 0.48 0.25 0.63 4 Male 173 68 1.25 2.32 2.96 4.65 5.62 7.74 0.44 0.15 0.26 0.63 1.02 1.17 5 Male 183 82 1.16 2.62 2.60 2.47 2.45 3.28 0.30 0.51 0.21 0.58 0.51 0.91 6 Male 171 73 1.38 1.98 2.50 2.91 4.65 3.77 0.13 0.19 0.33 0.32 0.63 0.70 7 Female 170 50 1.56 3.83 3.63 4.03 6.30 6.96 0.26 0.29 0.38 0.92 0.97 1.50 8 Female 173 53 2.18 2.32 2.39 4.63 6.54 10.4 0.20 0.42 0.38 0.58 1.12 1.68 9 Female 176 65 1.74 2.22 3.40 5.41 6.59 7.65 0.26 0.31 0.31 0.63 0.30 0.55 10 Female 163 48 1.74 1.96 2.19 3.50 5.25 7.12 0.37 0.25 0.32 0.79 1.15 1.42 Average 1.39 2.17 2.36 3.23 4.39 5.49 0.24 0.27 0.30 0.58 0.69 0.93 www.77susu.com -
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