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Heartbeat extraction based on a high order derivative for ultra-wideband impulse radar application

Remote sensing of heartbeat signals is an essential application of ultra-wideband (UWB) radar in smart homes and smart hospitals. UWB radar measures heartbeat signals by measuring the motion of the thorax, which is mixed with the motion of breathing activity. The heartbeat signal is usually much smaller than the respiration signal, thus, the detection of the heart rate could be wrong due to the fundamental and harmonic components of the respiration signal. This paper proposes a heartbeat extraction algorithm based on a high order derivative (HOD). The amplitude of the heartbeat signal is amplified, and the respiration signal is deduced in the HOD. Thus, the signal-to-noise ratio (SNR) of the heartbeat signal will be improved. The experimental results show that the SNR was improved for the ratio between heart rate and respiration rate. The SNR of the heartbeat signal by the second of the HOD method was improved by about 5.9 dB with different orientations of the person compared to the 64 orders of the band-pass filter. The HOD is a simple and lightweight method taking the derivatives of the input vital signal, which could help for real-time monitoring of heartbeat signals.