Effect of respiration harmonics on beat-to-beat analysis of heart signal

Doppler radar is a promising tool for non-invasive physiological monitoring. However, its output signal is affected by respiration harmonics interference due to inherent respiratory features and a radar detection method. Respiration harmonics present a challenge for sophisticated beat-to-beat analysis of heart signals for extraction of heart rate variability (HRV) parameters. This paper discusses causes of these harmonics along with proposing the utilization of maximal overlap discrete wavelet transform (MODWT) for minimizing their interference. The results are presented in terms of average heart rate and the standard deviation of interbeat intervals (SDNN). Adaptive notch filter is used for comparing the effect of harmonics cancellation on beat-to-beat analysis of heart signals. Compared to the results of the notch filter, the SDNN difference from MODWT is lowered by 5.12% to 91.43%.