Pseudo-period segment of ballistocardiogram based on joint time-frequency analysis

Heart beat causes the synchronous body vibration, which can be measured on the spine axis by sensitive force sensor called ballistocardiogram. Ballistocardiogram was a kind of nonstationary physiological signal, which couldn´t be analyzed and processed by traditional signal processing method. The generation and acquisition method of ballistocardiogram were explained. As examples of bilinear and linear time-frequency distribution, the Cohen class distribution and wavelet transform were discussed and used in ballistocardigram pseudo-period segment. In addition, the frequency range of ballistocardiogram and the levels of wavelet decomposition were determined by Cohen class distribution, but the performance of exponential distribution is better than that of Wigner-Ville distribution and has a fine correspondence to time domain wave of actual ballistocardigram. The experiment results show that, bilinear and linear time-frequency distribution are both able to divide ballistocardiogram into pseudo-periods corresponding to cardiac cycle, but the segment performance of wavelet decomposition is better than that of Cohen class distribution, and the latter one is terser to realize.