Fig. 1. Block diagram of acquisition method

Fig. 2. Simplified structure of testing platform

Fig. 3. Performance of improved threshold function

Fig. 4. Denoising principle of VMD-IWT

Fig. 5. Motion artifact in signal

Fig. 6. Simulated signals. (a) Pure signal; (b) signal after adding 5 dB Gaussian white noise; (c) signal after adding 15 dB Gaussian white noise; (d) signal after adding 25 dB Gaussian white noise

Fig. 7. Comparison chart of each evaluation metric. (a) SNR metric; (b) RMSE metric; (c) PRD metric

Fig. 8. Respiration and heartbeat signal acquisition experiment

Fig. 9. Respiration and heartbeat mixed signal

Fig. 10. Component diagrams of VMD

Fig. 11. Effect plots of each algorithm after denoising. (a) EEMD algorithm; (b) CEEMDAN algorithm; (c) EMD-ICA algorithm; (d) proposed method

Fig. 12. Detailed plots of signals. (a) EEMD algorithm; (b) CEEMDAN algorithm; (c) EMD-ICA algorithm; (d) proposed method

Fig. 13. Signal separation and frequency calculation. (a) Original signal; (b) denoised signal; (c) respiratory signal; (d) respiratory spectrogram; (e) heartbeat signal; (f) heartbeat spectrogram