Envelope Demodulation via Maximum Subsampling Applied to Impedance Plethysmography Signals

Abstract A demodulation method for impedance plethysmography (IPG) signals is proposed based on an envelope detection and maximum subsampling algorithm. The procedure was implemented and tested through numerical simulations in MATLAB, which model all relevant stages of a classical IPG measurement system. The algorithm’s performance was assessed by the mean absolute error (MAE), signal-to-noise ratio (SNR), and Pearson’s correlation coefficient ( r ), all computed on normalized amplitude signals. The results indicate that while the Lock-In method achieves high accuracy, it incurs a significant computational cost and affects signal stability. In contrast, the proposed sub-sampling algorithm is more computationally efficient and does not introduce distortions, making it a suitable alternative for resource-constrained systems.