Hybrid Signal Processing Framework Based on Second-Order Differentiation and Harmonic Superposition for Non-Contact Heart Rhythm Monitoring

In this article, a novel method was proposed to extract heartbeat information based on a 2<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nd</sup> order differential technique complemented by leveraging the elevated strong harmonics of heartbeat in frequency domain signal by superimposing their magnitude to the fundamental frequency. A theoretical analysis of the working principle of the algorithm has been provided, along with a simulation, to demonstrate the algorithm's advantage in the existence of strong respiration harmonics. An experimental analysis was conducted, and the accuracy achieved using the proposed method was 1.47 Bpm for five subjects with a mean average error of over two minutes of collected data.