Accurate Radar-Based Heartbeat Measurement Using Higher Harmonic Components

TL;DR

This paper introduces a novel radar-based heartbeat measurement technique that leverages the second derivative of the radar signal and variational mode extraction to improve accuracy over traditional phase-based methods.

Contribution

The study presents a new approach combining second-derivative analysis and variational mode extraction for more accurate radar-based heartbeat detection.

Findings

Higher correlation coefficient in interbeat interval estimation

Reduced root-mean-square error compared to conventional methods

Effective amplification of heartbeat components in radar signals

Abstract

This study proposes a radar-based heartbeat measurement method that uses the absolute value of the second derivative of the complex radar signal, rather than its phase, and the variational mode extraction method, which is a type of mode decomposition algorithm. We show that the proposed second-derivative-based approach can amplify the heartbeat component in radar signals effectively and also confirm that use of the variational mode extraction method represents an efficient way to emphasize the heartbeat component amplified via the second-derivative-based approach. We demonstrate estimation of the heart interbeat intervals using the proposed approach in combination with the topology method, which is an accurate interbeat interval estimation method. The performance of the proposed method is evaluated quantitatively using data obtained from eleven participants that were measured using a millimeter-wave radar system. When compared with conventional methods based on the phase of the complex radar signal, our proposed method can achieve higher accuracy when estimating the heart interbeat intervals; the correlation coefficient for the proposed method was increased by 0.20 and the root-mean-square error decreased by 23%.