A Novel Scheme of High-Precision Heart Rate Detection With a mm-Wave FMCW Radar

Millimeter wave (mm-Wave) radar has been widely employed for non-contact vital sign detection. This research proposes a novel processing scheme to improve the accuracy and stability of non-contact heart rate detection. Firstly, we propose an adaptive range bin selection method based on variance which can select accurate range bins containing phase information of vital signs. Secondly, the smooth spline is utilized to fit the original phase signal to obtain a relatively pure template signal. Subsequently, the pure template signal is used as the input signal for the matched filter to convolve with the phase signal. The matched filtering can eliminate interference and noise such as breathing and random body movements (RBM). Next, the heartbeat signal is extracted by the Variable Mode Extraction (VME) algorithm. Finally, a novel frequency measurement technique named as Double-Chirp Z-Transform (Double-CZT) is proposed. The frequency of the heartbeat signal is measured by the Double-CZT. Compared with the traditional frequency measurement techniques, the Double-CZT improves the accuracy of frequency measurement and allows for more accurate heart rate measurements. Many subjects were invited to participate in the experiment, and the mean absolute error (MAE) of heart rate was less than 1 beat per minute (bpm) on average. The experimental results demonstrate that the proposed scheme can improve the signal-to-noise ratio (SNR) of heartbeat signal and provide accurate heart rate estimation.