Respiration harmonics cancellation for Accurate Heart Rate measurement in non-contact vital sign detection

Measuring the respiration rate (RR) and heart rate (HR) simultaneously in non-contact vital sign detection requires large dynamic range which is caused by large difference in respiratory and heart induced displacements. Generated by the demodulation method and displacements, the higher order harmonics of RR near HR might appear and cause error in HR measurement. A respiration harmonics cancellation method is proposed to eliminate the interference. Experiments are performed by a 5.8-GHz non-contact Doppler radar vital sign detection system with an S12 Any-Touch ECG-Accurate Heart Rate Monitor as the reference to verify the method. HR is measured by searching the highest peak within the typical HR range in the frequency spectrum. Results of HR measurement with and without the respiration harmonics cancellation method are compared. When the harmonics of the respiration signal are strong, using the respiration harmonics cancellation method reduces the average error from 15.9% to 3.2%.