Research On Radar-based Vital Signs Detection Technology

Respiration and heartbeat are the most important indicators of human vital signs.Compared with contact respiration and heartbeat monitoring,radar-based detection methods bring a more comfortable and quick experience,and are widely used in medical care,disaster relief,and anti-terrorism and stability maintenance.The frequency modulated continuous wave radar has both the ranging ability of ultra-wideband radar and the speed measurement ability of continuous wave radar,which can distinguish different targets by distance and reduce clutter interference.Therefore,This article uses TI's IWR1642 frequency-modulated continuous wave radar to detect non-contact vital signs by collecting chest vibration signals caused by respiration and heartbeat.First,according to the characteristics of vital signs and the principle of millimeter-wave radar,a mathematical model between the chest cavity vibration and the phase of the radar intermediate frequency(IF)signal is established,and the respiration and heartbeat detection process is given based on the mathematical model.Secondly,in view of the noise interference problem caused by the surrounding environment clutter,the radar IF signal preprocessing process is established to extract the phase signal.Moving target detection(MTD)is used to remove static clutter,the target range bin is determined by range Fourier transform,and phase unwrap and impulse noise elimination are performed to extract the true phase difference signal of the target.Then,in view of the noise and respiratory harmonic interference in the phase difference signal,the band-pass filter and the variable modal decomposition(VMD)algorithm are combined to extract the respiratory and heartbeat signal.In addition,in order to improve the estimation accuracy of heartbeat frequency,this paper makes full use of target information and designs a millimeter wave radar vital sign extraction algorithm based on multi-range-MUSIC.The algorithm takes advantage of the feature that the same target contains similarity information in multiple range bins,and uses the phase signals of multiple range bins to estimate the respiratory and heartbeat frequencies at the same time.By comparing the estimated frequency of the multi-range-MUSIC algorithm with the reference frequency of respiration and heartbeat,the effectiveness of the algorithm is proved.Finally,use IWR1642 and DCA1000 data acquisition board to test the performance of the method proposed in this article.Experiments show that within the detection range of0.3-2m,the method in this paper can effectively suppress noise and harmonic interference,and the median heartbeat error does not exceed 2 times/minute,and under the interference of the target's own micro-motion,the median heartbeat error does not exceed 2.3times/minute.