Research On Non-contact Vital Signs Monitoring Radar Based On Noise Suppression And Harmonic Tags

Among the vital sign monitoring,the contact monitoring scheme is more common,which uses cables and electrodes for measurement.But for burn patients and psychiatric patients,the use of contact measurement will bring pain and inconvenience to the subjects.The combination of Doppler principle and short-range detection radar technology for vital signs monitoring can not only make up for the above shortcomings,but also be used for search and rescue personnel in natural disasters.However,there are still many problems in the monitoring of vital signs with Doppler bio-radar at present.1)In this paper,the principle of Doppler radar vital signs monitoring is deduced and a prototype is built.Through the experiment,it is concluded that the common Doppler radar can detect the heartbeat and respiration signals,and extract the vital signs signals.However,there are still some problems,such as low signal-to-noise ratio and human random motion interference,which need to be solved.2)In view of the noise factors that affect the signal-to-noise ratio of vital signs,through the derivation of the formula of signal-to-noise ratio,and generating the relationship between the signal-to-noise ratio and each noise in MATLAB,it is concluded that the residual phase noise contributes a lot to the signal-to-noise ratio of vital signs.By locking the demodulation beat signal on the low-noise reference signal,a noise suppression scheme based on phaselocked is designed,and the corresponding prototype is built.By comparing with the phase noise of the above-mentioned Doppler radar signals,the noise of the prototype based on the noise suppression scheme is improved by 13 d B under the respiratory and heartbeat signal frequency;through the vital signs monitoring experiment,the prototype based on the noise suppression scheme is improved by about 8d B compared with the common Doppler radar prototype.So as to verify the effectiveness of the noise reduction scheme for improving the signal-to-noise ratio.3)Aiming at the problem of human body random motion interference that affects the signal-to-noise ratio of vital signs,the paper adopts the Doppler harmonic radar monitoring scheme based on tag to deduce the principle of harmonic monitoring,and builds the principle prototype.Through the experiment,it is concluded that the label placed in the heart can be offset by harmonic and fundamental wave reception,reduce human body random motion interference,By changing the label position,the change trend of normalized amplitude of heart rate signal corresponding to harmonic and fundamental wave reception,the respiratory signal and heart rate signal are extracted respectively to realize the separation of respiratory and heart rate signals.Thus,the effectiveness of the tag based harmonic radar scheme to reduce the random motion interference of human body is verified.