Research And Design Of Vital Sign Detection System Based On FMCW Radar

With the gradual development of the economy,people’s quality of life and living standards are also increasing,and the demand for human health testing is gradually increasing.By detecting vital sign indicators such as respiration and heart rate,the current state of health of the human body can be determined and data can be provided to support subsequent treatment.Traditional medical devices often use contact sensors,which are not only limited in their application,but also have the potential to cause damage to the human body through direct contact with the body.Non-contact sensors are used in a wide range of applications as they do not require direct contact with the person to be measured and have the advantages of being interference resistant,low power consumption and small size.Among the various radar systems,FMCW radar can detect distance and thus achieve target extraction,while measuring the respiratory heartbeat frequency through phase changes is a more accurate detection method.The study of vital sign detection system based on FMCW radar is therefore of great importance.This thesis focuses on the work of separating respiratory heartbeat signals based on FMCW radar,with the following main research elements.Firstly,the current status of domestic and international research on various vital sign detection devices and vital sign signal extraction methods is investigated,and the advantages and disadvantages of existing technologies are analysed.Then,an improved vital sign signal model is established to address the problem of the presence of harmonic components in the respiratory and heartbeat signals in real situations.A detailed derivation of the working principle of FMCW radar is presented,and the principles of range,speed and angle measurement are analysed.A comparative analysis of single and multiple baseband receiver structures and operating principles is also presented.Then,multiple demodulation methods for radar baseband signals are studied.Through simulation and comparative analysis,extended DACM demodulation can effectively solve the problems of phase blurring and high frequency signal interference.Summarise the working principle and classification of digital filters,study and design the separation of vital sign signal based on IIR filters,and select IIR band-pass filters for high frequency noise filtering work.Finally,study and design vital sign signal separation algorithms based on empirical mode decomposition as well as improved methods,and compare and analyse the advantages and disadvantages of various empirical mode decomposition through simulation experiments.The vital sign signal separation algorithm based on variational mode decomposition is investigated and designed,and it is demonstrated through simulation experiments that it is more resistant to interference and extracts useful signals more intensively.By reconstructing the respiratory and heartbeat signals,the problem of multiple IMF components falling within the frequency band of the respiratory and heartbeat signals is solved.In addition,two sets of comparison experiments are designed and the experimental results proved that the system has better accuracy,and the VMD decomposition algorithm is selected for the separation of the respiratory and heartbeat signals based on the experimental results.The whole signal processing process is deployed to the hardware platform of the vital sign detection radar system designed in this thesis,and the signal processing flow is given.