Design And Research Of Vital Sign Measurement System Based On Bioradar

With the development of the social economy and the increasing aging of the population,people are paying more attention to their own health.Promoting the construction of a healthy China and improving the health of the people have become an important goal of our country.Respiration and heartbeat,as important vital signs,can accurately reflect the physical health of the patient and the measurement of these has important clinical significance.Since noncontact monitor has little impact on patient with the advantage of miniaturization and lowcost compared with traditional contact detection method,research on non-contact monitor has attracted more insterests.Frequency modulated continuous wave(FMCW)radar is an important branch of the radar field.It has the characteristics of simple structure,high resolution,strong stability,and low transmit power.It is suitable for the bioradar system.This thesis researchs and designs a low-power,low-cost vital sign detection equipment based on FMCW bioradar for household scenarios.The main research contents of this thesis are as follows:First,investigate and summarize the relevant literature to explain the development status and trends of bioradar,and provide the normal adult vital sign parameter range to provide reference for follow-up research;through derivation and research on radar ranging and micro-motion detection theories,a bioradar system based on FMCW is proposed.The radar system plan analyzes the influencing factors of important indicators such as the range resolution of the bioradar and the sensitivity of micro-motion detection.Secondly,according to FMCW theory,design a bioradar hardware platform based on 24 GHz integrated quadrature transceiver chip;use phase-locked loop circuit to generate a high precision,low noise triangular wave modulated FMCW signal,which bandwidth is 500 MHz and repetition period is 10ms;a low-cost MCU realizes the sampling and processing of radar signals,and designs a high efficiency,multi-threaded bioradar hardware system control flow based on the interrupt system.Then,research the method of phase demodulation and time-frequency analysis in FMCW radar.study the demodulation performance of complex signal demodulation and arctangent demodulation in phase demodulation applications.Aiming at the quadrature imbalance problem of arctangent demodulation,a digital domain demodulation method based on FMCW system is proposed.In the time-frequency analysis,this thesis proposes a timefrequency analysis method with a narrow sample window to eliminate the influence of nonstationary signal,and improve the accuracy of frequency estimation through the method of data zero padding;this thesis introduces several frequency estimation methods,and construct an error function to analyze estimation accuracy and stability.Finally,this thesis proposes to use the respiration signal fitting method to eliminate the harmonics and intermodulation interference,combined with the triangle wave fitting method through algorithm simulation and experiment to verify that it can effectively improve the accuracy of heartbeat frequency estimation;proposes a respiration signal based on the least square method.The fitting method solves the shortcomings of the triangular wave method in the time domain nonlinear signal fitting;a piecewise fitting method is proposed to reduce the calculation and stability of the least square fitting method,so that it can be applied to a low-cost processor.Experiment shows that the bioradar based on the FMCW system designed in this thesis has high detection accuracy and strong stability.