Research On Vital Signal Detection Technology With Millimeter Wave FMCW Radar

In recent years,non-contact radar detection technology has been able to achieve longterm and long-range detection for the breathing and heartbeat signals.Compared with contact-based detection methods,it brings a more comfortable and a faster experience to the human body,and it has gradually received attention in the field of radar sensing.Therefore,this paper extends the application of millimeter-wave radar to the field of health care.And this paper is based on the 77 GHz frequency modulated continuous wave(FMCW)radar to carry out the research of non-contact vital signs signal detection technology.The main research contents are as follows:Firstly,based on the signal parameter estimation principle of FMCW radar,the range,angle and velocity of the target detected by radar are estimated.Combined with the characteristics of human target signal,the human vital sign echo signal model is constructed.Then,by coupling range spectrum with time and coherent accumulation of multiple sweeps,the range-time diagram is constructed to determine the distance interval where the human target is located.Secondly,the methods of extracting vital sign information of human target are studied.After the influence of the DC offset of the circuit I/Q two channels is corrected by the circle center dynamic tracking algorithm,the arctangent demodulation technology combined with the extended differential and cross-multiply(DACM)algorithm is used for phase unwrapping to obtain the phase change information of the human vital signs signal caused by the heartbeat and breath.Thirdly,the harmonic and noise suppression methods of the heartbeat signal and breathing signal are studied.An orthogonal matching tracking algorithm based on compressed sensing is proposed to reconstruct the heartbeat and respiration signals to suppress spectral noise and harmonic interference.At the same time,a discrete wavelet transform is proposed to characterize the local characteristics of the heartbeat and respiration signals in the time and frequency domains.The above algorithm is combined with the related vital sign rate estimation method for experiments.The results show that the two algorithms effectively suppress the interference of harmonics and noise,and make the respiratory rate and heart rate detected by the radar coincide with the results measured by the mainstream wearable sensor to about 93%.Finally,the feasibility of multi-person vital sign signal detection is studied.Based on the realization of the aforementioned single human vital sign signal detection,it is expanded from a single person to multiple people.Through the use of Time Division MultiplexingMultiple Input Multiple Output(TDM-MIMO)virtual antenna expansion technology combined with digital adaptive beamforming algorithms to construct an range-angle map to separate multiple human targets.Then,the vital sign signal of each person is extracted by the above-mentioned extraction method of human vital sign signal information.The experimental results show that the proposed algorithm effectively realizes the extraction of multiple human vital signs.