Research On Life Signal Detection Method In Complex Environment Based On Millimeter Wave Radar

Millimeter wave radar has been commonly utilized in the field of life signal detection,such as driver status monitoring,patient cardiopulmonary signal detection,and home health monitoring.Currently,the commonly utilized millimeter wave radar in the field of life signal detection include ultra-wideband(UWB)radar,frequency modulated continuous wave(FMCW)radar,and continuous wave(CW)radar.FMCW radar has the capability of both CW radar velocity mearsurment and UWB radar ranging,and is very sensitive to tiny movement,hence FMCW radar is used to study the detection of life signal in complex environments in the paper.In the process of life signal detection,there is no guarantee that the measured target remains stationary state during the whole process,and random body movement(RBM)generated by the measured target distorts the phase of the life signal and produces phase noise,which makes it difficult to effectively identify and extract the life signal.With the increasing number of scenes equipped with FMCW radar,radar mutual interference will become a problem that seriously affects the extraction of life signal.Radar mutual interference can raise the noise floor level,causing the life signal to be buried in noise.Therefore,the life signal detection in the case of RBM and the life signal detection in the case of radar mutual interference are studied in the paper.The main work of this paper is as follows:Firstly,the environmental interference of life signal detection by millimeter wave radar is analyzed.For environmental clutter interference,the characteristics of environmental clutter generated by fixed objects and moving objects are analyzed.The interference generated by fixed objects can be described by Gaussian distribution,and the interference generated by moving objects can be described by the combination of amplitude distribution and power spectrum distribution,the distribution characteristics of environmental clutter interference are verified by simulation experiments.For RBM interference,it is analyzed that the RBM interference generated by the measured target is superimposed on the life signal,resulting in the phase distortion of the life signal,the effect of RBM interference on life signal phase is confirmed by experiment.For millimeter wave radar intereference,radar mutual interference is mainly studied in the paper.The models,characteristics and types of radar mutual interference are analyzed,it can be seen through simulation experiment that life signal is buried by the noise of radar mutual interference.Secondly,life signal detection under RBM interference is studied,and a method based on autoregressive model(AR)is proposed to remove RBM interference and extract life signal.Firstly,the front-end processing methods of life signal are analyzed.Then the model of RBM interference is established and analyzed.Finally,the RBM interference is removed through the AR model.It can be seen from the experimental results that the AR model can repair the phase of the life signal and eliminate the phase noise,so that the life signal can be effectively identified and extracted.Thirdly,the life signal detection of millimeter wave radar under mutual interference is studied,and an improved pruned exact linear time(IPELT)algorithm and AR model are proposed to suppress the interference signals,and variational mode decomposition(VMD)algorithm is used to remove the residual noise to extract the life signal.Firstly,the position of the interference signal is determined by the IPELT algorithm.Then,the AR model is used to suppress the interference signal.Although the interference signal is suppressed,there is still residual noise in the life signal band.Finally,VMD algorithm is used to eliminate residual noise in the life signal to extract life signal.The experimental results show that the IPLET algorithm and AR model can effectively suppress intereference signal,and VMD algorithm can significantly remove residual noise and extract vital signal.