Research On Target Detection Technology Based On Time Reversal

With the development of communication system,various new technologies emerge in endlessly,and the research of radar system has been widely studied in recent years.Radar detection is usually used in public and defense security fields,such as surveillance of air and sea level targets and air early warning.However,when radar is used to detect complex natural environment and the target characteristics are diverse,the detection characteristics of radar can not meet the specific requirements.In the complex natural environment,it is difficult for radar detection system to detect targets well.For example,"low,slow,small" target has the characteristics of low flight altitude,slow motion speed and small size,and low observability,which puts forward higher requirements for radar target detection.When radar detects in complex environment,multipath environment has adverse effects on radar detection.Time reversal technology has the characteristics of space-time focusing and has obvious advantages against multipath effect.In this thesis,time reversal technology is introduced into radar target detection to solve the problem of radar detection performance degradation in complex environment.Firstly,when the target is detected in a complex environment,the target signal is affected by the multipath environment and noise,and the target signal energy is low.Furthermore,when the target has the characteristics of low,slow,and small,and low observability,it will affect the radar detection performance.In response to the above problems,in the multiple input multiple output(MIMO)radar target detection problem,time reversal(TR)technology is added to improve the detection performance of the MIMO radar in a complex environment.The TR+MIMO detection system is proposed,and then the signal transmission process and target signal distribution are analyzed.Finally,the detector is designed based on the Nyman Pearson(NP)criterion and the approximate expression of the detection probability is calculated.Simulation results it shows that under the same signal-to-noise ratio,the proposed TR+MIMO system has certain advantages in target detection in complex environments.Secondly,in order to reduce the pressure of the traditional sampling theorem on signal processing,and improve the detection performance of radar in complex environment,therefore,a target detection scheme combining compressed sensing and time reversal is proposed.Through the time-reversed space-time focusing characteristics,reduce the impact of multipath effects and focus the target signal energy,and then design a new compressed measurement matrix that has certain noise reduction characteristics and does not need to reconstruct the signal,by directly processing compressed measurement samples for detection.Theoretical analysis and simulation results show that the scheme proposed in this thesis has advantages in anti-noise,reducing the influence of multipath environment and reducing the pressure of signal processing.