High Velocity Targets Detection Technology Based On Opportunity Illumination

Passive radar is radar detection system that uses electromagnetic background signals to illuminate targets in a specific airspace to obtain target-related information.It is also called opportunity radar,passive coherent location or passive covert radar.Passive radar systems have been developed the sources of illumination,including analog television signals,FM(Frequency Modulation)radio signals,digital audio broadcasting,digital video broadcasting,communication satellites and GPS(Global Positioning System)satellites.Since the target echo signal is usually a weak signal covered by noise,the detection performance of the radar can be improved by increasing the coherent time.However,for high-speed targets,the target echo will occur range migration and Doppler frequency migration with the increase of coherent time,causing a loss of coherent integration gain.Effectively solving the problem of target echo migration is one of the keys to efficient detection for high-speed moving targets by passive radar.This thesis specifically carried out the following aspects of work:1.The basic theory of high-speed moving target detection technology based on passive radar is introduced.Firstly,a passive bistatic radar system model is established,and the radar detectable range is analyzed from the perspective of energy.Secondly,the key technologies of passive radar were introduced,including direct wave and multipath suppression technology,target detection technology and target tracking technology.Thirdly,according to the characteristic of high-speed moving targets,the target echo model under the passive radar is established,and the simulation proves that the traditional MTD method can not achieve effective integration of high-speed moving targets.2.The method of coherent integration of high-speed targets in passive radar is studied.Radon-Fourier transform and Keystone transform are two methods to achieve target echo range migration correction,and the validity of algorithm is verified by simulation and measured data.Keystone+Dechirping based method can effectively correct the range migration and Doppler frequency migration of the target echo.3.A high-speed moving target detection method based on range framing is proposed.In this method,under the condition of known detection area,the echo signals are divided into frames by dividing the distance gates,and the Radon-Fourier transform and Keystone transform are used to solve the target's range migration,which can increase the signal processing real-time performance of the radar system.4.A multi-channel integration method based on DVB-S(Digital Video BroadcastingSatellite)passive radar is proposed.Firstly,according to the structure of multiple transponders of digital TV satellites,the echo characteristic of multi-channel signals are analyzed.Then use Keystone transform or Radon-Fourier transform to correct the range migration of echo signal in each channel.The structure based on Radon-Fourier transform reduced the Doppler frequency interval search compared to the structure based on Keystone transform,and the signal processing flow is more efficient.