Low-Slow-Small Target Detection And Tracking Technology Based On Passive Radar

With the increase in the number of unmanned aerial vehicles(UAVs),the low-altitude security of cities has been seriously challenged.Unmanned aerial vehicles may become an accomplice to such problems as terrorist attacks,violation of citizens’privacy,and interference with civil aviation flight.Therefore,much attention has been paid to the specification,detection and tracking of "low-slow-small" UAVs.As the primary method of target detection,radar has achieved a high level of maturity.In recent years,passive radar has gained increasing attention due to its advantages of strong concealment,small size,and low cost compared to active radar.However,the use of passive radar for the detection of "low,slow,small" targets also has some limitations and drawbacks.For example,the echo signal energy scattered from targets with a low radar cross section(RCS)is weak,and long-term correlation accumulation of the echo signal and reference signal is required to detect the target.The slow movement speed and near-zero Doppler shift of "low,slow,small" targets make it difficult to effectively distinguish multiple targets in the frequency domain using two-dimensional matching filters.In complex scenarios such as cities,multipath clutter generated by ground and object reflections can interfere with and mask the target echo signal,making it impossible to detect the target.Based on the above background,this paper studies the "low-slow-small" target detection and tracking technology based on passive radar system,and innovatively carries out the following research work:1)To overcome the problem of poor performance of two-dimensional time-frequency matched filter caused by long-term accumulation of target Doppler frequency,a fast Fourier transform based piecewise correlation incoherent accumulation algorithm is presented,which overcomes the problem of correlation gain reduction caused by Doppler.On this basis,a high-resolution estimation algorithm is applied to estimate the target Doppler frequency with high frequency estimation accuracy.Both simulation and hardware experiments verify the feasibility of the algorithm.2)In view of the difficulty of engineering deployment of the multi-receiver passive radar target detection system in practical deployment,this paper designs a passive radar single-station target detection and tracking system based on a planar rectangular array.The system uses piecewise correlation and incoherent accumulation in time and antenna dimensions to accumulate target signal energy.The 2D direction of arrival estimation algorithm is used to estimate the target angle,and the digital beam shaping technology is used to enhance the target signal,so that the 3D coordinates and Doppler velocity of multiple targets can be accurately estimated.A multi-target tracking system based on Kalman filter is designed to detect-track data association and track filtering for multiple targets.The performance of the proposed system is evaluated through simulation experiments.3)In order to simulate the multipath interference problem in the real propagation scene and verify the purity of direct wave signal,a passive radar signal propagation environment in urban scene is established by using ray tracing simulation software.A parabolic antenna can be used to align the radiation source to obtain a pure reference signal that meets the detection requirements.A multipath clutter cancellation algorithm based on channel estimation and filtering is proposed to overcome the direct and clutter interference in the surveillance channel.This algorithm combines physical shielding to achieve multipath clutter suppression of the surveillance channel and ensure the target detection ability in multipath interference scenarios.