Research On Detection And Tracking Technologies For Dim Targets In Radar

The developments of stealthy aircraft and cruise missiles bring great challenge to modern radar systems.It is urgent to solve the dim target detection and tracking problem in radar systems.Focusing on this problem,the following topics have been studied: difference beam aided target detection in monopulse radar,joint detection and tracking of a single point target with application to monopulse radars and pulse Doppler radars,joint detection and tracking of a single extended target with application to stepped-frequency radars,track-before-detect of unresolved targets in monopulse radars.The main contents are summarized as follows.Chapter 2 studies difference beam aided target detection in monopulse radar.The principle of monopulse angle estimation is introduced using a phase monopulse radar,and based on which,the signal model is established.Assuming the monopulse ratio is known,a generalized likelihood ratio test(GLRT)is derived.Simulation results show that high detection gain can be obtained when precise targeting information is available.A practical dual-stage detector is proposed assuming the monopulse ratio is unknown.Results of experiment via simulation and anechoic chamber show that performance of the dual-stage detector is superior to that of the classical detector,especially when the deviation angle is nearby the half-power point.As a result,the half-power beamwidth is increased equivalently in the detection performance sense,which is closely related to the scanning speed.Chapter 3 studies joint detection and tracking of a single point target.Bayes filtering using random finite set is introduced together with analytic expression of the Bernoulli filter.A new particle implementation of the Bernoulli filter is proposed.The proposed filter is applied to the monopulse radar.Through simulation,capture and close-loop tracking of a target in low signal-to-noise ratio scenarios is realized with a monopulse radar.Application of the filter to the pulse Doppler radar is presented,in which joint target detection,tracking and ambiguity resolving is realized.The method has solved the problem that classical ambiguity resolution techniques can not work in dense false alarms scenarios.Chapter 4 focuses on joint detection and tracking of a single extended target.The analytic expression and particle implementation of the Bernoulli extended target filter are derived based on the Poisson extended target model.the computational complexity of the proposed algorithm is much smaller than the existing method.Several examples are presented using different target extension models in the simulation part.The filter is applied to a typical wide band radar: the stepped-frequency radar.Simulation results show that joint target detection,tracking and range-velocity decoupling is realized.A Bernoulli filter for sensors with point spread function is proposed.The memory usage and transportation bandwidth are saved in comparison with the unthresholded methods.The Simulation results demonstrate the effectiveness of the proposed algorithm.Chapter 5 studies track-before-detect of unresolved targets in a monopulse radar.The signal model for unresolved target track-before-detect in a monopulse radar is established based on Swerlling II target model and the assumption that at most two targets are present.A particle filter based multi-target track-before-detect algorithm is developed for the problem.Two typical scenarios are used to evaluate the performance of the algorithm through simulation.Simulation results show that the proposed algorithm can effectively estimate the target number and the target states.Chapter 6 presents the conclusion of the dissertation,while the possible further works are pointed out.