Research On Target Detection Technology Based On Airborne Pulse Passive Bistatic Radar

Traditional radar for target detection needs to transmit signal by oneself.Airborne pulse passive bistatic radar system can overcome this deficiency of traditional radar by using noncooperative radar to transmit signals,which is not easily detected and has the advantages of strong anti-interference capability and easy distance measurement.The elevation of the airborne receiver platform enables wider detection of range,convenience in action and other advantages.So the system of radar has the value of in-depth research.However,when the airborne radar detects sea target,it is in down-looking state and there will be strong clutter and direct wave signals.These signals will affect the target detection performance of radar.Therefore,this paper carries out theoretical and simulation research on target detection of airborne pulse passive bistatic radar system from five areas,namely,signal modeling,clutter modeling,direct and clutter suppression,and target detection.Aiming to improve the target detection performance of this radar system.The main work of this paper is:(1)The signal modeling and simulation of airborne pulse passive bistatic radar under the ground-space configuration.First,the geometric structure of the passive bistatic radar with fixed radiation source and airborne receiver is established,and the signal model of the multireceiver channel with LFM signal as the radiation source transmitting signal is studied.Then,the scattering cell of the receiver irradiation range is divided and the grazing angle of each scattering cell is calculated to establish the sea clutter model under different antenna array configurations of the receivers.Finally,the space-Doppler frequency distribution characteristics of the clutter are analyzed.The simulation yields that the clutter has a linear relationship between clutter space and Doppler under side-looking array,and the clutter has non-dependence;the space distribution of clutter is not linear with Doppler under slant-looking array and forward-looking array,and the distance dependence of the clutter is negatively correlated with the distance of bistatic radar.(2)Direct wave and clutter suppression techniques of airborne pulse passive bistatic radar.In order to obtain the target echo signal of interest,the direct and clutter signals in the receiving system need to be processed,and the adaptive beamforming algorithm of linearly constrained minimum variance(LCMV)and the space-time adaptive processing(STAP)algorithm are proposed.Then,the computational effort of the space-time adaptive filtering is reduced by introducing the dimensionality reduction processing of the joint three-Doppler channel adaptive processing(3DT-STAP)and joint domain localized adaptive processing(JDL-STAP).Finally,the adaptive beam formation under different array element numbers is analyzed,and the results show that the notch can be formed accurately in the direct wave direction when the array element number is 8.By comparing the performance parameter related to STAP processing simulation,it is found that the performance of JDL is inferior to 3DT and the error of 3DT processing and full STAP performance is smaller.The notch formed under the different antenna array configurations processed by 3DT-STAP is consistent with the previous clutter simulation,which also proves the effectiveness of 3DT-STAP.The processing of the direct wave as well as the clutter signal can provide the prerequisite for the subsequent target detection.(3)OSSVI-based constant false alarm detection algorithm of airborne pulse passive bistatic radar.Firstly,three clutter background of uniform clutter,multi-target interference and clutter edge are introduced.Then,an adaptive strategy OSSVI-CFAR detector is proposed,which is a new detector based on the composition of the variable exponential constant false alarm(VI-CFAR),ordered statistics(OS-CFAR)and the switching constant false alarm(SCFAR).OS-CFAR is used instead of the cell averaging constant false alarm(CA-CFAR)in the presence of target interference in the front/back windows,and S-CFAR is used instead of the smallest of constant false alarm(SO-CFAR)in the case of both front and back windows with interference targets.Through comparative simulation analysis,it is obtained that OSSVI-CFAR is second only to CA-CFAR in uniform environment;in multi-target environment,the detection performance of OSSVI-CFAR reaches 99.32% when there is interference target only on one side,and the detection performance is 99.25% when there is interference target on both sides;the false alarm probability is controlled around 0.005 at the edge of clutter which proves it’s false alarm control ability.The angle,distance and Doppler information of the target can be seen from the distance-Doppler map and angle-Doppler map processed by OSSVI-CFAR,which are consistent with the information of the target injected in advance,verifying the feasibility of the method.