Study On Key Issues In Passive Radar Signal And Data Processing

Passive radars do not emit signals actively,they instead use the existing electromagnetic signals in the space to detect and track the potential targets.These signals are also termed as illuminators of opportunity(Io O).This technique has the advantages of reduced costs and system complexity,flexible and covert operation,no electromagnetic pollution,and the potential capability to combat stealth targets.Recently,passive radars have been attracting the interest of many researchers in the whole radar community.This paper investigates several key issues in the signal and data processing of passive radar,including ambiguity function analysis,direction of arrival estimation,the application of eight elements uniform circular antenna array(8-UCA)in passive radar,and target tracking in passive multi-static radar.The main content and contributions are summarized as follows:1.The paper studies the ambiguity function of the Inmarsat and Iridium satellites signals.The Io Os used in passive radar are usually communication and broadcasting signals.These signals are not dedicated for radar use,thus it is necessary to investigate the ambiguity function before they are used for radar purposes.The paper takes a detailed analysis of the ambiguity function of the Inmarsat and Iridium satellites signals.The paper first gives a brief introduction to the Inmarsat and Iridium communication systems,and then derives theoretically the ambiguity function of the two signals according to the signal protocols.Finally,the ambiguity function is analyzed according to the analytical formulation and the analysis is verified by simulation and real-life experiments.2.The paper studies the DOA estimation problems in passive radar.Passive radar usually has two physical channels,one termed as reference channel for collecting reference signals and the other one as surveillance channel for collecting target echoes.The target echoes are usually rather weak,sometimes even weaker than the noise.Clutter cancellation and range-Doppler cross correlation are necessary to increase the target signal to noise ratio(SNR)before DOA estimation.Typical DOA estimation methods assume the reference channel is free of target echoes,or the target echoes in the reference channel can be neglected.However,it will be shown in this paper the target echoes in the reference channel have significant influence on the DOA estimation.Target echoes in the reference channel can ‘go' to the surveillance channel during the process of clutter cancellation.These signals are integrated just as the already-existing target echoes in the surveillance channel.As a whole,the range-Doppler cross correlation results are changed.Typical DOA estimation methods did not take this effect into consideration,so their DOA estimation models mismatched with the reality,resulting in rapid degradation of the estimation performance.This paper takes a detailed analysis of such effect and proposes an improved method to mitigate the influence of target echoes in the reference channel on the DOA estimation.Simulation and real-life experiments demonstrate the effectiveness of the proposed method.3.The paper investigates the applications of 8-UCA in passive radar.8-UCA is a typical uniform circular antenna array with small aperture.This antenna is flexible and easy to deploy.The beam of this antenna is with a reasonable width and free of directional ambiguity and antenna gain loss.Therefore,8-UCA is rather suitable for passive radar use.This paper investigates several issues of this antenna when used in passive radar.Firstly,the paper studies the low-sidelobe multi-beam forming technique in 8-UCA.Typical beam forming methods get high sidelobe level;while this paper uses the partten synthesis method to obtain relatively low sidelobe level.Secondly,the paper derives the amplitude comparison based DOA estimation method in passive radar with the 8-UCA.The DOA estimation model is formulated and the influence of target echoes in the reference channel is analyzed.Finally,the paper studies the mutual coupling effect in the 8-UCA.A calibration method is proposed based on the compressed sensing technique.4.The paper studies the target tracking problem in passive multi-static radar.The goal of radar surveillance is to determine the position of the potential targets and even estimate their tracks.This paper investigates the target tracking problem in passive multi-static radar.An integrated track management method is proposed.The tracks are divided into four categories,i.e.initial tracks,tentative tracks,confirmed tracks and deleted tracks.A sophisticated track management rule is designed.Moreover,two multi-sensor joint probabilistic data association(MS-JPDA)methods are introduced for track maintenance,i.e.parallel MS-JPDA(P-MS-JPDA)and sequential MS-JPDA(S-MS-JPDA).The proposed method is tested sufficiently through a range of simulations and it is finally applied to a real FM based passive multi-static radar for aircraft detection and tracking.The real life results further demonstrate the effectiveness of the proposed method.