| Passive bistatic radar utilizes the signal emitted by non-cooperative illuminator to achieve target detection,since it does not radiate electromagnetic signals,it has strong battlefield survivability and can effectively make up for the shortcomings of traditional monostatic active radars in anti-jamming and anti-stealth,so it is very promising in military applications.However,the illuminator used in the passive bistatic radar system we researched is a kind of phased array radar with agile waveform parameters,and its complex waveform modulation form also brings many challenges to the signal processing of the passive bistatic radar system.Based on the prototype of the passive bistatic radar developed by our team,this paper focuses on the practical signal processing problems in the passive bistatic radar system,including the methods of time-frequency parameter synchronization and coherent integration,which could provide technical reference for the performance improvement and practical application of the passive bistatic radar system.The main contents of the paper are summarized as follows.In Chapter 2,in view of the difference between bistatic radar and monostatic radar in respect of location principle,radar equation,detection range,range resolution and velocity resolution due to the geometric relationship between the receiver and transmitter,this paper makes an in-depth analysis through geometric model,formula derivation and simulation experiment.Then,the characteristics of the non-cooperative phased array radar emitter are studied,and the performance of the signal with agile waveform parameters is analyzed using ambiguity function.At last,the signal processing flow of the passive bistatic radar system is introduced,and the problems brought by waveform parameter agility in time-frequency parameter synchronization and coherent integration are analyzed.In Chapter 3,aiming at the problem of time-frequency parameter synchronization of passive bistatic radar system based on waveform parameters agile radar,a method suitable for engineering application is proposed.In this method,the problem of time-frequency synchronization is divided into two steps: the preparation of direct wave parameter template library and the parameters estimation method based on template matching.Firstly,aiming at the feature that the direct wave signal contains multiple LFM components,the parameter estimation method based on LVD is used to estimate the parameters of a large number of direct wave signals,combined with the statistical analysis method,the parameter template library of carrier frequency,bandwidth and pulse width of the direct wave signal is built.Then,a time-frequency synchronization method based on template matching is proposed.This method combines the template matching,dechirp algorithm and CLEAN algorithm,which can quickly and accurately extract the pulse width,carrier frequency,bandwidth and time of arrival of the direct wave signal.The effectiveness of the method is verified by the measured data processing.In Chapter 4,aiming at the problem of coherent integration of frequency agile signal of passive bistatic radar,firstly,the signal model of moving target echo is constructed,and the problems caused by carrier frequency agility are obtained based on the signal model.Then,a fast coherent integration method combining Radon algorithm and nonuniform fast Fourier transform(NUFFT)based on low-rank approximation,i.e.,Radon-NUFFT,is proposed.In this method,the RCM is solved by Radon algorithm via target trajectory searching,the non-uniform phase fluctuations is solved by the NUFFT based on low rank approximation.The effectiveness of the proposed method is verified by simulation experiments.In Chapter 5,aiming at the problem of coherent integration of time domain parameter agile signal of passive bistatic radar,firstly,the signal model of moving target echo is constructed,and based on the signal model,the problems caused by PRI agility and pulse width agility in coherent integration are analyzed,and the problem of non-uniform phase fluctuation between pulses caused by PRI agility is transformed into the problem of spectral analysis of non-uniform sampling signal.Then,aiming at these problems,a coherent integration method based on Radon-IAA is proposed,which could improve the coherent integration gain and estimation accuracy of target speed parameter through local refinement analysis based on IAA.Finally,the effectiveness of the Radon-IAA method is verified by simulation experiments,and the performance of the proposed method in respect of multi-target detection,parameter estimation accuracy and target detection probability is analyzed. |
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