Microwave Coincidence Imaging Technique Research For Moving Target

Microwave Coincidence Imaging(MCI)technology has obtained wide-ranging discussions and broad investigations since the concept of optical coincidence imaging was introduced to microwave field.Based on the in-depth study of the radar resolution and thorough analysis of the effecting parameters of imaging quality,the microwave coincidence imaging techniques are studied deeply for moving target.The radar resolving performance of MCI radar is firstly studied,which focuses on the basic problems of radar resolution based on correlation function and average ambiguity function.With the help of correlation function,the effects on resolution performance are investigated for the array signals,and the radar resolving limits are derived.With the study of average ambiguity function,the analytical expressions of delay-Doppler average ambiguity function and spatial average ambiguity function are provided,which demonstrate the relationship between the resolution and radar parameters including waveform,signal bandwidth,array configuration,array aperture size and observation time.Simultaneously,the radar resolving limits are deduced based on the correlation theory.Chapter 3 is devoted to the study of the relationship between radar imaging qualities and the effecting parameters.Firstly,the relationship between effective rank and atom correlation performance is built for the coincidence matrix(i.e.,the reference matrix which is formed of the superimposing of transmitting signals in the imaging region.).The explicite expressions of the effective rank with these impacting parameters are derived,which are used as the imaging quality evaluation index.Secondly,the parameterized model of MCI radar is proposed for the moving target,which is used for the deduction of imaging error up-limit introduced by targets' motion.Thirdly,the noises are introduced into the MCI model,and their effects on imaging quality are investigated.Finally,the main imaging algorithms are studied and their performances are compared on stability and complexity,which provides the basic guidance for the selection of imaging algorithms in the following parts.Two kinds of imaging algorithms are designed for the moving target in the scenario of stationary observation platform in chapter 4.For moving target,the error between the calculative temporal-spatial stochastic radiation field(TSSRF)and the real TSSRF is introduced by target's motion.The imaging plane should be updated in real time so that the TSSRF can be computed correctly.Therefore,two sets of imaging schemes are proposed and investigated in detail for this scenario.One of the imaging process is presented as follow: the target velocity is firstly estimated by velocity measurement technology of wideband radar.The imaging plane is then considered to be stationary after the compensation of targets' motion with the knowledge of velocity.Finally,the imaging technique for the stationary target can be used to recovery the moving target.The other proposed imaging process is given as follow: the motion parameters are modeled as the unknown components in the coincidence equation,which are to be estimated together with the reflecting coefficients of target.The imaging problem thus becomes a multi-dimensional joint parametric estimation problem for moving target in MCI equation.In addition,the effects of system parameters on imaging performance for the imaging algorithms are studied.The imaging algorithm is investigated for moving target in the scenario of moving observation platform.Chapter 5 is devoted to focus on the extraction of target angle information and tracking algorithm for moving target under the precondition of keeping the MCI radar unchanged.The MCI procession is firstly modeled for moving target with moving observation platform.The effects of estimation error introduced by targets' position and motion are then analyzed.The results illustrate that the position estimation error is the main reason in reducing imaging quality but not the velocity estimation error especially for the low-speed target in short imaging time.The demands for tracking precision is given for keeping the imaging error on a certain degree.Based on this precondition,the imaging scheme of target tracking followed with reconstruction is provided.Because of the particularity of MCI radar system,it is difficult to capture the targets' angle information directly.Therefore,the Multiple signal classification(MUSIC)method,Spectral correlation-signal subspace fitting(SC-SSF)method and Multi-cycle focusing(MCF)method are proposed to extract angle information in the scenario of MCI radar.Moreover,the problem of angle ambiguity existed in these methods is discussed and the deblurring methods are proposed by moving the array.The innovative points and the future work of this dissertation are summarized in chapter 6.