Blind Target Detection Methods In MIMO Radar Based On Linear Shrinkage And Random Matrix Theory

Multiple-Input Multiple-Output(MIMO)radar,as a new type of radar system,has received extensive attention of domestic and foreign scholars.MIMO radar has a great application prospect since it can effectively overcome the disadvantages of the traditional radar system and significantly improve the target detection performance.At present,a series of methods have been put forward for MIMO radar,such as Neyman-Pearson detection,generalized likelihood ratio detection,etc.These methods have improved the detection performance in different degree,however,they all need to know or estimate in advance the priori information of the noise variance,target scattering matrix,etc.Therefore,they belong to the non-blind detection methods.Moreover,these methods usually assume that the number of snapshots is much greater than the number of arrays,so the sample covariance matrix of the received signal can be used as the maximum likelihood estimation of the statistical covariance matrix.With increasingly towards the application of MIMO radar technology,large arrays system has become an inevitable development trend.In a large array system,when the number of arrays can be compared with the number of snapshots,even larger than the number of snapshots,the eigenvalue distribution range of the sample covariance matrix will change.The traditional target detection methods have been no longer applicable in this case.Aiming at the problems above,the shrinkage estimation technique of the high dimensional covariance matrix and the large-dimensional random matrix theory have been used as tools.The blind target detection methods in MIMO radar have been deeply studied in this paper.The work is supported by the project “Robust target detection and estimation for MIMO radar based on large dimensional random matrix theory”(No.61371158),which is supported by the National Natural Science Foundation of China.The creative works of this paper are as follows:In allusion to MIMO radar system with large arrays in which the number of arrays is comparable in magnitude to the number of snapshots,a blind target detection method based on linear shrinkage-standard condition number(LS-SCN)is proposed by combining with the shrinkage algorithm of high dimensional covariance matrix estimation and the large-dimensional random matrix theory.By solving the optimization of the sample covariance matrix in the large dimensional regime and utilizing the M-P law,the relationship between the detection threshold and the shrinkage coefficient is derived.Single-target and multi-target detection algorithms based on LS-SCN are presented respectively.The method isn't sensitive to noise changes and suitable for large array systems,which needn't know the priori information of noise variance,target scattering matrix and target location.In view of snapshot-starving environment,a blind multi-target detection algorithm in MIMO radar based on shrinkage coefficient detection(SCD)has been proposed by analyzing the distribution characteristics of the linear shrinkage coefficient.And then,in order to reduce the computational complexity,the shrinkage coefficient has been simplified,and the ratio of eigenvalue moment(EMR)has been selected as test statistics.So a blind multi-target detection algorithm in MIMO radar based on EMR has been proposed.The simulation results show that two algorithms significantly improve the performance of blind multi-target detection in MIMO radar under snapshot-starving environment.In traditional target detection methods,the ideal white noise background is usually considered.However,in practice,some reasons such as array mutual coupling,etc,may lead to correlated noise.Aiming at this problem,the correlated noise model has been established in this paper.A blind target detection algorithm in MIMO radar based on random matrix theory has been put forward under correlated noise.This paper has derived the asymptotic eigenvalue distribution of the sample covariance matrix by using mathematical tools,such as multiplicative free convolution S-transform,additive free convolution R-transform and Stieltjes transform,etc.By combining the test of standard condition number,the decision threshold has beencalculated.Therefore,the blind target detection in MIMO radar under correlated noise has been achieved.