| The concept of Multiple-Input Multiple-Output(MIMO)radar was formally put forward at the international radar conference in 2004,which attracted the strong attention of domestic and international industry and academia,and became one of the mainstream development directions of the modern radar.The MIMO radar by using the MIMO technology in the field of communication,and according to the different configuration of the transmit-receive array of the MIMO radar,the spatial diversity gain and waveform diversity gain are fully utilized,then it has more advantages than the traditional phased array radar,such as more degrees of freedom,high spatial resolution and better target detection performance.With the increasing complexity of the environment,such as low interception rate and stealth technology,fast maneuvering characteristics of the target,as well as a variety of intentional or unintentional electromagnetic interference and so on.All these effects will cause the MIMO radar faces with the problem of small sample and color noise.At the same time,there are array errors in the practical application system,which will lead to the performance of traditional angle estimation methods to deteriorate or even fail to work.Therefore,it has great theoretical significance and application value to study the robust high-resolution estimation of target angle under the condition of limited snapshots,colored noise and array errors.In this paper,under the conditions of limited snapshots,array errors and colored noise,the tensor analysis is used as a mathematical tool to study the robust and high-precision angle estimation method of MIMO radar.The main contents of this paper are as follows:1.Establish the MIMO radar signal model,and sort out and analyze the current subspace angle estimation algorithms based on the covariance matrix decomposition in MIMO radar.This algorithm can be divided into two categories: the angle estimation algorithm based on spatial spectrum search and the angle estimation algorithm based on the subspace rotation invariance.The above two methods are introduced by theoretical analysis and simulation results,and their advantages and disadvantages are summarized,which will lay a good foundation for the following research.2.How to improve the target angle estimation performance by using the tensor structure and noncircular structure of MIMO radar in the case of small snapshots is studied.The first step is to create the tensor signal model of MIMO radar,analyze the multi-dimensional structure characteristics of MIMO radar signals,and then elaborate the MIMO radar angle estimation scheme based on the high-order singular valuedecomposition,which fully verifies the multi-dimensional structure characteristics of MIMO radar to improve the performance of target angle estimation.Then,taking into account the non-circular structure of MIMO radar signal,an algorithm of MIMO radar angle estimation based on the non-circular tensor analysis is proposed.The algorithm effectively captures the tensor structure and non-circular structure of the signal at the same time,which significantly improves the accuracy of target angle estimation.Finally,the simulation results show that the proposed algorithm is more effective and has better performance.3.Under the condition of gain-phase error,a scheme is discussed to improve the performance of the target Angle estimation by utilizing the multi-dimensional tensor structure characteristics of the signal.Firstly,the MIMO radar signal model under the condition of gain-phase error is established,and the ESPRIT-like algorithm based on the subspace decomposition is studied to realize the robust angle estimation under the condition of gain-phase error.Then in order to make use of the tensor structure of signal,the characteristics of signal in MIMO radar under the condition of phase error is analyzed,and a robust Angle estimation method based on tensor analysis under the condition of gain-phase error is proposed.The proposed algorithm can effectively suppress the effect of gain-phase error,at the same time increase the accuracy of the target Angle estimation by utilizing the tensor structure characteristics of the signal.Finally,better effectiveness and superiority of proposed method are proved by the simulation results.4.Under the condition of mutual coupling error and color noise,a scheme is studied to increase the recognition rate of target Angle estimation by utilizing the multi-dimensional tensor structure characteristics of the signal.In the first step,the MIMO radar signal model under the condition of color noise is formulated,and the Angle estimation method based on the tensor analysis of the time-domain cross-correlation is investigated.This method suppresses the influence of colored noise in the tensor domain via utilizing the non-correlated characteristics of colored noise in the time domain,meanwhile avoids the losing of the array aperture and obtains good angle estimation performance,but the algorithm does not consider the mutual coupling characteristics between transmit and receive antennas.Aiming at the coexistence condition of colored noise and mutual coupling error,a tensor signal model under the condition of mutual coupling error and colored noise is first constructed,and then an angle estimation algorithm based on robust tensor analysis is proposed.The proposed method can not only effectively eliminate color noise in the tensor domain,but also eliminate the influence of mutual coupling at the same time to obtain excellent Angle estimation results.Eventually,the simulation results show that the proposed algorithm is effective and superior. |
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