Near-field Target Localization Methods For MIMO Radars Based On Joint Parameter Estimation

Recently, as the key technologies of multiple-input-multiple-output(MIMO)radars, target localization and parameter estimation have recently drawn wide attention in many military and civilian applications. Currently, many methods have been put forward for the direction-of-departure(DOD) and the direction-of-arrival(DOA) estimation in MIMO radars, mainly including Capon-based algorithms,reduced-dimension MUSIC, ESPRIT, ESPRIT-MUSIC, polynomial root finding and some joint estimation methods for different environment. However, the existing target localization algorithms using DOD and DOA estimation are based on the assumption that the target is located in far field and the echo wave front of the target is plane wave.In the scenario that a target enters into the Fresnel region of the transmit or receive array apertures of a radar system, the plane-wave approximation to the spherical wave-fronts will lead to serious performance degradation. Therefore, it is of significance to improve the accuracy of near-field target localization for MIMO radars.In this paper, the near-field localization methods of MIMO radar based on joint parameter estimation is deeply studied. The research background of MIMO radar and the research status of near-field source localization technology are first reviewed, and the mathematical tools used in the research are introduced. Then, three near-field target localization algorithms based on joint parameter estimation in MIMO radar are respectively proposed for monostatic MIMO radar and bistatic MIMO radar, and simulations of these algorithms are carried out. Finally simulation results demonstrate the effectiveness of the algorithm.The research work of this paper is supported by the National Science Fundation Project(No:61371158). The innovative research work in this paper is as follows.The joint diagonalization technology of far field is combined with the localization for near-field target in MIMO radar, then a near-field localization algorithm in monostatic MIMO radar based on joint diagonalization method is proposed. In this algorithm, the cross shaped transceiver arrays model is employed to estimate three dimensional parameters. It can effectively solve the problem ofnear-field target localization in monostatic MIMO radar, and the accuracy is high.The near-field parameter estimation algorithm based on the traditional two order statistics and the subspace algorithm are combined, then near-field target localization algorithm based on four-dimensional parameter estimation is proposed for bistatic MIMO radar. The algorithm is based on centro-symmetric transmit and receive arrays,four cross-covariance matrices of the received array data are employed and the eigenvalues and eigenvectors of two constructed matrices are obtained to estimate DOD, DOA, the range from transmitter to target, then the range from target to receiver is obtained by using the spectral peak search. The algorithm only needs five transmit arrays to solve the problem of the near-field source localization, and it can accurately estimate the four dimensional parameters of the near-field target and the four parameters can be paired in the case of multiple targets.Since that above parameter matching process is complicated and spectrum peak research increases the running time, an improved algorithm for near field localization in bistatic MIMO radar is further proposed. The improved algorithm only needs three transmit arrays to locate the near-field source, which further simplifies the complexity of the system, and the algorithm avoids spectral peak search, and does not have the problem of phase ambiguity.