I. Introduction
Target localization and detection in the near- field region is a hot topic in the field of array signal processing, as this technique has been widely applied in science and engineering fields, including automatic driving [1], indoor positioning [2], and shallow geophysical survey [3]. Similar to conventional approaches applicable for the far-field target, it is possible to achieve a high resolution by utilizing the multiple-input-multiple-output (MIMO) technique in near-field related applications, owing to the diversity gain from the MIMO system [4]. Even though there are similarities both in far- field and near-field applications, it will experience the problem of performance degradation if directly extending the thoroughly studied far- field applicable approaches to near-field situations, because the wavefront can't be considered as a planar wave in near-field cases. Therefore, it is necessary to further investigate this problem.