New Transmit-Receive Array Configurations for the MIMO Radar With Enhanced Degrees of Freedom

This letter proposes a new sensor array geometry for the multiple-input multiple-output (MIMO) radar with enhanced degrees of freedom (DOFs) to improve the direction-of-arrival (DOA) estimation performance. The configuration utilizes the sum coarray of the difference coarray (SCDC) method to achieve the increased DOFs, which subsequently provides a wider virtual array aperture (VAA). The array geometry produces a resultant hole-free uniform linear array (ULA) by effectively increasing the inter-sensor spacing of the transmitter. The nested-coprime array with displaced subarrays (CADiS) governs the transmitting sensor locations, whereas the receiver follows a new three-level antenna array scheme, with its initial level designed using the nested-CADiS structure. This receiving approach is easier to realize and applicable for any sparse array producing a hole-free difference coarray. The element positions and DOFs are determined analytically by the closed-form expressions. Monte-Carlo simulations are conducted, and the results of estimating the DOA of several sources in under-determined conditions, Cramer-Rao bound (CRB) performance, and the achievable DOFs validate the effectiveness of the proposed configuration.