Sparse Enhancement of MIMO Radar Exploiting Moving Transmit and Receive Arrays for DOA Estimation: From the Perspective of Synthetic Coarray

In this paper, we consider monostatic sparse MIMO radar with the transmit and receive arrays mounted on a moving platform and exploit array motions to increase the number of degrees of freedom (DOFs) and continuous lags for direction of arrival (DOA) estimation. A synthetic sum coarray of difference coarray (SSCDC) concept is proposed to interpret the virtual arrays collected from the sparse MIMO radar with multiple array positions, followed by a dilated sparse MIMO radar family by enlarging the transmit and receive array geometries of the existing sparse MIMO radar. Properties of the dilated sparse MIMO radar in terms of the uniform SSCDC and the number of continuous lags related to array motions are derived. To further increase the DOFs, a uniform sampling moving (USM) strategy is introduced and then a nested sampling moving (NSM) strategy is designed by utilizing the sparsity of array motion. Furthermore, theoretical performance of the moving sparse MIMO radar is evaluated via the synthetic coarray Cramer-Rao bound (CRB). Closed-form expressions for uniform DOFs for the dilated sparse MIMO radar with the proposed moving array strategies are derived and numerical simulations are provided to demonstrate their performance.