Joint 2D-DOD and 2D-DOA Estimation in Bistatic MIMO Radar via Tensor Ring Decomposition

In this letter, tensor ring decomposition (TRD) was proposed to estimate the two-dimensional direction-of-departure (2D-DOD) and two-dimensional direction-of-arrival (2D-DOA) in bistatic multiple-input multiple-output (MIMO) radar with uniform planar array structure. The advantages of TRD lie in its ability to flexibly establish a connection between adjacent two factors in a higher order tensor. To effectively utilize TRD, it is necessary to have a high-order tensor with real-value factors. Initially, an eight-dimensional (8D) tensor was derived through the delay cross-covariance tensor. Then, by employing tensor permutation and the generalized tensorization of the 8D tensor, a four-dimensional (4D) tensor with factor matrices containing the difference coarray of transmit and receive arrays was obtained. Subsequently, four unitary matrices were applied to perform real-valued processing on the constructed 4D tensor factor matrix. The TRSVD algorithm was then used to estimate the three-dimensional (3D) TR core tensors of the 4D real-valued tensor. Finally, the 2D-DOD and 2D-DOA were successfully estimated by utilizing the obtained 3D sub-tensors. Simulation results demonstrate the effectiveness of the proposed algorithm.