Coarray Tensor-Based Angle Estimation for Bistatic MIMO Radar with a Dilated Moving Receive Array

Utilizing sparse arrays is a very effective and commonly used method to enhance the degrees of freedom (DOFs) of multiple-input multiple-output (MIMO) radar. Unfortunately, as research on sparse arrays has matured, it has become difficult to greatly improve the DOFs by relying on array structure design only. Moreover, the existing angle estimation methods for sparse MIMO radar would process data under a matrix-based framework rather than the entire coarray tensor, thus suffering some loss in angle estimation performance. In this article, we extend the DOFs of MIMO radar by exploiting sparse array motion and propose an angle estimation method exploiting coarray tensor. First, we not only use sparse arrays at the transmitter and receiver parts of MIMO radar but also dilate the interelement spacing of the receive array on a moving platform. We set the transmitted signal as periodic, and further expand the DOFs and virtual aperture of MIMO radar by using the aperture synthesis technique introduced by array motion. Second, we build a self-correlation tensor model and reshape it to produce an optimal tensor with the highest DOFs that can be obtained under the uniqueness condition of parallel factor decomposition. Third, we theoretically analyze the achievable DOFs of the proposed method and show that the maximum number of detectable targets of bistatic MIMO radar can be increased to about three times. Simulation results verify the correctness of the theoretical analysis and demonstrate the superior estimation performance of our proposed method.