A dual-resolution unitary ESPRIT method for DOA estimation based on sparse co-prime MIMO radar

In this article, a novel structure of sparse co-prime multiple input multiple output (MIMO) radar is proposed. The proposed sparse co-prime MIMO radar employs one co-prime planar subarray (CPSA) as transmit array and multiple separated co-prime planar subarrays as receive arrays. The receive subarrays are deployed separately yielding long aperture baselines to improve the direction of arrival (DOA) estimation accuracies. A dual-resolution 2-D unitary ESPRIT method is derived for DOA estimation based on such sparse co-prime MIMO radar. First, a noncoherent unitary ESPRIT method is employed to yield coarse DOA estimates using the output signals of sparse co-prime MIMO radar noncoherently. Second, a coherent 2-D unitary ESPRIT method is derived to obtain fine DOA estimates and resolve DOA ambiguity utilizing the coarse DOA estimates. The DOA estimation in presence of unknown inter-subarray phase offsets is also addressed. Then an optimization method is developed to select the appropriate shift distances of the receive CPSAs. Finally, the Cramer-Rao Bound (CRB) of DOA estimation is given to evaluate the accuracy of the proposed estimator. Simulation results confirm that the 2-D DOA estimation accuracies of the proposed approach outperform unitary ESPRIT methods employing conventional co-prime MIMO radar and MIMO radar with rectangular arrays.