DOA estimation using an extended spatial smoothing with coprime MIMO radar

The direction of arrival (DOA) estimation problem for a coprime multiple-input multiple-output (MIMO) radar is studied. To improve the angular resolution with limited elements, a sparse uniform linear transmitting array and a uniform linear receiving array are adopted in the MIMO radar, which lead to virtual sparse non-uniform linear array (SNLA) has large aperture. By setting the inter-sensor spacing to be mutually coprime integer multiples of half-wavelength, the angular ambiguity prblem caused by spatial subsampling is completely avoided due to the coprime property. To develop a DOA estimator for coherent targets, an extended spatial smoothing technique is proposed by taking advantage of the special array structure of the virtual SNLA, then the search-free root-multiple signal classification is extended for DOA estimation by taking the virtual SNLA as a part of a uniform linear array (ULA). Simulations results are provided to verify the good performance of the proposed algorithm.