Robust Off-Grid DOA Estimation for Noncircular Signals With Virtual SDCA

In this letter, a robust off-grid direction of arrival estimation algorithm based on sum-difference co-array (SDCA) under nonuniform noise environment is proposed for noncircular signals. The proposed method combines the coprime array (CA)’s features with those of noncircular signals, and it is further expanded to produce an SDCA with a larger array aperture. The off-grid data model is obtained after the spatial discretization. And the variational signal model is reconstructed by using the covariance vector with nonuniform noise. And then, the grid refine process based on the expanded covariance vector model is derived, which enables high-resolution DOA estimation. The proposed method can realize underdetermined DOA estimation with small physical array elements. Numerous simulations are run to make sure the suggested strategy is reliable and strong in nonuniform noise environments.