DOA Estimation of Mixed Circular and Noncircular Sources Using Nonuniform Linear Array

In this article, an algorithm for accurately estimating the directions-of-arrival (DOAs) of mixed circular and noncircular signals with a nonuniform linear array is devised. Via applying coarray interpolation on the difference and sum coarrays, we first formulate two nuclear norm minimization problems to reconstruct an augmented covariance matrix and an augmented unconjugated covariance matrix, respectively. Based on the reconstructed matrices, we further build the extended covariance matrix in the coarray domain. Finally, we construct several spectral functions to successively estimate the DOAs of the nonstrictly noncircular, strictly noncircular, and circular signals. Unlike the existing schemes, the proposed algorithm can identify accurately circular, strictly noncircular, and nonstrictly noncircular signals. Numerical results demonstrate the superiority of the proposed algorithm over existing techniques.