Two-step MUSIC algorithm for improved array resolution

High resolution methods such as MUSIC fail to separate closely spaced sources in difficult contexts (low SNR, short sample size,...). Halder et al.(1997) have applied an interleaving technique to improve the resolution as well as the performances in the case of frequency estimation. Here we extend this work and deal with the application of this technique to array processing. We aim to estimate closely spaced DOAs. After a first estimation with MUSIC, a second step of the algorithm consists in refining the angle resolution using downsampled covariance matrices together with a joint estimation strategy (JES) similar to that proposed by Gershman et al. (1996). This method improves MUSIC performances especially for low SNRs. Simulations examples are provided to illustrate the performance of the proposed method referred to as two step-MUSIC (TS-MUSIC).