Improved rare methods for DOA estimation in uniform circular arrays with unknown mutual coupling

Mutual coupling between array elements is known to seriously degrade the direction of arrival estimation performance of most super-resolution techniques. The rank-reduction (RARE) methods, which are variations of the MUSIC algorithm, can reduce these performance loss. But their spatial spectra may still be disturbed by the spurious peaks caused by unknown mutual coupling. In this work, we focus on uniform circular arrays and try to mitigate the influence of these peaks to the self-calibration performance of RARE methods. According to our analysis, the spurious peaks can be divided into predictable and unpredictable sets, and the former can be identified and located by utilizing the special structure of mutual coupling matrix. Based on this, three different methods are proposed to improve existing RARE methods. The validity and effectiveness of our analysis is demonstrated via numerical experiments.