Conditioning of restricted Fourier matrices and super-resolution of MUSIC

This paper studies stable recovery of a collection of point sources from its noisy M+1 low-frequency Fourier coefficients. We focus on the super-resolution regime where the minimum separation of the point sources is below 1/M. We propose a separated clumps model where point sources are clustered in far apart sets, and prove an accurate lower bound of the Fourier matrix with nodes restricted to the source locations. This estimate gives rise to a theoretical analysis on the super-resolution limit of the MUSIC algorithm.