Resolution of signals by antenna arrays

Three problems associated with signal resolution by antenna arrays are examined: (1) the minimum angular distance between sources of signals resolvable by discrete arrays, (2) the maximum number of resolvable signal-sources having unknown power, and (3) the character of optimal processing for the resolution of near signal-sources with unknown power. It is shown that the resolving power of an array can exceed the Rayleigh limit and is determined by the output SNR, while the number of resolved signals depends on the number of spatial frequencies in the array aperture.