SIMPLE APPROXIMATIONS TO THE CRAMER-RAO LOWER BOUND ON DIRECTIONS OF ARRIVAL FOR CLOSELY SPACED SOURCES

It is demonstrated that the Cramer-Rao lower bound (CRLB) on the direc tions of arrival (DOA's) of two closely spaced uncorrelated plane wave sources impinging on a uniform line array can be approximated by simp le algebraic formulas which provide insight into the behavior of the b ound with respect to signal-to-noise ratios (SNR's), source separation , etc. These formulas are sufficiently accurate for general use with t he number of sensors between about 6 and 60, for source separations do wn to about 0.1 of a classical beamwidth, and for SNR's from - 30 to 30 dB.