A GENERALIZED APPROXIMATION FOR THE CRAMER-RAO LOWER-BOUND ON DIRECTION-OF-ARRIVAL ESTIMATES FOR A PAIR OF CLOSELY SPACED SOURCES

It is demonstrated that the Cramer-Rao lower bound on direction-of-arr ival estimation with two closely spaced, narrow-band plane waves, with an arbitrary correlation coefficient, impinging on a uniform line arr ay, is well-approximated by an empirically derived, nonmatrix expressi on combining two previously published, special-case approximations. Th e approximation is useful for a number of sensors down to about 6, sig nal-to-noise ratios from about -30 to +30 dB, and source separations d own to about one-sixth of a Rayleigh beamwidth. The root mean square e rror is about 11%. (C) 1996 Acoustical Society of America.