Application of ESPRIT to coherent source direction finding

We suggest a pre-processing technique that allows the application of rotational invariance technique (ESPRIT) of Paulraj et al. for estimating the Directions-of-Arrival (DOA) in the presence of multipath propagation. We show that one can use a form of spatial smoothing on both the auto and cross covariance matrices to restore the rank of the associated generalized eigenvalue problem before estimating the signal parameters via rotational invariant techniques. This technique shares the common disadvantage associated with the conventional spatial smoothing due to which the number of sources d (when all of them are fully correlated) is limited to (N-1)/2 where (N-1) is the number of doublets in the array