... A. N. Willson Jr., “Adaptive spectral estima-tion using the conjugate gradient algorithm,” in Proceedings of IEEE International Conference on Acoustics, Speech, and SignalProcessing (ICASSP ... methodfor adaptive direction -of- arrival estimation of coherent sig-nals,” in Proceedings of IEEE International Conference on Acous-tics, Speech, and Signal Processing (ICASSP ’97), vol. 3, ... yield-ing that in this case gcg,Pshould be zero or a linear combina-tion of the other gradient vectors which is not possible sinceit is orthogonal to all of them. In view of Proposition 1,...