Decoupled maximum likelihood angle estimation for coherent signals

We present an algorithm for estimating the directions of arrival (DOAs) and signal amplitudes of known, possibly coherent signals impinging on an array of sensors. The algorithm is an extension to the DEML method of Li et al. (see IEEE Transactions on Signal Processing, vol.43, no.9, 1995), used to handle coherent multipath which may be present in the signals. We derive a large-sample maximum likelihood estimator for the signal parameters. The algorithm is computationally efficient because the nonlinear minimization step decouples into a set of minimizations of smaller dimension. We also derive the asymptotic statistical variance of the parameter estimates, develop an analytical expression for the CR bound for this signal scenario, and compare the two both theoretically and numerically.