Bearing estimation for a distributed source of nonconstant modulus ounds and analysis

The paper considers the problem of estimating the bearing of a single, far-field source, surrounded by local scatterers, using passive sensor array measurements. An associated source-bearing estimation problem is formulated, and the Crame´r-Rao lower bound is evaluated. In addition, a comprehensive analysis is performed of the maximum likelihood estimates that (due to mismodeling) assume a constant modulus source, and the degradation in performance is quantified as a function of the source´s empirical variance. It is shown that, for a limited price in terms of mean square error, the constant modulus maximum likelihood estimator can replace the optimal nonconstant modulus estimator.