Bearing Estimation for a Distributed Source of Nonconstant Modulus - Bounds and Analysis

This 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 Cramér-Rao lower bound is evaluated. In addition, a comprehensive analysis of the maximum likelihood estimates, that (due to mismodeling) assume a constant modulus source, is performed, 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.