A UNIFIED ESTIMATOR FOR SOURCE POSITIONING AND DOA ESTIMATION USING AOA

Angles of Arrival (AOAs) are popular measurements to locate a signal source. They can yield a position if the source is near the sensors or a DOA if it is far away. Point positioning and DOA localization require different estimators and the knowledge if the source is near or far is needed. Nevertheless, such knowledge about the source range is often not available in practice. This paper first analyzes the consequences of point positioning of a distant source and DOA estimation of a near one. It next proposes a unified estimator that provides a position estimate if it is near or a DOA estimate if it is far, without requiring any prior knowledge about the range region of where it lies. The estimator is derived using the Maximum Likelihood criterion with the Gauss Newton implementation, using the modified polar coordinates to represent the source location. A preliminary solution using the semi- definite relaxation is developed to initialize the estimator. Simulations validate the performance of the proposed estimator in reaching the CRLB performance.