Performance evaluation of the MDOAM and SSM methods

The Modified Direction-of-Arrival (DOA) matrix (MDOAM) method and the Signal Space Matrix (SSM) method are two Subspace Rotation-Based (SRB) techniques that estimate 2-D DOA angles of narrowband signals impinging on a nonlinear sensor array with a built-in displacement invariant structure, First, the paper evaluates the performance of the MDOAM and SSM methods for locating far-field sources by relating the estimation error to the Cramer-Rao lower bound. Second, the paper identifies the conditions under which the methods can be used to detect near-field sources. We evaluate the MDOAM and SSM methods because they have many advantages over the previous SRB techniques of ESPRIT, the DOAM method, and the SR method