Enhancements of unitary ESPRIT for non-circular sources

Estimating the directions of arrival of several wavefronts impinging on an array of sensors is a requirement in a variety of applications including radar, mobile communications, sonar, and seismology. Subspace based high-resolution parameter estimation schemes like ESPRIT and MUSIC have become very popular. Such parameter estimation algorithms often use forward-backward averaging to enhance their resolution, especially in the case of correlated sources. Further enhancements can be achieved if the source signals are non-circular. We derive an efficient subspace estimation scheme that exploits the non-circularity of the sources and already includes forward-backward averaging. Moreover, appropriate spatial smoothing techniques are introduced. Completely real-valued implementations of 1D and 2D unitary ESPRIT for non-circular sources are presented as examples. In these cases, NC unitary ESPRIT improves the resolution capability and the noise robustness of standard ESPRIT as well as unitary ESPRIT and can handle more sources than sensors.