Fast method for DOA estimation with circular and noncircular signals mixed together

Most of the existing algorithms to estimate the direction of arrival (DOA) of signals deal with the situation that all signals are circular. However, it is quite often in practical engineering that circular and noncircular signals appear in the same time. To effectively detect DOA of signals in such circumstances, we propose a novel algorithm. Firstly, using received data and its conjugate, we can detect more signals because of the doubled array aperture. Secondly, through unitary transform and multistage Wiener filter (MSWF) technology, we can obtain the noise subspace of array without performing eigendecomposition. Finally, by employing the improved MUSIC algorithm,we can acquire the DOA of the mixed circular and noncircular signals through two-stage search. Simulation results clearly demonstrate the effectiveness of the proposed algorithm.