Improved MUSIC Under the Coexistence of Both Circular and Noncircular Sources

In array signal processing, the inner structure of the signals could possibly be exploited to improve the performance of the direction-of-arrival (DOA) estimations. One typical scenario has been discussed in P. Chage, Y. Wang, and J. Saillard, ldquoA Root-MUSIC Algorithm for Non-Circular Sources,rdquo Proc. Int. Conf. Acoustics, Speech, Signal Processing (ICASSP), Salt Lake City, UT, May 2001, pp. 7-11, where all the incoming signals are supposed to be sent by noncircular PAM/BPSK sources. A modified MUSIC algorithm was then developed to improve the DOA estimation accuracy, as well as to increase the maximum number of detectable signals. However, it is more realistic that some users send noncircular symbols while other users still send circular symbols. In this correspondence, we develop an algorithm to cope with this more general scenario. By exploiting the redundancy existing in the noncircular signals, the proposed algorithm can still increase the maximum number of detectable signals and improve the performance accuracy compared to the conventional MUSIC algorithm. Simulation results clearly show the effectiveness of our proposed algorithm.