Direction-finding methods for cyclostationary signals in the presence of coherent sources

By exploiting the signal cyclostationarity, conjugate cyclic MUSIC presented by Gardner (1994), has been shown to be effective in performing signal-selective direction finding. However, a direct application of conjugate cyclic MUSIC in the presence of coherent signals of interest (SOIs) will result in ambiguity. To tackle the drawback of conjugate cyclic MUSIC, we present a scheme called the Hankel approximation method (HAM) in conjunction with conjugate cyclic MUSIC to cope with the performance deterioration due to coherent SOIs for a uniform linear array. Theoretical analysis shows that at least 2K sensor elements are required to resolve K coherent SOIs. Making use of the forward/backward (F/B) technique presented by Pillai and Kwon (1989), F/B HAM is further developed, which requires [3K/2] sensor elements to decorrelate K coherent SOIs, where [x] represents the integer part of x. Several simulation examples are also presented for illustrating the effectiveness of the proposed methods.