Optimum beamforming for a nearfield source in signal-correlated interferences

In this paper, the problem of optimum beamforming using a uniform linear array is considered, for the purpose of avoiding target signal cancellation, which normally results when signal-correlated interferences are present in the environment. A convenient and direct characterization of the interference subspace in terms of its orthogonal complement is provided, leading to the estimation of a signal free covariance matrix directly from the observed data. This characterization enables us, not only to improve the performance of the farfield beamformers suggested by Bresler et al. [Optimum beamforming for coherent signal and interferences, IEEE Trans. Acoust. Speech Signal Process. ASSP-36(6) (1988) 833-843], but it also allows us to generalize the results of [Y. Bresler, et al. Optimum beamforming for coherent signal and interferences, IEEE Trans. Acoust. Speech Signal Process. ASSP-36(6) (1988) 833-843] to obtain the corresponding nearfield beamformers. The three beamformers proposed, work equally well even in scenarios where interferences are correlated with the signal of interest. Computer simulations are presented to validate the performance of these beamformers in the presence of correlated and uncorrelated interferences.