Robust widely linear beamforming against look direction error

A class of robust beamformers that are insensitive to the look direction error is herein proposed by employing the second-order noncircularity of the signal-of-interest (SOI) in a widely linear framework. The first method is a widely linear extension of the constrained Hung-Turner beamformer, which exploits the prior knowledge about the interference directions. The second method represents a widely linear version of the constrained generalized sidelobe canceller, which uses a derivative constraint on the blocking matrix. The third method uses the covariance matrix reconstruction technique from a widely linear perspective. Simulation results are included to illustrate the robustness performance of the proposed beamformers in terms of output signal-to-interference-plus noise ratio versus input signal-to-noise ratio and snapshot number.