A class of diagonally loaded robust Capon beamformers for noncircular signals of interest

•Three schemes for determining the diagonal loading level of the diagonally loaded robust Capon beamformer are proposed.•The schemes are based on the exploitation of the noncircularity property of the signal of interest.•The schemes require no knowledge of or assumption on the uncertainty of the steering vector.•The schemes involve no user-defined parameters.

Diagonal loading is a simple and effective method for robustness enhancement of the Capon beamformer against perturbation in the presumed steering vector of the signal-of-interest (SOI). However, the determination of an appropriate diagonal loading level is not a trivial task. Three noncircularity restoral based methods are herein proposed for selecting the diagonal loading level to recover a noncircular SOI buried in circular and/or noncircular interferences plus circular background noise. Monte Carlo simulations are performed to verify the efficacy of the proposed methods.