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.