Robust wideband Capon beamforming in the presence of coherent interferences

The robust Capon beamformer (RCB) is an extension of the standard Capon beamformer (SCB) in the case of uncertain steering vectors and is devised under the narrowband and incoherent signals assumption. However, in many practical applications the signal of interest (SOI) is intrinsically wideband and coherent interferences exist, as either a natural result of a multipath propagation effect, or intentional unfriendly jamming. For wideband signals, we can use the fast Fourier transform (FFT) to divide the array outputs into many narrowband frequency bins and then apply the RCB to each bin separately. However, the main lobe beamwidth of the RCB decreases with frequency, which is undesirable in some applications such as power estimation in source localization. In this paper, we present an algorithm that do a trade-off between array aperture and decorrelation ability to build a wideband coherent RCB that has constant power width for each frequency bins, and is robust against both coherent interferences and steering vector errors.