Using robust Capon beamforming to minimise the impact of angle of arrival errors in 2-D arrays

When sampling only a coarse set of azimuth and elevation angles for a 2-D array, the resulting angle of arrival errors often lead to target nulling in adaptive beamformers. Methods currently used to alleviate these errors often prevent target nulling at the expense of source localisation. In this paper, we show how the robust Capon beamformer, exploiting a flat ellipsoidal uncertainty set of the array steering vector, can be used to prevent target nulling at far less cost to source localisation. Furthermore, we present a new, computationally efficient technique for estimating the ellipsoids associated with angle of arrival uncertainty.