Robust Adaptive Beamforming for Antenna Array

1) The document discusses robust adaptive beamforming techniques to improve robustness against uncertainties in array manifold, such as direction-of-arrival mismatch. 2) It proposes an alternative realization of robust linearly constrained minimum variance beamforming that uses an ellipsoidal uncertainty constraint on the steering vector. 3) A key contribution is integrating diagonal loading techniques by deriving an optimum variable loading level, providing "loading-on-demand" instead of fixed loading. This allows accurate computation of the diagonal loading level based on the uncertainty constraint.