Roubust Adaptive Beamforming with Variable Diagonal Loading

Significant effort has gone into designing robust adaptive beamforming algorithms to improve robustness against uncertainties in array manifold.These uncertainties may be caused by uncertainty in Direction of Arrival(DOA),imperfect array calibration,near-far effect,mutual coupling,and other mismatch and modeling errors.An alternative realization of the robust adaptive linearly constraint on the steering vector is proposed.More specifically,the genuine steering vector is estimated from the presumed steering vector using Recursive Steepest Descent(RSD)algorithm with the ellipsoidal constraint imposed on the estimated steering vector.A diagonal loading technique is obligatory to satisfy the ellipsoidal constraint.The main drawback of the diagonal loading technique is that it is not clear how to get the optimal value of diagonal loading level based on the recognized level of uncertainty constraint.In this paper,this drawback is tackled whereas the diagonal loading technique is integrated into the adaptive update scheme by means of Variable Loading(VL) technique rather than fixed diagonal loading or Ad Hoc technique.