Performance analysis of narrow-band adaptive arrays using projected perturbation sequences

When signals on the elements of an array are not accessible, algorithms for adjusting the weights of an adaptive array may employ perturbation techniques to obtain a gradient estimate for weight adaptation. To reduce the amount of noise introduced into the receiver by perturbation of the weights and to maintain constant gain in the signal direction during adaptation, the application of projected orthogonal perturbation sequences to adaptive beamforming is required. An analysis of the performance of projected orthogonal perturbation sequences is presented, and the performance of two specific sequences is investigated. Two methods of performance analysis are presented. They confirm that, in general, the projected perturbation sequences generate smaller variance in the gradient estimate and hence lower misadjustment than conventional perturbation techniques. Results of computer studies of the performance of the new sequences are presented