Adaptive Interference Cancelling in Multiple Beam Antennas With Application to Multipath

Abstract

<p>This dissertation presents the adaptive interference cancelling procedure for use in multiple beam antenna systems. To constrain the processor from responding to a target signal, a set of orthogonal beams is used to provide the input data, and the main beam is excluded from the procedure for calculating the weights of the adaptive interference canceller. Two different adaptation algorithms are used to adjust the weights, namely, the LMS adaptation algorithm and the recursive algorithm based on Kalman filtering theory. To accelerate the convergence of the LMS algorithm, a procedure is devised to extrapolate the optimum weight vector after a short learning period.</p> <p>An adaptive interference cancelling scheme is described, and a new method (based on this scheme) is developed for elevation angle estimation in the presence of multipath, as encountered in low-angle tracking radar. The adapted weight provides information about the elevation angle through a calibration curve, which does not depend on signal and multipath parameters. Theoretical RMS error bounds on estimation on accuracy are determined for varying system and environmental conditions. These bounds are confirmed by means of computer simulation.</p> <p>Finally, the effect of misadjustment of the adaptive procedures and the effect of percentage error in the horizon reference on the estimation error are evaluated.</p>