Application of eigenstructured-based techniques for tracking low angle targets in multipath

A technique using recursive eigendecomposition together with frequency-agile waveforms for tracking low-elevation targets in multipath has been developed. The proposed high-resolution, eigenstructure-based algorithm for solving the low-angle tracking problem can be implemented in three steps: updating the covariance matrix; updating the eigenvalue decomposition of the covariance matrix; and updating the angle estimates by searching for the peak of the updated multiple signal classification (MUSIC) spectrum or solving the zeros derived by the minimum-norm polynomial coefficient. A phased-array implementation using three orthogonal simultaneous beams placed at half null-beamwidth apart is developed. The angles can be determined by explicit computation or by a calibration curve in a lookup table such as in monopulse processing for angle estimation using two simultaneous beams.