An adaptive low-angle tracking system

A system for source tracking down to a fraction of a beamwidth of a surface with unknown multipath reflecting properties is described. The system has three major features: (1) the multipath returns are decorrelated by frequency diversity; (2) an efficient broad-band multiple beam antenna design is employed such that the data are characterized by a highly symmetrical (Toeplitz) correlation matrix; and (3) Burg's reflection coefficient technique is employed to obtain rapid convergence to the maximum entropy spectrum from which the target location is determined. Realistic simulations including imperfect decorrelation, antenna errors, and transient results show that the system can provide accurate low-angle estimates using a practical antenna and reasonable data-processing time.