Monopulse tracking of two unresolved Rayleigh targets

When two targets are closely-spaced with respect to the resolution of a radar, the measurements of the two targets will be merged when the target echoes are not resolved in angle, range, or radial velocity (i.e., Doppler processing). Monopulse processing is considered for Direction-Of-Arrival (DOA) estimation of two unresolved Rayleigh targets with known relative Radar Cross Section (RCS). The probability distribution of the complex monopulse ratio is developed for two unresolved Rayleigh targets. The Fisher information matrix and Cramer Rao bounds are developed for the DOA estimation of two unresolved Rayleigh targets using a standard monopulse radar. When the two Rayleigh targets are separated by more than one-half of the radar beamwidth, DOA estimation is accomplished for each target by treating the other target as interference. When the two targets are separated by less than one-half of a beamwidth, the antenna boresight is pointed between the two targets, and the mean of the in-phase (i.e.,the real part) monopulse ratio and the variance of the in-phase and quadrature monopulse ratios are utilized to estimate the DOAs of the two targets. Simulation results that illustrate performance of the DOA estimators are given along with a simple tracking example.