Cramér-Rao lower bounds for monopulse calibration using clutter returns

Successful geolocation of ground moving targets utilizing monopulse techniques requires accurate characterization of the array manifold (i.e. monopulse response to off-boresight targets) and antenna pointing information. Utilizing techniques similar, in spirit, to those applied in synthetic aperture radar (SAR) to estimate the Doppler centroid of an image, we develop techniques to accurately estimate azimuth monopulse slope and boresight shift of an airborne ground moving target indicator (GMTI) antenna utilizing clutter returns from normally scheduled CPIs that are also used for target detection and geolocation. A statistical signal model is developed for the clutter returns as observed through the monopulse channels. Cramér-Rao lower bounds (CRLB) are developed for monopulse slope and boresight shift and compared to CRLB developed with SAR centroiding techniques as summarized in the literature. Analytical and numerical CRLB results show potential gains of one to two orders of magnitude at moderate to high clutter to noise ratios for a sum-difference system.