Phase-Amplitude Monopulse System

Phase monopulse, amplitude monopulse, and phase-amplitude monopulse are compared. The latter uses only two antenna feeds and by controlling the aperture illumination from these feeds has a separation of the illumination phase centers in one axis and opposed tilts of the phase fronts, or squint, in the other axis. It is described as more fundamental or less redundant than four-horn or other multihorn monopulse designs. In lacking redundancy it is less complex, but has fewer degrees of freedom to optimize performance. The earliest example of phase-amplitude monopulse, the AN/APG-25 (XN-2), is described and its performance given.