Abstract: A monopulse radar system includes sum and difference receivers, and an auxiliary receive beam offset from the sum and difference beam axis. The received sum and difference signals are processed to produce first and second weighting signals which, when multiplied by the auxiliary signal, produce first and second weighted auxiliary signals which are approximately equal to the magnitude of, and are in a particular phase with, the received sum and difference signals, respectively. In the presence of a jamming signal in the main lobe of the monopulse receiver, the weighted auxiliary signals are summed with the sum and difference signals to produce adapted sum and difference signals, in which the jammer signal is suppressed by a null in the effective receive antenna pattern. The null perturbs the sum and difference patterns, so that the ratios of the sum and difference signals no longer accurately represent the off-axis angle of the target.