Abstract: An improved airborne target tracking monopulse radar system is disclosed which includes a null command generator, designed to provide an error signal which represents the angle between a target direction and the antenna's monopulse null direction. The generator is supplied with signals on sum and difference channels and a frequency which represents a selected target. The error signal is produced by first differentiating the sum channel signals and subtracting the differentiated output from the difference channel signals. The difference output is then multiplied with properly phased sum channel signals to produce the desired error signal.