Abstract: Anti-jamming apparatus and method for a radar system having a main antenna utilizes a single electronic-scan auxiliary antenna having a plurality of radiating elements each coupled to appropriate phase shift means. The auxiliary antenna is successively sighted in directions of each of a plurality of jammers. First and second receiving chains respectively coupled to the main and auxiliary antennas supplies a processor with components of the signals received by the antennas. The computer supplies control signals to control the sighting of the auxiliary antenna so that it radiates in the direction of each jammer maximum radiation values, the components of which are those of the field radiated by the main antenna in the direction of the sighted jammer. The processor also provides an output signal comprising a vectorial combination of the signals received by the main and auxiliary antennas. The auxiliary antenna is thus successively used as an auxiliary adjusting antenna, and then used as an anti-jamming antenna.

Abstract: A method of measuring the altitude of a target maneuvering at very low elevations is used to determine the instantaneous deviation of the target at various operating frequencies of a monopulse tracking radar. The quadrature component of the difference signal is evaluated at these frequencies, the mean values of the instantaneous deviation and of the quadrature component are determined for a certain number of frequency samples, and an extreme value of the mean value of the quadrature component is found to allow the corresponding mean value of deviation to be validated.