range gate pull off/stealing

range gate pull off/stealing (RGPO)

An ECM (electronic countermeasures) technique used against ground tracking radar generally deployed with surface-to-air weapon systems. The aim is to confuse the radar tracker and launch the missile at a wrong range and thus save the actual target. The jammer initially returns an exact copy of the skin echo or its own reflection immediately after receipt of the radar pulse from the target radar. During the next few pulses, the jamming signal is returned with increasing amplitude. The radar signal processing circuit accepts the jamming pulse as a true reflection and reduces the gain of the radar receiver as the jammer pulses grow in magnitude. Slowly, the radar receiver becomes too insensitive to detect the true signal, and the jammer thus captures the radar range gate. The jammer now delays the returns of the successive radar pulses by a growing period, so that the range gate becomes adjusted to accept progressively greater range reflections. At a certain stage, the jammer stops transmissions. The radar is now left without any signal and must commence a range search; during which period the angle circuits are inactive. The jammer repeats the whole process as soon as the radar has reestablished the track.
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