What is the velocity gate pull-off technique in deceptive jamming and how does it work?

The velocity gate pull-off (VGPO) technique in deceptive jamming works by first capturing the victim radar's Doppler tracking gate and then gradually moving the gate away from the true target's velocity, causing the radar to track a false velocity and eventually lose lock on the real target. The VGPO sequence: Step 1 (capture): the jammer transmits a replica of the radar's return at the correct Doppler frequency, matching the real target's velocity. The jammer signal is slightly stronger than the real echo (J/S > 3-6 dB), so the radar's Doppler tracking gate locks onto the jammer signal. Step 2 (pull-off): the jammer gradually shifts the Doppler frequency of its transmitted signal away from the real target's velocity. The shift rate must be slow enough that the radar's tracking loop follows (typically 10-100 Hz/s Doppler shift rate), but fast enough to pull the gate away in a useful time (2-10 seconds). Step 3 (break lock): once the radar's velocity gate is pulled sufficiently far from the real target's velocity (typically 500-2000 Hz Doppler offset): the real target falls outside the tracking gate and is no longer tracked. The jammer ceases transmission, and the radar must re-acquire the target (searching for the correct Doppler), buying time for the protected aircraft to maneuver. The VGPO is implemented using a DRFM (Digital Radio Frequency Memory): the DRFM captures the incoming radar pulse, applies a progressive Doppler shift (phase modulation), and retransmits the modified pulse.