Target detection system in a medium PRF pulse doppler search/track radar receiver

摘要

In a medium PRF pulse doppler type radar receiver, target detection is achieved in both search and track modes. In the search mode, the video signal from the receiver section is notch filtered to cancel the main beam clutter. The remainder of the signal is threshold detected, followed by ranging each of the thresholded signals to resolve the range ambiguity of the signals. The unambiguous signals are gated through a range sensitive threshold which operates along a power curve of R4, resulting in true target returns being thresholded by the range sensitive threshold circuit and blocking out discrete sidelobe returns. In the track mode, the video signal from the receiver is clutter cancelled to remove main beam clutter, as in the search mode, and the remaining signals pass through a velocity track filter with a narrow band window. The true target return signal ranged during the search mode, is passed by the velocity track filter which is adjusted to match the true target return doppler shift during the correct range gate. The velocity track filter is controlled to track the true target return signal and is narrow enough to reject discrete sidelobe signals which occur in the same range cell. The signals passed by the velocity track filter are subsequently monitored, and guard gates are established in both adjoining range cells to insure that lock on the tracked target will not be lost due to interfering signals such as returns from moving ground targets. When the interfering signals are detected in the guard gates, the system goes on memory until the interfering signal passes.