Clutter Fortified Moving-Target Tracking System

摘要

1,185,781. Pulse radar. NORTH AMERICAN ROCKWELL CORP. 8 Feb., 1968, No. 6335/68. Heading H4D. In angle-tracking of moving targets in ground clutter by a non-coherent monopulse radar, the target signal becomes the Doppler reference if it exceeds the clutter and tracking of the clutter or a direction intermediate the clutter and target may ensue. It is known to enhance the clutter to reduce this (U.S.A. Specification 3,365,715) but tracking errors due to asymmetry of the enhanced clutter arise. According to the present invention such tracking errors are reduced by injecting a sample of the signal in either channel E A , E B into the other. Like delays 26, 27 correspond to half the gate interval of a range tracker or, if the latter is not provided, to three times the width of the transmitted pulse. To improve further the symmetry of the clutterreference signals, " sample-and-hold " means 32, 33 are each connected to the normalized sum channel E s and have a gate input from the range. tracking circuit 35; the gate input to means 33 being delayed by an interval equal to that of delays 26, 27. Differential means 36 provides a gain control bias which is injected via a gate 39 into the A.G.C. input line 37; gate 39 is operative from the input and output of delay 34. Further clutter enhancement may be added by incorporating a delay 40 to provide a sum channel clutter sample from a range interval removed from the target range; the injection of that sample into the E A , Eg channels may be controlled by a gate 43 actuated when the output of a summer 42 is less than a threshold level.