The United States of America

Government of the United States

Bernard L Lewis

Frank F Kretschmer, Jr

An adaptive N-pulse MTI processor for obtaining optimum clutter cancellation with a minimum of hardware, comprising a first input pulse line; first delay means for providing an interpulse delay T to pulses on this first input line; a first adaptive canceller with its auxiliary input connected directly to take pulses from the first input line, and with its main input connected to take delayed pulses from the first delay means; and N-2 series-connected canceller circuits, with each canceller circuit associated with a different level of pulses. The nth canceller circuit, where 1.ltoreq.n.ltoreq.N-2, includes an nth adaptive canceller; an nth input pulse line; n series connected delay means for providing a series of interpulse delays T to pulses propagating on the nth input pulse line, and with n+1 terminals for taking pulse outputs in front of each of the n delay means and after the last of the n delay means; and nth commutating switch means with a plurality of switch positions connected for applying pulses from the n+1 terminals to the main and auxiliary inputs of the nth adaptive canceller. The commutating switch means operates to provide appropriate sets of two pulses from the n+1 terminals to the main and auxiliary inputs to effect the n+2 canceller level of Gram-Schmidt pulse decorrelation on the output line of the nth canceller. The output from the n=1 adaptive canceller is connected to the first input pulse line. The output from the first adaptive canceller then provides the Gram-Schmidt decorrelation. With this configuration, only N-1 cancellers are required to implement the optimum Gram-Schmidt decorrelation for an N-pulse MTI.

Generalized adaptive MTI system

A radar system for cancelling radar clutter with a minimum of equipment comprising an N-point Fast Fourier Transform for dividing the radar's doppler space into N contiguous frequency subbands; a delay line disposed at each frequency output port for the FFT for obtaining a set of M+1 consecutive samples from each subband, with the sampling performed at the radar's pulse repetition rate divided by N; a single M degree-of-freedom adaptive-canceller moving-target indicator; and M+1 commutating switches for consecutively applying different sets of M+1 subband samples to the MTI. This operation permits clutter cancellation in each subband with N different frequency zeros placed in the radar's doppler space for each MTI degree-of-freedom.

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Satellite Beach, FL, United States of America

Bernard L Lewis