Adaptive clutter velocity cancellation system for pulsed digital MTI system

摘要

A digital MTI radar system for improved handling of "moving clutter" which employs a double phase detector scheme to provide both Doppler sine and Doppler cosine terms which are separately digitally encoded in a series of range increments throughout each pulse repetition interval. The discrete digitally encoded values thus represent instantaneous echo signal phase angle in each corresponding range increment. This angle data is compared by range increments with that of the last previous pulse repetition period, to provide net signal phase angle change in digital form (a velocity related term) by range increments successively. The remaining circuitry comprises a device for sampling this net phase angle change over a predetermined number of range increments to compute average clutter velocity with respect to the radar system location.P PA bona fide signal in the moving clutter may then be recognized on the basis of its exceeding the average clutter velocity. A quantized output is effected by means of a logic arrangement which detects the condition of signal presence in one or two adjacent ones of the range increments provided these increments are preceded and followed by a predetermined relatively small number of range increments exhibiting no signal above the said average clutter velocity.