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Abstract

An AMTI radar employs a dual cancellation format to cancel the clutter in the radar returns received by the apertures of an interferometric radar antenna. The three-aperture antenna presents the radar returns to three receivers which demodulate the returns to a complex in-phase signal I and a quadrature signal Q which are sampled at a pulse repetition interval at all ranges of interest. After conventional motion compensation four data sets are derived from the returns of the three apertures, L(t), C(t-.tau.), C(t) and R(T-.tau.) which represents samples taken over multiple pulse repetition intervals for each range interval or bin of interest. The data is processed by both adjacent array processing and outer array processing, the latter only requiring a minimal amount of additional capacity. Compensation phase is further adjusted in a clutter/clutter-free phase calculator allowing a much reduced phase quantity to be applied to the delayed data sets as the second part of the dual cancellation signal. Following subtraction of doppler filter outputs of the delayed data sets from the undelayed data sets in the cancellation/enhancement unit, maximum clutter cancellation is achieved in the clutter region and optimal moving target response is obtained in the clutter-free region. The two-range maps that result after subtraction of the doppler filter outputs are presented to a detection and validation processor to determine range, doppler, amplitude and angle measurements to the moving targets with a high degree of accuracy.

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First Claim