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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. Fast Fourier transforms change the data sets into the frequency domain and phase compensations for the data sets are calculated in a triple interferometric signal calibration unit. Compensation phase is further adjusted in a clutter 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 unit, maximum clutter cancellation is achieved. The resulting clutter-cancelled signals are presented to a detection and validation processor to determine range, doppler, amplitude and angle measurements to the moving targets with a high degree accuracy.

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First Claim