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Dual cancellation interferometric AMTI radar

  • US 5,559,516 A
  • Filed: 11/27/1981
  • Issued: 09/24/1996
  • Est. Priority Date: 11/27/1981
  • Status: Expired due to Term
First Claim
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1. An airborne moving target indicator (AMTI) for effectively detecting and measuring slowly moving targets in main beam clutter from a moving platform, comprising:

  • antenna means having a transmit aperture for transmitting radar pulses at a pulse repetition frequency (PRF), and having three spaced-apart receive apertures;

    a left aperture (12), a center aperture (14), and a right aperture (16) for receiving radar return signals;

    receiver means (18, 20,

         22) for providing in-phase (I) and quadrature (Q) component signals associated with each receive aperture in response to the radar return signals;

    clock means (51) for providing a timing signal (52) related to each transmitted radar pulse;

    delay means (53) for providing a delay signal in response to platform movement, PRF and interaperture spacing;

    storage means (70, 72, 74,

         76) for providing delayed and undelayed sets of data in a time domain format in response to the timing signal, the delay signal and the in-phase and quadrature component signals;

    FFT means (84, 94, 104,114) for providing delayed and undelayed sets of data in a frequency domain format in response to the delayed and undelayed sets of data in time domain format;

    interferometer means (158) connected to the FFT means for providing phase calibration signals (126,

         146) indicative of the measured angle versus doppler characteristic for a left/center interferometer comprising the left and center apertures and a center/right interferometer comprising the center and right apertures in response to the delayed and undelayed sets of data in frequency domain format, and for providing amplitude calibration signals (134,

         154) indicative of the ratio of the average clutter powers for the left/center and center/right interferometers in response to the delayed and undelayed sets of data in frequency domain format;

    phase computation means (169) for providing a phase difference signal indicative of the phase difference between the delayed and undelayed delta sets of data in response to the delay signal;

    phase calculation means (160) for providing phase correction signals for the left/center and center/right interferometers indicative of a time delay phase correction, the positional phase relationship between adjacent apertures, and a phase due to motion of the targets in response to the coherent addition of the phase difference signal and the phase calibration signals;

    cancellation means ( 250 ) for providing clutter-cancelled in-phase and quadrature component signals that have significantly suppressed clutter characteristics in response to the phase correction signals, the amplitude calibration signals and the delayed and undelayed sets of data in frequency domain format; and

    detect ion means (350) for providing range (rt), doppler (ft), amplitude (at), and angle (θ

    t) signals indicative of target motion in response to the clutter cancelled in-phase and quadrature component signals.

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