초록 ▼

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 quadra

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-tt

대표청구항 ▼

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-apar

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 including a first array storage (70) for providing an undelayed set of data (80, 82) in time domain format in response to the timing signal and the in-phase and quadrature component signals associated with the left aperture, a second array storage (72) for providing a delayed set of data (90, 92) in time domain format in response to the timing signals, the delay signal and the in-phase and quadrature component signals associated with the center aperture, a third array storage (74) for providing an undelayed set of data in time domain format in response to the timing signal and the in-phase and quadrature component signals associated with the center aperture, and a fourth array storage (76) for providing a delayed set of data in time domain format in response to the timing signal, delay signal and the in-phase and quadrature component signals associated with the right aperture; FFT means including a first FFT processor (84) for providing an undelayed set of data in frequency domain format associated with the left aperture in response to the undelayed set of data in time domain associated with the left aperture, a second FFT processor (94) for providing a delayed set of data in frequency domain format associated with the center aperture in response to the delayed set of data set in time domain format associated with the center aperture, a third FFT processor (104) for providing an undelayed set of data in frequency domain format associated with the center aperture in response to the undelayed set of data in time domain format associated with the center aperture, and a fourth FFT processor (114) for providing a delayed set of data in frequency domain format associated with the right aperture in response to the delayed set of data in time domain format associated with the right aperture; interferometer means (158) for providing a left/center phase calibration signal (126) indicative of the measured angle versus dopper characteristic for a left/center interferometer comprising the left and center apertures in response to the undelayed sets of data in frequency domain format associated with the left and center apertures, for providing a left/center amplitude calibration signal (134) indicative of the amplitude difference in clutter spectrum between the left and center apertures in response to the undelayed sets of data in frequency domain format associated with the left and center apertures, for providing a center/right phase calibration signal (146) indicative of the measured angle versus doppler characteristic for a center/right interferometer comprising the center and right apertures in response to the delayed sets of data in frequency domain format associated with the center and right apertures, for providing a center/right amplitude calibration signal indicative of the amplitude difference in clutter spectrum between the center and right apertures in response to the delayed data sets in frequency domain format associated with the center and right apertures; phase computation means (169) for providing a phase difference signal indicative of the phase difference between the delayed and undelayed sets of data in response to the delay signal; phase calculation means (160) for providing a left/center phase correction signal (176) for the left/center interferometer indicative of a time delay phase correction, the positional phase relationship between the left and center apertures, and a phase due to motion of the targets in response to the phase addition of the phase difference signal and the left/center phase calibration signal, and for providing a center/right phase correction signal (178) for the center/right interferometer indicative of the time delay phase correction, the positional phase relationship between the center and right apertures, and the phase due to motion of the targets in response to the phase addition of the phase difference signal and the center/right phase calibration signal; cancellation means for providing left/center clutter cancelled in-phase and quadrature component signals (214, 216) that have significantly suppressed clutter characteristics in response to the left/center phase correction signal (176), the left/center amplitude calibration signal (134), and the difference (210, 212) between the undelayed set of data in frequency domain format associated with the left aperture (86, 88) and the delayed set of data in frequency domain format associated with the center aperture (96, 98); for providing center/right clutter cancelled in-phase and quadrature component signals (234, 236) that have significantly suppressed clutter characteristics in response to the center/right phase correction signal (178), the center/right amplitude calibration signal (154), and the difference (230, 232) between the undelayed set of data in frequency domain format associated with the center aperture (106, 108) and the delayed set of data in frequency domain format associated with the right aperture (116, 118); and for providing left/right clutter cancelled in-phase and quadrature component signals (254, 256) that have significantly suppressed clutter characteristics in response to the difference (177) between the left/center phase correction signal (176) and the center/right phase correction signal (178), the ratio (196) of the left/center amplitude calibration signal (134) and the center/right amplitude calibration signal (154), and the difference between the (251, 252) delayed set of data in frequency domain format associated with the right aperture (116, 118) and the undelayed set of data in frequency domain format associated with the left aperture (86, 88); and detection means (350) connected to the cancellation/enhancement means, for providing range (rt), doppler (ft), amplitude (at), and angle (qt) signals indicative of target motion in response to the clutter cancelled left/center, center/right, and left/right in-phase and quadrature signals.