Multiplatform GMTI radar with adaptive clutter suppression
First Claim
1. A radar system comprising:
- a data input portion including a first channel configured to receive first radar return samples from a first GMTI radar receiver disposed on a first mobile platform and at least one second channel configured to receive second radar return samples from at least one auxiliary GMTI radar receiver disposed on at least one second mobile platform, the first mobile platform and the at least one second mobile platform defining a distributed array, the first radar return samples and the second radar return samples corresponding to radar return signals originating from a radar transmitter;
a non-adaptive processing portion coupled to the data input portion, the non-adaptive portion being configured to derive Doppler filtered radar return samples that include a plurality of first clutter signals from the first radar return samples, a plurality of second clutter signals from the second radar return samples and a target signal, the plurality of second clutter signals being characterized by at least one phase delay relative to the plurality of first clutter signals; and
an adaptive processing portion coupled to the non-adaptive processing portion, the adaptive processing portion being configured to calculate a weight value as a function of the plurality of first clutter signals and the plurality of second clutter signals but not the phase delay, the weight value being employed in a weight vector w for a space-time adaptive processing (STAP) filter that applies the weight vector w to a signal vector corresponding to the Doppler filtered radar return samples, the STAP filter implementing an open loop feedback configured to create beam pattern nulls at angles corresponding to a plurality of first interference signals within each of the Doppler bins without substantially tracking a position or velocity of the first airborne platform or the at least one second airborne platform.
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Abstract
The present invention is directed to a ground moving target (GMTI) radar that can detect targets, including dismounts, with very small minimum detectable velocities by combining signals from antennas on different spatially separated platforms in a main beam clutter-suppressing spatially adaptive process without requiring that the relative positions of the antenna phase centers be accurately tracked. The clutter nulling is in addition to that provided by the Doppler filters. The spatial displacement provides a narrow main beam clutter null reducing undesired target suppression. The clutter-suppressing spatially adaptive structure is used in both the sum and delta channels of the monopulse processor so that the beam distortion caused by the spatial nulling is compensated for, and the monopulse look-up process is preserved to maintain angle accuracy. Noncoherent integration is employed to recover signal to noise loss resulting from the uncertain relative locations of the platforms.
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Citations
36 Claims
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1. A radar system comprising:
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a data input portion including a first channel configured to receive first radar return samples from a first GMTI radar receiver disposed on a first mobile platform and at least one second channel configured to receive second radar return samples from at least one auxiliary GMTI radar receiver disposed on at least one second mobile platform, the first mobile platform and the at least one second mobile platform defining a distributed array, the first radar return samples and the second radar return samples corresponding to radar return signals originating from a radar transmitter; a non-adaptive processing portion coupled to the data input portion, the non-adaptive portion being configured to derive Doppler filtered radar return samples that include a plurality of first clutter signals from the first radar return samples, a plurality of second clutter signals from the second radar return samples and a target signal, the plurality of second clutter signals being characterized by at least one phase delay relative to the plurality of first clutter signals; and an adaptive processing portion coupled to the non-adaptive processing portion, the adaptive processing portion being configured to calculate a weight value as a function of the plurality of first clutter signals and the plurality of second clutter signals but not the phase delay, the weight value being employed in a weight vector w for a space-time adaptive processing (STAP) filter that applies the weight vector w to a signal vector corresponding to the Doppler filtered radar return samples, the STAP filter implementing an open loop feedback configured to create beam pattern nulls at angles corresponding to a plurality of first interference signals within each of the Doppler bins without substantially tracking a position or velocity of the first airborne platform or the at least one second airborne platform. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A method for processing radar signals in a distributed array radar that includes a first GMTI radar receiver, disposed on a first airborne platform, configured to receive first radar return samples and at least one auxiliary GMTI radar receiver, disposed on at least one second airborne platform, configured to receive second radar return samples, the first airborne platform and the at least one second airborne platform defining a distributed array, the method including:
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obtaining Doppler filtered radar return samples that include a plurality of first clutter signals from the first radar return samples, a plurality of second clutter signals from the second radar return samples and a target signal, the plurality of second clutter signals being characterized by at least one phase delay relative to the plurality of first clutter signals; calculating a weight value as a function of the plurality of first clutter signals and the plurality of second clutter signals but not the phase delay, the weight value being employed in a weight vector w for a space-time adaptive processing (STAP) filter; applying the weight vector w to a signal vector corresponding to the Doppler filtered radar return samples; and implementing an open loop feedback configured to create beam pattern nulls at angles corresponding to a plurality of first interference signals within each of the Doppler bins without substantially tracking a position or velocity of the first airborne platform or the at least one second airborne platform. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36)
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Specification