Method and system for adaptively cancelling clutter from the sidelobes of a ground-based radar

A system for adaptively reducing clutter or EMI from the sidelobes of a ground-based radar comprising:

• a plurality of radar subarrays configured to receive radar signals containing near-horizon clutter or EMI;
• a digital receiver adapted to convert the radar signals received by the radar subarrays to complex subarray I/Q samples, the subarray I/Q samples containing near-horizon clutter or EMI;
• a coherent integration processor that coherently integrates the complex subarray I/Q samples to increase the CNR or ENR of the complex subarray I/Q samples;
• a range gate responsive to the coherent integration processor for providing the integrated I/Q data samples with increased CNR or ENR from range cells over a target range extent associated with the range of the received clutter or EMI to be cancelled;
• an adaptive clutter processor that receives the gated integrated data samples from the range gate and modifies a complex beamforming vector according to said integrated data samples to generate a modified complex beam steering vector;
• and
• a digital beamformer coupled to the digital receiver for receiving complex subarray I/Q data samples and configured to apply the modified complex beamforming vector to said received complex subarray I/Q data samples and output a set of complex beam I/Q samples of a radar beam having a spatial sidelobe null in the direction of the received clutter or EMI.

A method comprising:

• a) receiving complex I/Q data samples from a ground based digital beamforming radar antenna, the I/Q samples representing a radar signal containing near-horizon clutter from a set of range cells over a target range of interest;
• b) coherently integrating in at least one processor, the received I/Q data samples to increase the ratio CNR of the I/Q data samples;
• c) applying amplitude and phase perturbations to nominal beamsteering weights of the digital beamforming radar antenna and using clutter information contained in the coherently integrated data samples to generate a modified beam steering vector having reduced gain over the solid angle occupied by the near horizon clutter;
• and
• d) applying said modified beam steering vector to an input of a digital beamformer of said digital beamformer radar antenna receiving complex I/Q data samples representing a radar signal containing near-horizon clutter, to form a spatial sidelobe null in the direction of the received clutter.

A method of providing to a digital beamformer of a radar a modified complex beam steering vector for use in digital beamforming of complex I/Q data samples representing a radar signal containing near-horizon clutter, the method comprising:

• obtaining subarray I/Q samples from a plurality of subarrays of the digital radar;
• coherently integrating the subarray I/Q samples to increase the CNR;
• adaptively modifying nominal beam steering weights using clutter information contained in the coherently integrated subarray I/Q samples to generate a modified beam steering vector adapted to reduce receive gain over the solid angle occupied by the near horizon clutter;
• beamforming complex I/Q data samples representing a radar signal containing near-horizon clutter and using the modified beam steering vector, to generate a beamformed signal having an elevated mainlobe and a spatial sidelobe null in the direction of the received clutter.