Range-doppler keystone processing for direct sampled radar data from targets with long range and high velocity using waveforms with high bandwidth, high duty factor, and long dwell

A method, comprising:

• receiving a plurality of radar returns associated with a scene being illuminated by a plurality of pulses;
• forming, for each radar return in the plurality of radar returns, a respective receive processing window containing the radar return as an unbroken radar return;
• generating, for each respective unbroken radar return, a two-dimensional (2-D) array of data associated with the respective unbroken radar return, wherein one dimension of the 2-D array comprises overlapped receive range data;
• providing a matched filter configured to:
• create a motion model for a reference point target disposed at a predetermined location within the scene based on the 2-D array of data and on a set of motion compensation parameters for range and range rate;
• compensate for at least some effects of fast time Doppler on the reference point target;
• and
• output a two dimensional (2-D) array of information associated with the scene, the 2-D array comprising a first dimension comprising fast time frequency information and a second dimension comprising slow time information;
• performing a keystone interpolation on the 2-D array of information associated with the scene, the keystone interpolation comprising:
• associating the slow time information in the 2-D array with a first scale;
• and
• rescaling the slow time information to a predetermined second scale, to produce a keystone-interpolated 2-D output array of information associated with the scene, the information associated with the scene comprising a first-dimension of fast frequency and a second dimension of slow time;
• applying phase modulations to the keystone-interpolated 2-D output array of information associated with the scene, to shift each range rate bin in a range-Doppler map associated with the keystone-interpolated 2-D output array, in range, to ensure proper registration;
• and
• generating, based on receiving a phase modulation output array, a range-Doppler map output of the scene having a predetermined range rate extent.

A circuit, comprising:

• a receive processing window formation subsystem configured to receive a plurality of radar returns from a scene, the plurality of radar returns associated with a scene being illuminated by a plurality of pulses transmitted by a radar transmitter, to form, for each radar return in the plurality of radar returns, a respective receive processing window containing the radar return as an unbroken radar return, and to generate, for each respective unbroken radar return, a two-dimensional (2-D) array of data associated with the respective unbroken radar return, wherein one dimension of the 2-D array comprises overlapped receive range data;
• a matched filter subsystem in operable communication with the receive processing window formation subsystem and configured to create a motion model for a reference point target disposed at a predetermined location within the scene based on an output of the receive processing window formation subsystem and on a set of motion compensation parameters for range and range rate, wherein the matched filter subsystem is configured to compensate for at least some effects of fast time Doppler on the reference point target, and wherein the matched filter subsystem is configured to output a two dimensional (2-D) array of information associated with the scene, the 2-D array of information comprising a first dimension comprising fast time frequency information and a second dimension comprising slow time information;
• a keystone interpolation subsystem configured to receive the 2-D array of information associated with the scene, from the matched filter subsystem, wherein the slow time information in the 2-D array of information is associated with a first scale, and wherein the keystone interpolation subsystem is configured to rescale the slow time information to a predetermined second scale, to produce a keystone interpolation subsystem output, comprising a keystone-interpolated 2-D output array of information associated with the scene, the information associated with the scene comprising a first-dimension of fast frequency and a second dimension of slow time;
• a phase modulation subsystem configured to receive the keystone interpolation subsystem output and to apply phase modulations to the keystone-interpolated 2-D output array of information associated with the scene, to shift each range rate bin in a range-Doppler map associated with the keystone-interpolated 2-D output array, in range, to ensure proper registration;
• and
• an image forming subsystem configured to generate, based on receiving a phase modulation output array, a range-Doppler map output of the scene having a predetermined range rate extent.