Interferometric moving vehicle imaging apparatus and method

A method of imaging a ground moving vehicle using an airborne interferometric synthetic aperture radar system having at least three apertures which each provides a received RF return signal over a certain dwell period to its own dedicated receiver channel which digitizes the received RF signal to provide a received digitized RF signal from each channel, the method comprising the steps of:

• A) processing the received digitized RF signal from each aperture by
• 1) motion compensating each of the received digitized RF signals to correct for aircraft motion during the dwell period and provide motion compensated RF signals;
• 2) storing each of said motion compensated RF signals during the dwell period to form a plurality of temporal subdwell data blocks of return data each non-overlapping and adjacent in time;
• 3) performing a two dimensional FFT on the temporal subdwell data blocks from each of the apertures to transform to the range doppler domain and providing transformed temporal subdwell data block indicative thereof;
• B) compensating the transformed temporal subdwell data blocks from two of the apertures such that the transformed temporal subdwell data blocks from all three of the apertures have the same phase center;
• C) interferometrically combining corresponding transformed temporal subdwell data blocks for a first set of apertures selected from the three apertures to provide a first clutter canceled subdwell data block, wherein interferometrically combining the subdwell data blocks cancels the energy from stationary objects;
• D) interferometrically combining corresponding transformed temporal subdwell data blocks for a second set of apertures selected from the three apertures provide a second clutter canceled subdwell data block;
• E) processing the first and second clutter canceled subdwell data blocks to detect moving vehicles;
• F) determining the location of the detected moving vehicles;
• G) tracking the detected moving vehicles;
• and
• H) imaging the detected moving vehicles and providing a range doppler image of each moving vehicle.

An interferometric ground moving vehicle imaging radar system which transmits a pulsed waveform from an antenna having at least three apertures and receives backscattered energy from stationary and moving objects at each of the apertures and processes the signals received by each aperture separately to provide a plurality of received signals which are motion compensated and transformed to the range doppler domain to provide a plurality of compensated received signals which are processed to form images of moving vehicles, the system comprising:

• means responsive to each of the motion compensated signals for interferometrically attenuating the energy associated with the stationary objects to provide two clutter canceled signals with improved moving vehicle signal to noise ratio;
• means responsive to said two clutter canceled signals for detecting and locating moving vehicles;
• means for determining the azimuth location for each detected vehicle based upon the interferometric phase of the return signals;
• means for tracking the detected moving vehicles and for providing track file information indicative of the moving vehicles movement;
• means for coherently combining said clutter canceled signals to provide a coherent sum;
• means for correcting the return signals in said coherent sum for range walk of the moving vehicles using said track file information and for providing a range walk corrected coherent sum;
• and
• means for processing said range walk corrected coherent sum to form an image of the moving objects.