System for extraction of a region of interest (ROI) from a composite synthetic aperture radar (SAR) system phase history

A synthetic aperture radar (SAR) system for extraction of a region of interest (ROI) from a composite SAR phase history data, comprising:

• a memory;
• one or more processing units;
• and
• a machine-readable medium on the memory, wherein the machine-readable medium stores instructions that, when executed by the one or more processing units, cause the SAR system to perform operations comprising:
• receiving the composite SAR phase history data of a plurality of backscattered return signals produced as a function of the SAR system illuminating a scene with a SAR beam;
• obtaining a location of a ROI within the scene;
• and
• extracting from the composite SAR phase history data a component SAR phase history data corresponding to the ROI at the location of the ROI;
• wherein the extracting the composite SAR phase history data comprises:
• sectorizing the SAR beam into a plurality of sectors, wherein each sector is defined between a first sectoral angle and a second sectoral angle and each sector corresponds to a Doppler frequency interval having a first frequency value and a second frequency value;
• and
• decomposing the composite SAR phase history data into a plurality of sectoral SAR phase history data via Doppler processing of an induced azimuth signal,
• wherein each sectoral SAR phase history data corresponds to a unique sector of the plurality of sectors, the component SAR phase history data corresponds to a first sectoral SAR phase history data corresponding to a first sector of the plurality of the sectors, and the first sector corresponds to a first Doppler frequency interval;
• wherein the Doppler processing the induced azimuth signal includes:
• determining a first Doppler frequency in the induced azimuth signal from the backscattered return signals received at a first directional angle (θ1) from the normal direction to the travel path, wherein the first Doppler frequency (f1) is defined by the first directional angle, a velocity of the SAR system along the travel path and a wavelength of a carrier frequency of the SAR system, and
• bandpass filtering the induced azimuth signal, with a bandpass filter having a passband, to produce a new induced azimuth signal that includes frequency components of the induced azimuth signal that fall within the passband.

A method for region of interest (ROI) detection and localization with synthetic aperture radar (SAR) phase history data, the method comprising:

• receiving, by a system comprising a processor, the SAR phase history data of a plurality of backscattered return signals produced in response to a SAR system illuminating a scene with a SAR beam;
• creating, from a subset of the plurality of backscattered return signals, a pseudo-image of the scene via angular decomposition, the pseudo-image having a lower resolution than a full image of the scene, the full image being defined by, and obtainable using, the subset and one or more additional backscattered return signals of the plurality of backscattered return signals, the subset being smaller than needed for the full image reconstruction;
• detecting salient features of energy in the pseudo-image, including:
• adaptive thresholding the pseudo-image to produce a binary image, and,
• identifying an object in the binary image utilizing morphological operations with connected component labeling, wherein identifying the object includes generating after the connected component labeling a centroid, a major axis, a minor axis, and an orientation of the object, wherein the centroid, major axis, minor axis, and orientation of the object define a bounding ellipse around the object,
• wherein magnitudes of the subset of the plurality of backscattered return signals are determined as magnitudes of backscattered return-quadrature I/Q signal representations;
• and
• detecting the ROI within the scene from the detected salient features of energy;
• wherein the creating the pseudo-image comprises adding magnitudes of the subset of backscattered return signal representations, wherein each magnitude is added to its corresponding location in the pseudo-image.