A method of determining feasible swaths of a synthetic aperture radar (SAR) includes determining a first plurality of swaths that are transmit-feasible and nadir-feasible, determining a second plurality of swaths of the first plurality of swaths that satisfy at least one hard constraint, the at least one hard constraint being an image quality constraint or a system constraint, and generating a graph of the second plurality of swaths. The method may include assigning each feasible swath of the second plurality of swaths to a node in a directed graph, and adding a directed edge in the directed graph when a pair of swaths of the second plurality of swaths satisfy one or more defined constraints. The method may include configuring the SAR to operate based at least in part on the generated graph of the second plurality of swaths. Operating the configured SAR may include obtaining SAR images.
A method of determining feasible swaths of a synthetic aperture radar (SAR) includes determining a first plurality of swaths that are transmit-feasible and nadir-feasible, determining a second plurality of swaths of the first plurality of swaths that satisfy at least one hard constraint, the at least one hard constraint being an image quality constraint or a system constraint, and generating a graph of the second plurality of swaths. The method may include assigning each feasible swath of the second plurality of swaths to a node in a directed graph, and adding a directed edge in the directed graph when a pair of swaths of the second plurality of swaths satisfy one or more defined constraints. The method may include configuring the SAR to operate based at least in part on the generated graph of the second plurality of swaths. Operating the configured SAR may include obtaining SAR images.
A synthetic aperture radar (SAR) is operable in an interrogation mode and in a self-imaging mode, the self-imaging mode entered in response to determining a response to interrogation pulses have been received from a ground terminal and position information specifying a ground location has been received from the ground terminal. A ground terminal is operable to receive interrogation pulses transmitted by a SAR, transmit responses, and transmit position information to cause the SAR to enter a self-imaging mode. The ground terminal receives first and subsequent pulses from the SAR where subsequent pulses include backscatter and are encoded. The ground terminal generates a range line by range compression.
A synthetic aperture radar (SAR) system generates an image of a first swath. The SAR includes at least one SAR antenna, at least one SAR processor and at least one SAR transceiver. In operation the SAR defines a first beam to illuminate the first swath and one or more second beams to illuminate area(s) of ambiguity associated with the first beam. The SAR transmits a pulse via the first beam and receives backscatter energy. The SAR generates a first signal associated with the first beam and one or more second signals associated with the second beam(s). The second signal(s) are combined with determined complex vector(s), generating ambiguity signal(s) and the ambiguity signals are combined with the first signal to generate an image associated with the first swath.
A synthetic aperture radar (SAR) is operable in an interrogation mode and in an imaging mode, the imaging mode entered in response to determining a response to interrogation pulses have been received from a ground terminal and position information specifying a ground location has been received from the ground terminal. A ground terminal is operable to receive interrogation pulses transmitted by a SAR, transmit responses, and transmit position information to cause the SAR to enter a imaging mode. The ground terminal receives first and subsequent pulses from the SAR where subsequent pulses include backscatter and are encoded. The ground terminal generates a range line by range compression. If the SAR is a multi-band SAR the transmitted pulses can be in two or more frequency bands, and subsequent pulses in one frequency band can include encoded returns from pulses transmitted in a different frequency band.
G01S 13/90 - Radar or analogous systems, specially adapted for specific applications for mapping or imaging using synthetic aperture techniques
G01S 7/00 - Details of systems according to groups , ,
G01S 13/28 - Systems for measuring distance only using transmission of interrupted, pulse modulated waves wherein the transmitted pulses use a frequency- or phase-modulated carrier wave with time compression of received pulses
G01S 13/30 - Systems for measuring distance only using transmission of interrupted, pulse modulated waves using more than one pulse per radar period
6.
Synthetic aperture radar imaging apparatus and methods for moving targets
A synthetic aperture radar (SAR) system may employ SAR imaging to advantageously estimate or monitor a transit characteristic (e.g., velocity, acceleration) of a vehicle, for example a ground based vehicle or water based vehicle. A dual-beam SAR antenna illuminate a moving target with a first radar beam and a second radar beam at an angular offset relative to the first radar beam. Pulses may be transmitted and backscattered energy received simultaneously by the SAR transceiver via the first and second radar beams. A SAR data processor may generate a first image from the first radar beam and a second image from the second radar beam, co-registering the first and second images, comparing the location of the moving target in the first and second images, and estimate a velocity of the moving target based at least in part on the angular offset.
A synthetic aperture radar (SAR) is operable in an interrogation mode and in a self-imaging mode, the self-imaging mode entered in response to determining a response to interrogation pulses have been received from a ground terminal and position information specifying a ground location has been received from the ground terminal. A ground terminal is operable to receive interrogation pulses transmitted by a SAR, transmit responses, and transmit position information to cause the SAR to enter a self-imaging mode. The ground terminal receives first and subsequent pulses from the SAR where subsequent pulses include backscatter and are encoded. The ground terminal generates a range line by range compression.
A synthetic aperture radar (SAR) is operable in an interrogation mode and in an imaging mode, the imaging mode entered in response to determining a response to interrogation pulses have been received from a ground terminal and position information specifying a ground location has been received from the ground terminal. A ground terminal is operable to receive interrogation pulses transmitted by a SAR, transmit responses, and transmit position information to cause the SAR to enter a imaging mode. The ground terminal receives first and subsequent pulses from the SAR where subsequent pulses include backscatter and are encoded. The ground terminal generates a range line by range compression. If the SAR is a multi-band SAR the transmitted pulses can be in two or more frequency bands, and subsequent pulses in one frequency band can include encoded returns from pulses transmitted in a different frequency band.
A synthetic aperture radar (SAR) system and method of operation advantageously implements dynamic self-cueing or autonomous cueing of successive high-resolution SAR data collection based on previously collected wide-swath SAR data, for instance without the intervention of ground-based resources. For example, target detection may be performed on-board a spaceborne or airborne SAR platform using wide-swath SAR data acquired via a first beam at a first frequency band, the first beam pointed at a first angle relative to an along-track direction. Subsequent activities are cued by the platform based on the previously collected wide-swath SAR data. For instance, the SAR platform may cue subsequent acquisition of SAR data via a second beam at a second frequency band, the second beam pointed at a second angle relative to an along-track direction. The SAR platform may advantageously employ a multi-band SAR antenna.
A digital beamforming synthetic aperture radar (SAR) mixes a first analog signal to generate a frequency-shifted first signal having a first spectral band, mixes a second analog signal to generate a frequency-shifted second signal having a second spectral band, positioned at a defined frequency offset from the first spectral band, and positioned non-overlapping relation with the first spectral band, combines the first and second frequency-shifted signals to generate a combined analog receive signal, and band-pass samples the combined analog receive signal to generate a digital baseband signal representative of the first and second analog signals. The SAR may mix the second analog signal to position the second spectral band in the Nyquist bandwidth, and in non-overlapping relationship with the first spectral band. Mixing may include down converting the analog signal.
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