Bistatic inverse synthetic aperture radar imaging
First Claim
1. A bistatic synthetic aperture radar (SAR) imaging method, the method comprising:
- receiving a plurality of radar return pulses acquired by at least first and second airborne radar platforms, wherein each radar return pulse is generated in response to a corresponding transmission pulse reflected from two or more radar scattering locations on a target;
combining each radar return pulse with a sinusoid to reduce the radar return pulses to a base band frequency;
deskewing each reduced radar return pulse to remove effects of its corresponding radar transmission pulse;
estimating motion parameters of the target based on a maximum likelihood estimation (MLE) applied to the deskewed radar return pulses;
performing MLE motion correction to the deskewed radar return pulses based on the estimated motion parameters to generate motion corrected radar return pulses;
acquiring position and velocity estimates of the two or more airborne radar platforms and the one or more scattering locations on the target;
defining bistatic range and velocity vectors based on the position and velocity estimates of the first and second airborne radar platforms, the one or more scattering locations on the target, and the motion corrected radar return pulses;
defining new bistatic range and velocity vectors by redefining the bistatic range and velocity vectors in a new set of orthogonal axes;
projecting vector distance differences between the target radar scattering locations along the new set of orthogonal axes to generate new range and velocity measurements along the new set of orthogonal axes;
converting the new range and velocity measurements in order to map Doppler frequency into cross-range, measured in physical units of length; and
forming a bistatic SAR image in range and cross-range based on cross-range extent derived from the Doppler frequency mapping;
wherein the steps in the method are carried out by a processor.
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Abstract
A bistatic synthetic aperture radar (SAR) imaging system and method include: combining each radar return pulse from airborne radar platforms with a sinusoid; deskewing each reduced radar return pulse; estimating motion parameters based on a maximum likelihood estimation (MLE); performing MLE motion correction to generate motion-corrected radar return pulses; acquiring position and velocity estimates of the airborne radar platforms and scattering locations; defining bistatic range and velocity vectors; defining new bistatic range and velocity vectors in a new set of orthogonal axes; projecting vector distance differences between the radar scattering locations along the new set of orthogonal axes to generate new range and velocity measurements along the new set of orthogonal axes; converting the new range and velocity measurements to map Doppler frequency into cross-range; and forming a bistatic SAR image in range and cross-range based on cross-range extent derived from the Doppler frequency mapping.
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Citations
10 Claims
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1. A bistatic synthetic aperture radar (SAR) imaging method, the method comprising:
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receiving a plurality of radar return pulses acquired by at least first and second airborne radar platforms, wherein each radar return pulse is generated in response to a corresponding transmission pulse reflected from two or more radar scattering locations on a target; combining each radar return pulse with a sinusoid to reduce the radar return pulses to a base band frequency; deskewing each reduced radar return pulse to remove effects of its corresponding radar transmission pulse; estimating motion parameters of the target based on a maximum likelihood estimation (MLE) applied to the deskewed radar return pulses; performing MLE motion correction to the deskewed radar return pulses based on the estimated motion parameters to generate motion corrected radar return pulses; acquiring position and velocity estimates of the two or more airborne radar platforms and the one or more scattering locations on the target; defining bistatic range and velocity vectors based on the position and velocity estimates of the first and second airborne radar platforms, the one or more scattering locations on the target, and the motion corrected radar return pulses; defining new bistatic range and velocity vectors by redefining the bistatic range and velocity vectors in a new set of orthogonal axes; projecting vector distance differences between the target radar scattering locations along the new set of orthogonal axes to generate new range and velocity measurements along the new set of orthogonal axes; converting the new range and velocity measurements in order to map Doppler frequency into cross-range, measured in physical units of length; and forming a bistatic SAR image in range and cross-range based on cross-range extent derived from the Doppler frequency mapping; wherein the steps in the method are carried out by a processor. - View Dependent Claims (2, 3, 4, 5)
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6. A bistatic synthetic aperture radar (SAR) imaging system, the system comprising:
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one or more processor; and a memory, the memory including executable code representing instructions that when executed cause the system to; receive a plurality of radar return pulses acquired by at least first and second airborne radar platforms, wherein each radar return pulse is generated in response to a corresponding transmission pulse reflected from two or more radar scattering locations on a target; combine each radar return pulse with a sinusoid to reduce the radar return pulses to a base band frequency; deskew each reduced radar return pulse to remove effects of its corresponding radar transmission pulse; estimate motion parameters of the target based on a maximum likelihood estimation (MLE) applied to the deskewed radar return pulses; perform MLE motion correction to the deskewed radar return pulses based on the estimated motion parameters to generate motion corrected radar return pulses; acquire position and velocity estimates of the two or more airborne radar platforms and the one or more scattering locations on the target; define bistatic range and velocity vectors based on the position and velocity estimates of the first and second airborne radar platforms, the one or more scattering locations on the target, and the motion corrected radar return pulses; define new bistatic range and velocity vectors by redefining the bistatic range and velocity vectors in a new set of orthogonal axes; project vector distance differences between the target radar scattering locations along the new set of orthogonal axes to generate new range and velocity measurements along the new set of orthogonal axes; convert the new range and velocity measurements in order to map Doppler frequency into cross-range, measured in physical units of length; and form a bistatic SAR image in range and cross-range based on cross-range extent derived from the Doppler frequency mapping. - View Dependent Claims (7, 8, 9, 10)
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Specification