EP0239022A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Extended sar imaging capability for ship classification
Assignee: Grumman Corp
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Filing: 1987-03-20
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Granted: —
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Expires: 2007-03-20
Abstract
Abstract Capability is provided using coherent synthetic aperture radar (SAR) techniques for substantially extending the useful range for producing 3 scaled high resolution orthogonal image projections on a CRT (29) of a translating ship under the influence of rotational motions arising from sea state conditions, for the purpose of ship classification and weapon delivery from an airborne platform at long stand-off ranges. This advantage is brought about by determining image coordinates on the basis of range, doppler, and doppler rate measurements of individual scatterers and from ship angular rotational velocities derived from a weighted multivariate regression solution to doppler processed interferometric azimuth and elevation angle measurements of all significant ship target scatterers. In this manner, the image degradation suffered by plotting angular measurements directly, whose location accuracies are known to deteriorate rapidly with increased range due to high signal-to-noise requirements, is circumvented.
Inventors
- 👤 Sol Boles
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-30 00:19
CPC Classifications
G; G01; G01S; G01S13/00; G01S13/88; G01S13/89; G01S13/90; G01S13/9021; G01S13/9023; G01S13/904; G01S13/9092
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
108 words
A method for forming high resolution synthetic aperture radar imagery of a ship target under the influence of sea state conditions, characterized in the steps of: (a) processing signals received from ship scatterers comprising the ship target to obtain estimates of (1) range, velocity, and acceleration of ship scatterers, and (2) ship rotational velocities and rotational velocity rates; (b) determining from these estimated ship scatterer motional parameters the coordinate values of the ship scatterer centers to form a high resolution image of the ship target; and (c) displaying the formed imagery of the ship target including a range/azimuth projection, an elevation/azimuth profile projection, and a range/elevation profile projection.
Claim 2
Independent Claim
108 words
A method for forming high resolution synthetic aperture radar imagery of a ship target under the influence of sea state conditions, characterized in the steps of: (a) processing signals received from ship scatterers comprising the ship target to obtain estimates of (1) range, velocity, and acceleration of ship scatterers, and (2) ship rotational velocities and rotational velocity rates; (b) determining from these estimated ship scatterer motional parameters the coordinate values of the ship scatterer centers to form a high resolution image of the ship target; and (c) displaying the formed imagery of the ship target including a range/azimuth projection, an elevation/azimuth profile projection, and a range/elevation profile projection.
Claim 3
Dependent Claim
56 words
A method as recited in claim 1, characterized in that the step of processing the received signals includes: (a) determining scatterer velocities from polynomial curve fitting to interpolated and sorted doppler processed frequency measurements over a prescribed tracking time interval; and (b) determining scatterer accelerations from the time derivatives of polynomial curve fits to frequency data.
Claim 4
Independent Claim
80 words
A method as recited in claims 1 or 2, characterized in that the step of processing the received signal includes: (a) performing a weighted multivariate regression fit to processed doppler, azimuth, and elevation angle measurements to obtain cross-line-of-sight ship rotational velocities using an iterative process of minimizing error residuals; and (b) determining line-of-sight ship rotational velocity using sorted azimuth and elevation angle measurements, in conjunction with elevation angle rates determined for several bright scatterers and estimated cross-line-of-sight ship rotational velocity.
Claim 5
Independent Claim
48 words
A method as recited in any one of the preceding claims, characterized in that the step of processing the received signals includes: (a) obtaining cross-line-of-sight ship rotational velocity rates from time derivatives of polynomial curve fits to stored estimates of the cross-line-of-sight rotational velocities derived from regression solutions.
Claim 6
Independent Claim
34 words
A method as recited in claims 3 or 4, characterized in that said doppler, azimuth and elevation angle measurement are determined from Fourier transform signal processing using interferometric or phase monopulse antenna arrangements (10).
Claim 7
Dependent Claim
122 words
An airborne synthetic aperture radar system for forming high resolution synthetic aperture radar imaging of a ship target under the influence of sea state conditions, characterized in (a) means for processing signals received by an antenna (10) from ship scatterers comprising the ship target to obtain estimates of (1) range, velocity, and acceleration of ship scatterers, and (2) ship rotational velocities and rotational velocity rates; (b) means (27, 28) for determining from these estimated ship scatterer motional parameters the coordinate values of the ship scatterer centers to form a high resolution image of the ship target; and (c) means (29) for displaying the formed imagery of the ship target including a range/azimuth projection, an elevation/azimuth profile projection, and a range/elevation profile projection.
Claim 8
Dependent Claim
122 words
An airborne synthetic aperture radar system for forming high resolution synthetic aperture radar imaging of a ship target under the influence of sea state conditions, characterized in (a) means for processing signals received by an antenna (10) from ship scatterers comprising the ship target to obtain estimates of (1) range, velocity, and acceleration of ship scatterers, and (2) ship rotational velocities and rotational velocity rates; (b) means (27, 28) for determining from these estimated ship scatterer motional parameters the coordinate values of the ship scatterer centers to form a high resolution image of the ship target; and (c) means (29) for displaying the formed imagery of the ship target including a range/azimuth projection, an elevation/azimuth profile projection, and a range/elevation profile projection.
Claim 9
Dependent Claim
57 words
The system of claim 6, characterized in that said processing means includes: (a) means (21-24) for determining scatterer velocities from polynomial curve fitting to interpolated and sorted doppler processed frequency measurements over a prescribed tracking time interval; and (b) means (25, 26) for determining scatterer accelerations from the time derivatives of polynomial curve fits to frequency data.
Claim 10
Independent Claim
82 words
The system of claims 6 or 7, characterized in that said processing means includes: (a) means (17, 20) for performing a weighted multivariate regression fit to processed doppler, azimuth, and elevation angle measurements to obtain cross-line-of-sight ship rotational velocities using an iterative process of minimizing error residuals; and (b) means (17, 20) for determining line-of-sight ship rotational velocity using sorted azimuth and elevation angle measurements, in conjunction with elevation angle rates determined for several bright scatterers and estimated cross-line-of-sight ship rotational velocity.
Claim 11
Independent Claim
44 words
The system of claims 6, 7 or 8, characterized in that said processing means (17, 20) includes means for obtaining cross-line-of-sight ship rotational velocity rates from time derivatives of polynomial curve fits to stored estimates of the cross-line-of-sight rotational velocities derived from regression solution.
Claim 12
Independent Claim
32 words
The system of any one of claims 6 - 9, characterized in a multiple section interferometer antenna (10) connected to a two channel receiver (13, 24) and a doppler processing system (15-26).
References Cited (Backward Citations)
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