Multibeam single frequency synthetic aperture radar processor for imaging separate range swaths
First Claim
1. In a multibeam synthetic aperture radar system, wherein each beam is directed to a different range and azimuth defined target area, a method for processing return data from pulses periodically transmitted simultaneously in each beam at a single frequency, a method for imaging separate range swaths over a range greater than otherwise possible for the interval between periodic pulses comprising the steps of range correlating the return radar data separated in successive interpulse periods to form image data for a plurality of range swaths, and separating in azimuth the return radar data thus correlated in range by filtering a unique Doppler frequency spectrum for each beam to form a plurality of distinct range and azimuth defined beams for imaging a beam selected at a unique azimuth angle in each range swath defined by an interpulse period, said azimuth angle being an angle on either side of a direction from said radar system normal to said range swaths.
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Abstract
A single-frequency multibeam synthetic aperture radar for large swath imaging is disclosed. Each beam illuminates a separate "footprint" (i.e., range and azimuth interval). The distinct azimuth intervals for the separate beams produce a distinct Doppler frequency spectrum for each beam. After range correlation of raw data, an optical processor develops image data for the different beams by spatially separating the beams to place each beam of different Doppler frequency spectrum in a different location in the frequency plane as well as the imaging plane of the optical processor. Selection of a beam for imaging may be made in the frequency plane by adjusting the position of an aperture, or in the image plane by adjusting the position of a slit. The raw data may also be processed in digital form in an analogous manner.
55 Citations
15 Claims
- 1. In a multibeam synthetic aperture radar system, wherein each beam is directed to a different range and azimuth defined target area, a method for processing return data from pulses periodically transmitted simultaneously in each beam at a single frequency, a method for imaging separate range swaths over a range greater than otherwise possible for the interval between periodic pulses comprising the steps of range correlating the return radar data separated in successive interpulse periods to form image data for a plurality of range swaths, and separating in azimuth the return radar data thus correlated in range by filtering a unique Doppler frequency spectrum for each beam to form a plurality of distinct range and azimuth defined beams for imaging a beam selected at a unique azimuth angle in each range swath defined by an interpulse period, said azimuth angle being an angle on either side of a direction from said radar system normal to said range swaths.
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3. In a multibeam synthetic aperture radar system wherein each beam is directed with a different range and azimuth as said system is carried along a flight line, a method for imaging multiple swaths of range with a single transmitted frequency comprising the method of separating radar data for each successive range to form range resolved image data, separating images in the range resolved image data by Doppler frequency spectra filtering data from beams at different azimuth angles, each azimuth angle being an angle on either side of a direction from said radar system normal to said flight line, and selecting data at only one azimuth at a time for imaging.
- 4. In a synthetic aperture radar system wherein each beam is directed with a different range and azimuth as said system is carried along a flight line, a method for single frequency imaging of multiple range swaths at high range intervals yielding one image for each range by selecting range resolved data at one distinct azimuth angle at a time, each azimuth angle being an angle on either side of a direction from said radar system normal to said flight line, the steps of correlating radar data resolved in range, and selecting range correlated data for mapping images at different azimuth angles in the respective range swaths by Doppler frequency spectra separation of the data, one spectrum for each range.
- 9. In a multibeam synthetic aperture radar system wherein each beam is directed with a different range and azimuth as said system is carried along a flight line, apparatus for processing return data from periodic pulses at a single frequency, wherein said data are separated in range for each successive pulse period to form range resolved data, comprising means for separating Doppler frequency spectra in the range resolved data for different azimuth angles to form azimuth selected images, one image at each range, and means for selecting azimuth separated image data for mapping selected range swaths.
Specification
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Current AssigneeAtul Jain, Frosch Robert A Administrator of The National Aeronautics and Space Administration With Respect To An Invention of
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Original AssigneeAtul Jain, Frosch Robert A Administrator of The National Aeronautics and Space Administration With Respect To An Invention of
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InventorsJain, Atul, Frosch, Robert A. Administrator of the National Aeronautics and Space Administration, with respect to an invention of
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Primary Examiner(s)Buczinski, S. C.
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Application NumberUS06/165,910Time in Patent Office838 DaysField of Search343/5 CM, 343/9 PS, 367/88US Class Current342/25.00ACPC Class CodesG01S 13/9005 with optical processing of ...
