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Phase difference auto focusing for synthetic aperture radar imaging

  • US 4,999,635 A
  • Filed: 03/29/1990
  • Issued: 03/12/1991
  • Est. Priority Date: 03/29/1990
  • Status: Expired due to Term
First Claim
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1. An apparatus for automatically focusing range compressed SAR data stored in an array of range bins and azimuth lines comprising:

  • means for unpacking the range compressed data in each range bin;

    means for generating a first and second subarray from the unpacked data;

    means for conjugating the first subarray;

    means for multiplying the conjugated first subarray and the second subarray to create a first product array;

    means for performing a fast Fourier transform of the first product array to produce an FFT filter bank output;

    means for calculating the magnitude of the FFT filter to form a correlation function;

    means for integrating the correlation function over the range bins;

    means for detecting a peak in the correlation function after integrating over range bins;

    means for calculating a quadratic phase error responsive to the detected peak; and

    means for removing the calculated phase error from the range compressed data.

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