The invention belongs to an imaging method for nonlinear
frequency modulation label change in the
synthetic aperture radar imaging technology, which comprises the steps of two-dimensional
frequency domain unfolding, filtering
processing, nonlinear
frequency modulation label change, distance compression, distance migration correction, rest
phase compensation and position compression. In the method of the invention, the characteristics of orthogonality and minimum
square error of the
Legendre polynomials are utilized for carrying out three-order unfolding on the two-dimensional
frequency domain signals of the obtained echo signals according to the Legendre orthogonality polynomials, and then, the focusing imaging on targets is realized through carrying out filtering
processing and the like on three-order phase items in
echo signal two-dimensional
frequency domain expression. When the method of the invention is adopted, the
maximum phase error under the same condition is less than 0.2 percent of the
maximum phase error in the prior art, so the assurance is provided for the high-precision imaging under the large-inclination
view angle condition. Therefore, the method of the invention has the characteristics that the
phase error in the imaging process can be effectively reduced, the
imaging processing of the large-inclination
view angle is realized, in addition, the imaging effect is good, the
imaging processing efficiency and the precision are high, and the like.