In image formation of large-squint and large-beamwidth SAR

a high coupling and range-variant migration echo must be processed so that it is difficult to get a fine focusing synthetic aperture radar (SAR) image.In this paper

we first compared about the source and degree of the coupling in those two models by the mathematical two-dimension spectrum expression of SAR echoes.Next

we mainly discuss the method of uncoupling in the nonlinear chirp-scaling algorithm and attain a relation of residual coupling and two parameters

which is mapping slant-range width and most far slant-range distance.Finally

we give the difference of those two parameters when that algorithm is used to large-squint and large-beam width SAR image formation.