A Nonlinearity Measurement Method for Frequency-Modulated Continuous Wave Synthetic Aperture Radar Imaging

One crucial limiting factor to the use of frequency-modulated continuous wave synthetic aperture radar (FMCW SAR) sensors is the well-known presence of frequency nonlinearities in the transmitted signal, which highly deteriorates the range resolution because of the pair-echo effect. By analyzing the FMCW SAR nonlinear signal model, a novel nonlinearity measurement method is proposed based on the time-shift characteristic of the Fourier transform. With the accurate estimation of the nonlinearity term, the modified frequency scaling algorithm is applied with nonlinearity correction to complete the imaging process. The validity of the proposed algorithm is demonstrated with multi-point targets simulation, confirming its superiority in terms of resolution, PSLR, ISLR, and final focused images.