Modified frequency scaling processing algorithm for nonlinear FMCW SAR

The combination of compact frequency-modulated continuous wave (FMCW) technology and synthetic aperture radar (SAR) paves a way for the development of the lightweight, cost-effective, high-resolution miniaturized airborne imaging radar. One limiting factor to the use of FMCW SAR sensors is the well-known presence of nonlinearities in the transmitted signal, which highly deteriorates the range resolution and image quality because of the pair-echo effect. Moreover, the so-called stop-and-go approximation for pulsed SAR is no longer valid in FMCW SAR because of the continuous radar motion during the transmission of the relatively long sweep and the reception of the corresponding echo, which will induce serious Doppler frequency shift. A novel modified frequency scaling algorithm is proposed in this paper to compensate this Doppler shift, at the same time effectively correcting the range frequency non-linearity without extra computation load. The validity of the proposed algorithm is demonstrated with point target simulation results.