Intra-pulse Doppler effect and experimental result on nonlinear frequency modulation airborne SAR

Nonlinear frequency modulation (NLFM) waveforms have been investigated in recent years. The main advantages of the waveform include fine resolution, good signal-to-noise ratio, and good interference mitigation. However, for synthetic aperture radar (SAR), there are hitherto no real applications of NLFM. It is known that Doppler intolerance is the drawback of NLFM waveform. Therefore, in this paper, the two-dimensional NLFM SAR signal model with Doppler shift is formulated and the influences of Doppler shift on airborne SAR imaging are analysed in detail. Furthermore, the first experimental result of airborne NLFM SAR is demonstrated.