Demonstration of NLFM Waveforms With Experiments and Doppler Shift Compensation for SAR Application.

Range sidelobe suppression in synthetic aperture radars (SARs) is conventionally realized using amplitude weighting with windowing functions in either time or frequency domains, which would result in a reduced signal-to-noise ratio (SNR) of the output. To counterbalance the loss, a system with more complexity and cost is needed, especially for spaceborne SAR. Fortunately, nonlinear frequency modulation (NLFM) chirp waveforms, which can shape the signal’s power spectral density and offer radar matched filter output with lower sidelobes at no cost of reduced SNR, is a promising candidate. In this letter, the proof-of-principle experiment is presented to construct NLFM transmitting pulses using a real SAR system platform on the ground and analyze the characteristics of the pulses. Two approaches are developed to perform system-specific predistortion and the advantage of NLFM waveforms with better SNR is demonstrated using the theoretical derivation and experimental results. For spaceborne NLFM SAR, the effect of Doppler shift on NLFM SAR imaging cannot be neglected. Therefore, for further promoting the application of NLFM in SAR, one effective compensation approach is developed. All the experimental results and analysis validate the promising potential of NLFM for SAR application. [ABSTRACT FROM PUBLISHER]