Range-Doppler Processing of High-Speed Target in Nonlinear Stepped-Carrier OFDM Radar for Automotive Applications

Stepped-carrier orthogonal frequency division multiplexing (SC-OFDM) radar is an emerging low-cost alternative to traditional OFDM radar for automotive applications. It offers high-range resolution without increasing the sampling rate. However, it suffers from the Doppler intolerance in high-speed target detection, which arises from Doppler-induced inter-carrier interference (ICI), resulting in peak power loss and increased range sidelobes in the range-velocity map. In addition, the maximum unambiguous velocity is reduced by the number of frequency steps. This paper proposes a novel range-Doppler processing method for nonlinear stepped-carrier OFDM (NSC-OFDM) radar systems to mitigate the problems. The proposed method employs a two-stage Doppler compensation approach: initially applying all-cell Doppler correction under unambiguous velocity assumption, followed by ambiguous-cell Doppler correction for ambiguous targets identified through range sidelobes. The method can automatically resolve velocity ambiguity by selecting the hypothesis with optimal sidelobe suppression, achieving effective ICI mitigation. Finally, simulation results validate the effectiveness of the proposed method; meanwhile, the good performance of the proposed method on range sidelobe reduction, estimation accuracy, and computational complexity are shown by comparisons with three other methods.