Designing Interference-Immune Doppler-Tolerant Waveforms for Radar Systems

Dynamic target detection using linear frequency modulation (LFM) waveform is challenging in the presence of interference for different radar applications. Degradation in the signal-to-noise ratio is irreparable, and interference is difficult to mitigate in time and frequency domains. In this article, a waveform design problem is addressed using the majorization–minimization framework by considering peak sidelobe level (PSL)/integrated sidelobe level (ISL) cost functions, resulting in a code sequence with Doppler-tolerant characteristics of an LFM waveform and interference-immune characteristics of a tailored polyphase sequence (unique phase code + minimal ISL/PSL). The optimal design sequences possess polynomial phase behavior of degree $Q$ among its subsequences and obtain optimal ISL and PSL solutions with guaranteed convergence. By tuning the optimization parameters such as degree $Q$ of the polynomial phase behavior, subsequence length $M$, and the total number of subsequences $L$, the optimized sequences can be as Doppler tolerant as LFM waveform in one end, and they can possess small cross-correlation values similar to random-phase sequences in polyphase sequence on the other end. The numerical results indicate that the proposed method is capable to computationally design chirplike sequences, which, prior to this work, were obtained by mimicking phase variations of LFM waveform. An application of the proposed method for the automotive scenario is also illustrated in the numerical results.