Radar waveform diversity using nonlinear chirp with improved sidelobe level performance

Abstract Radar system with high range-resolution can be obtained through discrete frequency-coding waveform (DFCW). In this paper, we investigate the design process of DFCW using nonlinear chirp (DFCW-NLC), with improved autocorrelation sidelobe peak (ASP) and cross-correlation peak (CCP) levels, to attain radar waveform diversity. In this context, we present a parameterized waveform design model and derive NLC functions for designing the required NLC waveform, thereby simplifying the waveform design process. We derive analytical expressions of autocorrelation and cross-correlation functions for the NLC waveform. To achieve a waveform with desired properties, we present an optimization process based on genetic algorithm, and the optimization of parameterized NLC waveforms attains improved ASP performance over existing designs. Subsequently, we propose the design of a set of DFCW-NLC, double the number as compared to the reported designs. We derive analytical expressions of ambiguity function to investigate waveform performance. We perform a joint optimization of frequency hopping sequence and associated chirp-pulse type of the DFCW-NLC. Numerical results prove that the designed DFCWs-NLC achieve significant improvement in ASP and CCP levels of ≈ 5.0 dB and ≈ 5.47 dB, respectively in comparison with the state-of-the-art designs, and makes the proposed waveforms a superior candidate for multiple-input-multiple-output (MIMO) and multiuser radar applications.