Piecewise Nonlinear Frequency Modulation Waveform for MIMO Radar

We propose a piecewise nonlinear frequency modulation (PNLFM) waveform for a multiple-input multiple-output (MIMO) radar. Each subpulse in the waveform set is divided into three segments. The first and the third segments are linear frequency modulation (LFM) signals, whereas the second segment is a nonlinear frequency modulation (NLFM) signal. The bandwidths and durations of subpulses are the same, whereas they can be different for each segment in the subpulse. In addition, the nonlinear time-frequency function of the second segment is controlled to improve the range and Doppler sidelobe suppression. A genetic algorithm is implemented to optimize the performance by maximally suppressing the autocorrelation sidelobe and cross correlation in range, Doppler, and angle. The MIMO radar performance is demonstrated via computation of the ambiguity function, autocorrelation function, and cross-correlation function. Numerical results are presented to show waveform properties and to compare with some existing MIMO radar waveforms. The proposed PNLFM waveform has low autocorrelation sidelobes and low cross correlation in range and Doppler, which sits at a level determined largely by the chosen time-bandwidth product.