A Novel Pulse-Agile Waveform Design Based on Random FM Waveforms for Range Sidelobe Suppression and Range Ambiguity Mitigation

In this article, a novel pulse-agile waveform design based on random frequency modulation (RFM) waveforms is proposed for range sidelobe suppression and range ambiguity mitigation to improve the system performance of radar detection and imaging. The time-frequency relationships of the proposed RFM waveforms are characterized by random Fourier coefficients, which are different from other RFM waveform models. To determine the number and the range of random Fourier coefficients, an RFM waveform design framework based on the theoretical derivation of spectral distribution is presented. The proposed framework has the ability to generate spectral-compact pulse-agile RFM waveforms with high efficiency even under a large waveform number and a large time-bandwidth product (TBP). The designed RFM waveforms have random sidelobe, good quasi-orthogonality, high spectral compactness, and constant amplitude. By exploiting the advantage of pulse-agile RFM waveforms, range sidelobes can be reduced by the plural accumulation of the pulse compression results of multiple RFM waveforms. Meanwhile, range ambiguity can be mitigated using different filter banks for the corresponding range intervals. Compared with other low sidelobe quasi-orthogonal waveforms, the designed pulse-agile RFM waveforms using random Fourier coefficients perform better in peak-to-sidelobe level ratio (PSLR) and cross correlation peak (CCP) levels with a large waveform number. The PSLR and the average CCP level for 1000 RFM waveforms are -49.0 and -25.8 dB, respectively. Finally, a series of simulations and experiments of microwave imaging that transmit pulse-agile RFM waveforms are conducted, which demonstrate the ability of range sidelobe suppression and range ambiguity mitigation.