HRRP Synthesis and Imaging of Frequency Agile Waveform With Multidimensional Nonideal Factor Errors for High-Speed Targets

Acquiring high-resolution range profile (HRRP) image of noncooperative targets holds substantial significance in the field of radar automatic target recognition due to its higher range resolution and richer target information compared with narrowband signal. To overcome the high hardware requirements for signal generation and reception in transmission of wideband signals, the utilization of step-frequency agile waveform (FAW) is a favorable choice for HRRP synthesis. The high-speed motion of noncooperative targets and the instability of radar systems will lead to multidimensional nonideal factor errors such as motion errors, carrier frequency offset (CFO), and time-varying amplitude (TVA) in radar echoes, resulting in poor quality of HRRP images with traditional HRRP synthesis methods. To address the above problems, this article proposes an HRRP synthesis method of FAW with multidimensional nonideal factor errors for high-speed targets. In this technique, a fine-grained signal model with multidimensional errors is established, enabling the acquisition of high-precision HRRP through parameter estimation and compensation. Based on this, a joint optimization algorithm of sparrow search algorithm and simulated annealing algorithm (SSA-SAA) is proposed to solve the optimal parameter search. Moreover, a multicriterion fusion cost function is designed to enhance the robustness of parameter search compared with the single-criterion cost function. High-precision HRRP synthesis of FAW for high-speed targets is achieved by effectively eliminating the errors caused by nonideal factors. Furthermore, high-precision inverse synthetic aperture radar (ISAR) based on long-term observation of HRRP sequences is generated. Extensive experimental results based on both simulated and real data are provided to demonstrate the effectiveness and robustness of the proposed method.