A Coupled Error Self-Calibration Method for High-Speed Space Target Imaging in Stepped-Frequency Radar Based on Minimum Entropy

Stepped-frequency chirp radar achieves range high resolution through wideband synthesis, yet it harbors systemic errors. These errors coupled with the motion errors of high-speed space target, render error calibration more challenging and compromise the quality of imaging. To tackle this problem, this article proposes the coupled error self-calibration method for high-speed space target imaging in stepped-frequency based on minimum entropy. First, a parameterized model of echo signals incorporating complex coupled errors is established. This model not only takes into account the errors introduced by the amplitude–phase response characteristics of the stepped-frequency radar system, but also considers errors arising from the motion of high-speed targets. Then, analytical relationships between entropy and errors after range pulse compression of subband data, after 2-D imaging of subband data, and after high-resolution synthesis of all subband images are constructed. This stepwise processing strategy decomposed complex errors into three distinct components. Subsequently, employing an adaptive matrix estimation method to separately estimate and calibrate the three decoupled error components ensures a gradual improvement in imaging quality. Finally, the effectiveness of the proposed method is verified through computer simulation and a real experiment.