Near-Field Micro-Doppler Effect and Spectrum Characteristics of Rotating Targets: Theoretical Analysis and Parameter Estimation Method

Micro-Doppler effect is of great significance in radar-based rotating target detection, classification, and micromotion monitoring leveraging on the containing rich physical information. However, there is a lack of theoretical analysis for spectrum characteristics of the near-field micro-Doppler signal of rotating targets, and the targets with 2-D and 3-D complex-shaped blades in reality are commonly not considered. Furthermore, the rotating parameter estimation is mainly depends on the traditional time–frequency distribution (TFD) method, which has limitations in stability, efficiency, and practicability. In this article, a theoretical analysis method with the Taylor formula and Jacobi–Anger formula expansion for spectrum characteristics of the near-field micro-Doppler signal is proposed. The characteristics of spectral line interval and critical frequency are theoretically demonstrated by the established analytical expression of the spectrum. Then, the proposed approach is broadened to the 2-D blade model of arbitrary shape and the 3-D blade model of complex space surface. Based on the theoretical analysis, the spectrum characteristic-based parameter estimation (SCPE) method for rotation motion parameter extraction is provided. Finally, the high accuracy, high efficiency, and good stability of the proposed SCPE method are demonstrated by simulations and experiments with various scenarios, offering an appealing near-field and far-field micro-Doppler analysis approach of rotating targets with blades of various shapes.