Estimation of motion parameters of rotating targets based on rotational Doppler effect

Vortex electromagnetic waves exhibit unique detection capabilities when dealing with targets moving perpendicular to the radar line of sight, which are not achievable with conventional plane electromagnetic waves. This paper introduces a novel method for estimating the motion parameters of rotating targets based on the rotational Doppler effect. The primary goal is to accurately determine the number of blades and the angular velocity of multi-blade rotating targets. The method starts with a time-frequency analysis of the radar echo signals from multi-blade rotating targets. It employs a second-order synchrosqueezing transform, built upon the short-time Fourier transform, to extract the time-frequency ridge. By analyzing the distinct curves in the time-frequency ridge, the number of rotating blades can be effectively identified. Furthermore, the angular velocity can be estimated by examining the changes in the periods of these curves. Simulation results demonstrate that this method can accurately estimate the number of blades of rotating targets, and the error in angular velocity extraction can be controlled with an error of about 1% for targets with relatively simple motion states. This study offers a new and effective approach for estimating the parameters of rotating targets, providing significant theoretical and practical value.