Micromotion Parameters Estimation for Helicopter Under Low-Pulse Repetition Frequency Condition

The article proposes a micromotion parameter estimation method based on multidomain feature fusion and least squares estimation (LSE). For rotor-type targets, in practice, the spectral line interval in the time–frequency domain is equal to the product of the number of blades and the rotation rate, which means there is the coupling of micromotion parameters, making it difficult to accurately estimate the micromotion parameters of noncooperative rotor-type targets. This method comprehensively utilizes the information of peak interval in time domain and spectral line interval in frequency domain from helicopter echoes under narrow-band radar, and achieves equivalent decoupling of micromotion parameters through combined parameter optimization. By utilizing the LSE, the combined solution of micromotion parameters (such as rotation rate, blades length, and the number of blades) is determined and extracted. Finally, the effectiveness of the proposed method is verified through simulations and measured data. This method can achieve micromotion parameter estimation of helicopters at low-pulse repetition frequency and with less prior information. It is a simple and effective algorithm that is convenient for engineering applications.